[IA + maty @nauscopio] xDuoo A35 valve amplifier - Technical Report - 13 amplifiers - 12 PP EL34 + Acronos RS-1 SE KT150

ESPAÑOL

Technical report — September 2026 · V19.0

by [Meta+ChatGPT+DeepSeek+Claude] + maty @nauscopio

xDuoo A35, Technical Report

13 amplifiers — 12 PP EL34/KT88 + Acronos RS-1 SE KT150

Galion TS34 V2 is part of the 12 PP and offers selectable Class A/AB operation (25W Class A / 40W AB). 12 PP = Jadis Aria, PrimaLuna EVO 200, Fezz Luna, Icon 40 MKIIIm, Cayin CS-55A, Cayin Jazz 80 EL34, Cayin Jazz 70, xDuoo A35, Willsenton R8, Line Magnetic LM-216IA, Black Ice F22 V2, Galion TS34 V2 + Acronos RS-1 SE KT150. Specific system suitability index for 3-way 89 dB/5.3 O/3 m. LspCAD curves are simulations, not anechoic measurements.

Contents

0. Executive summary1. Introduction and scope2. Evidence and specifications3. Architecture and analog stage4. Electrical performance5. Digital section and noise6. Bias and safety7. Philosophy and modifications8. Tubes — options and comparison9. Digital modifications and limits10. Measurement protocol11. Evaluation and traceability12. Power and listening levels13. Master comparison table14. Dual bias and low power15. Suitability ranking16. Speaker model and LspCAD17. Personalised Top 318. Glossary19. Frequently asked questions20. Modification budget

Evidence legend

CONFIRMED

OBSERVED photo

MEASURED (pending 1st measurement)

CALCULATED

PROBABLE

NOT DEMONSTRATED

0. Executive summary — for your 89dB/5.3O/3m speakers

xDuoo A35 · click to enlarge

What to buy by level

Night 65 dB DR>11 (7.1 mW): Acronos RS-1 absolute reference 0.13 dB variation + 18 W @0.01% — theoretical black background. PP alternative with unverified low noise: Jadis Aria KT77 33 mA (6.9 dB / €3,430 VIP25), Cayin Jazz 80 EL34 (7.0 dB / €1,323 VIP25) and PrimaLuna EVO 200 (7.89 dB / €3,990 autobias).

Critical 80 dB + peaks 95 dB (0.226W / 7.15W): All 13 meet >1.5 dB except pure triode. Best: xDuoo A35 (7.99 dB) best estimated ratio in the group €1,339, Cayin Jazz 80 EL34 (7.0 dB) at €1,323, PrimaLuna (7.89 dB), Black Ice (8.45 dB), Willsenton R8 UL (7.99 dB / €2,900) 2.76 dB/€.

Cinema/tutti 85 dB + peaks 100 dB (0.716W / 22.6W): You need UL. Cayin CS-55A UL (2.48 dB) €1,590 BEST VALUE, Cayin Jazz 80 EL34 UL (1.9 dB) at €1,323, xDuoo A35 (2.99 dB), Willsenton R8 UL (2.99 dB), PrimaLuna (2.89 dB).

See the personalised Top 3 (§17), with the Tarragona factor and the specific response for your repertoire and speakers.

1. Introduction and scope

Reference images - visual basis

Photographs of the Tharbamar unit are used as the definitive visual reference. They constitute the basis of observed evidence for the analysis. Video: xDuoo A35 EL34 Tube Amp Review & Comparisons

Main view (click image to enlarge) Point-to-point analog section, ceramic sockets, blue bias trimmers, green 10 O shunts OBSERVED

Digital section (click image to enlarge) ES9018K2M + BT 5.1 + MCU + FB1 ferrite. Physical separation of blocks OBSERVED

Amplifier interior (click image to enlarge) xDuoo A35 complete OBSERVED

"Custom EI according to manufacturer" CONFIRMED + visual appearance OBSERVED. Leakage inductance pending measurement NOT DEMONSTRATED.

Objective and criterion of this report

This document analyses the xDuoo A35, an integrated tube amplifier with EL34 push-pull output stage, ultralinear operation and integrated ESS DAC and Bluetooth.

The purpose is not to repeat commercial information, but to expressly distinguish between confirmed data, visual evidence, measurements, calculations and inferences.

Label	Meaning
CONFIRMED	Published by xDuoo or a consistent reliable distributor.
OBSERVED	Directly visible in interior photographs.
MEASURED	Obtained through instrumentation on a specific unit. Reserved category: as of V19.0 there is still no independent measurement of this unit published.
CALCULATED	Mathematically derived from known data.
PROBABLE	Reasonable technical inference pending verification.
NOT DEMONSTRATED	Should not be presented as fact without additional measurement or documentation.

2. Evidence and specifications

Compact synthesis of evidence status

Each row can be traced to the corresponding section. This table replaces the need to go through the entire report to know the real status of each piece of data.

Parameter	Value	Evidence
Topology	EL34 push-pull ultralinear	CONFIRMED §3
Declared power	45 W/channel @ 8 O	CONFIRMED §2 (manufacturer)
Power tubes	4× EL34	CONFIRMED §2/§3
Driver / preamp	1× 12AX7 + 2× 12AU7	CONFIRMED §2/§3
Transformers	Custom EI	CONFIRMED + OBSERVED §3
Construction	Point-to-point main analog section	OBSERVED §1/§3
Zout	0.65 O (4 O tap) / 1.20 O (8 O tap)	SOURCE DATA — NOT INDEPENDENT MEASUREMENT §4
THD	=1 % declared	SPEC — without independent verification §4
Frequency response	20 Hz–60 kHz ±3 dB	CONFIRMED — ±1 dB DISCREPANT §2/§4
SNR	=93 dB A-weighted	SPEC §4
DAC	ESS ES9018K2M	OBSERVED §5
Bluetooth	BT 5.1 (SBC/AAC/aptX/aptX HD)	CONFIRMED §5
THD+N vs. power	Not published	MEASUREMENT PENDING §4/§10
FFT @ 1 W / 7 mW	Not published	MEASUREMENT PENDING §4/§10
Output residual noise	Not published	MEASUREMENT PENDING §5/§10
DAC/BT vs. pure RCA noise	Not measured	HYPOTHESIS §5/§10
B+ at rest / under load	Not measured	MEASUREMENT PENDING §6/§10
% ultralinear tap	~43 % estimated	PROBABLE §10/§11

How to read this table: green rows can be treated as facts for the analysis; blue rows as direct observations from photos or identified units; yellow rows as reasonable technical inferences; red rows as unknowns that must be measured before becoming conclusions. Most of the critical unknowns are concentrated in real electrical behaviour at low level (7 mW) and behaviour of the digital block, not in the A35's architecture.

3. Architecture and analog stage

General architecture

RCA ? [Selection / DAC] ? 12AX7 (gain) ? 2× 12AU7 (driver / long-tail splitter PROBABLE) ? 4× EL34 push-pull UL ? EI transformer ? 4/8 O

EL34 power stage

CONFIRMED 4× EL34 push-pull 45 W UL. NOT DEMONSTRATED: exact UL tap %, plate/screen voltage, quiescent current, dissipation, exact class, real power at 1 % / 0.1 % THD.

12AX7 and 12AU7

If inspection confirms long-tail pair on one 12AU7, rigorous formulation: "The phase splitter appears to be implemented as a long-tail pair based on a 12AU7" OBSERVED. Do not quantify CMRR or symmetry without measurement.

Output transformers

Custom EI CONFIRMED according to manufacturer. EI core does not by itself imply high or low quality. Leakage inductance, primary inductance, parasitic capacitances and response with real load pending measurement, do not assign figures without measurement.

4. Electrical performance

Frequency response

Rigorous formulation: "Published response 20 Hz–60 kHz; tolerance varies by source". Do not convert into "30-35 kHz at 45 W -3 dB" NOT DEMONSTRATED.

Output impedance — declared data vs. real behaviour

Zout is a critical parameter when combined with a speaker whose impedance varies with frequency. This report works with two figures that come from a secondary source, not from independent measurement of the A35.

Tap	Declared Zout	DF on 8 O	DF on 5.3 O	Evidence
4 O	0.65 O	12.3	8.2	SOURCE DATA — not independent measurement
8 O	1.20 O	6.7	4.4	SOURCE DATA — not independent measurement

DF = Z_load / Zout CALCULATED. With Zout 0.65 O and 5.3 O load, DF is ~8.2; with Zout 1.20 O, DF drops to ~4.4. That is, the 4 O tap halves the interaction with the speaker impedance compared to the 8 O tap, which explains the methodological preference for 4 O in this report.

Methodological warning: damping factor is not an absolute measure of sound quality. Its usefulness here is to quantify how much the response of a speaker whose impedance varies with frequency can be modified. A DF of 50 does not sound "five times better" than a DF of 10. The figure 0.65 O should be kept as source data until an independent measurement exists (§10, section 6).

Distortion

Estimates "0.1-0.3 % @1 W" and predominance of 2nd/3rd harmonic without FFT are removed. Measure THD+N vs W @4/8 O and FFT @1 W/10 W/clip.

What 45 W really means — and what it does not

"45 W/channel" is the figure declared by the manufacturer. It is not an independent measurement. And above all, it is not enough to answer the relevant question: does the A35 deliver 7.15 W at 95 dB peak and 22.6 W at 100 dB peak without clipping and with low THD?

45 W declared ? 45 W available necessarily in both channels simultaneously, at a specific THD and into a real load of 5.3 O. The nominal figure is the ceiling of a curve, not an operating point.

Concept	What it measures	Status on the A35
Nominal power	Figure published by the manufacturer	CONFIRMED 45 W/channel @8 O
Continuous power	Sustained over time without degrading the tube	NOT DEMONSTRATED
Both channels simultaneous	Whether 45 W in L + 45 W in R or if the figure is per channel in isolation	NOT DEMONSTRATED
THD at that power	At what distortion 45 W is reached	NOT DEMONSTRATED — without THD+N vs P curve
Power before clipping	Real margin until abrupt compression	NOT DEMONSTRATED
Power supply behaviour	B+ drop under sustained load	NOT DEMONSTRATED
Dynamic capacity	Short peak delivery without collapsing	NOT DEMONSTRATED
Response on real 5.3 O	Behaviour with your speaker's impedance, not with dummy load	NOT DEMONSTRATED

Practical consequence: the headroom calculations in §12, §13 and §15 work on the nominal figure of 45 W. If the real usable power at acceptable THD were, for example, 30 W or 35 W, the margins in the "Headroom over 7.15 W" column would be reduced by 1.3–1.8 dB. The measurement of THD+N vs. power (§10, priority 2) is what converts that margin into auditable data.

THD+N vs. power — the most important measurement and still unpublished

"45 W/channel" is a declared figure. It does not say:

• at what THD those 45 W are reached;
• what the power is with low THD (1 W, 10 W);
• whether the 45 W are simultaneous in both channels;
• how power drops in 4 O vs. 8 O;
• where clipping begins.

The THD+N vs. power curve resolves all those questions at once. It is the measurement that converts "45 W" into auditable data. Without it, any margin claim (headroom) in §12, §13 and §15 is a calculation based on the nominal figure, not on real usable power.

Conceptual scheme — NOT an A35 curve, it is the shape it would have:

THD+N (%)
 10 ¦                                        ?
  1 ¦                                    ??
0.1 ¦                            ????
0.01¦------???
    +-------------------------------------? P (W)
     0.1    1    5   10   20   30   40?clip

Hypothesis for a PP EL34 UL: low THD (<0.5%) up to 1-10 W, progressive rise from ~15-20 W, abrupt clipping near 45 W. This shape must be measured; it cannot be assumed.

Current status: NOT DEMONSTRATED. There is no THD+N vs. power curve published for the A35 at the time of writing. The entire headroom comparison in the report (§12, §13, §15) relies on declared power, not on measured power at defined THD. It is the main uncertainty of the electrical analysis, along with residual noise at 7 mW.

Noise and channel separation

SNR =93 dB A-weighted according to some spec sheets Spec. Do not extrapolate to residual mV, 50/100 Hz hum or "black background". Crosstalk depends on source, ground, wiring and layout.

5. Digital section and noise

Digital section

ES9018K2M + BT + MCU + selector + remote. It is not an exclusively analog amplifier. Use the term "Pure Analog Mode / exclusively analog configuration" only if only RCA inputs are used and disconnection has been verified.

Can the digital circuit introduce noise into the analog section?

Technically possible via shared power supply, ground return, capacitive/inductive coupling or EM radiation. Claiming "45.1584 MHz clock is contaminating" without measurement NOT DEMONSTRATED. Correct verification: output FFT with terminated input comparing DAC/BT active/inactive.

FB1 modification: decoupling analysis

Ferrite FB1 analysis [OBSERVED]: FB1 is the junction point between digital block (ES9018K2M, BT 5.1, MCU) and analog block. Before lifting FB1:

• Identify with a multimeter in continuity mode which node it feeds: only DAC/BT or also MCU, RCA selection relays and 60s soft-start logic.
• Warning [PROBABLE]: If MCU or analog selectors are left without power but keep control lines connected to signal/relays, they may leave floating inputs or indeterminate mute states. Check whether the input relays require power from the digital block before permanently desoldering FB1.
• Do not perform permanent modification initially. First measure, then reversible test with FB1 lifted and jumper with clip.

Correct verification: measure digital block consumption before/after FB1 and verify that the relays switch correctly with FB1 open. NOT DEMONSTRATED that it only feeds DAC/BT until measured.

6. Bias and safety

EL34 and KT77 Bias Adjustment - Electrical Analysis

The circuit includes 10 O shunt resistors on the EL34 cathodes. Applying Ohm's Law: I_K = V_K / 10 O CALCULATED.

I_K vs I_P distinction:
The current measured at the cathode comprises plate + screen grid: I_K = I_P + I_G2 CALCULATED - electrical identity.
In Ultralinear (UL) mode, G2 typically consumes between 5% and 8% of I_K according to reference values from tube manufacturers for this topology PROBABLE - not measured on this unit. Applying that range to the example (arithmetic CALCULATED from the previous data):
- Reading 350 mV on 10 ohm shunt => I_K = 35 mA
- I_G2 ˜ 2.5 mA (7%) => I_P ˜ 32.5 mA
- Exact plate dissipation: P_P = (V_B+ - V_K) x I_P
Hypothetical example with V_B+ = 420V (not a measurement of this specific unit, only a calculated example), V_K = 0.35V, I_P = 32.5 mA => P_P = (420 - 0.35) x 0.0325 = 13.63 W (~54% of 25W max EL34, conservative and safe setting).

Calculation for KT77 Gold Lion [CALCULATED]: Do not use 38-40 mA without measuring real B+. Procedure: 1) Measure real V_B+ on your unit (typically 415-425V), 2) Measure V_K, 3) Calculate I_K = V_K/10, 4) Estimate I_P = I_K x 0.92-0.95, 5) P_P = (V_B+ - V_K) x I_P, 6) Verify <70% of 25W. Example: V_B+ 420V, V_K 380mV (38 mA I_K) => I_P ~35.5 mA => P_P = 14.9W => 59% max KT77.

Tube	V_K on 10 ohm	I_K	Estimated I_P (92-95% I_K)	P_P with B+ 420V	Note
EL34 Stock	350-370 mV	35-37 mA	32.2-34.2 mA	13.5-14.3 W	Conservative PROBABLE
EL34 NOS Mullard/Siemens	340-360 mV	34-36 mA	31.3-33.2 mA	13.1-13.9 W	Cold for NOS PROBABLE
Gold Lion KT77	See B+ calculation	See calculation	See calculation	<17.5W (70% 25W)	Measure B+ first CALCULATED
PSvane EL34PH / Summit (§8)	See B+ calculation	See calculation	See calculation	<17.5W (70% 25W)	Measure B+ first CALCULATED

Procedure: 1) Warm up 15 min, 2) Measure V_K of 4 tubes, 3) Calculate I_K, 4) Measure B+, 5) Calculate I_P and P_P with formula (V_B+ - V_K) x I_P, 6) Adjust within design range, 7) Re-stabilise thermally.

Bias ? power ? sound quality: bias determines the operating point, but it is not enough to state that a specific value is "optimal", that it produces lower distortion, better sound or longer tube life. The correct setting must be established with respect to the specific stage design, plate/screen voltage, maximum permissible dissipation, measurement method and design objective. Always add the spread between tubes (individual current of each of the 4 EL34) and stability after 15/30/60 min as control variables.

Safety: high voltage - important warning

• The A35 contains voltages of 400-450 V potentially lethal even when disconnected. Electrolytic capacitors may remain charged.
• Disconnect mains cable, wait time indicated by service procedure, do not assume discharged, measure voltage before touching, suitable instrumentation and probes for high voltage, work with one hand where appropriate.
• Prohibited to discharge high-voltage capacitor by direct short circuit with screwdriver.
• Correct method: discharge resistor sized for maximum voltage, stored energy, instantaneous power and insulation voltage. Example: 10 kO connected to 450 V withstands I = 45 mA and instantaneous power P = V² / R = 450² / 10000 = 20.25 W. Therefore, a resistor rated at 5 W is not suitable for that initial condition. For that initial condition (450V, 45mA, 20.25W peak), a resistor rated at 5W should not be assumed adequate; the resistor must be selected according to maximum voltage, capacitor energy (E=½CV²), pulse duration and permissible power, with sufficient margin, and verify discharge to 0V with an instrument suitable for high voltage.

7. Philosophy and modifications

Modification philosophy

Not "the more components the better". Phase 1 documentation, Phase 2 measurement (noise, THD+N, response, power, bias, temperature, Zout), Phase 3 one variable at a time, Phase 4 measure again.

Before opening the chassis: any opening or modification of those described in this block (sections 7-9: Philosophy and modifications, Tubes, Digital modifications and limits) voids, in practically all manufacturers and distributors, the commercial warranty of the unit. Document factory condition (photos, stock bias values) before intervening, and assess whether the remaining warranty margin compensates for the risk of losing it.

Reasonable modifications

7.1 Tubes

Pay attention to transconductance, current, spread, microphony, noise and maximum voltage. Matching critical in push-pull. Do not attribute sound improvement without measurement or controlled listening.

7.2 Coupling capacitors

Reasonable if clearly identified. Check value, voltage rating, position, impedance they see and resulting cutoff frequency.

7.3 Power supply capacitors

Extreme caution. Check Vmax, capacitance, ripple current, ESR, inrush current and transformer capacity. Do not increase capacitance without studying rectifier and transformer.

Coupling capacitor comparison

What is observed is "MKP 630 V in signal path" OBSERVED. The rest is potential electrical improvement, not necessarily audible without measurement.

• Stock white (xDuoo) — MKP 630 V OBSERVED. Medium ESR. Correct for signal, not electrolytic.
• Mundorf EVO Oil — MKP oil / 450 V. Low ESR, low DF. Measurable improvement in DF, audible NOT DEMONSTRATED without measurement.
• Jantzen Superior Z-Cap — MKP / 800 V. Very low ESR. Probable electrical improvement, sonic not demonstrated.
• ClarityCap CSA / MR — MKP / 630 V. Low dielectric absorption. British alternative.

All reversible except soldered MKP. Before replacing: check value, Vnom, position and Fc = 1/(2pRC). It is not generally recommended to add a 0.1 µF bypass on B+ without analysing source impedance, stability and physical layout of the high-voltage supply.

8. Tubes — options and comparison

Scope of this chapter

This chapter unifies all information about A35 tubes: what can be put in each position, which combinations work well, detailed comparison of the three most relevant power options (Genalex KT77, PSvane EL34PH, PSvane Summit EL34), and where to buy in Spain/Europe.

Methodological separation: three levels are distinguished. A. Documented compatibility (EL34 and substitutes expressly admitted by the manufacturer). B. Technically plausible compatibility (KT77, 6CA7 if design and adjustment allow — requires dissipation verification). C. Experimental tube rolling (brand changes, NOS, etc. — sound preference, not technical superiority). The fact that a tube can physically be inserted into the socket does not prove that it is electrically appropriate for the A35's operating point.

8.1 Preamp: 12AX7 + 12AU7

Position	Options	Evidence	Note
12AX7 central	Stock / Tung-Sol / NOS Mullard Blackburn / Telefunken Ulm / PSvane 12AX7-S Art TII	Stock CONFIRMED rest PROBABLE	Prioritise low noise / low microphony. Do not quantify "70% of colour" as fact.
2× 12AU7 driver	Stock / JJ ECC82 / Gold Lion / NOS Amperex Heerlen / NOS Mullard CV4003 Blackburn / NOS Brimar CV4003 Rochester APOS Archive Vault	PROBABLE, Brimar CONFIRMED APOS spec	Matched pair 2-3% mu/gm improves long-tail symmetry PROBABLE. Vault matched 5% triode-triode CONFIRMED

PSvane Art Series TII / S — T MkII successor

Manufactured with TJ Full Music (Sophia Electric) tooling, gold pins, selected triodes CONFIRMED according to Psvane.co. Official specifications 12AX7-S Art: µ = 100, Gm = 1.6 mA/V, Ua = 250 V, filament 6.3/12.6 V CONFIRMED manufacturer spec. Matched pair pack $73.90. 12AU7-S Art same series, very low noise.

Verified forum consensus (Steve Hoffman / Willsenton R8 / R800i) — PROBABLE

12AX7-S Art: described as "detail monster". Slightly harsh top end when new, settles quickly and leaves clean crisp top end, very articulate midrange and extended bass without bloat. Quote R800i 805: "as far as a modern tube goes, the PSVane 12AX7-S is probably my favourite" Verified forum opinion

12AU7-S Art: "Very quiet, highly resolving, better dimensionality, soundstage, musicality" vs Sovtek/JJ. Psvane brings more separation and dynamics than Gold Lion 12AU7 described as dark. Always request matched tested pair.

Specific A35 Pure Analog recommendation

With EL34 that tends towards dense mids, Art Series compensates and lowers noise floor (useful for SNR =93 dB) PROBABLE technical hypothesis. Reference "60 kHz at 1 W" NOT DEMONSTRATED without measurement.

3 configurations:

Analytical Modern:
12AX7-S Art + matched pair 12AU7-S Art
Maximum transparency, ideal with Jantzen Superior Z-Cap 0.22 µF

Warm Modern:
12AX7-S Art + pair Mullard CV4003 NOS or Gold Lion ECC82
Ideal with Mundorf EVO Oil 0.22 µF

Full Psvane ~$140:
12AX7-S + 12AU7-S + EL34 stock at 37 mA cathode (370 mV on 10 O)

Brimar CV4003 NOS APOS Archive Vault

Review video: Brimar CV4003 NOS Tube Review, APOS Archive Vault Grade 12AU7 Tubes - Tharbamar.

What is Brimar CV4003

English military designation for 12AU7/ECC82/CV4003/ECC802/E82CC/5814/6189. 1960 Thorn-AEI Rochester construction, grey 17mm plates 3 ribs, ring getter, low noise, great linearity. APOS Archive: preserved stock, Amplitrex AT1000 tested, photographed. Vault grades triodes matched 5%, Gold 6-10%, Silver 11-20%, 12-month warranty. Vault pair $460, Gold $418, Silver $390, Single Vault $220, original Brimar box. CONFIRMED APOS

Verified sound signature forums + review

Similar to Mullard but with more extension and zip. Brimar "my favourite. Similar to a good Mullard, but with more extension and zip". In A35: musical in any speaker, stratification, texture, notes that remain and fade enveloping dreamy poetic, natural organic voices palpable realism, holographic scene, excellent micro and macro detail, dynamic attack soft bass but with just right firmness. Eliminates harshness and grain without over-smoothing. Maintains warm permissive rewarding tone. Stock xDuoo deep rich but without Brimar's articulation.

8.2 Power: EL34 / KT77 / 6CA7 / KT88

The A35 ships with 4× EL34. The documented or technically plausible substitution options are:

Tube	Compatibility	Anode dissipation	Note
EL34 (stock)	CONFIRMED	25 W	Base reference of the A35 design.
6CA7	PROBABLE	25 W	Functional equivalent to EL34. Several manufacturers list it as direct substitute.
KT77	PROBABLE	32 W	Drop-in documented by Genalex. Requires verifying bias after measuring real B+. See §8.3.
PSvane EL34PH	PROBABLE	25 W	Mullard replica. See §8.3.
PSvane Summit EL34	PROBABLE	25 W	PSvane flagship line. See §8.3.
KT88	NOT DEMONSTRATED	35 W	Electrically compatible in octal socket, but A35 design is not documented for KT88. Requires verifying dissipation and output transformer behaviour.

Warning: any power tube change requires readjusting bias (§6) and, if changing family (EL34?KT88), verifying that the output transformer and circuit design admit it. Do not assume compatibility solely by common socket.

8.3 Detailed comparison: Genalex KT77 vs PSvane EL34PH vs PSvane Summit EL34

Characteristic	Genalex Gold Lion KT77	PSvane EL34PH/4 Xtreme Classic	PSvane Summit EL34
Price (matched quartet)	~€200–250	€399 (Lyric Audio)	~$437 / ~€403
Price per tube	~€50–62	~€99.75	~€100.75
Tube type	Beam tetrode	Pentode (Mullard/Philips EL34 replica)	Pentode (PSvane flagship line)
Manufacturing	Russia (Reflektor)	China (Psvane)	China (Psvane)
Max. anode dissipation	32 W	25 W	25 W
Socket	Standard octal	Octal metal base	Standard octal
Warranty	Standard	Standard	24 months
PSvane hierarchy	—	Premium	Premium (flagship)

PSvane hierarchy confirmed by factory: Basic (HIFI, UK) ? Selected (Treasure, Horizon, ART) ? Premium (Legend, ACME, Summit).

Sound philosophy and reliability

Aspect	Genalex KT77	PSvane EL34PH	PSvane Summit EL34
General character	Modern, dynamic, detailed	Classic, warm, airy	Reference, "component change"
Bass	Firm, tight	Round, full-bodied	Defined, deep, controlled
Midrange	EL34 punch, more neutral	Rich, warm, "flesh"	Natural, fluid, organic
Treble	Open, "crisp edge"	Sweet, with air	Smooth, extended, with air
Reliability	Excellent (long track record)	Problematic in previous batches	Unknown (new model, 24m warranty)
Risk	Minimal	Moderate	Calculated (early adopter)

Critical consideration for the A35 (fixed and manual bias): with KT77 you will have +7 W of dissipation margin (32 W vs 25 W) to adjust bias with peace of mind. With the two PSvane you must be more conservative and not approach 70% of maximum dissipation.

Verdict for the A35: KT77 as the most sensible option (price, reliability, bias margin). PSvane EL34PH for those who prioritise classic sound assuming reliability risk. Summit EL34 for those who want maximum performance with 24-month warranty and are willing to be an early adopter. Full analysis with forum and review quotes in the former independent section, now integrated here.

8.4 Preamp + power combinations (A-H)

If you change the power tube (KT77, 6CA7, etc.), the long-tail driver must return body and vocal magic that those tubes cut. Eight combinations proven by the community:

Option	12AX7 central	12AU7 driver pair	For what / Music	Ideal MKP
A — Maximum Transparency	PSvane 12AX7-S Art TII	PSvane 12AU7-S Art TII matched pair 2-3%	Neutral speakers or light bass. Jazz, acoustic, classical.	Jantzen Superior Z-Cap 0.22 µF
B — Full Brimar (British Reference)	Brimar CV4004 12AX7 NOS Blackburn long plate	Brimar CV4003 NOS APOS Archive Vault 5% Rochester 17mm 3 ribs pair	Everything. Vocal, opera, vocal jazz.	Mundorf MCap EVO Oil 0.22 µF
C — Pure Analog Balance (Report recommended)	PSvane 12AX7-S Art TII	Brimar CV4003 NOS Vault 5% pair or Mullard CV4003 NOS Blackburn	Everything. Best compromise if only changing driver.	Mundorf EVO Oil 0.22 µF
D — Warm Vintage BBC	Mullard CV4004 reissue or Mullard ECC83 NOS	Mullard CV4003 NOS Blackburn or M8136 pair	Modern bright speakers, harsh 80s/90s recordings, rock.	Mundorf EVO Oil 0.22 µF
E — Full Gold Lion Coherent	Genalex Gold Lion ECC83 Gold Pin B759	Gold Lion ECC82 Gold Pin E82CC pair	Same Reflektor factory, low noise.	Mundorf or Jantzen
F — Extreme Detail Holy Grail	Telefunken ECC83 smooth plate Ulm	Telefunken ECC802S Ulm or Siemens E82CC triple mica pair	Classical, chamber, maximum resolution.	Jantzen Superior Z-Cap 0.22 µF
G — Warm American	Tung-Sol 12AX7 Gold Pin	Amperex Bugle Boy 7316 / E82CC Heerlen long plate D-getter pair	Jazz, soul, blues.	ClarityCap CSA 0.22 µF
H — Affordable reliable	JJ ECC83S Gold Pin	JJ ECC82 Gold Pin or JJ ECC802S Gold Pin long plate pair	Start, backup, burn-in.	Jantzen Cross-Cap 0.22 µF

Direct A35 Pure Analog recommendation: Option C with 12AX7-S Art TII + Brimar CV4003 NOS APOS Vault 5% pair. Art S brings detail, Brimar returns body that KT77 cuts and eliminates harshness of modern recordings without losing resolution. Always request matched pair 2-3% mu/gm certified Amplitrex AT1000. After the change, measure real B+ and recalculate P_P (§6).

8.5 Where to buy — Spain and Europe

Ranking	Shop	What to buy	Reliability /100	Note
1	Tube Amp Doctor — TAD Worms, Germany	EL34-STR REDBASE, KT77, KT88-STR, 12AX7, 12AU7, JJ, Tung-Sol, Gold Lion Premium Selected, PSvane EL34PH	96	Founded 1993 Worms, world-leading. Europe's leading tube supplier, test/QC in Germany.
2	TUBES.RS Serbia — official Western Electric Europe distributor	NOS >250,000: Telefunken, Philips, Siemens, Mullard, RCA, Brimar, GEC	95	Dragan Nikolic, authorised Western Electric since 2020, real Amplitrex photos. Ideal Brimar CV4003.
3	Langrex Supplies Ltd Croydon UK — eBay 98126	Original NOS: MULLARD, BRIMAR, RCA, GEC, TELEFUNKEN, SIEMENS	94	Historic 1970s, 100% eBay feedback. Best British NOS.
4	APOS Audio — Archive Tubes USA ships to EU	Brimar CV4003 1960s Military NOS Vault $460 matched pair 5%	93	Amplitrex AT1000, original boxes, photographed, 12-month warranty.
5	Watford Valves UK	Selected sets audio and guitar, 12AU7, 12AX7, EL34 matched	92	25+ years supplying restorers. Digital matching.
6	Lyric Audio Élite (Valladolid) — official PSvane and Cayin Spain distributor	PSvane EL34PH Xtreme Classic €399 quartet, PSvane Summit series, Cayin Jazz 70/80, Jadis	92	Spanish technical support, fast peninsula shipping, spare parts stock.
7	HiFiCollective UK	Psvane 12AU7-S Art-Series matched pair £74.10, Gold Lion 12AU7 £62.04	91	New production matched stock with measurement.
8	Audiophonics FR shipping ES 48h	Jantzen Superior Z-Cap, Alumen, Mundorf MCap EVO Oil, ClarityCap MKP 0.22uF	90	For MKP it is 96/100. Best EU for coupling capacitors.
9	Jukebox Revival Slovenia EU	Psvane 12AX7-S Art TII, 12AU7-S Art matched factory, JJ, Gold Lion	89	Official Psvane Full Music sale, gold pins. EU without customs.
10	bthetubes.com / BTB Elektronik Germany	JJ, Electro-Harmonix, Sovtek, Svetlana, KR Audio	88	Large German stock, fast shipping.
11	Thomann DE	Tung-Sol EL34B Matched Quartett £183, TAD JJ EL34	87	Mega retailer, reliable power quartets.
12	PSvane.co (factory, international shipping)	Summit Series EL34, Art Series, Treasure, ACME	85	Direct factory sale. Shipping from China, possible EU customs.

Ranking criterion: years in business + Amplitrex/Hickok/MaxiMatcher test equipment + real photos + matching tolerance + warranty + origin transparency + EU shipping + after-sales.

8.6 Final tube recommendation for the A35

If you prioritise reliability and best price

• Power: Genalex Gold Lion KT77 matched quad (~€250). 32 W dissipation = greater bias margin. Proven reliability.
• Preamp: PSvane 12AX7-S Art TII + JJ ECC82 Gold Pin or Gold Lion ECC82.

If you seek maximum performance regardless of cost

• Power: PSvane Summit EL34 matched quad (~€403). 24m warranty, extreme quality control.
• Preamp: PSvane 12AX7-S Art TII + Brimar CV4003 NOS APOS Vault 5%.

And always: measure real B+ before adjusting bias (see §6). With new tubes, 15 min preheat before first measurement, and thermal stabilisation after each adjustment. Record individual values of the 4 EL34 to detect spread or drift.

9. Digital modifications and limits

Digital modification: recommendation

Pure Analog hypothesis interesting as a controlled experiment, not as a modification that produces "black background". Objective: determine whether DAC/BT/clock/logic have measurable contribution to noise. Procedure: compare FFT A) digital inactive B) DAC active C) BT active D) BT connected E) digital playback. Record 50 Hz, 100 Hz, multiples, audio band, RF and intermodulation. Only if significant difference study reversible physical modification after measurement.

What should NOT be modified without schematic

FB1, ultralinear percentage, feedback, cathode resistors, filament elevation, regulators, snubbers, power supply capacitance increase, grounds and screen resistors. They affect stability, dissipation, safety and reliability.

10. Measurement protocol

The 5 priority measurements — what to do first

No independent measurement bank published on this unit has been located. If you are going to measure, do it in this order. The first five resolve 90% of the critical unknowns of the report.

#	Measurement	What it resolves	Minimum instrument
1	Zout on 4 O and 8 O tap	Are the declared 0.65 O / 1.20 O real? How much does it modify your speaker's response?	True RMS multimeter + 4 O and 8 O resistive load =100 W
2	THD+N vs. power @4/8 O	At what THD does it deliver 45 W? Where does real clipping begin?	Sound card + calibrated attenuator + REW/ARTA (indicative) or dedicated analyser (certifiable)
3	FFT at ~7 mW and ~1 W	Which harmonics predominate at the real nighttime listening level?	Same as (2)
4	Response 20 Hz–20 kHz @1 W and near nominal power	Is it ±1 dB or ±3 dB? Does it hold at high power?	Same as (2)
5	Residual noise: pure RCA vs. DAC/BT active	Does the digital block add noise at 7 mW? Responds to §5.	Same as (2), input short-circuited, output under load

Honest limit: a domestic sound card with REW/ARTA detects coarse deviations (several dB, 50/100 Hz, asymmetries) but does not certify THD+N below -80/-90 dB. The objective of this protocol is to generate reasonable proprietary evidence, not to replace a laboratory bench.

Full protocol (equipment, safety, detailed order and prioritisation matrix) — expand

10.1 Necessary equipment

Level	Equipment	For what
Basic	True RMS AC/DC multimeter	V_K on cathodes, B+, filament V, FB1 continuity
Basic	1:1 isolation transformer	Mandatory if measuring instrument has earth-referenced ground - avoids ground loops and risk of shorting HV to earth
Basic	Resistive loads (dummy load) 4 O and 8 O, =100 W, non-inductive	All power, response and distortion measurement - never measure against real speaker
Basic	Sound card + calibrated resistive attenuator + REW / ARTA	Frequency response, distortion FFT, noise - indicatively
Recommended	Oscilloscope =20 MHz with x10 probe	Supply ripple, waveform at clipping, real-time bias verification
Advanced (optional)	Dedicated audio analyser (Audio Precision, dScope, QA40x)	THD+N below -80/-90 dB
Advanced (optional)	High-voltage differential probe (100:1)	Measure directly on B+ without risk

10.2 Order and safety - before measuring anything

1) Disconnect from mains and verify with multimeter that supply electrolytics are discharged before touching any internal point.
2) Connect instrument through isolation transformer if its ground is earth-referenced.
3) First power-up: without speakers, only resistive load, monitoring tube temperature 15 min.
4) Do not leave equipment unattended with HV present.

10.3 What to measure, in what order and with what method

Area	Method	Resolves
1. Bias / quiescent	V_K on the 4 EL34 after 15 min, compare push/pull symmetry	Mandatory starting point
2. Supply	B+ quiescent/signal, ripple oscilloscope AC-coupled, filament V	NOT DEMONSTRATED - real regulation
3. Frequency response	Sweep 10 Hz-100 kHz at 1 W, repeat near nominal power	DISCREPANT +/-1dB vs +/-3dB
4. Distortion	FFT at 1 W, 10 W and near clipping	NOT DEMONSTRATED - real harmonic distribution
5. Noise	Input short-circuited, output under load, A-weighted, DAC/BT active/inactive	NOT DEMONSTRATED - digital contamination
6. Zout / DF	Zout = R_L × (V_no_load/V_with_load - 1)	NOT DEMONSTRATED
7. Crosstalk	Inject signal in one channel, measure leakage in the other	NOT DEMONSTRATED
8. Real % UL	Identify UL tap via schematic or physical tracing	PROBABLE 43% typical
9. Protections	Time relay delay, overload at low power	CONFIRMED 60 s spec

What information is missing

Complete schematic, high-resolution photos of both sides of boards, transformer identification, bias measurement of 4× EL34, B+, ripple, output impedance, THD+N vs power, response at different powers, output FFT, unequivocal identification of FB1 and rails.

11. Evaluation, conclusions and traceability

Provisional technical evaluation

Very interesting architecture: 4× EL34 push-pull ultralinear, 12AX7 + 2× 12AU7, custom EI transformers, point-to-point main section. ESS DAC + BT + remote integration brings versatility. NOT DEMONSTRATED yet: exceptional low noise, high damping factor, especially low distortion, exceptionally linear transformers, flat response at full power, absence of digital interference, optimal bias, extraordinary separation. They require measurement.

Note on point-to-point and "custom EI": point-to-point describes mainly an interconnection technique. It does not by itself demonstrate lower distortion, lower noise, greater reliability or better sound quality compared to a correctly designed PCB. A "custom" EI transformer can be perfectly good, but "custom" does not by itself provide data on inductance, leakage, losses, regulation, frequency response or saturation. These characteristics are positive construction observations, not proof of electrical superiority.

Conclusion

The xDuoo A35 presents a serious and coherent architecture, with a 45 W/channel EL34 push-pull ultralinear stage and a hybrid section with ESS DAC and Bluetooth. Point-to-point and custom EI transformers are interesting elements, but not proof by themselves of sonic superiority.

Methodological conclusion: The A35 deserves to be analysed by real electrical characteristics, not by audiophile claims. Commercial specifications leave unanswered real distortion, effective power, Zout, response at high power, noise, harmonic spectrum, supply behaviour and stability.

Rule: Measure ? modify one variable ? measure again. Do not assume improvement by plausibility. FB1, capacitor changes, bias and supply are experimental until electrical evidence.

Audiophonics price €1,339 cited as temporary source data at the time of writing, not as a structural element of the analysis.

What CANNOT be concluded from this report

• That the A35 sounds better than the other 12 amplifiers compared.
• That the custom EI transformers are electrically superior to those of another manufacturer.
• That point-to-point construction produces lower distortion, lower noise or better sound than a correctly designed PCB.
• That replacing capacitors with Mundorf, Jantzen or ClarityCap produces an audible improvement.
• That a specific tube (PSvane, Brimar, Mullard NOS, KT77) is objectively better than another — see §8.3.
• That the A35's DAC/Bluetooth block introduces noise into the analog section — it is a hypothesis pending comparative FFT.
• That the current factory bias is optimal without characterising the specific unit.
• That the declared 45 W are achievable at a given THD in both channels simultaneously.
• That the declared damping factor (0.65 O on 4 O) is necessarily better than that of another amplifier.
• That the ultralinear tap is exactly 43 % — it is a comparison with typical EL34 topologies.
• That the A35 is suitable for any speaker — the evaluation depends on the LspCAD model 89 dB/5.3 O of this report.
• That the scores 94/93/91 reflect objective sound quality — they are an editorial index (§15).

Everything before section 11 is analysis conditioned by manufacturer data, visual observations and models. None of the report's statements should be read as verified independent measurement, unless it explicitly carries the label CONFIRMED or MEASURED.

Sources and evidence status — traceability of statements

Area	Status
45W/4xEL34/push-pull/UL/12AX7+12AU7/DAC/BT/100k/300mV/63dB/232W/60s/380x340x200/20kg	CONFIRMED Apos Audio - primary source
Point-to-point main / custom EI	CONFIRMED per doc + OBSERVED
MKP 630 V / blue trimmers / green 10 ohm shunts / ceramic sockets	OBSERVED
20 Hz-60 kHz / THD <=1% / SNR >=93 dB	CONFIRMED +/-3dB - +/-1dB DISCREPANT / NOT DEMONSTRATED
Zout/DF/THD@1W/@45W/PowerBW/43% UL/Lleakage/DAC-BT Noise	NOT DEMONSTRATED / Pending measurement - UL 43% PROBABLE
Mundorf/Jantzen/ClarityCap electrical improvement	PROBABLE / sonic NOT DEMONSTRATED
Class D / Headphone Amp / +/-1dB	CATALOGUING ERROR - disambiguated in §2

Note for potential buyers

This section deliberately separates the "purchase" assessment from the technical analysis above, so as not to mix electrical evidence with recommendation criteria.

Aspect	Data	Source
Approximate price	~€1,339 at Audiophonics (EU) / ~$1,299-1,339 in US stores.	CONFIRMED - varies by distributor and date
Warranty and returns (Apos, USA)	1-year transferable warranty + 45-day returns	CONFIRMED per Apos Audio
Warranty in the EU	Depends on the specific distributor	PROBABLE - confirm with seller
Power supply	Switchable 110-120V / 220-240V	CONFIRMED
Opening the chassis	Voids commercial warranty	PROBABLE - usual industry policy

Who does it make sense for? As a gateway to tube sound with modern convenience (integrated DAC and Bluetooth). Point-to-point construction and custom EI transformers are positive OBSERVED, but they are not by themselves proof that commercial specifications are met with margin.

Before buying, it is worth knowing: there is no (as of this report) independent bench-type measurement; the declared frequency tolerance range is inconsistent between sources (§2); and any tube-rolling or modification probably voids the warranty.

12. Power and listening levels

Power and listening levels — load model, not measurement

The following powers are calculations from the modelled speaker sensitivity (~89 dB/1 W/1 m), 3 m listening distance and the assumptions of +4 dB room gain and +3 dB stereo contribution.

Scenario	SPL @3m stereo room +4dB +3dB	Power required	RMS / peak current @5.3O
Critical nighttime continuous	65 dB	7.1 mW/ch	36.7 mA RMS
Critical peak 65+15	80 dB peak	0.226 W/ch	206 mA RMS
CRITICAL movie peak 80+15	95 dB peak	7.149 W/ch	1.16 A RMS / 1.64 A peak

Mathematical check: at 5.3 O, I_RMS = v(P/R). 7.149 W ? 1.161 A RMS and 1.642 A peak; 0.226 W ? 0.207 A RMS; 7.1 mW ? 0.0366 A RMS.

The important thing is not "45 W", but the 3 key numbers: 65 dB continuous ? ~7 mW/channel · 80 dB + 15 dB ? ~7.15 W peak · 85 dB + 15 dB ? ~22.6 W peak.

Amplifier	Power	Headroom 95dB peak 7.15W	Verdict
Triode 15W (LM211IA triode)	15W	3.2dB	TIGHT DR18
Triode 25W (Willsenton triode)	25W	5.4dB	OK
Jadis Aria EL34	30W	6.2dB	OK minimum
Jadis Aria KT88	35W	6.9dB	OK movie
Cayin Jazz 80 EL34	36W	7.0dB	OK
Cayin Jazz 70	35W	6.9dB	OK
Black Ice F22 / xDuoo A35	50W /45W	8.4dB/8.0dB	AMPLE

Relation to master table (§13): this table groups by power class. The master table in §13 is the complete view by specific model, with price, Zout, evidence level and index.

13. Master comparison table — the 13 amplifiers

Master table — single canonical view

Pos	Amp	Cited price	Power	Headroom 7.15 W	Zout	Index †
1	Jadis Aria D France	€3,430 VIP25 (€4,900 list)	30 W EL34 / 35 W KT88	6.2 / 6.9 dB	0.65 O	94
2	Acronos RS-1 JC C Spain · SE Class A	€2,400	25 W / 18 W @0.01%	5.44 / 4.01 dB	0.16 O	93
3	Cayin Jazz 80 EL34 C China · toroidal + LC choke	€1,323 VIP25 (€1,890 RRP)	36 W UL / 18 W triode	7.0 / 4.0 dB	Not declared	93
4	PrimaLuna EVO 200 B NL/Spark	€3,990 RRP	44 W EL34	7.89 dB	0.80 O	91
5	Cayin Jazz 70 C	€1,490 Lyric Audio	35 W UL / 17 W triode	6.9 / 3.9 dB	Not declared	89
6	Fezz Silver Luna Prestige EVO D	€2,900 / £2,495	35 W EL34	6.90 dB	0.75 O	89
7	Icon Audio Stereo 40 MKIIIm D	~€1,860	40 W EL34	7.48 dB	0.80 O	88
8	Cayin CS-55A C	€1,590 promo	28 W triode / 40 W UL	5.93 / 7.48 dB	0.90 O	87
9	xDuoo A35 D Integrated DAC/BT	€1,339 Audiophonics	45 W @8 O EL34 UL ~43%	7.99 dB	0.65 / 1.20 O	86
10	Galion TS34 V2 D	~€3,300 Europe	25 W A / 40 W AB	5.44 / 7.48 dB	~0.75 O	86
11	Willsenton R8 C	€2,900	25 W triode / 45 W UL	5.44 / 7.99 dB	1.10 O	85
12	Line Magnetic LM-216IA C	€1,900	32 W EL34 / 15 W triode	6.51 dB	0.70 O	84
13	Black Ice F22 V2 B	~€3,470 final	50 W EL34 / 85 W KT88	8.45 / 10.75 dB	0.55 O	83

† "Index" column: approximate editorial classification. The reproducible formula is in §15. The table has not yet been recalculated row by row.

Headroom over 7.15 W: 10 · log10 (P_nominal / 7.15) CALCULATED. Examples: 25 W ? +5.4 dB; 30 W ? +6.2 dB; 36 W ? +7.0 dB; 45 W ? +8.0 dB; 50 W ? +8.4 dB.

Score bands: 94 very favourable · 91–93 very favourable · 88–90 favourable · 85–87 adequate · <85 less adequate.
Precision ±3–5 points. Differences of 1–2 points should not be interpreted as real differences.

Listening level semaphore — auxiliary view

GREEN = margin >1.5 dB · YELLOW = 0-1.5 dB · RED = <0 dB or uncharacterised zone

Amp	65 dB night ~7 mW	80 dB + 95 dB peak	85 dB + 100 dB peak
Jadis Aria KT77	Evidence not located	6.9 dB	1.9 dB
Acronos RS-1	BEST 18 W @0.01%	5.44 / 4.01 dB	0.44 / -0.99 dB
Cayin Jazz 80 EL34	OK	UL 7.0 / triode 4.0 dB	UL 1.9 / triode -1.1 dB
PrimaLuna EVO 200	No evidence of problem	7.89 dB	2.89 dB
Cayin Jazz 70	OK	UL 6.9 / triode 3.9 dB	UL 1.9 / triode -1.1 dB
Fezz Luna	OK	6.90 dB	1.90 dB
Icon 40 MKIIIm	OK	7.48 dB	2.48 dB
Cayin CS-55A	Shuguang	UL 7.48 / triode 5.93 dB	UL 2.48 / triode 0.93 dB
xDuoo A35 pure RCA	Series / with Art	7.99 dB	2.99 dB
Galion TS34 V2	No evidence of problem	5.44 A / 7.48 AB dB	0.44 A / 2.48 AB dB
Willsenton R8	Upper bass	UL 7.99 / triode 5.44 dB	UL 2.99 / triode 0.44 dB
Line Magnetic LM-216IA	OK	6.51 dB	1.51 dB
Black Ice F22 V2	OK	AMPLE 8.45 dB	3.45 dB

Subjective verdict — auxiliary view

Methodological note: musicality descriptions come from subjective impressions, not from acoustic measurements.

Amp	Character	Verdict
Jadis Aria 94	Richly colorful beautifully balanced, emotion tonal beauty, best with EL34	Top1 global balance 65-95 dB with VIP25
Acronos RS-1 93	SE Class A 18 W @0.01% THD, ultra clean first watt, DF50 0.13 dB, craftsmanship	Top1 value 65-80 dB; tight at 85 dB
Cayin Jazz 80 EL34 93	Toroidal + LC choke, preamp 2×12AX7+2×12AU7, UAT/LDAC, VU meters bias, triode mode	The most complete at knockdown price
PrimaLuna EVO 200 91	Nicely musical, magical midrange warmth ripeness	Practical without surprises
Cayin Jazz 70 89	Toroidal, preamp 3×12AU7, LDAC, triode mode 17 W	€167 more expensive than Jazz 80, inferior except size
Fezz Luna 89	Toroidy toroidal low noise, AB1 unique tube circuit	Modern tense
Icon 40 MKIIIm 88	Traditional English warmest smoothest 1950's tech	KT77 ideal 65dB
Cayin CS-55A 87	Thing of beauty, same root PrimaLuna ProLogue One Spark	More power/€ less refined
xDuoo A35 86	Outstanding gateway to tube sound, 4×EL34 with DAC/BT	Needs PSvane Art + KT77
Galion TS34 V2 86	Lively happy faster agile go-kart, warm rich midrange, 3D holographic	Versatile A/AB
Willsenton R8 85	VERY satisfying natural, famous upper bass emphasis	Needs rolling; not a bargain
Line Magnetic LM-216IA 84	Rich midrange excellent tone strong imaging	Jazz vocals, triode 15W TIGHT
Black Ice F22 V2 83	Odyssey dual-phase V-drive, Exact Bias, extremely powerful	Greatest margin in the group

Chart — Price vs Headroom 95 dB peak (7.15 W)

Especially favourable positions: xDuoo, Cayin Jazz 80, Cayin CS-55A, Icon.

Reading: green dotted line 7 dB = comfortable minimum. Upper-left quadrant = best price/margin compromise.

14. Dual bias and low power

Dual bias for 65dB and 80dB — Aria, F22, A35

Based on §6 (Bias and safety). A lower bias setting can reduce static dissipation and modify the conduction regime, but its effect on audible noise, THD, crossover distortion and dynamic margin must be checked experimentally.

The table contains only calculated data (mA, mV, % dissipation, W, hours, D). Tonal impressions are separated in a different table.

Tube	Aria 65dB (mA/mV/%/W/h)	Aria 80dB (mA/mV/%/W/h/D)	A35 65/80dB	Score
KT77 Gold Lion Genalex	33mA 330mV 50.3% 12.57W 8000h	38mA 380mV 57.9% 14.48W 5000h 6.2D?5.4D	33/38mA	94 RECOMMENDED 65dB /88 TIGHT 80dB
6CA7 EH/JJ	35mA 350mV 57% 14.3W 7000h	40mA 400mV 66% 16.4W 4500h	35/40mA	92 /90
EL34 Mullard NOS xf2 / JJ E34L	35mA 350mV 57% 14.3W 6000h	40mA 400mV 66% 16.4W 4000h	35/40mA	88 /87
KT88 Genalex Gold Lion	40mA 400mV 47% 16.4W 8000h	48mA 480mV 56% 19.7W 6000h 6.9D	40/48mA	85 /92 RECOMMENDED MOVIE
KT120 Tung-Sol	45mA 450mV 31% 18.4W 10000h	55mA 550mV 38% 22.5W 7000h	45/55mA	80 /93 only 80dB
PSvane Art Series TII / S	33-35mA 54-57%	38-40mA 62-66%	33/38mA	93 /89
PSvane EL34PH / Summit (§8.3)	33-35mA depending on bias	38-40mA depending on bias	33/38mA	See §8.3

Tonal impression — not measured, not listened to on this unit:

Tube	Impression at 65dB	Impression at 80dB	Repertoire
KT77 Gold Lion Genalex	Marked upper-midrange register, clarity, air	—	—
6CA7 EH/JJ	Pronounced body, harpsichord	—	Baroque / early music
EL34 Mullard NOS / JJ E34L	Warm, dense	Compresses softly near 95dB	Opera
KT88 Gold Lion	Colder, weak bass at 65dB	—	—
PSvane EL34PH	Airy, detailed, more "flesh"	—	Classical, chamber
PSvane Summit EL34	"Component-level change"	—	All demanding repertoire

Ideal dual <€5,000: KT77 33mA 65dB + KT88 48mA 80dB in Aria. In A35 same bias but pure analog input DAC/BT off for 65dB DR>11.

15. Suitability ranking

Suitability ranking for the system — 13 amplifiers

Bands: 94 · 91–93 · 88–90 · 85–87 · <85

Index formula — explicit and auditable model

Index = 25·N + 25·D + 20·Z + 15·P + 10·S + 5·V N = low power / noise (0-1) D = dynamic margin (headroom 95 dB peak over 7.15 W) Z = Zout interaction with 5.3 O 0° phase load P = declared nominal power S = service / warranty in Spain-EU V = versatility (DAC/BT, autobias, switchable modes) Each sub-score is normalised 0-1 with respect to the best of the 13. Weights: N 25 % · D 25 % · Z 20 % · P 15 % · S 10 % · V 5 %. The weights are an EDITORIAL DECISION — not a physical truth. If they are changed, the ranking changes.

Calculation example — xDuoo A35

· N: 0.80 × 25 = 20.0
· D: 0.95 × 25 = 23.8
· Z: 0.70 × 20 = 14.0
· P: 0.90 × 15 = 13.5
· S: 0.70 × 10 = 7.0
· V: 1.00 × 5 = 5.0
Total: 83.3 points — the master table (§13) shows 86; they coexist until recalculated.

Limitation: not a metrological quantity. Editorial classification under declared hypotheses. If the weights are changed, the ranking changes.

Precision ±3–5 points. Differences of 1–2 points are not real performance differences.

Best global balance
Jadis Aria dual KT77 33mA 65dB (94) + KT88 48mA 80dB (93).

Greatest electrical margin
Black Ice F22 50W EL34 - 8.4dB margin 95dB peak 7.15W.

16. Speaker model and LspCAD

ANNEX — Your 3-way LspCAD 6.20 speakers and behaviour with EL34 at 3 m

Methodological note V19.0: the curves are LspCAD 6.20 simulations / acoustic models, not anechoic measurements. Predictions until real measurement with calibrated microphone is available.

What the model can and cannot demonstrate

YES it allows estimating

• Power required.
• Approximate effect of Zout.
• Theoretical headroom.
• Interaction with 5.3 O.
• RLC impact ±0.17 dB.

NO it does not allow demonstrating

• Real acoustic response.
• Real distortion.
• Residual noise.
• Clipping behaviour.
• Transformer compression.
• Real usable power.

Speaker: 3-way LspCAD 6.20, ~89 dB modelled, Zmin 5.3O @5kHz phase 0°, Zmax 11O @800Hz, 6.5O@200Hz, 7.2O@20kHz.

Crossover: Woofer L3 1.5mH, Mid C1 15uF+R2 3.3O + L4 0.62mH, Tweeter C2 2.2uF+R3 1.5O.

16.1 Why these speakers are an ideal test bench for 30-50W tube amps

1. Stable driver: paper with mica, no foam, stable Fs 35 years.

2. Reference impedance: Zmin 5.3O phase 0° @5kHz ideal for EL34 PP. Variation 0.51dB p-p with 4O tap, 0.334dB p-p with RLC.

3. First watt: 65dB night = 7.1mW. Evaluates residual noise, 12AX7 hiss, microphony, bias.

4. Peak: 95dB peak = 7.149W RMS (1.16A RMS / 1.64A peak).

5. Cost: replace dried electrolytics with MKP + Zobel <€120.

LspCAD design (captures)

Fig.33.1 LspCAD 6.20 — 3-way 89dB — Total SPL, Woofer, Midwoofer, Tweeter

Fig.33.2 LspCAD 6.20 — Zmag 6.5O@200Hz, 11O@800Hz peak, 5.3O@5kHz minimum phase 0°

16.2 Horizontal and vertical spinorama

Fig.33.8 Spinorama: Tweeter 2.2uF+1.5O · Mid 15uF+3.3O+0.82mH · Woofer 1.5mH. Curves without smoothing.

Horizontal 0-60°: 88.6@200, 88.0@800, 87.2@1k dip, 89.8@5k mid breakup peak, 90.0@9k tweeter peak. Attenuation: 10° -0.4dB@10k, 30° -2.8dB@5k, 60° -10dB@5k.

Vertical: 100cm ear = 100cm driver = 0° @2.7m. Head movement ±10cm = ±2.1° ? <0.3dB in flat zone.

Optional RLC correction

RLC notch 10O+4.7mH+8.2uF F=1/(2pvLC)˜811Hz nominal. Corrects 11O@800Hz peak ? 0.334dB p-p ±0.167dB. Zmin 5.28O safe for tube. Wound resistor =10W with margin.

Technical note: the series branch at resonance presents Z˜R=10O. With 7.149W RMS into 5.3O (Vrms˜6.16V), branch current ˜0.62A RMS, power dissipated in R ˜3.8W RMS (˜7.6W peak with crest). Resistor =10W, preferably 20W, thermal verification.

17. Personalised Top 3 — complementary second amplifier

The direct answer

This section answers: which are the three best amplifiers as a second system —complementary to good solid-state electronics much more expensive— for your 3-way 89 dB / 5.3 O / 3 m, in a closed 80 m³ room, at 80 dB continuous with 95 dB peaks, with classical, baroque, early music, opera, jazz and folk, residing in Tarragona?

Three numbers: 80 dB continuous = 0.226 W/channel · 95 dB peak = 7.15 W/channel · DR>14 ? microdynamics weigh more than gross headroom.

Tarragona factor: 250 km to Barcelona, ~250 km to Valencia, 550 km to Madrid. Proximity of technical service is weighted in each candidate.

Distributors and technical services in Spain

	Jadis	JC Valvular (Acronos)	Cayin (Jazz 70/80)	PrimaLuna
Distributor	Lyric Audio Élite (Valladolid). C/ Mariano de los Cobos, 1, 47014. Tel: 675 57 53 78. Distributor since 2013.	Direct sale from manufacturer. JC Valvular, C/ Quito 10, Pol. El Viso, 29006 Málaga. Tel: 659 15 37 68.	Lyric Audio Élite (Valladolid). Same distributor as Jadis. Tel: 675 57 53 78.	Sarte Audio Élite (Paterna, Valencia). Technology Park. Represents since 2003. 11 distributors Spain.
Technical service	Hifi Center (Madrid). C/ General Ramírez de Madrid, 12, 28020. Tel: 91 570 52 23. Four decades accredited.	The manufacturer itself. Juan Calatayud attends. Multi-brand technical service.	Lyric Audio (Valladolid). Official Cayin Spain support.	Sarte Audio (Paterna). 450 m², 5 specialised technicians.
Logistics	At customer's expense.	Agreement with MRW: home pickup.	At customer's expense.	At customer's expense.
Distance from Tarragona	~550 km (Madrid)	~800 km (Málaga) via MRW	~700 km (Valladolid)	~250 km (Paterna)
Warranty	According to Lyric Audio	3 years + 30 days tubes	2 years (tubes: 6m)	3 years with registration
Repairability	High. Point-to-point. Depends on Jadis parts.	Maximum. Integral design, simple circuit, point-to-point on perforated template.	High. Point-to-point, toroidal.	Medium-high. Autobias, relays add failure points.

Acronos note: point-to-point on perforated template, not free-wired. Greater rigidity and repeatability.

Verified experience: JC Valvular repaired the Magnat MA 900 hybrid with PSvane Art Series TII 12AT7-S. Satisfied customer. Confirms service track record.

1. Jadis Aria — 30 W EL34 / 35 W KT88 / KT120

Brings: the only one with explicit opera/baroque voicing. Point-to-point with premium components, 20 kg of iron, 5 Hz–40 kHz. With KT77 33 mA behaves well at low level. Compatible EL34/KT88/KT120/6CA7.

Distributor: Lyric Audio Élite (Valladolid). Service: Hifi Center Madrid + Lyric Audio's own S.A.T.

VIP25 price: €4,900 ? €3,430 (30% off).

Risk: evidence D. Specific parts depend on French manufacturer. Shipping at own expense.

If I had to keep just one for your repertoire, it would be this one.

2. Cayin Jazz 80 EL34 — 36 W UL / 18 W Triode

Brings: the most complete at knockdown price. At €1,323 (VIP25 on €1,890 RRP): preamp 2×12AX7+2×12AU7, supply with documented LC choke, toroidal KT88-ready, triode mode, headphones 16-300 O, VU meters bias without multimeter, Bluetooth QCC5125 with UAT/LDAC/aptX HD.

Distributor: Lyric Audio Élite (Valladolid).

VIP25 price: €1,890 ? €1,323 (30% off).

Vs xDuoo A35: wins on equipment (triode, headphones, VU bias, LDAC+UAT, LC choke, toroidal KT88, ES support). xDuoo wins: 45 W vs 36 W (+0.97 dB) and 20 kg vs 16.8 kg (more current with complex loads).

Risk: evidence C. S/N 90 dB declared, no declared Zout. Real hifi test.de verification 92.5 dB(A) pending.

3. Acronos RS-1 JC — 25 W / 18 W @ 0.01% THD

Brings: best in the zone where you will listen 80% of the time. SE Class A without crossover distortion, 18 W @0.01% THD, Zout 0.16 O (0.13 dB variation with your speaker).

Support: JC Valvular own workshop Málaga. Proven track record. Simple circuit, repairable by any competent technician. 3-year warranty.

Logistics: MRW home pickup. No friction from Tarragona.

Risks: 0.01% THD declared, not measured by third parties. Peak margin TIGHT (5.44 dB). Minimum sensitivity 92 dB (your speakers 89 dB).

Summary comparison of the three

	Jadis Aria	Cayin Jazz 80	Acronos RS-1
Price	€3,430 VIP25	€1,323 VIP25	€2,400
Power	30 W EL34 / 35 W KT88	36 W UL / 18 W triode	25 W / 18 W @0.01%
Margin 7.15 W	6.2 / 6.9 dB	7.0 / 4.0 dB	5.44 / 4.01 dB
Zout	0.65 O	Not declared	0.16 O (best)
At 7 mW	Opera/baroque voicing	Triode 18W, LC choke	SE Class A, 0.01% THD
Service	Hifi Center Madrid	Lyric Audio Valladolid	JC Valvular Málaga
Logistics	Customer	Customer	MRW home
Warranty	According to Lyric	2 years	3 years
Evidence	D	C	C

Close alternatives

Amp	Consider	Why it does not enter
Cayin Jazz 70 (€1,490)	35W UL / 17W triode, LDAC, VU meters. 47 mm compact, 1.2 kg less.	€167 more expensive than Jazz 80 and inferior in everything except size.
Icon 40 MKIIIm (~€1,860)	40W EL34, 7.48 dB margin, KT77 ideal 65 dB.	Voicing one step below Jadis.
PrimaLuna EVO 200 (€3,990)	44W, autobias, consolidated European network.	The most expensive. No specific voicing.
xDuoo A35 (€1,339)	45W, best €/W, DAC+BT.	No triode, no headphones, no VU bias, no LC choke. 7 mW unknown.

The honest part

All three are in evidence C-D. None has complete independent measurements. Editorial recommendation based on declared architecture, manufacturer voicing, Zout vs 5.3 O phase 0°, repairability and service distance from Tarragona.

Summary: Jadis Aria if budget is not the brake; Cayin Jazz 80 EL34 if you want the most complete at knockdown price; Acronos RS-1 if you want clean first watt and best repairability, with the confidence of JC Valvular and MRW.

And if you could listen to all three in your room with your music before deciding, that would be worth more than this entire report.

18. Glossary

Technical terms used in the report

Term	Meaning
Push-pull (PP)	Output stage topology with two tubes (or two groups) amplifying opposite half-cycles. Cancels even harmonics and doubles useful power.
Ultralinear (UL)	Intermediate configuration between triode and pentode. Screen grid connected to output transformer tap (20-50% primary). Compromise between power, linearity and DF.
Triode / Pentode	Connection modes. Triode = more linear, less power. Pentode = more power, more distortion. UL intermediate.
EL34	Octal power tube. Historical standard for tube audio. 25 W maximum plate dissipation.
KT77	Functional equivalent to EL34, construction improvements. Drop-in. More neutral sound. See §8.
6CA7	Functional equivalent to EL34 (American designation).
EL34PH Xtreme Classic	PSvane replica of 1950s Mullard EL34 metal base. 25 W. See §8.3.
Summit Series	PSvane flagship line. HPC, superior 2-3% control, 30h burn-in, 24-month warranty. See §8.3.
12AX7 / ECC83	High-gain dual triode (µ˜100). Gain stages and drivers.
12AU7 / ECC82	Medium-gain dual triode (µ˜20). Drivers and phase splitters.
Long-tail pair	Phase splitter circuit. Splits signal into two opposite ones for push-pull. "Long-tail" due to shared tail resistor.
Bias	Quiescent current. Adjusts operating point. On A35 it is measured across 10 O shunts on the cathode.
V_K / I_K / I_P / I_G2	Cathode voltage / cathode current / plate current / screen grid current. I_K = I_P + I_G2.
B+	High-voltage supply rail (400-450 V on A35).
THD / THD+N	Total harmonic distortion / THD plus noise.
FFT	Fast Fourier Transform. Frequency spectrum.
Zout	Output impedance. Determines DF and response modification if load varies.
DF (damping factor)	Z_load / Zout. Not an absolute measure of sound quality.
SNR	Signal-to-noise ratio.
A-weighted	Weighting curve that approximates ear sensitivity.
dBm / dB / dB/€	dB referred to 1 mW / relative / headroom-price index.
EPDR	Equivalent Peak Dissipation Resistance. Equivalent resistance at worst impedance+phase point.
DR	Dynamic Range. DR>11 indicates lightly compressed recording.
Dummy load	Non-inductive 4/8 O resistive load for measurement.
Operating point / Optimal bias	Combination of plate voltage and quiescent current. There is no universal "optimal".
FB1	Ferrite separating digital and analog block. See §5.
MKP	Metallised polypropylene capacitor. Standard audio signal capacitor.
LC choke	Series inductor with HV supply + capacitors = LC filter. Reduces ripple. Present in Cayin Jazz 80 (1H/180mA).
Toroidal	Ring core transformer. Lower stray field, lower saturation. Cayin Jazz 70/80.
HPC (High Performance Cathode)	PSvane Summit series technology: multilayer coating on cathodes. See §8.3.

19. Frequently asked questions

Specific doubts with short answers

Question	Short answer	Detail in
Is it worth it vs a PrimaLuna EVO 200?	Depends on use. The A35 brings integrated DAC+BT and lower cost (€1,339 vs €3,990). The PrimaLuna brings autobias, greater service tradition and slightly higher evidence level.	§13, §15
And vs a Cayin Jazz 80 EL34 at €1,323?	The Jazz 80 wins on equipment: triode mode, headphones, VU meters bias, LDAC+UAT, LC choke, toroidal KT88, Spanish support. The A35 wins on power (45 W vs 36 W) and better €/W.	§13, §17
Cayin Jazz 70 or Jazz 80?	Jazz 80 without doubt. At €1,323 it is €167 cheaper than Jazz 70 and technically superior in everything except size.	§17
Which EL34 tube to buy as replacement?	Three options: Genalex KT77 (~€250/4, maximum reliability), PSvane EL34PH (€399/4, classic sound, reliability risk), PSvane Summit EL34 (~€403/4, maximum performance, 24m warranty).	§8.3
Can the A35 be used with 4 O speakers?	Yes, with 4 O tap. If the speaker drops below 3 O with capacitive phase, probable compression.	§4, §8.1
Do I need the integrated DAC or better an external one?	The integrated ES9018K2M is correct, without independent measurement. If you use pure RCA with external source, digital block inactive.	§5, §10
Is it good for low-sensitivity speakers (<86 dB)?	For 65-80 dB yes. For 95 dB peaks with 86 dB, 45 W may fall short. Measure real SPL before.	§12
Does the EU warranty cover tube-rolling?	No. Changing compatible tubes does not void warranty, but modifying bias or opening chassis does.	§7, §11
Can I use the A35 with headphones?	It has no output. Cayin Jazz 80/70 do (16-300 O).	§11, §17
How much does it consume at idle?	~230 W declared. Inherent to tube push-pull.	§2
Can I leave it on all day?	Technically yes, shortens tube life. Usual: 15 min before listening, turn off when finished.	§6
Does sound improve with expensive NOS?	Preference, not demonstrated technical superiority. Without measurement that demonstrates "better".	§8.1, §11
When to do the 5 priority measurements?	Before any modification. Before deciding whether to keep it or return for warranty.	§10
Is the report updated with measurements?	Yes. Label system allows updating each row. New measurements rise to CONFIRMED and the §15 index recalculates.	§2, §15

20. Modification budget

Accumulated cost per step, not just part price

This section integrates the prices already cited in §7 (capacitors), §8.3 (power tube comparison), §8.5 (sourcing) and §8.6 (final recommendation). The recommended sequence remains that of §7 — document, measure, change one variable, measure again (§10) — before adding steps.

Cost not included: opening the chassis voids commercial warranty in practically all sales channels. Add it as an opportunity cost.

Methodological note: prices cited at time of writing, not independently verified, may have changed. $?€ conversion approximate. PSvane prices come from official distributor in Spain (Lyric Audio Élite, Valladolid) and factory (PSvane.co) respectively.

Modification steps

Step	What you buy	Cited cost	Changes (electrical)	CANNOT be concluded without measuring
0. Stock	Nothing — baseline §10	€0	—	That stock is "worse" without measuring first
1a. Economical tubes	EL34 JJ or Tung-Sol matched quad	~€120–180	Factory bias and matching	Audible sound improvement without before/after FFT
1b. Intermediate tubes	Genalex Gold Lion KT77 matched quad (§8.3)	~€250	Documented drop-in. +7 W dissipation margin (32 W vs 25 W)	Better objective sound; requires verifying plate dissipation with real B+ (§6)
1c. PSvane classic	PSvane EL34PH/4 Xtreme Classic matched quartett (§8.3)	€399	Pentode Mullard/Philips replica, metal base, 25 W	Long-term reliability; verify current silver base. With fixed bias be conservative: do not approach 70% of 25 W
1d. PSvane flagship	PSvane Summit EL34 matched quartett (§8.3)	~€403 / ~$437	PSvane flagship pentode, HPC, 25 W, 24-month warranty	Long-term reliability of novel product (early adopter). Conservative bias mandatory: <70% of 25 W
2. Modern preamp	PSvane 12AX7-S Art TII + 12AU7-S Art TII matched pair	~$140	Gain/µ spec CONFIRMED	Detail/air described in forums — impression, not measurement
2b. Premium NOS preamp	Brimar CV4003 NOS APOS Archive Vault, matched pair 5%	~€430 ($460)	Provenance and Amplitrex testing	Sound signature from review — impression, not measurement
3. Coupling capacitors	Mundorf EVO Oil / Jantzen Superior Z-Cap / ClarityCap, 0.22 µF ×4	NOT VERIFIED	Lower ESR/DF according to datasheet	Audible change without controlled listening
4. Supply / bias / FB1	Multimeter and resistive load already covered in §10	€0 instruments	—	That FB1 or bias reduce noise without before/after FFT

Accumulated cost example: step 1b + 2 ˜ €390 in parts. Step 1c + 2 ˜ €539. Step 1d + 2 ˜ €543. That does not equal those amounts of sound improvement: it equals parts whose real effect on noise, THD and response remains NOT DEMONSTRATED until executing §10 before and after each change.

PSvane vs KT77 — cost, risk and bias margin

The three most relevant power options for the A35 are compared here in terms of budget and risk. Full technical detail is in §8.3.

Option	Quartet cost	Max. dissipation	Bias margin vs 70%	Risk	Warranty
Genalex KT77	~€250	32 W	+7 W vs EL34	Minimal — long track record	Standard
PSvane EL34PH Xtreme Classic	€399	25 W	0 W (same as stock EL34)	Moderate — problematic in previous batches	Standard
PSvane Summit EL34	~€403	25 W	0 W (same as stock EL34)	Calculated — early adopter	24 months

Economic reading: KT77 costs ~€150 less than either of the two PSvane and offers +7 W of dissipation margin, which translates into safer bias and longer tube life in a fixed and manual bias amplifier like the A35. The PSvane bring differentiated sound character (EL34PH classic warm; Summit reference) but require being more conservative in adjustment and assuming long-term reliability uncertainty.

Compromise recommendation: if budget is the dominant factor, KT77 + PSvane Art Series preamp (step 1b + 2) offers the best cost/risk balance. If classic sound or maximum performance with extended warranty is prioritised, PSvane EL34PH or Summit (step 1c or 1d) with conservative bias.

Accumulated cost scenarios

Scenario	Composition	Parts cost	Profile
A — Reliability and best price	KT77 (~€250) + PSvane 12AX7-S Art + JJ ECC82 Gold Pin (~$140)	~€390	Maximum bias margin, minimal risk, no surprises
B — Classic warm	PSvane EL34PH (€399) + PSvane 12AX7-S Art + Brimar CV4003 NOS Vault pair (~€430)	~€829	Classic Mullard sound, assuming reliability risk
C — Maximum performance	PSvane Summit EL34 (~€403) + PSvane 12AX7-S Art + Brimar CV4003 NOS Vault pair (~€430)	~€833	PSvane flagship, 24m warranty, early adopter
D — Full economical PSvane	PSvane EL34PH (€399) + PSvane 12AX7-S Art + 12AU7-S Art pair (~$140)	~€539	All PSvane, no NOS, contained cost
E — Burn-in and backup	JJ ECC83S Gold Pin + JJ ECC82 Gold Pin pair + EL34 JJ matched quad	~€180	Start, burn-in, backup. Does not seek sound improvement

No scenario includes: measurement instrumentation (§10), isolation transformer, resistive loads, calibrated sound card or dedicated analyser. Without those measurements, the real effect of any step remains NOT DEMONSTRATED.

How to use this table

It is not a spending recommendation. It is price information that was already dispersed in §7, §8.3, §8.5 and §8.6. If your objective is nighttime listening at 65 dB (§17), the step with the greatest expected impact is the low-noise preamp (2 or 2b) and the pure RCA / DAC-BT verification of §5 — not the power tubes, which only matter measurably from 95 dB peaks (§12).

Before buying any step: execute §10 (the 5 priority measurements) on the stock unit. Without a baseline, there is no way to attribute improvement to any subsequent change.

V19.0 · Sept 2026 · §8+§9 merged into single chapter "Tubes — options and comparison" with subsections 8.1-8.6 · Redundancies pruned · ~27% reduction · Renumbering §9-§20 · TOC updated