GM-70 Single Ended Class A Amplifier- Model 1

This is the prototype custom made to order Single Ended amplifier with separate power supply unit. The output tube is Russian NOS GM-70 running in pure Class A1 generating 30 watt RMS/CH. The circuit utilizes famous SILK I-311-S interstage transformer driven by NOS 6BL7. Input is NOS 6N1P.
The output transformer for this amplifier has been specifically design & wound to withstand +1,000 Volts while capable of response from 10Hz to 70,000Hz at -3.0dB at full power level. The two most important aspects in our output transformer design are to reduce insertion loss and distortion factor. Insertion loss can be viewed as the power loss in output transformer (normally in heat and vibration form) whereas it could have been transfered to drive loudspeaker. We understand the utmost important to improve our output transformer design and aware that every 0.1dB of insertion loss reduction, we can hear more not only dynamic, but also details. Distortion factor in output transformer is the topic that most specification sheets do not refer to. It is one of the major causes that make each output transformer sound different. Ideal output transformer should only transfer signal and should not add any impurity to the signal. Real world output transformer is far from ideal. The lower distortion factor in output transformer, the better the output transformer, thus the purer sound. Low distortion factor output transformer will not make tube circuit sound like solid state; however, low distortion factor output transformer will make you hear more tube sound. We believe that real tube sound is not neccessory mean higher harmonic distortion than solid state counterpart, rather it is more about life, feel and esthetic.
The drive circuit to drive GM-70 is very critical since big Triode like GM-70 need more than 250V drive signal in order to get clean power of 30 watt RMS. The best approach in building such high driving capability circuit with low harmonic distortion is the use of Interstage coupling. Our popular SILK I-311S is the best candidate in this circuit since it can handle large DC current of 6BL7 with ease. This setup can deliver full drive required by GM-70 with less than 1% distortion.
Traditional point to point wiring assembly with well component layout ensure top sonic performance and reduce noise.
Robust separated power supply unit also features point to point wiring to maximize current driving capability. We also address the noise issue usually associated with high power, high voltage tube circuit. We use regulated filament supply mixed with AC filament that allow us to lower noise and hum level while not forget to address the sonic issue.
Overall sounding performance of this GM-70 SE amplifier is awesome. Unlike most conventional big triode SE amps which has big sound yet slow pace (due to big output transformer with high insertion loss, and high distortion), SILK Interstage coupling transformer in this circuit does improve speed and impact of the sound performance while retain details, dedicacy and refinement from ultra low distortion output transformer. Drive performance is also excellent due to low insertion loss output transformer. It displays absolute control over the large 15" woofer of JBL studio monitor of our Client.
GM-70 Single Ended Class A Amplifier- Model 2
This is additional variant of our Custom made to order service.