Burning Amp BA-3

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#64
After a longer hearing I can say the BA-3 frontend with crippled F4 has a clearness and a articulation I first heard in a similar way with F1J......

it is not a sweet sound ....

But I still can try P3.....forth and back.....

- end or comments- 😀
 
#69
This remark is very intriguing, well worth a try, imho only doable if you have a distortion meter:
Adjustment of P3 will bring the second harmonic out, and as you turn the wiper toward the Source of Q1 you favor the positive going waveform. When you turn the wiper toward the Source of Q2 you favor the negative going waveform. Favoring the positive going waveform is possibly preferred – with proper speaker polarity, this mimics the acoustic character of air.
Click to expand...
albert
 
#71
Oh, at the moment I use simply 1uF Silmic II, I measured the voltage over the cap and it was about 6V, so I thought enough to keep the Silmic working.....

Later I will try others....

this morning I had first time in my diy career the beginning of an ugly noise over the speaker in one channel of BA-3 and crippled F4.....

I must search what happened.........

I had to much euphoria with my quick built .....

better buy the boards......point to point is even more reliable because you are fully concentrated, so you think board will do everything....only some small changes....and you do not see other "small changes"

he,he,he😀😀😀
 
#72
Papa writes:
R8 and R9 help set the voltage gain, and they also help stabilize the bias of Q3 and Q4, else it would tend to drift upwards as the parts warm up.
Click to expand...
and further down:
achieve the correct bias voltages across R8 and R9 (about 1 volt)
Click to expand...
you can experiment with higher bias, remembering that the parts are rated at 25 watts, and that it costs you voltage losses across R8 and R9. If you want to play with even higher bias, you can consider lowering the values of R8 and R9 and also R13, all in proportion.
Click to expand...
I think he means R10, R11 :scratch1:
R8/R9 in the diagram are for (V)HF stabilisation.
albert
 
Last edited:
#74
generg said:
Oh, at the moment I use simply 1uF Silmic II, I measured the voltage over the cap and it was about 6V, so I thought enough to keep the Silmic working.....

Later I will try others....

this morning I had first time in my diy career the beginning of an ugly noise over the speaker in one channel of BA-3 and crippled F4.....
Click to expand...

Hi generg,
Did you mean 10uF?

From Nelson's earlier post:
It sounds really good.
especially if you use the parts specified.
 
#80
crackling in one channel is away,🙂

for "research purposes" I had cranked up the bias to 2V over R10 and R11 and there was a carbon resistor R10 with 22 Ohm and I forgot to get the bias back, and one Piazolla cd later he had 33 Ohm...... and was depressive.....and moaning through the speakers..... 😉

changed him against a maniac Dale...:bomb:.
 
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