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Amadeus Audio




YPSILON SET 100 monoblock amplifier.

The most musically involving and naturally sounding amplifiers are those of single-ended topology. Single-ended triode (SET) amplifiers are usually low powered. There is also a question mark concerning the reliability and sonic signature of the output tubes. Sets also suffer from a high output impedance (between 1.5-2 ohms if no feedback is used).In most cases, at least 3 gain stages are required in order to achieve adequate overall gain. A consequence of this is that there are more capacitors or interstage transformers in the signal path.

Ypsilon’s aim in designing the SET100 was to produce a single-ended amplifier with only two gain stages, and having output power of around 100wrms with low enough output impedance. Their aim was not only to capture the magic of the midrange, so typical of a small power S.E.T amplifier, but was also that it should be able to reproduce the realistic scale and authority of an orchestra in full flow (for example the finale to the organ symphony by Saint-Saens), which has so far escaped all the other SET designs of the past.

Through painstaking evaluation work of nearly all types of output tubes and solid state devices (transistors, IGBTs and Mosfets), it was found that, with a specific power mosfet, the sonic glory of a big NOS output triode could be matched. Of course, the mosfet had to be incorporated and implemented within the design in a perfect way. So a bank of 16 paralleled power mosfets that are perfectly matched, work in single-ended Class A operation, without the use of any tricks (moving bias, plateau bias, active current source etc.) The load is a very special magnetic circuit -an inductance- developed with exotic core materials of a huge size. It is similar to the load within a single-ended triode amplifier having an output transformer, but in the case of the Ypsilon design there is no output transformer and the magnetic circuit is in series with the signal path.

The first stage is a tube-a high transconductance triode- selected for its sonic capabilities and reliability. It is powered by a separate power supply with tube
rectification and choke regulation.

The result is a single-ended amplifier of
-120Wrms/8 ohm output power with relatively low distortion
-no overall feedback
-low output impedance (around 1 ohm)
-two gain stages having an overall gain of x34 times (30db)

Compared with state of the art single-ended triode amplifiers, the Ypsilon SET100 is more direct sounding, more musical and with more instrument body, lower frequency extension, frightening dynamics and, most of all, magically three dimensional.
Any comparison between the Ypsilon SET-100 and all types of push-pull amplifiers is like comparing a Grand Master’s original with a faked copy.





120Wrms 8 Ohm
130Wrms 5.6 Ohm
100Wrms 4 Ohm


5 Hz-80 KHz (-3db)


1 Ohm


x34 (30 db)


240x610x672 mm (WxHxD)


400 W constant


80 Kg each


Tel: 07799812271 - E-mail: glyn@amadeus-audio.co.uk
1 Hoewood, Millglade, Small Dole, West Sussex