Now using my newly developed modified Pi wound output transformers for fully balanced DC resistance, AC impedance, and low distortion.
The new output transformers measure 20hz to 20khz +/-0.2db.
What this means to you is the output tansformers are not a limiting factor so no design compromises are needed to compensate.
Transformers used in some sub $3K amplifiers can measure as poorly as 20hz to 20khz +/- 5db. In these cases, massive circuit design compromises need to be made just to achieve barely acceptable sonic and measured results.
The Topaz 6CA7 is a stereo (two-channel) amplifier rated at over 30 watts per channel into 8 ohms.
The input stage of the Topaz can have a big impact on the sound quality of the amplifier, and good quality driver vacuum tubes should be used. The Topaz comes supplied with a set of three new re-issue Tung-sol 6SL7GT small signal valves. The output stage of the Topaz 6CA7 is a standard self biasing setup that, whilst not giving maximum output, gives maximum reliability. It also avoids the use of silicon diodes in the bias network.
The sound from this amplifier is extremely musical, being a true ultralinear connected Class A amplifier, it will give a sound that isn’t fatiguing and is very accurate especially through the critical vocal ranges. It will drive difficult speakers quite well and has very good bass control. Running in class A is the best possible sound for this type of design. The 6CA7’s (=EL34) in this amplifier give a beautiful full musical sound with plenty of controlled bass punch and crystal clear highs.
The Topaz uses very little negative feedback (less than 4db), this is testament to its stable design and use of quality parts.
Power Output - 33 watts per channel
Frequency response -3db - 8hz to >70khz
Signal to Noise - >90db A Weighted
Signal to Hum - > 80db
Distortion - <0.05% at 1 watt rms
Hum Level - <2.0 millivolt
Sensitivity - 700mV
Input impedance - 100K
Speaker output 8 ohm (6 to 10 ohm is fine)
Damping Factor >6 (20hz to 20khz 8 ohm)
Weight ~20kg (~44lb)
Dimensions 440mm x 370mm x 220mm (width x depth x height)
Can also run KT77 and EL34 type output tubes.