Hi, I have constructed a Zen Version 4 amp and am in the testing phase. I tested the amp circuit without the regulator by feeding 42 volts to the drain of Q2. All is well, with all the voltage checkpoints and bias currents measured as expected. I have tested the zener regulator: 50 volts in, 46 volts on the zener stack and 42 volts output from Q5. I have loaded the regulator with a 20ohm resistor (to simulate a 2 amp current draw) and it works fine. The problem is that when I connect the regulator to the amp circuit the output voltage from the regulator drops to 33 volts. Q1 stays biased at 23 volts, but only 33 volts are at the drain of Q2. I tried removing the r/c feedback to the gate of Q5 with no change. I am using the PASS labs circuit board and have triple checked all components and connections. I have replaced all of the transistors also but still have the same problem. Where did the lost voltage go??? TIA, Bill
when i built Zen V4 and tested it, it made some oscillation at 166kHz if the wires and interconnects from Powers supply to the PCB are bad. I used some very thin, long and and cheap Crococables and they made bad PS and regulator ? oscillation. I had less than the voltgage expected behind the regulator. After using short 1,5mm^2 hard CU wire and soldering the interconnects everything was fine.
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