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Old 18th October 2017, 04:01 PM   #1
nobody special is offline nobody special  United States
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I was playing with a few circuits today:

1st: 6W single supply
2nd: 25W single supply
3rd: 25W dc output

What do you think? Anyone try this yet?
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Old 18th October 2017, 04:55 PM   #2
Nelson Pass is offline Nelson Pass  United States
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As a concept it will work fine, but this circuit can do that trick without
driving the Gate of the current source transistor. You can feed the output
of the speaker directly to the top of R6.
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Old 18th October 2017, 05:22 PM   #3
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I guess I'm not seeing it. What exactly do you mean by the output of the speaker?
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Old 18th October 2017, 05:37 PM   #4
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I think I have it now:
You have to split R6 up.
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Old 18th October 2017, 05:38 PM   #5
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Cool! Thank you, Nelson.
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Old 18th October 2017, 09:38 PM   #6
Nelson Pass is offline Nelson Pass  United States
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Usually the function of Q1 for this is as a constant voltage source (for AC
anyway), so you might want to experiment with filtering its action at audio
frequencies, maybe starting with a big cap across Q1's Collector to Emitter
and maybe increasing R8.
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Old 19th October 2017, 01:50 AM   #7
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Is the idea to fix the voltage at the gate of the current sink for the DC bias using Q1, and then modulate the Vgs using the speaker current? Is this what the bootstrap is doing on your Aleph source?
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Old 19th October 2017, 02:18 PM   #8
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How about using a separate bias network, like this? I know that it removes the bias loop, but it seems better than a cap across the bias transistor. I tried a 5V active reference and it looked very good.
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Old 19th October 2017, 02:35 PM   #9
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Or, is it better to switch to a P-channel and just implement the standard type of Aleph sink?
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Old 19th October 2017, 05:00 PM   #10
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or you can take upper part of ACA and invert polarity , as lower part of this one
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