After completing the last power supply, I finally did some real tests on the 4-65A SE amplifier. Given the DC coupled design it is a bit tricky to do the initial calibration. I had to set the operating point of both 46 DHTs by adjusting the anode voltage through the individual gyrator load presets. Also had to balance at the same time the Salas Shunt current and output voltage to the desired levels. After playing a while with it I managed to stabilise the Salas shunt regulator.
Set the 46 to drive the output stage to 200Vpp with a 3.7Vpp (1.33Vrms) input. That is a gain of approximately 54. Here is the distortion profile:
Breadboard is really quiet with the 50 and 100Hz noise below -95dB. It’s great to see the nice 46 Super Silvertone performing only 0.09% at 200V peak to peak!
Results are promising, just need final tweaks to 600V supply and then hook the 4-65a!
Ale
Bravo, Ale! This is a remarkable amplifier. A Rite of Passage for the devoted and fastidious. Superb work. Thank you for this. -Edward
Thanks Edward! Just finished the amp and is fantastic! See my latest post
Ale