another small tip
once constructed one amp that schmatic was "given" to me together with allready made pcb by one designer ....
on this design much more simple than yours the vas ( on the pcb ) had a proper position and driling so a small heatsing together with one screw was there to attach the vas horizontally on the pcb with heat sink
the heatsink and screw it shelf was enough to drive the amp to serious oscilation.... replace the all assembly with a vertical installation of transistor away from pcb traces and isolated from the heatsink and amp works grate !!!!!!
i think your problems lay arround c4,5,6,7,8,9,10,11 and so on .... i would focus there
once constructed one amp that schmatic was "given" to me together with allready made pcb by one designer ....
on this design much more simple than yours the vas ( on the pcb ) had a proper position and driling so a small heatsing together with one screw was there to attach the vas horizontally on the pcb with heat sink
the heatsink and screw it shelf was enough to drive the amp to serious oscilation.... replace the all assembly with a vertical installation of transistor away from pcb traces and isolated from the heatsink and amp works grate !!!!!!
i think your problems lay arround c4,5,6,7,8,9,10,11 and so on .... i would focus there
Yes I builded this amp also in a PCB made by me with correct layout "I believe" (I will post picures when I can). In simulations works like a charm having THD somewhere If remember 0.0005, I will check anyway. The think is that it oscillates easily.
Saki thnx for your comments. My current class AB amplifier which I builded and is working years is using exactly the same OP stage with this capacitors in +-49volt rails. In the amplifier we discussing I tried to remove the 680 pf but I had the same results. As a final try I will remove also the 47 pf capacitor and I will also play with the vas from 22 to 100 pf.
Thnx
Saki thnx for your comments. My current class AB amplifier which I builded and is working years is using exactly the same OP stage with this capacitors in +-49volt rails. In the amplifier we discussing I tried to remove the 680 pf but I had the same results. As a final try I will remove also the 47 pf capacitor and I will also play with the vas from 22 to 100 pf.
Thnx
Yes is oscillation free but with transistors TIP31C-32C and 2SB817 2SD1047. The input stage is completely different with bipolars of coarse. Today I am trying to do the same with input fets and new output stage of 2sc5200, .... The second zobel is not inductor only parallel wired resistors. The rated power is ~110 rms/ch (100 ma bias /per device)
hmmmm
you may not like this ....and i am sorry but its just my opinion and you are very welcome to call back ....
on second look i had at your circuit ...more carefully i think i dont like it ....
i will remember once Carlos Destroyer x used to say that when he used multiple outs in one amplifier he could actually listen the second pair of transistors "ringing" or at least this is what he thought ....
i clearly dont see the benefit of the second pair of drivers ( you are welcome to tell me about it )
and then again it is clearly stated that in multiple sziklai outputs it is needed to have resistors both in the collector and the emiter ....
unless very carefully matched ?????? also not sure about that ....
it seems obvious to me that each pair of transistor and driver will perform .....actually as it likes ....meaning that with fast transistors this is going to oscilate like hell
it seems to me that this only, is a very good reason to make amp unstable ....let us not forget that in this output configuration the output itself provides some gain and this could be easilly create problems ....
any way regrdless my comments this will be interesting to play with to see if possible to make work properly ....if so that would be a very nice amp ....
regards sakis
PS
( since your signature says that you are Athenian it would be very interesting to meet and why not work this out together )
you may not like this ....and i am sorry but its just my opinion and you are very welcome to call back ....
on second look i had at your circuit ...more carefully i think i dont like it ....
i will remember once Carlos Destroyer x used to say that when he used multiple outs in one amplifier he could actually listen the second pair of transistors "ringing" or at least this is what he thought ....
i clearly dont see the benefit of the second pair of drivers ( you are welcome to tell me about it )
and then again it is clearly stated that in multiple sziklai outputs it is needed to have resistors both in the collector and the emiter ....
unless very carefully matched ?????? also not sure about that ....
it seems obvious to me that each pair of transistor and driver will perform .....actually as it likes ....meaning that with fast transistors this is going to oscilate like hell
it seems to me that this only, is a very good reason to make amp unstable ....let us not forget that in this output configuration the output itself provides some gain and this could be easilly create problems ....
any way regrdless my comments this will be interesting to play with to see if possible to make work properly ....if so that would be a very nice amp ....
regards sakis
PS
( since your signature says that you are Athenian it would be very interesting to meet and why not work this out together )
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