maybe a late reply, but comparing sony D6C and PMD430 side by side, the famous D6C stands no chance. I mean both recording and playback. 430 wins hands down. I have not heard D5M yet, but I assume D5M has pretty good playback ( not recording though) 

Quote: I agree, while I was testing the output wave form, I found out even though this circuit has overall flatter FR, but I also tried loading the upper two transistors with resistors or CCS load. and resistor load clips very clean and smooth, sounds like a triode, CCS is a little harsh...

Hi W, the base of Q8 and Q9 shall connect to the upper side of each 150K resistor.    Sorry about the confusion but my schematic was pretty clear about where the base of the Q8 and Q9 shall be connected at.    Let me explain a little about this circuit, this circuit is like a class A...

Sorry. Power supply is 400v. Bias set at 200v. First stage at 1.3ma and the second stage at 3.9ma. Donny

Q2 and Q3 are bjts that will take inputs, + and - or can be unbalanced  Output are from the emitters of Q8 and Q9.    This is a SRPP + emitter follower. almost flat down to 30Khz, according to my scope measurement 

Quote: Hi W, Can help comment on this circuit? I come up with this last night and did a quick build, it performs very nicely with almost no distortion, yet no feedback is used.   

Quote: thank you for your comments. I built the circuit using actual transistors and resistors as shown in the circuit, and based on my experience, once adjusted, the bias is pretty stable and will not drift that much ( Once adjusted, within in 60 seconds the DC output will move up and down...

Quote: Thank you very much for your help running the simulation. looks great to me. I dont know how THD is measured but 1.6% is a lot. I am looking to optimize it by altering the resistor values. I set up this circuit last night for a quick listen and some tests shows resistor value can...

I don't know why but simulators never likes my design. Haha. But I tested the circuit as shown and it works perfectly fine. R7 R3 and R4 are not accurate and needs to be trimpots. otherwise the bias won't be 1/2 of the power supply.

Sorry the bias is not right. The capacitor connects to the upper side of 20k resisitor and provide bias via two 20k resistors to q3 and q4

I am looking at the circuit as well, it's a great little circuit but it has op amps in it. My experience with op amps is that it requires another supply(12v) and also introduce high freq noises. I used to own sr001 and I really enjoyed its smooth sound, I guess the 130k resistor really helped to...

I did a quick draw out of the circuit I have, if any of you feel this can be a interesting project, you can do a quick PCB prototyping. I don't mind if any of you want to produce it or not, I already post the schematic so I am sharing it and giving it away for free. But if anyone designed a PCB...

test:  triangle wave, 1khz, +-100V output:         6KHZ square wave, because i only have fiio e10 as the source and the wav is 44.1Khz, so only 7 points per cycle, very poor resolution there, and this output is actually very close to the input:       saw wave at 1Khz...

Test done under 260V power supply.  basically the 100K load resistor has about 1.3ma idle current in it.  the lower transistor is taking about 4-5ma current( didnt bother to measure it, but its biased with one LED and 240 Re, so about 4-5ma). Then I adjust the variable resistor of the upper...

Today I come up with this circuit, not really SRPP, not really a cathode follower. its a hybrid, dont know what to call it, but it is now my newer version of the dirt cheap amp.  please see the attached circuit.