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Old 9th June 2012, 04:51 PM   #41
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The building quide is saying adjust to 370mA(P1) but where do you've to hold your probes?Voltage drop over source resistors would be much easier.
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Old 9th June 2012, 05:15 PM   #42
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hugh's reply to me when i asked the same question .

I measure the bias current across the 0.1R source resistors. I set 40mV, which corresponds exactly to 400mA. You'd find it's rock steady and quite non-critical to set. The use of three diodes in a string and a much reduced rheostat (read 'pot') all in series makes this adjustment a doddle.

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Old 9th June 2012, 07:59 PM   #43
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Setting of the offset with open or shorted input?
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Old 10th June 2012, 08:59 AM   #44
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Short the input with a dummy zero ohm load. Fit a dummy infinite load to the speaker terminals, i.e. no cables , no speaker.
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Old 10th June 2012, 09:03 AM   #45
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Quote:
Originally Posted by Woody1911a1 View Post
......... measure the bias current across the 0.1R source resistors. I set 40mV, which corresponds exactly to 400mA. ......
That is equivalent to 80mVdc from TP1 to TP2 where there are two source resistors in series. 80mVdc arrives at the same 400mA of Ib.
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Old 10th June 2012, 09:18 AM   #46
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The offset setting isn't steady it keeps dancing around
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Old 10th June 2012, 09:36 AM   #47
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Both my FetZillas do the same.
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Old 10th June 2012, 09:41 AM   #48
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only one channel ready
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Old 10th June 2012, 09:49 AM   #49
AndrewT is offline AndrewT  Scotland
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The Forum does not like me repeating my posts, but the FetZilla outputs are the noisiest I have ever tested for a correctly operating amplifier.
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Old 10th June 2012, 10:29 AM   #50
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Andrew,your answers are very precious for me cause I know your background and you're skilled.What's the reason for not a steady offset?
The amp is playing sounds good but when I insert a DC protection unit between my speaker cable it kicks in right away.
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