Now that is what I call a burning amp.
What bias current will you be using?
I look forward to seeing the finished product.
I have no idea what bias current I will be using it won't be class A all the way, that would require a refrigerator to keep it cool. I would like to have 10 to 15 watts class A before going into AB.
I want to thank everyone for the help.
I want to thank everyone for the help.
Do you think it sounds best at 3 amps, or did you just use the most your heatsinks could handle?
Yes, I am in this trap.😱 8 Ohm loudspeaker, 88 db. Result, very nice sound with BA-1, but only small power for Stanley Clarkes bass, a little helpless.
I have three output devices at 2 A. More is not possible with my heat-sinks
BA- 2 with the same current has much more dynamics and Stanley feels good, but the overall sound is a little bit dull and dark in my chain. Especially compared to the Semisouth variation on BA-1.
I think I will buy new heat-sinks and go to four or five devices with BA-1.
OK! Everything its fine but I have dc offset on the speaker terminals 460mV.and trimmer P102 is on the end. (CW) mosfets are
fqa12p20 ana irfp240? Should I replace trimmer with 2kr, 5kr? bias is 3A
fqa12p20 ana irfp240? Should I replace trimmer with 2kr, 5kr? bias is 3A
It was the same with me, only 100 mA offset. 🙂
Check out if trimmer is at the zero position, than maybe you have to change the 15 k resistor ....... I suppose. I did not do it because for short soundcheck I did not want to make the effort.😛
Check out if trimmer is at the zero position, than maybe you have to change the 15 k resistor ....... I suppose. I did not do it because for short soundcheck I did not want to make the effort.😛
I suppose you have to lower one of the two 15k resistors to get the balance, but I cannot say you which one. Lowering only a small amount let us say 1k.
That was my idea when I had the problem, but as I said I was too lazy to do it......... Sorry
That was my idea when I had the problem, but as I said I was too lazy to do it......... Sorry
Yes, I am in this trap.😱 8 Ohm loudspeaker, 88 db. Result, very nice sound with BA-1, but only small power for Stanley Clarkes bass, a little helpless.
I have three output devices at 2 A. More is not possible with my heat-sinks
BA- 2 with the same current has much more dynamics and Stanley feels good, but the overall sound is a little bit dull and dark in my chain. Especially compared to the Semisouth variation on BA-1.
I think I will buy new heat-sinks and go to four or five devices with BA-1.
Why don't you do the semisouth variation on BA-2?
Toshibas at the output might help a little bit also.
3 devices should easily do 4A with 25V rails (1.33A per device).
You might also need a bigger transformer (eg 500VA or higher per channel depending on how high you set the bias).
Anyway go for it, you definitely don't want to upset Stanley.
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That doesn't really answer my question.
By the way, for push-pull output stage, 3A bias gives you 6A class A.
It would be nice if you could give some description of the sound at different bias points (eg at 1A, 2A, and 3A).
Assuming the minimum pot setting (I hope you measured it with a multimeter) gives you the minimum dc offset (ie 460mV) then you need to change R25 from 15k to 14k.
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I meant putting it at Q203. Change IRF610 for Semisouth. I think Nelson suggested it earlier.
If you can fit a heatsink on it you could also also experiment with biasing of the driver stage.
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Oh, I did this already ...... Sounds better for me, than 610. Although I do not really know what to change for the lower Vgs.
I have heard BA-1 with SS in the front stage and as a substitute for the half of the 240s and it spoiled me for any other combinations, no more F5, no BA-2, no F4 etc. ......am I crazy?
It sounds like you need to get the biggest heat sinks you can find.
You could try something like an Aleph 3 chassis but with bigger heatsinks eg 4 of these MF35-151.5 per channel (So you need 8)
Conrad Heatsinks - Products
That should allow somewhere between 300W to 400W dissipation per channel, or 6A to 8A with 25V rails.
You might not need to go that extreme.
If you could do some measurements with the BA2 while running Stanley you could determine what bias current you need for the BA1 (Probably add another 30% for good measure).
You could try something like an Aleph 3 chassis but with bigger heatsinks eg 4 of these MF35-151.5 per channel (So you need 8)
Conrad Heatsinks - Products
That should allow somewhere between 300W to 400W dissipation per channel, or 6A to 8A with 25V rails.
You might not need to go that extreme.
If you could do some measurements with the BA2 while running Stanley you could determine what bias current you need for the BA1 (Probably add another 30% for good measure).
You might also wanna look at this:
HeatsinkUSA
btw:NOT affiliated with them
I just couldn't find any cheaper ones for their sizes, if you find any please PM me.
Greetz Ava
HeatsinkUSA
btw:NOT affiliated with them
I just couldn't find any cheaper ones for their sizes, if you find any please PM me.
Greetz Ava