Check if 100pF at input is correctly soldered. If it is then install two 22pF to the VAS transistors, between base and collector pins. If zobel still burns then replace them with 47pF. If it still burns then one or more transistor is dead(or too alive) and you will need to unsolder and check the input and VAS transistors.
Hope this helps.
hello, 100pf correct.
33pf vas transistor, still zobel burn.
will go 66pf tomorrow. but they 140/139. no issue, no need comp cap before.
how can vas, input transistor be dead/too alive and still make glorious sound??
and could you explain what mean by too alive?
thank you 😀
oh.. i use 220pf instead 100pf to gnd at input. this ok?
also, if transistors all ok, can wiring cause oscillation? mine one pcb, 2 mono boards together with psu. all input output return star ground. speaker +, input +, not twisted.
33pf vas transistor, still zobel burn.
will go 66pf tomorrow. but they 140/139. no issue, no need comp cap before.
how can vas, input transistor be dead/too alive and still make glorious sound??
and could you explain what mean by too alive?
thank you 😀
oh.. i use 220pf instead 100pf to gnd at input. this ok?
also, if transistors all ok, can wiring cause oscillation? mine one pcb, 2 mono boards together with psu. all input output return star ground. speaker +, input +, not twisted.
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Yes, as is the amp doesn't need comp cap. But if it needs a couple of them then it does for stability. In your case it is either damaged transistor or wiring that is causing the problem.
Do the VAS tranristors share a common heatsink?
dead=dead.
too alive=change of specs by overload. 😀
A device that isn't dead but works totally abnormally is too alive. 😀
220pF ok. Parasitic oscillation is possible with incorrect wiring with good transistor. Can you upload a few pictures?
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I had a difficult time with the first Peeceebee I built. It turned out to be damaged output devices.
Hello,
in simulation, 2N5416 / 2N3440 are better than BD139/140 in VSSA schem
What do you think about using them in PEECEEBEE ?
thanks
in simulation, 2N5416 / 2N3440 are better than BD139/140 in VSSA schem
What do you think about using them in PEECEEBEE ?
thanks
They seem okay. Heatsinking could be a problem if you choose to run them at or higher than 10mA, which is a requirement while driving MOSFETs. Well, in subwoofer application 5mA will be sufficient. But if you are planning to run the fullrange signal then try to get TO126 devices. They are also easy to attach a heatsink to.
All the best.
p.s. Simulation results indicate almost nothing about how a device will behave in a real world circuit, although it helps us understand how a particular circuit works.
i have tried both 140/139 and faster bjts. same board, same comp cap 33pf. 140/139 sounds more 'mellow' and warmer. definitely preferred. 😀
You are right donovas. Superfast bjts often bring with them a strange bright characteristic even when properly compensated. The cheap, old and faithful BD pair seems to be just the right choice for PeeCeeBee.
Hi thimios.
Splendid job! Love the solid build and looks.
Just make sure that both the BD trannies have their metal backs facing the input section.
All the best.
Splendid job! Love the solid build and looks.
Just make sure that both the BD trannies have their metal backs facing the input section.
All the best.
Thimios, here is a tip for offset trimming:
Populating the positive "OFF" resistor will make the offset negative, and vice-versa.
Your board looks the closest to the ones I use. I hope you succeed at making them sing as soon as I did. Looking forward...
Populating the positive "OFF" resistor will make the offset negative, and vice-versa.
Your board looks the closest to the ones I use. I hope you succeed at making them sing as soon as I did. Looking forward...
The PeeCeeBee is a little less 'clinical' than the CCS bearing VSSA versions, though they do have a similar character. It's a nice little amplifier.
You know me. All special amps sound the same. The Peeceebee is the best sounding 6 device amp I've heard. The PMI version has 8 devices and sounds just as good. I've built two Peeceebee's. One with TO-3 and one with 2SK1058/J162. Then I built PMI version and then JKuetemann version. Can you tell I like them?
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