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Old 28th November 2011, 06:39 AM   #71
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At 35Vdc supply, can BBA3 reach that output power with just 4 X 25W TO-220?
For BBA3, what should be the minimum size of the heatsink for 50-100mA output stage bias?
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Old 28th November 2011, 06:48 AM   #72
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-which output power ?

-calc dissipation , then choose heatsink
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Old 28th November 2011, 07:12 AM   #73
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post #2 blue line
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Old 28th November 2011, 07:12 AM   #74
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Isn't it all against the second merit of BA-3 front end i.e.:
"Potentiometer P3 is provided for those of you who have distortion analyzers or want to play with the mix of second vs third harmonic. As with the F5 amplifier, you will find that you can iteratively trim P1 through P3 for minimum distortion. I do so at approximately the 1 watt output level (2.8 V). You should start out with the setting at the mid-point. The minimum distortion point will generally be where the plus and minus halves of the amplifier balance to such a degree as to null out the second harmonic. By introducing an imbalance you can variably re-introduce the second harmonic, and depending on which way you turn the pot, you can choose the absolute phase of the second harmonic."
I mean with balance version get rid of second harmonic. (the first merit of BA-3 is lack of negative feedback of course).

Last edited by Dzius; 28th November 2011 at 07:22 AM.
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Old 28th November 2011, 07:29 AM   #75
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by rolandong View Post
post #2 blue line
that's with output stage
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Old 28th November 2011, 07:32 AM   #76
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Quote:
Originally Posted by Dzius View Post
Isn't it all against the second merit of BA-3 front end i.e.:
"Potentiometer P3 is provided for those of you who have distortion analyzers or want to play with the mix of second vs third harmonic. As with the F5 amplifier, you will find that you can iteratively trim P1 through P3 for minimum distortion. I do so at approximately the 1 watt output level (2.8 V). You should start out with the setting at the mid-point. The minimum distortion point will generally be where the plus and minus halves of the amplifier balance to such a degree as to null out the second harmonic. By introducing an imbalance you can variably re-introduce the second harmonic, and depending on which way you turn the pot, you can choose the absolute phase of the second harmonic."
I mean with balance version get rid of second harmonic. (the first merit of BA-3 is lack of negative feedback of course).
you have symmetry effect between halves due to common 200 ohms resistor and overall effect of bridging .
if Papa sez that invoking 2nd harmonic can still be higher than symmetry effects , I'm not doubting that ....
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Old 28th November 2011, 09:42 AM   #77
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Quote:
Originally Posted by generg View Post
I will hear today first time BBA-3 with crippled F4
I hope to be listening to standard BA3 tonight while doing a Renasas(lateral) vs IRF output comparison. IF only I had some Fairchild fets
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Old 28th November 2011, 10:47 AM   #78
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Fairchild are on the way........to you!
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Old 28th November 2011, 10:55 AM   #79
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Yours as well. Good luck with BA3B.
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Old 28th November 2011, 01:03 PM   #80
generg is offline generg  Germany
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O.k. BBA-3 sounds pretty darned good.

I have now too much gain........for Lowthers, F4 with 1:5 xformer ( must stay in! For my golden ears!)

I looked at Zen Mods recommendations and

lowered R13 and brothers to 116 Ohm and increased R10/11 to 44Ohm, now I am in a region I can use my pots in the lower positions.

Does anybody see a problem in doing this? Of course I increased the voltage over R10/11 to 2V.
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