I've had the same problem but only with ordinary PSU. It disappeared when I put Cap multiplier. I am surprised that you have that problem with cap multiplier.
Could it be that some component was bad or damaged during soldering/assembly?
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Hi Pete
I have a question about your layout. Do you have places for compensation caps? My breadboard Peeceebee is an oscillator using the higher voltage transistors. I am wondering if there should be places for compensation caps on each pair of transistors.
My heavily compensated VAS stage continues to oscillate but at <1Hz. Obviously there needs to be some compensation somewhere else. It could also just be the breadboard has outlived its usefulness and I need to get the amp built on a well layed out PCB.
I have a question about your layout. Do you have places for compensation caps? My breadboard Peeceebee is an oscillator using the higher voltage transistors. I am wondering if there should be places for compensation caps on each pair of transistors.
My heavily compensated VAS stage continues to oscillate but at <1Hz. Obviously there needs to be some compensation somewhere else. It could also just be the breadboard has outlived its usefulness and I need to get the amp built on a well layed out PCB.
Yeah. That's what my conclusion is as well. I'm sure there's something simple I've overlooked that I haven't found yet. I've swapped positions of xformer and psu but the hum is actually worse now. Will continue to work on it. I also swapped out psu to no effect. Both channels continue to have same characteristics. I want also to change out xformer too. Will keep trying.
I also want to build Pete's latest version/layout of Shaan's peeceebee. The hum is not audible until I do nearfield listening. I switch to my incredible p3a/PMI cap multiplier for nearfield sessions. Thanks all. -freeman
I also want to build Pete's latest version/layout of Shaan's peeceebee. The hum is not audible until I do nearfield listening. I switch to my incredible p3a/PMI cap multiplier for nearfield sessions. Thanks all. -freeman
I've had the same problem but only with ordinary PSU. It disappeared when I put Cap multiplier. I am surprised that you have that problem with cap multiplier.
Could it be that some component was bad or damaged during soldering/assembly?
Thanks for the compliments, everyone, and also for the earlier feedback and suggestions. To answer some questions/comments:
I may open another thread to have a place to post some of the details, parts discussion, etc.
However, both the caps and the heatsinks need to be close to the transistors, one can't have both components with the largest possible footprint. Some older types of Silver Mica caps are just too big. Most people can probably use fairly small and inexpensive NP0-type caps.
Circuit boards, around $20 for a set of two boards. Parts, I am still working on that, and not ignoring the questions from earlier from other people: Thanks to help from a couple other members, I have enough of the KSC3503 E-grade parts and BC546C/556C (for supply voltage over 45V), as well as some other options. I am looking forward to some comments and suggestions for other options.
My first goal is to make a few boards for the people who follow the PeeCeeBee thread, and who have provided feedback and suggestions that have helped me in the past. This way they will get a set with minimal waiting. As long as the manufacturer lets me use the prototype discount for these, it is manageable. I also wanted to avoid confusion with LC's second VSSA group buy for the original modules.This is an excellent alternative for VSSA fans who prefer TH parts (like me
I may open another thread to have a place to post some of the details, parts discussion, etc.
Yes, good question. I already had pads for compensations caps, but some caps did not fit well with larger heatsinks. In the revised layout, I allowed more room around the VAS transistors, for bigger heatsinks, and two sets of pads for caps. I hope this time, there is enough room to experiment.
However, both the caps and the heatsinks need to be close to the transistors, one can't have both components with the largest possible footprint. Some older types of Silver Mica caps are just too big. Most people can probably use fairly small and inexpensive NP0-type caps.
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So much for my idea... Try moving the wires from the rear RCA jacks/inputs around a bit with power on and no music playing, and listen for the hum changing. If the hum changes, especially with the distance of the input cable from the transformer, then there is some EMI-type effect taking place.
The other thing I would try is to rotate the transformer a bit back and forth around its bolt, which will change the position where the secondary winding wire is positioned, and listen to the hum. What kind of transformer are you using?
Hi Pete,
Using antek, 24v/300va. I have an Avel 25v/330va that I will swap in eventually. I may just turn full attention to building your new layout if you have extra boards. Pretty sure that my issue is some simple rookie mistake that I will uncover any minute now. Thanks, Pete.
Using antek, 24v/300va. I have an Avel 25v/330va that I will swap in eventually. I may just turn full attention to building your new layout if you have extra boards. Pretty sure that my issue is some simple rookie mistake that I will uncover any minute now. Thanks, Pete.
You are welcome,
It does not actually have to be a "mistake", wiring can be an art, sometimes with some black magic thrown in for good measure. Two people can do the same thing, and get different results. I have already noticed that P3A is much less susceptible to radiated noise than other diy amp circuits. No idea why.You were already on it, from earlier. I have not forgotten about the lower-voltage version of the power supply, but it has been a busy few weeks, and not enough time to play,
No problem Pete. In fact I'm having second thoughts about using the LV CM for my preamp build. I'm using the Elliot p125 xover buffer section as preamp. It is of course opamp-based and I've come to learn it may not benefit from the CM psu. I will continue this discussion with you elsewhere but no need for you to divert attention from this fine amp project on my behalf.
You were already on it, from earlier. I have not forgotten about the lower-voltage version of the power supply, but it has been a busy few weeks, and not enough time to play,
That looked like a cool option from the start, sort-of a PeeCeeBee on steroids... and, I believe you can get Alfets in that package!
BUZ and ALFET are modern parts that are suitable for the build. Apparently Terry had a dead amp with some of the original Hitachis like the ones I had on hand that check out to be good. I'm hoping to make the build pretty much bomb proof for him so he has a good experience with the build. One could mount the Renesas TO-247 parts under board on my design too.