Fezz Audio Titania MK2, 60 W push-pull valve amplifier
Technical report based on the official manuals of the integrated amplifier and its power stage, photographic analysis of the interior, reading of the PCB silkscreens, cross-check with independent reviews and explanation of the standardised damping-factor measurement method. Device manufactured in Poland by Fezz Audio with Toroidy toroidal transformers. EISA 2026-2027 award for Best Valve Amplifier.
Main sources: TITANIA-MK2-Integrated-ENG-230-V and Fezz-EVO-NEW-TITANIA-PA-MK2-ENG-110-230-V manuals, Fezz Audio website, reviews from Stereolife, Audiodrom, HiFiNews and The Audio Tailor, OCR analysis of internal photographs, specialist distributor datasheets and cross-check of valve compatibility. Reference system: Crossover A v2.4 MR-A-01 3-way loudspeaker, 6 Ω nominal / 4.9 Ω minimum / 89 dB/W/m (calculation hypothesis, not measured), listening at 3 m.
What it is. A 60 W per channel push-pull valve integrated amplifier. It carries four KT88 valves in the power stage and three 12AX7 (ECC83) valves in the small-signal stage. It is manufactured in Poland, with Toroidy toroidal transformers. It won the EISA 2026-2027 award as Best Valve Amplifier. It accepts valves of the KT family: KT88 as standard and 6550 as a direct equivalent are confirmed; KT90, KT120 and KT150 are reported by distributors, pending confirmation from the manufacturer. It does not accept EL34, KT77, 6CA7, 6L6 or 5881.
The central unknown. Both official manuals declare a damping factor greater than 40. However, no independent measurement of the MK2 exists to verify it. The only measurement available for the family is that of the previous generation's power stage — Titania EVO Gen 1 (MK1), 45 W — and it gave a value of 1. That datum is from another product and cannot be extrapolated to the MK2 without measuring it. See §5.2 and §5.3.
What is not known. The output impedance in ohms, the internal circuit topology, the core type of each transformer and the exact electronic implementation of the Auto Bias.
GETTING STARTED — WITH NO PRIOR KNOWLEDGE (Basic guide G1–G2)
GETTING STARTED — WITH NO PRIOR KNOWLEDGE
High-school physics — logarithms, electrical power, impedance and series circuits — is enough to understand everything that follows. This guide covers two blocks: how a push-pull amplifier works and how much each datum can be trusted; and how power, impedance and damping relate. The technical details begin in Part I.
Basic guide
The idea that organises the whole report. The Fezz Audio Titania MK2 comes with two complete official manuals. In them the manufacturer declares very specific figures: 60 W per channel, distortion below 0.05 %, a damping factor greater than 40. Most of these figures can be verified against the device. But there is one that cannot be verified with the available documentation: the damping factor. The manuals declare it, but nobody independent has measured it on the MK2. The only thing that exists is a measurement of the power stage of the previous generation, which gave a very different value. That is the report's open question.
An amplifier converts the weak signal from the player — in the order of 1 V — into a signal with enough voltage and current to drive a loudspeaker. In valve amplifiers there are two blocks. The preamp increases voltage. The power stage supplies current. Everything is fed by a supply that produces a high DC voltage called B+.
Source → Preamp → Power stage → Output transformer → Loudspeaker
(≈ 1 V) (voltage) (current) (matches impedance) (4–8 Ω)
↑
Power supply (B+)In the power stage there are two configurations. The first, the most common, is push-pull: two valves share the work and their currents combine in the output transformer. Advantages: the DC components cancel in the transformer core (it does not saturate) and many even harmonics cancel each other (less distortion). The second, less frequent, is single-ended: a single valve per channel, with high linearity but low efficiency. The Acronos RS-1 in Annex D is single-ended.
The output transformer matches impedances. If the turns ratio between primary and secondary is n, impedance is multiplied by n²: with n = 27, an 8 Ω loudspeaker is presented to the valves as 27² · 8 ≈ 5832 Ω.
The Titania MK2 uses four KT88s in Class AB push-pull. Class AB means that each valve conducts for slightly more than half a cycle. There are two variants. In AB1, the usual one in domestic audio, the grid never goes positive with respect to the cathode. In AB2, the grid may go positive on peaks, and that requires a driver stage able to deliver current to the grid. The AB1 variant is the most likely in the MK2 — the driver stage with 12AX7s can hardly deliver the grid current required by AB2 — but the manual does not specify it. PROBABLE
How much each datum can be trusted
A technical report mixes statements of very different natures. Some come from the manufacturer's official manual. Others we see in a photograph. Others result from applying a formula. And others are only reasonable intuitions. Mixing levels would be a mistake: the reader would end up giving the same credibility to a confirmed datum as to a suspicion. That is why each statement in the report carries an evidence label. The side column (visible on desktop) shows the summary legend; Annex A develops it.
| Label | What it means | Example in this report |
|---|---|---|
| CONFIRMED | Datum published in the manufacturer's official manual. | 60 W per channel, THD < 0.05 %, 21.5 kg. |
| OBSERVED | Visible in photographs or on the silkscreen. | Titania rev. 2/2025, the 220 µF/350 V capacitors. |
| MEASURED-EXT | Measurement published by an independent laboratory. It may be from another product. | DF ≈ 1 measured by HiFiNews on the power stage Titania EVO Gen 1 (MK1), 45 W. It is not the MK2. |
| PROBABLE | Reasonable physical inference, pending verification. | Location of the Auto Bias servo on the control sub-board. |
| CALCULATED | Result of a formula applied to known data. | Zout estimated < 0.2 Ω if the declared DF > 40 were correct. |
| REPORTED-EXT | Datum from a reliable third party, without our own measurement or manufacturer confirmation. | Compatibility with KT90/KT120/KT150 according to distributors. |
| ND | Cannot be asserted with the current evidence. | Internal circuit topology, Zout in ohms of the MK2. |
How many watts are needed. You must start with the loudspeaker and the listening distance. The decibel (dB) is logarithmic: +10 dB multiplies power by 10, +3 dB by 2 (because 100.3 ≈ 1.995). The calculation follows four steps.
- Sensitivity. The reference loudspeaker produces 89 dB with 1 W at 1 m. HYPOTHESIS of calculation from the Crossover A report, not measured.
- Distance. The level falls according to 20·log₁₀(d). At 3 m: 89 − 9.54 = 79.46 dB.
- Power. To reach a level L: P = 10^((L − 79.46)/10). For 100 dB: 113 W with a single loudspeaker.
- Stereo. With two loudspeakers and a decorrelated signal, +3 dB. Each channel contributes half.
With 60 W per channel, the Titania MK2 covers domestic listening with a wide margin and 100 dB peaks with a tight margin. For 105 dB it falls short. The manual recommends using the 8 Ω tap with 6 Ω nominal loudspeakers, not the 4 Ω one.
Impedance and damping factor. A "6 Ω" loudspeaker does not always have 6 Ω: its impedance changes with frequency. The reference loudspeaker drops to 4.9 Ω around 1.4 kHz and rises at the bass peak. An amplifier behaving as a voltage source delivers more current when impedance falls. The output impedance (Zout) is a resistance in series with the loudspeaker. The damping factor summarises it: DF = Zload / Zout. The higher, the better the control.
The attenuation imposed by Zout follows the voltage-divider formula, with 20·log₁₀ because we work with voltages:
With Zout = 0.2 Ω into 6 Ω: −0.29 dB. The variation between 4.9 Ω and 16 Ω is ≈ 0.24 dB, inaudible. The qualitative conclusion — excellent control, inaudible alteration — holds if the DF really is greater than 40.
| Damping factor | Estimated Zout (8 Ω) | Practical meaning |
|---|---|---|
| > 40 | < 0.2 Ω | Excellent control. The response follows the signal, not the loudspeaker curve. |
| 10 – 40 | 0.2 – 0.8 Ω | Very good control. Spectral variation between 0.3 and 0.9 dB. |
| 3 – 10 | 0.8 – 2.7 Ω | Moderate control. There may be audible colouration. |
| < 3 | > 2.7 Ω | Low control. The response is clearly coloured. |
Quick exercises
- A loudspeaker has 92 dB/W/m. What level does it produce with 1 W at 2 m?
- With the 89 dB/W/m loudspeaker, what power is needed for 100 dB peak at 3 m with a single loudspeaker?
- If the Titania MK2 has DF > 40 into 8 Ω, what is its maximum Zout? And if the DF were 1, what would it be?
- With Zout = 0.2 Ω, what attenuation does the signal suffer into a 4.9 Ω loudspeaker?
See solutions
- 92 − 20·log₁₀(2) = 92 − 6.02 ≈ 86 dB.
- 10^((100 − 79.46)/10) ≈ 113 W.
- DF > 40 → Zout < 0.2 Ω. DF = 1 → Zout ≈ 8 Ω.
- 20·log₁₀(4.9 / 5.1) ≈ −0.35 dB.
PART I — FEZZ AUDIO TITANIA MK2 REPORT
This report brings together both official Fezz Audio manuals (the integrated MK2 and the power stage PA MK2), the interior OCR, the EISA 2026-2027 award, the history of Toroidy with discrepancies between sources, the compatibility of the power valves, the record of the declared damping factor and its pending independent verification, and the standardised method for measuring DF. Annex D includes the Acronos RS-1 SE KT150 reference case as a methodological comparison.
0. Executive summary
20-second read
What it is. A 60 W per channel push-pull valve integrated amplifier, with four KT88 valves in the power stage and three 12AX7 (ECC83) in the small-signal stage. Manufactured in Poland by Fezz Audio, with Toroidy toroidal transformers. EISA 2026-2027 award for Best Valve Amplifier.
Valve family. KT88 (standard) and 6550 (direct equivalent) confirmed. KT90, KT120 and KT150 reported by distributors, pending manufacturer confirmation. Requires matched quartets. Detail in Annex B.
Pending verification. Both manuals declare DF > 40. No independent measurement of the MK2 exists. The only measurement in the family — previous-generation power stage, Titania EVO Gen 1 (MK1), 45 W — gave DF ≈ 1. The matter is developed in §5.2.
What is not known. Zout in ohms of the MK2, internal circuit topology, core type of each transformer, exact electronic implementation of the Auto Bias.
1. Method, evidence and limits
The reference listening system is the Crossover A v2.4 MR-A-01 3-way loudspeaker: 6 Ω nominal, 4.9 Ω minimum and 89 dB/W/m sensitivity. Listening is done at 3 metres. The question guiding the report is simple: what does the Titania MK2 offer and how does it differ from other valve amplifiers?
The documentary advantage. The manufacturer publishes two complete manuals — the integrated one and the power stage one — and the OCR analysis of the interior photographs has provided information that is not normally available: designer's name, board revisions, visible components, failure LEDs, capacitor values. But there are no independent measurements published on the real performance of the MK2 at full power, and the only measurement available for the family — HiFiNews on the previous-generation power stage — corresponds to a different product.
The table below summarises the most relevant parameters of the equipment with an indication of the evidence level. The data from the official manual, the interior OCR and the board revisions have been incorporated.
| Parameter | Fezz Audio Titania MK2 |
|---|---|
| Configuration | Push-pull AB CONFIRMED · AB1 PROBABLE |
| Origin | Poland — Fezz Audio CONFIRMED |
| Award | EISA 2026-2027 Best Valve Amplifier CONFIRMED |
| Designer | Jakub Korpacz M.Sc.Eng OBSERVED |
| Main board revision | Titania rev. 2/2025 OBSERVED |
| Control sub-board | Universal Control System rev. 4/2023 OBSERVED |
| Standard power valves | 4× KT88 (2 per channel), JJ Electronic as standard CONFIRMED |
| Compatible KT family | KT88 and 6550 confirmed; KT90, KT120 and KT150 reported by distributors, pending manufacturer confirmation REPORTED-EXT — see Annex B |
| Input/driver valves | 3× 12AX7 (ECC83) CONFIRMED |
| Transformers | Toroidal, by Toroidy CONFIRMED · core type ND |
| Rated power | 60 W per channel CONFIRMED |
| Distortion (THD) | < 0.05 % at 1 kHz at full power CONFIRMED |
| Frequency response | 16 Hz – 120 kHz (−3 dB) CONFIRMED |
| Damping factor | Declared > 40 in both MK2 manuals CONFIRMED (manufacturer). No independent measurement of the MK2 ND. Measurement of the power stage EVO Gen 1 (MK1), 45 W: DF ≈ 1 MEASURED-EXT, other product — see §5.2 |
| Sensitivity | 0.7 V CONFIRMED |
| Input impedance | 50 kΩ CONFIRMED |
| Output impedance (Zout) | Not published. Estimable < 0.2 Ω if the declared DF > 40 were correct; ≈ 8 Ω if the MK2 behaved like the EVO Gen 1 (MK1) ND |
| Bias | Automatic (Auto Bias) CONFIRMED |
| Valve protection | Independent circuit per KT88 with indicator LED CONFIRMED |
| Soft start | 2-minute preheating cycle with logo colour change CONFIRMED |
| Burn-in | 10 h preliminary; 40–60 h full; minimum 1 h per session CONFIRMED |
| Standby mode | Yes CONFIRMED |
| Inputs | 3× RCA + 1× Direct CONFIRMED |
| Outputs | 4 Ω / 8 Ω, Sub Out CONFIRMED |
| Recommended impedance | 6 Ω loudspeakers → 8 Ω tap CONFIRMED (manual) |
| Optional modules (FEBS) | 2 slots: MM Phono, DAC, Bluetooth, XLR/RCA CONFIRMED |
| Remote control | Yes, infrared (volume, source, standby) CONFIRMED |
| Voltage selector | 230 V / 115 V selectable CONFIRMED |
| Main fuse | 3.15 A type T CONFIRMED |
| Signal ground switch | Yes, on/off on rear panel CONFIRMED |
| Coupling capacitors | Red film capacitors; Wima MKP10 PROBABLE |
| Filter capacitors | 8× 220 µF / 350 V OBSERVED · brand ND |
| Internal trimmers | 4–5 blue Bourns OBSERVED · exact function ND |
| Weight | 21.5 kg integrated · 21 kg power stage PA MK2 CONFIRMED |
| Dimensions | 420 × 380 × 200 mm CONFIRMED (official manual). Distributors publish 240 mm height REPORTED-EXT; it is likely PROBABLE that this corresponds to the height with the valve cage installed, but it is not confirmed by the manufacturer. |
| Consumption | 170 W at idle (manual); 160 W according to official website CONFLICTING DATUM |
| Price | ≈ €3,750 base; FEBS modules ≈ €299 each REPORTED-EXT — indicative as of 2026-10, varies by distributor and country |
It is worth distinguishing four situations that are sometimes confused under the generic label "we don't know": missing datum (the manufacturer does not publish it, e.g. Zout in ohms), deduced datum (inferred with uncertainty, e.g. compatibility with KT90/KT120/KT150), unknown datum (no basis for inference, e.g. exact internal topology) and datum from another product (independent measurement of another device in the family, e.g. the DF of the EVO Gen 1 / MK1 power stage).
The master table in §1.2 has 37 rows. Some carry more than one label — "Transformers" carries CONFIRMED and ND; "Damping factor" carries CONFIRMED, ND and MEASURED-EXT. The counter recounts the total number of labels present in those rows, not the number of rows.
| Label | Occurrences in §1.2 |
|---|---|
| CONFIRMED | 27 |
| OBSERVED | 5 |
| MEASURED-EXT | 1 (from another product: Titania EVO Gen 1 (MK1) power stage) |
| REPORTED-EXT | 3 (KT90/KT120/KT150 · dimensions with cage · price) |
| PROBABLE | 3 (Wima MKP10 · Dimensions · AB1) |
| ND | 5 (core, Zout, MK2 DF, capacitor brand, trimmer function) |
| Total labels | 44 |
| CONFLICTING DATUM | 1 separate row (Consumption) |
The Titania MK2 is one of the best-documented devices in the series. The official manual provides most of the confirmed data. The interior OCR provides the observed data. The HiFiNews measurement is recorded as MEASURED-EXT but referred to another product (Titania EVO Gen 1 (MK1) power stage, 45 W), not to the MK2. The real unknowns of the MK2 reduce to Zout in ohms, the internal circuit topology, the core type of each transformer and the exact electronic implementation of the Auto Bias.
2. Identity and architecture
The Titania MK2 has a clean-lined chassis with a minimalist front panel housing the power switch, the input selector, the volume control and the infrared receiver for the remote control. The toroidal transformers are housed in cylindrical cases within the chassis. The device is available in several metal finishes.
Marks identified on the boards. The main PCB silkscreen shows “Titania rev. 2/2025”, “Designed by Jakub Korpacz M.Sc.Eng”, the reference TA6E-12 next to the upper terminal block and the label POWER AMPLIFIER ONLY near the right connector. Near the valve sockets the references KT88 and ECC83 appear repeatedly. In the bottom-right corner an independent sub-board “Universal Control System rev. 4/2023” is also identified, likewise signed by the same designer, which houses the control logic.
General architecture
The Titania MK2 is a Class AB push-pull stereo integrated amplifier. The power stage uses four KT88s, two per channel. The small-signal stage uses three 12AX7 (ECC83): two for the left and right channels, and a third that the manual explicitly designates as the "driver tube". The Toroidy toroidal transformers (one power, two output) are inside cylindrical cases that also act as electromagnetic shielding.
The main signal PCB (rev. 2/2025) and the control sub-board (Universal Control System, rev. 4/2023) are connected by a ribbon cable. This physical separation between the signal path and the control logic is unusual in this segment and reinforces the design's modern vocation.
The power stage uses four KT88s — beam tetrode, 42 W maximum plate dissipation, 800 V maximum voltage — two per channel, with an individual failure LED at each socket. The small-signal stage uses three 12AX7s (ECC83) — high-gain double triode (μ ≈ 100), low transconductance, widely used in audio — also serving as driver for the output stage. Using the three 12AX7s in the same positions simplifies maintenance: only one valve type is needed for the entire small-signal section.
Fezz Audio uses JJ Electronic KT88s as standard. It offers an upgrade set consisting of Electro Harmonix KT88s and PSVane 12AX7-TIIs, sold together for around €200.
The diagram below summarises the signal chain, the power supply chain and the control subsystems of the Titania MK2 in a single pass. The ND labels mark unavailable parameters, and OBS marks elements confirmed by OCR or the manual. It is a functional-architecture map, not a traced electrical schematic.
╔══ FEZZ AUDIO TITANIA MK2 · push-pull AB 60 W · Polish in-house design ══╗
║ Main board: Titania rev. 2/2025 · Designed by Jakub Korpacz M.Sc.Eng ║
║ EISA 2026-2027 award · Best Valve Amplifier ║
SIGNAL
[RCA ×3 / Direct In] → [12AX7 ×2] → [12AX7 ×1] → [4× KT88 PP] → [Toroidal output trafo] → [Loudspeaker 4/8 Ω]
(obs: TO XLR prep) (preamp) (driver) (2 per channel) (Toroidy · parameters ND)
· 2 channels · 1 shared · Auto Bias (obs: TA6E-12 as
· 1 shared valve · 4 individual service label)
valve · ECC83 (obs) failure LEDs
· ECC83 (obs) · matched quartets
(obs) (manual)
POWER VALVES CONFIRMED: KT88 (standard) · 6550
POWER VALVES REPORTED: KT90 · KT120 · KT150
POWER VALVES NOT COMPATIBLE:
EL34 · KT77 · 6CA7 · 6L6 · 5881
(different family; the Silver Luna is Fezz's EL34 model)
MK1 → MK2 CONTRAST (HiFiNews):
MK1: 2× ECC83 driver/phase-inverter
MK2: 3× 12AX7 (2 preamp + 1 driver)
POWER SUPPLY
[AC] → [230/115 V switch] → [Toroidy toroidal trafo] → [SS rect. ND] → [8× 220µF/350V] → [B+ ND]
(manual · obs) (not a valve) (obs) brand ND
├→ [Fuse 3.15 A T · manual]
├→ [Auto Bias · logic on UCS rev. 4/2023 sub-board]
├→ [Individual protection per KT88 · dedicated LED per valve · manual]
├→ [2-min preheating cycle · logo red→white · manual]
└→ [Standby mode · manual]
CONTROL SUB-BOARD
[Universal Control System · rev. 4/2023 · Fezz Audio]
├→ [Auto Bias servo · calibrated via 4–5 Bourns trimmers (obs)]
├→ [Individual electronic protection per valve]
├→ [FEBS module switching control]
└→ [Start-up timing and preheating cycle]
SERVICE AND ADJUSTMENTS
[Signal ground switch on/off · rear panel · manual]
[Test points TP2, TP3 · silkscreen · obs]
[Service labels POWER AMPLIFIER ONLY, TO XLR · obs]
EXPANSION (modular · 2 FEBS slots)
[Slot 1] → [MM Phono · DAC · Bluetooth · XLR/RCA] (≈ €299 per module)
[Slot 2] → [MM Phono · DAC · Bluetooth · XLR/RCA]
[Global NFB: ND] · [Class: AB (AB1 likely; manual/review)]
[DF declared > 40 (both MK2 manuals) · NO INDEPENDENT MEASUREMENT OF THE MK2]
[DF ≈ 1 measured on the previous generation power stage (EVO Gen 1 / MK1, 45 W) · other product]
[THD < 0.05 % @ 1 kHz] · [Response: 16 Hz – 120 kHz (−3 dB)]
[60 W / channel] · [Mass: 21.5 kg]
[Burn-in 10 h preliminary / 40–60 h full · manual]Three observations from the diagram: Fezz Audio is committed to vertical integration (three in-house-designed toroidal transformers, core type ND); the control architecture is physically separated from the signal path (Universal Control System rev. 4/2023 sub-board, with Auto Bias logic, per-valve protection and FEBS management); and the protection system is individual per valve, not global (each KT88 has its own failure LED).
The pure power-stage version of the Titania — PA MK2, without preamp or FEBS, with 12 V trigger — is described in Annex C.
3. Power supply
The Titania MK2's power supply uses a toroidal transformer designed and manufactured by Toroidy, Fezz Audio's sister brand. The output transformers are also toroidal and the supplier is the same. The sources differ on the exact founding dates of Toroidy (HiFiNews: 1991; Stereolife: 1992) and on the debut of Fezz Audio as a brand (HiFiNews: 2000; Stereolife: Audio Video Show 2015). According to Stereolife Magazine, the output transformer design was carried out by Tomasz Lachowski, son of the founder. HiFiNews does not mention this detail.
The filtering capacity of the supply determines the amount of ripple reaching the valves. The manual does not specify the brand, the value or the origin of the Titania MK2 filter capacitors.
- 8× 220 µF / 350 V in total OBSERVED
- Brand: ND (not legible in the available images)
- Possible distribution: 4 capacitors per channel, each channel in 2S2P configuration would give 220 µF effective @ 700 V per channel. HYPOTHESIS — the actual wiring is not verified.
4. Control, bias and protection
The Titania MK2 incorporates an automatic bias system (Auto Bias). Both manuals describe "automatic bias control" and add that it guarantees "maximum reliability and truly maintenance-free operation". The circuit continuously monitors the operating parameters of the valves and keeps the bias ideal without user intervention.
The Titania MK2 brings together in its control subsystem three elements unusual in its category: individual protection for each power valve, FEBS modularity and control logic physically separated on the Universal Control System sub-board.
Individual protection per valve
The integrated amplifier manual describes in its section 7 ("Power tubes protection circuit"): "Every power tube has its own circuit protection system with separate light indicator". Each of the four KT88s has its own protection circuit and its own failure indicator LED. The documented procedure is:
- If the red LED comes on, switch off the amplifier.
- Check that the valves are correctly installed.
- Switch it back on.
- If the red LED stays on, the valve is faulty and must be replaced.
The PA MK2 power stage manual is more explicit about its version's technology: it speaks of a "safety auto fuse" per power valve. When a valve fails, the auto-fuse trips and the corresponding red LED lights up. The procedure is: switch off for 2 minutes, switch on again, and if it persists, replace the valve. Both systems fulfil the same objective with different philosophies. Which one acts earlier or more effectively is not documented ND.
FEBS expansion modules
The Titania MK2 has two FEBS (Fezz Extension Board System) expansion slots. The available modules are MM Phono, DAC, Bluetooth and XLR/RCA, at an indicative price of ≈ €299 each REPORTED-EXT. The PA MK2 power stage, on the other hand, has no FEBS slots: its only expansion is XLR or RCA selection via a rear switch.
Control sub-board — Universal Control System
The photographic analysis of the interior has revealed the existence of an independent sub-board in the bottom-right corner of the chassis, identified as "Fezz — Universal Control System — rev. 4/2023", also designed by Jakub Korpacz M.Sc.Eng. It is connected to the main board by a ribbon cable. It is the natural candidate to house the Auto Bias logic, the management of the electronic protection system, the switching of the FEBS modules and the preheating cycle. The "Universal" reference suggests it is used across several models in the Fezz range. The exact architecture of this sub-board (what ICs it carries, how it implements the bias servo, how it detects anomalies) remains ND.
5. Power, SPL and damping
With 60 W per channel, the Titania MK2 offers a wide margin for domestic listening and a tight margin for high-intensity peaks. For the reference system (89 dB/W/m, listening at 3 m), the distance loss is about 9.5 dB.
| Scenario | Target peak SPL @3 m | W/channel needed (+3 dB) | Margin over 60 W |
|---|---|---|---|
| Domestic | 95 dB | 18.0 W | +5.2 dB |
| Loud | 100 dB | 56.8 W | +0.2 dB |
| Monitoring | 105 dB | 179.6 W | −4.8 dB |
SPL and required power calculator
Formulas: SPL_1W@d = sens − 20·log10(d) and P = 10^((SPL_target − SPL_1W@d − factor)/10). Results per channel.
This section is the heart of the report. Everything else rests on it.
What the manufacturer declares. Both official Fezz manuals — the integrated MK2 and the power stage PA MK2 — declare a damping factor greater than 40. If that figure were correct, the output impedance would be below 0.2 Ω, which is an excellent value for a valve amplifier. The amplifier would control the loudspeaker as a voltage source.
What has been measured. No independent measurement of the MK2 is on record to verify that figure. What does exist is a measurement of the power stage of the previous generation. The HiFiNews review of the power stage Titania EVO Gen 1 (MK1) — 45 W, January 2025 — concluded that the 8 Ω and 4 Ω taps offer a source impedance approximately equal to the nominal impedance of each tap, i.e. a DF ≈ 1. HiFiNews summarises it by pointing out that, under those conditions, the real response of the device is governed by the reactive impedance of the connected loudspeaker, and recommends always using the 4 Ω tap, regardless of the loudspeaker.
Why that measurement cannot be extrapolated. That measurement is from another product: the power stage, not the integrated; and from the previous generation, not the MK2. Fezz describes the MK2's topology as "completely new circuit topology" compared with the previous generation. The family clue is relevant — same manufacturer, same transformer supplier, same design philosophy — but it does not allow predicting the MK2's behaviour without measuring it.
The attenuation imposed by Zout on the signal is calculated with the voltage divider:
The table below shows the correctly calculated attenuation at 4.9 Ω and at 8 Ω for different hypothetical Zout values, including the two scenarios at stake (DF > 40 and DF = 1):
| Hypothetical Zout | DF @8 Ω | Attenuation @4.9 Ω | Attenuation @8 Ω |
|---|---|---|---|
| 0.1 Ω | 80 | −0.18 dB | −0.11 dB |
| 0.2 Ω | 40 | −0.35 dB | −0.21 dB |
| 0.5 Ω | 16 | −0.84 dB | −0.53 dB |
| 1.0 Ω | 8 | −1.61 dB | −1.02 dB |
| 8.0 Ω | 1 | −8.41 dB | −6.02 dB |
What has been measured and what has not — the method
- With a pure resistive load of 8 Ω and 4 Ω, at sufficient power not to saturate.
- At several frequencies: at least 20 Hz, 100 Hz, 1 kHz, 10 kHz and 20 kHz.
- With an oscilloscope or True RMS multimeter to measure the voltage drop accurately.
- Recording the signal level of each measurement, because Zout may vary with drive level.
There is no single IEC or AES standard that defines "how the damping factor is measured". What exists is a de facto standard procedure for measuring output impedance (Zout), of which DF is a simple derivative. That general procedure is indeed covered in standards such as IEC 60268-3, which describes how to measure amplifier electrical parameters by the voltage-drop method. What the standard does not fix are the specific conditions — reference frequency, bandwidth, load type — under which DF must be expressed as a catalogue figure.
5.3.1 The voltage-drop method
The method is known as the voltage-drop method or resistance-insertion (On-Off) method. It is the one used by laboratories such as HiFiNews and audio analysers such as those from Audio Precision. It has four steps:
- Measurement without load (Vnl). A signal of known frequency is injected — usually 1 kHz — and the output voltage is measured without connecting a loudspeaker. It is advisable to use a minimum safety load (for example 100 Ω) instead of a pure open circuit.
- Measurement with load (Vl). A pure resistive load (typically 8 Ω or 4 Ω) is connected and the output voltage is measured again.
- Calculation of Zout. Zout = Rload · (Vnl − Vl) / Vl.
- Calculation of DF. DF = Rload / Zout.
Why it is preferable. The output transformer is inductive: measuring without load can generate overvoltages that damage the transformer or the valves. The two-load measurement is safer and is the variant used, for example, by JC Valvular (manufacturer of the Acronos RS-1).
5.3.2 Why the conditions are not standardised
Although the method is standard, the exact conditions are not. That is where discrepancies between catalogue figures arise: the signal frequency (usually measured at 1 kHz to give the "official" figure, but Zout varies with frequency), the load type (pure resistive load is standardised, which does not resemble the complex impedance of a real loudspeaker) and the bandwidth (some manufacturers measure over a wide range, others only at 1 kHz).
The methodological parallel with other valve amplifiers in the same field is developed in Annex D — Acronos RS-1 SE KT150 reference case.
6. Operation, burn-in and safety
The manual precisely describes the power-on cycle: switch on the source first, then the amplifier; lower the volume to minimum and switch on the Titania MK2. The device enters a 2-minute preheating cycle. After 2 minutes the Fezz logo on the front changes from red to white. Verify that the source is playing and gradually raise the volume. The power-off sequence is the reverse. The PA MK2 follows the same procedure, with the caveat that the volume is controlled by the external preamp.
Both manuals also specify the burn-in: about 10 hours of preliminary preheating and between 40 and 60 hours of full burn-in, with minimum sessions of 1 hour to avoid short sessions during the initial period. The manuals justify it by "the presence of residual polarization of dielectric elements and due to a necessary stabilization of working parameters of the vacuum tubes".
The integrated amplifier's rear panel documents three service elements unusual in its category: 230 V / 115 V voltage selector, 3.15 A type T main fuse and signal ground on/off switch (to eliminate ground loops when integrating several devices). The PA MK2 adds a 12 V trigger to automatically switch other devices in the system on and off. The safety warnings in the manuals: do not switch on without valves or without loudspeakers connected; do not open the cover (risk of high voltage even when unplugged); keep at least 10 cm of ventilation; replace fuses only with the original specification.
7. Assessment by axes: signal and control
This report assesses the Titania MK2 along two axes. Axis A (signal modernity) measures the degree to which the amplifier incorporates contemporary technical solutions for treating the musical signal. Axis B (control modernity) measures how it manages its own operation: monitoring, protections, maintenance and connectivity.
| Axis | Element | Fezz Titania MK2 | Assessment |
|---|---|---|---|
| A | Input/driver stage | 3× 12AX7 (ECC83) CONFIRMED | Classic, proven solution |
| A | Coupling capacitors | Red film capacitors; Wima MKP10 PROBABLE | High-quality polypropylene |
| A | Output transformers | Toroidal Toroidy CONFIRMED | Low emission, high stability |
| A | Topology | Push-pull AB (AB1 likely), redesigned (rev. 2/2025) CONFIRMED | Redesigned signal path |
| A | Power valves | 4× KT88 standard · KT family compatible CONFIRMED | Robust and flexible beam tetrode |
| A | Rectification | Solid state (not valve) PROBABLE | Modern solution |
| B | Bias | Automatic (Auto Bias) with internal calibration points CONFIRMED | Low maintenance for the user |
| B | Valve protection | 4 independent circuits with LED per KT88 CONFIRMED | Superior granularity |
| B | Valve compatibility | KT88, 6550 confirmed; KT90, KT120, KT150 reported REPORTED-EXT | Sonic flexibility with caveats |
| B | Control sub-board | Universal Control System rev. 4/2023 OBSERVED | Physical separation logic/signal |
| B | Soft start | 2-min preheating cycle with logo colour change CONFIRMED | Modern |
| B | Standby mode | Yes CONFIRMED | Modern |
| B | Remote control | Infrared: volume, source, standby CONFIRMED | Modern |
| B | Expansion modules | 2 FEBS slots (Phono, DAC, BT, XLR/RCA) CONFIRMED | Modularity uncommon in valve integrateds |
| B | Ground switch | Signal ground on/off on rear panel CONFIRMED | Unusual function |
| B | Voltage selector | 230 V / 115 V CONFIRMED | Standard in international market |
| B | 12 V trigger | Only on the PA MK2 power stage (not on the integrated) CONFIRMED | Integration in automated systems |
| B | Documentation | Complete official manual + identifying silkscreen OBSERVED | Very good |
| B | Distribution network | Established distributors | Good support |
8. Closing
What we know.
- The device is officially documented: both manufacturer manuals publish all the essential specifications.
- EISA 2026-2027 award as Best Valve Amplifier.
- The interior OCR provides traceability: designer (Jakub Korpacz M.Sc.Eng), board revisions and filter capacitor values (8× 220 µF / 350 V).
- Excellent control architecture: Auto Bias, individual protection per KT88, FEBS modularity, remote control, standby and ground switch.
- Compatible with the standard KT family (KT88, 6550 confirmed; KT90, KT120 and KT150 reported by distributors). Requires matched quartets. Not compatible with EL34, KT77, 6CA7, 6L6 or 5881 (for EL34 there is the Silver Luna).
- Uses Toroidy toroidal transformers.
- THD < 0.05 % at 1 kHz at full power: an excellent figure for a valve amplifier.
- Its FEBS modularity is uncommon in valve integrated amplifiers in its category: it allows adding DAC, phono, Bluetooth or XLR/RCA without changing equipment.
- A sister power stage exists (PA MK2) with the same valve complement, same power and 12 V trigger, without preamp or FEBS.
What we do not know or is pending.
- MK2 damping factor. Both manuals declare more than 40, but there is no independent measurement of the MK2. The only measurement available in the family is that of the previous-generation power stage (Titania EVO Gen 1 (MK1), DF ≈ 1). It is the most critical datum pending verification. See §5.2.
- Zout in ohms of the MK2. It depends on resolving the previous point: if the declared DF were correct, it would be below 0.2 Ω; if the MK2 behaved like the EVO Gen 1 (MK1) power stage, it would be approximately 8 Ω.
- Internal circuit topology. Phase splitter, driver, KT88 driver, NFB topology.
- Core type of each transformer.
- Exact electronic implementation of Auto Bias.
- Actual behaviour of KT90/KT120/KT150 in the MK2. Distributors report them as compatible, but the manufacturer does not confirm it in writing.
| If your priority is… | Guidance |
|---|---|
| Automation and low maintenance | Titania MK2 — Auto Bias and individual per-valve protection |
| Easy valve failure diagnosis | Titania MK2 — 4 individual LEDs per KT88 |
| Sonic flexibility with the standard KT family (KT88, 6550) | Titania MK2 — confirmed by manual |
| Experimenting with KT90/KT120/KT150 | Titania MK2 with caution — reported by distributors, requires manufacturer confirmation |
| EL34 / KT77 sound | Fezz Audio Silver Luna — not compatible with Titania MK2 |
| Modularity and future connectivity | Titania MK2 integrated — two FEBS slots |
| Integration in automated systems | Titania PA MK2 — 12 V trigger |
| Integration in complex systems (integrated) | Titania MK2 — signal ground switch |
| International use | Both — 230/115 V selector |
| Loudspeaker control with low Zout | Pending verification of the real MK2 DF — if the declared DF is correct, good control; if the MK2 behaved like the EVO Gen 1 (MK1) power stage (DF ≈ 1), the loudspeaker choice becomes critical |
| Complete official documentation | Both — exhaustive manuals |
| Highest-quality transformers | Both — Toroidy toroidal |
ANNEXES
Support material. Annex A explains how to interpret the evidence labels. Annexes B and C expand on compatible valves and on the sister power stage. Annex D develops the parallel Acronos RS-1 case. Annex E details the protocol for pending measurements. Annex F gathers the sources and credits.
ANNEX A — HOW TO READ THE EVIDENCE LABELS
Annex A — How to read the evidence labels
Each statement in the report carries an evidence label indicating its level of support. This annex expands the summary legend in the side column (visible on desktop) for the mobile version and printing, where the aside is hidden.
The eight labels, one by one
| Label | What it means | What would be needed to move up a level |
|---|---|---|
| CONFIRMED | Datum established by official manufacturer documentation (manual) or by verified silkscreen. | It is already at the highest level. It can only be downgraded if a documentary contradiction appears. |
| OBSERVED | Directly visible in photographs or on the PCB silkscreen. | Confirm the interpretation with the manufacturer, or measure the component directly. |
| CALCULATED | Mathematical result obtained by applying a formula to known data. | Experimentally verify the result with an instrument. |
| PROBABLE | Reasonable physical inference, coherent with what is observed, but unverified. | Direct measurement or documentary confirmation. |
| HYPOTHESIS | Possibility coherent with the available data, but not sufficiently supported. | Additional evidence to make it PROBABLE or to discard it. |
| REPORTED-EXT | Datum provided by a reliable third party (distributor, specialist publication), without our own measurement or manufacturer confirmation. | Official manufacturer confirmation or independent measurement. |
| MEASURED-EXT | Measurement published by an independent laboratory, with identifiable conditions. It may refer to another product. | Measurement of the product under review in the same conditions. |
| ND | Not determinable with the current evidence. | Direct measurement, manufacturer schematic or additional documentation. |
How several labels combine in the same row
The same statement can carry several labels at once, because different parts of the sentence have different levels of evidence. The damping factor row in the master table of §1.2 reads:
Each part of the sentence responds to a different source. The reader who reads the three parts with the same label will not understand the real state of the question. The reader who distinguishes the three levels will clearly see that the question remains open and will know what kind of measurement would close the matter.
ANNEX B — POWER VALVE COMPATIBILITY
Annex B — Power valve compatibility
The Titania MK2 does not run on KT88 only. The manufacturer optimises the design for that model, but the amplifier accepts other valves from the same electrical family. This annex gathers what is documented, what specialist distributors report and the practical conditions the user must respect.
B.1 Compatible valves
| Valve | Type | Status in the MK2 | Notes |
|---|---|---|---|
| KT88 | Beam tetrode | STANDARD | Reference valve. JJ Electronic as standard; upgrade to Electro Harmonix KT88 + PSVane 12AX7-TII. |
| 6550 | Beam tetrode | COMPATIBLE | American cousin of the KT88. Very close electrical characteristics. Requires matched quartets. |
| KT90 | Beam tetrode | REPORTED-EXT | Evolution of the KT88 with more dissipation. Auto Bias re-adjusts automatically. Filament consumption similar to KT88. Not confirmed by the manufacturer. |
| KT120 | Beam tetrode | REPORTED-EXT | More power. Filament consumption 1.7–1.95 A. Verify with the manufacturer. |
| KT150 | Beam tetrode | REPORTED-EXT | Maximum-power option. Filament consumption ~2 A. Requires explicit manufacturer confirmation. |
B.2 NOT compatible valves
| Valve | Type | Status in the MK2 | Notes |
|---|---|---|---|
| EL34 | Pentode | NOT COMPATIBLE PROBABLE | Different electrical family. Lower plate power and voltage. Fezz's model for EL34 is the Silver Luna (2×35 W, 4× EL34). |
| KT77 | Beam tetrode | NOT COMPATIBLE PROBABLE | Direct substitute for the EL34. Same limitations. |
| 6CA7 | Pentode | NOT COMPATIBLE PROBABLE | American equivalent of the EL34. Same limitations. |
| 6L6 / 5881 | Beam tetrode | NOT COMPATIBLE PROBABLE | Different electrical family (lower voltage and power than KT88). The MK2 manual does not mention them explicitly, but by electrical family they are not compatible. |
- Plate voltage: EL34/KT77 and 6L6/5881 handle voltages far below those of the KT88. The MK2 circuit is designed for KT88 voltages.
- Dissipation: EL34 25 W; KT77 32 W; 6L6 30 W; KT88 42 W. The MK2 operating point is calibrated for the KT88.
- Auto Bias: its adjustment range is designed for the KT88 family. It cannot compensate for the different curves of an EL34 or a 6L6.
- Consequence: attempting to use any of these valves in the MK2 may cause unstable operation, damage to the valves or the output transformer, and is not covered by the warranty.
B.3 The role of Auto Bias
The Auto Bias system of the Titania MK2 is what makes valve changes within the KT family viable without manual intervention: when the quartet is replaced, the circuit automatically re-adjusts the bias point. This does not exempt the user from complying with the matching requirement of the manual, but it does eliminate the need to manually recalibrate bias after each change.
- Detects the new quiescent current of each valve.
- Adjusts the negative grid voltage to bring it back to the optimal operating point.
- Corrects drift during use (valve ageing).
B.4 Practical conditions for valve change
| Condition | Why it matters |
|---|---|
| Matched quartets | Explicit manual requirement. Without prior matching, Auto Bias may compensate poorly and some valve may operate outside its safe point. |
| Verify filament consumption | The KT88 and 6550 draw 1.6 A; the KT120 may reach 1.95 A; the KT150 approximately 2 A. Four of these valves plus the three 12AX7s (≈ 0.3 A each) imply a total consumption around 7.3 A with KT88 versus 8.9 A with KT150 (+22 %). It is worth confirming with the manufacturer that the transformer has margin. |
| Confirm with Fezz Audio or the distributor | For KT120 and KT150, it is worth ensuring in writing that the power transformer and the rest of the circuit operate within their safety margins. |
| Preamp valves: 12AX7 / ECC83 | For the small-signal section, the manual requires replacement with the same type or a direct equivalent. |
| Burn-in after change | The manual recommends 40–60 h burn-in for full sound stabilisation. |
- With previously matched quartets.
- After confirming with Fezz Audio or the authorised distributor the specific electrical compatibility.
- Verifying that the total filament consumption does not exceed the transformer's capacity.
- Respecting the manual's safety procedures: unplug from the mains before touching valves, wait for them to cool, do not open the cover.
ANNEX C — THE SISTER POWER STAGE: TITANIA PA MK2
Annex C — The sister power stage: Titania PA MK2
Fezz Audio also sells a version of the Titania as a pure power stage, without an integrated preamp. It is called the Titania Power Amplifier (PA) MK2 and shares most of the electrical architecture with the integrated, but not all of it. It is the same 60 W MK2 generation as the integrated; it must not be confused with the power stage of the 45 W Titania EVO Gen 1 (MK1), which is the previous generation.
C.1 Differences with respect to the integrated
| Feature | Titania MK2 integrated | Titania PA MK2 power stage |
|---|---|---|
| Inputs | 3× RCA + 1× Direct | 1× RCA + 1× XLR (switchable) |
| Volume control | Yes, integrated in the chassis | No; controlled by the external preamp |
| FEBS modules | 2 slots | No |
| 12 V trigger | No | Yes, input/output |
| Weight | 21.5 kg | 21 kg |
| Valves | 4× KT88 + 3× 12AX7 | 4× KT88 + 3× 12AX7 |
| Power | 60 W | 60 W |
| THD | < 0.05 % at 1 kHz full power | < 0.05 % at 1 kHz full power |
| Bandwidth | 16 Hz – 120 kHz | 16 Hz – 120 kHz |
| Declared DF | > 40 | > 40 |
| Zin | 50 kΩ | 50 kΩ |
| Sensitivity | 0.7 V | 0.7 V |
| Consumption | 170 W / 270 W | 170 W / 270 W |
| 230/115 V switch | Yes | Yes |
| Signal ground switch | Yes | Yes (labelled "GND audio loop switch") |
| Preheating | 2 min, logo red→white | 2 min anode voltage delay |
C.2 Why it matters for this report
The PA MK2 power stage is part of the same 60 W MK2 generation as the integrated. The fact that both manuals declare the same DF greater than 40 indicates that it is a coherent specification within the MK2 family, not a one-off figure from a single document. However, there is still no independent measurement of the MK2 — integrated or power stage — to verify that value. The only independent measurement available in the family is that of the 45 W Titania EVO Gen 1 (MK1) power stage, carried out by HiFiNews in January 2025, which gave DF ≈ 1. It cannot be called a direct contradiction between the manufacturer and the measurement, because they refer to different generations of the product, and the measurement is only of the power stage. What exists is a manufacturer declaration without verification and a family precedent that advises caution.
C.3 Protection system: interesting difference
Both products protect each valve independently, but with different technologies: the integrated documents an electronic protection circuit, while the power stage documents individual resettable auto-fuses. Both manuals record the same number of LEDs (four), one per KT88. Which of the two technologies acts earlier or more effectively is not documented ND.
ANNEX D — REFERENCE CASE: ACRONOS RS-1 SE KT150
Annex D — Reference case: Acronos RS-1 SE KT150
The Fezz Titania case is not unique in the valve audio landscape. A Spanish product in the same field, the Acronos RS-1, is a good example of how a declared DF figure can be subject to the same caution. The full RS-1 report, with the NFB modelling, the Class A ceiling and the manufacturer's testimony, is published at Nauscopio.
D.1 What the Acronos RS-1 is
The Acronos RS-1 is a single-ended (SE) KT150 valve amplifier, with one valve per channel. It belongs to a different topological family from the Fezz (which is push-pull). Its architecture is that of the pure SET, with the advantages and disadvantages this entails: high intrinsic linearity, no crossover distortion, but low efficiency and, typically, high Zout.
D.2 Empirical precedents in SE KT150
Commercial single-ended KT150 amplifiers tend to have high Zout. Two documented precedents, one with independent measurement and one with a manufacturer-declared figure:
| Model | Power | Global NFB | Reported DF |
|---|---|---|---|
| Icon Audio ST30SE | 28 W UL | Low-feedback design | ≈ 6 (Hi-Fi World) · DF ≈ 7–17 depending on mode, in HiFiNews measurements |
| Dared Saturn Signature | 25 W | −39 dB global | ≈ 6 (declared) — internally inconsistent: with −39 dB of NFB and an open Zout of 5–6 Ω, the DF should be around 130, not 6. One of the two data does not mean what it seems. |
D.3 The figure published by Et Sona and its traceability
The figure that circulates for the Acronos RS-1 — DF ≈ 50 and THD 0.01 % @ 18 W — comes from the Et Sona review, not from an official JC Valvular datasheet. This has an important consequence for the analysis: there is no evidence that the manufacturer publishes them in its official datasheet.
D.4 What can and cannot be concluded
| Statement | Status |
|---|---|
| The RS-1 is an SE KT150 with one valve per channel | OBSERVED |
| The documented SE KT150s have low DFs, between 6 and 17 depending on mode and publication | MEASURED-EXT (one) + REPORTED-EXT (the other) |
| Et Sona publishes DF ≈ 50 for the RS-1 | REPORTED-EXT |
| Et Sona's measurement methodology is known | ND |
| The RS-1 has a deep-loop global NFB | ND |
D.5 Parallelism between the two cases
Both the Fezz Titania MK2 and the Acronos RS-1 are European products in the same field, with pure valve architectures. In both cases, the declared DF figure is not backed by an independent measurement of the product itself:
| Aspect | Fezz Titania MK2 | Acronos RS-1 |
|---|---|---|
| Topology | Push-pull KT88 | Single-ended KT150 |
| Declared DF | > 40 (official MK2 manual) | ≈ 50 (Et Sona, not the manufacturer) |
| Source of the datum | Manufacturer (two MK2 manuals) | External review |
| Independent measurement of the current product | No record for the MK2. Yes for the EVO Gen 1 (MK1) power stage (DF ≈ 1, HiFiNews). | No independent measurement published |
ANNEX E — PROTOCOL FOR PENDING MEASUREMENTS
Annex E — Protocol for pending measurements
To close the unknowns in this report — and, above all, to verify the MK2's declared damping factor — a series of measurements on a physical unit would be needed. These are the five priorities:
| Priority | Measurement | Purpose |
|---|---|---|
| 1 | Zout by the resistive-divider method, on each tap (4 Ω and 8 Ω), at several frequencies (20 Hz – 20 kHz) | Verify the MK2's declared DF (> 40): check whether the MK2 behaves as a voltage source (high DF) or follows the pattern of the previous-generation power stage (DF ≈ 1). |
| 2 | Square-wave step response of the OPT into an 8 Ω load | Reveals primary inductance, leakage inductance and high-band behaviour. |
| 3 | Distortion curve vs power | Establishes P@1 % THD, a datum no manual publishes. |
| 4 | Verification of the wiring of the 8 capacitors (per-channel distribution and exact topology) | Confirms the real effective capacity of the filter bank per channel. |
| 5 | Consultation with the manufacturer on DF, transformer margins and full KT120/KT150 compatibility | Confirm in writing the DF figure, the admissible filament consumption and the compatibility of the valves reported by distributors. |
Additional desirable measurements: macro photograph of the Universal Control System rev. 4/2023 sub-board (to identify the ICs of the Auto Bias and the protection system); power-supply ripple with an oscilloscope; and a direct comparison between the Titania MK2 integrated and the PA MK2 power stage on the same loudspeaker.
ANNEX F — REFERENCES AND CREDITS
Annex F — References and credits
Primary sources
- Fezz Audio · official integrated MK2 manual. TITANIA-MK2-Integrated-ENG-230-V. Official PDF document in English, 8 pages. Authoritative source of all specifications and functions documented in the integrated. (consulted 2026-10)
- Fezz Audio · official power stage PA MK2 manual. Fezz-EVO-NEW-TITANIA-PA-MK2-ENG-110-230-V. Official PDF document in English, 8 pages. Authoritative source of the PA MK2 specifications and the resettable auto-fuse protection system. (consulted 2026-10)
- Fezz Audio · official page. fezzaudio.com. (consulted 2026-10)
- EISA 2026-2027 award. EISA (Expert Imaging and Sound Association). eisa-awards.org. Official quote: "The Titania MK2 significantly advances Fezz's KT88-based integrated tube amplifier, delivering up to 60Wpc of power to partner confidently with a wider range of loudspeakers." (consulted 2026-10)
- HiFiNews · review of the power stage Titania EVO Gen 1 (MK1), January 2025. hifinews.com — Fezz Audio Sagita Prestige/Titania pre/power amp. The unit measured by HiFiNews is the power stage of the Titania EVO Gen 1 (MK1) — 45 W, previous generation of the family — not the Titania MK2 under review. The review documents an output impedance of 7.4–8.0 Ω on the 8 Ω tap, over the 20 Hz – 20 kHz range, corresponding to DF ≈ 1. It also documents that the MK1 used two ECC83s as driver/phase-inverter valves and that it already had auto-bias. The MK2 report cites the review as a family precedent, with the methodological caution explained in §5.3.2. (consulted 2026-10)
- History of Toroidy and Fezz Audio, with discrepancies between sources. HiFiNews places the founding of Toroidy in 1991 and Fezz Audio's entry into the market in 2000. Stereolife Magazine, article "From transformers to tube amplifiers: the story of Fezz Audio" (April 2026), places it "probably" in 1992 and dates the debut of Fezz as a brand at the 2015 Audio Video Show. The data on the repurposing of Biazet machinery, the role of Tomasz Lachowski in the design of the output transformers and the anecdotal origin of the name "Fezz" come only from Stereolife Magazine; HiFiNews does not mention them. (consulted 2026-10)
- Fezz Audio Titania MK2 · photographic analysis. High-resolution photographs of the interior. OCR source: Titania rev. 2/2025, Designed by Jakub Korpacz M.Sc.Eng, Universal Control System rev. 4/2023, TA6E-12, KT88, ECC83, POWER AMPLIFIER ONLY, TO XLR, TP2, TP3. Capacitor reading source: 8× 220 µF / 350 V. (consulted 2026-10)
- Specialist distributor datasheets. Commercial documentation confirming compatibility with the KT family (6550, KT90, KT120, KT150) and the Silver Luna model for EL34. Source also of the 240 mm height datum, complementary to the 200 mm of the official manual. (consulted 2026-10)
Complementary sources
- Titania MK2 reviews. Stereolife, Audiodrom, The Audio Tailor, Hifi-voice. The Audiodrom review rates the sound at 98 % and highlights "ultra-high-endová kultivovanost".
- Valve datasheets. JJ Electronic (KT88, 12AX7), Genalex/New Sensor (KT88 Gold Lion), Electro Harmonix (KT88, KT90, KT120, KT150), PSVane (12AX7).
- Historical reference design. Mullard Ltd. Circuits for Audio Amplifiers (Booklet TP413).
- Reference system. Crossover A v2.4 MR-A-01, 6 Ω nominal / 4.9 Ω minimum / 89 dB/W/m (calculation hypothesis, not measured).
- Cross-reference comparative report. Acronos P52 vs Cayin Jazz 90 (nauscopio, V3.3, October 2026).
- DF measurement methodology. IEC 60268-3 "Sound system equipment — Part 3: Amplifiers" describes the general procedure for measuring electrical parameters, including output impedance by the voltage-drop method. However, the standard does not fix specific conditions (frequency, bandwidth, load type) under which DF should be expressed as a catalogue figure, which explains the disparity of conditions between manufacturers and laboratories. HiFiNews, Audio Precision (instrument manufacturer) and others apply the method with different conditions.
- Acronos RS-1 reference case. The full RS-1 report is published at nauscopio.blogspot.com/p/acronos-rs-1-single-ended-kt150.html. It includes the loop-gain modelling, the Class A ceiling calculation, the manufacturer's testimony on DF calculation, the list of the 12 factors that determine DF and a 16-measurement verification protocol. The DF ≈ 50 and THD 0.01 % @ 18 W figures come from the Et Sona review, not from an official manufacturer datasheet. The empirical precedents of the Icon Audio ST30SE and Dared Saturn Signature sit in low DF values. For the Icon Audio ST30SE, Hi-Fi World published DF ≈ 6 and HiFiNews's own laboratory gave different figures (DF between 7 and 17 depending on mode), illustrating that even two measurements of the same device can differ according to conditions.
- JC Valvular testimony on DF calculation. The designer of JC Valvular — manufacturer of the Acronos RS-1 — has explained, within the framework of the RS-1 report, that in his case DF is set as a target in the output transformer design based on 12 factors, and that the commercial figure is an average verified at 1 kHz with fixed resistive loads. (2026-10)
- Two-load method for measuring Zout. Variant of the voltage-drop method used by some manufacturers to avoid measuring in open circuit, given the inductive nature of the output transformer. Formula: Zout = R₁·R₂·(V₁−V₂) / (R₁·V₂ − R₂·V₁).
