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Old 17th July 2013, 02:24 AM   #1041
bcmbob is offline bcmbob  United States
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I'm being a little dense also.

I have the BA-3 FE boards ready to go, but the initial adjustment procedure from 6L6 refers to the R10 & R11 resistors. Is that on the FE before the output boards are attached , which also have an R10 & R11.

I ask thinking there must be some influence on this FE adjustment when the bias boards and output boards are in the circuit. I've completed the same adjustments on the F5 successfully a couple times, but can't determine if I need the whole package when doing it on this build. What is the sequence?
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Old 17th July 2013, 02:35 AM   #1042
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It can be done either way. The two stages can be truly independent and functional. If adjusting for certain THD, then they need to be connected.
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Old 17th July 2013, 02:37 AM   #1043
bcmbob is offline bcmbob  United States
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Thanks, clears up my confusion.
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Old 17th July 2013, 03:54 AM   #1044
bcmbob is offline bcmbob  United States
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Ah Ha! Made it to first base.

All the trimmers are functional without that nasty green smoke. Due to my handy-dandy home-made heat sinks I had to add some extensions to reach the resistors. I didn't want to buy the Audyn Plus caps for C3 yet, so I have to steal one from an old crossover to get the twin for this one - in the morning.

Haven't decided stereo, dual mono or mono-block yet so I used the F5 PS for the power feed.

Thanks all for the assists.
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Old 17th July 2013, 11:03 AM   #1045
bcmbob is offline bcmbob  United States
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Next step - new question.

Can someone explain the function of "S" on the bias and output boards. I found some references among the various threads, but no clear definition. Don't see it in NP's introductory docs either.
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Old 17th July 2013, 11:14 AM   #1046
generg is offline generg  Germany
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The S point feels the voltage at the first source resistor and feeds it back to the bias circuit, to keep the bias constant, even when heating up.
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Old 17th July 2013, 11:22 AM   #1047
bcmbob is offline bcmbob  United States
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Now that's what I call a clear definition - thanks. So for a single output board having an S pad on both ends is for convenience/flexability, correct? If I add a second output board to each channel, do I need some sort of "S" continuity between those to feed back to the bias board?
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Old 17th July 2013, 11:41 AM   #1048
generg is offline generg  Germany
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Both ends is for conveniance, right.

Connecting one more board.....hm, hm, .....I have the impression the S point feels only the voltage at one resistor and adjusts the current accordingly for all the other pairs without any more connection....but

I am not quite sure in this case.....logical thinking is often difficult for me....

Andrew T. are you here....?
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Old 17th July 2013, 11:45 AM   #1049
bcmbob is offline bcmbob  United States
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Yea Andrew, where are you !
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Old 17th July 2013, 05:16 PM   #1050
AndrewT is online now AndrewT  Scotland
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I don't understand the question?
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