Pre/Power Amplifiers

Launched in 1991, the family-run transformer business (www.toroidy.pl) was joined by the hi-fi focused Fezz Audio in 2000, the latter receiving funding in 2020 for an ‘increase of competitiveness and innovativeness’ courtesy of the Operational Programme of Eastern Poland, ‘co-financed by the European Regional Development Fund’. While this has helped boost the diversity, and perceived value, of Fezz Audio’s tube amps, none of this would have been possible without Toroidy’s prior expertise in specialist transformer design.

Fezz Audio’s use of toroidal speaker-coupling transformers in its amplifiers is an illustration of this – the use of cold-rolled grain-oriented steel in its impregnated cores, very tight windings for reduced magnetostriction, and a high primary inductance promises both a wide frequency response and reduced saturation (distortion) at low frequencies. However, whether as a consequence of design, or a very literal view of impedance/power matching, the Titania’s 8 and 4ohm output transformer taps offer, broadly, an 8 and 4ohm source impedance (a damping factor of 1). As a result, the Titania’s real world response is almost entirely governed by the swings in (reactive) load impedance of the attached speaker – the system response rising with increasing speaker impedance and falling with decreasing speaker impedance.

The severity of these response variations is determined by the magnitude of the swings in speaker impedance. The Graph compares the Titania’s response into 8 and 4ohm resistors via its 8/4ohm taps [black/red dashed traces, respectively] with that driving a real speaker [solid black/red traces] – the SA Signature 5 [HFN Feb ’25]. The Sig. 5’s ‘double bump’ 4.7-24ohm swings in impedance through the bass are typical for a reflex-loaded design, and realised here as 6dB swings in bass response. The 43ohm peak in midrange impedance, again a regular feature of rising mid/tweeter voice-coil inductance, produces an ~8dB lift from 200Hz-2kHz. This will surely be audible (!) though the effect is halved via the lower 4ohm tap impedance [red trace].

In practice the Titania will only achieve a ‘flat’ response if the speaker offers an unvarying (or largely unvarying) impedance trend, or is equipped with a conjugate matching network. As neither is especially commonplace my advice would be always to use the 4ohm output, regardless of speaker. And then bear in mind the following – every review you read will be an impression of this amp and the speaker chosen as its partner. In this instance, only audition with your own loudspeakers, for the Titania is a chameleon among tube amps! PM