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24th August 2010, 03:26 AM
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#1 |
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diyAudio Member
Join Date: Feb 2010
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6SN7 / 6V6 power amp : very odd behavour
I built this from scratch but it is acting very strange.
A. It sounds distorted unless you run it at ~85vac. B. The louder the input, the higher the B+ goes and the lower the AC input current goes  C. the output tube is running on the hot side. |
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24th August 2010, 03:31 AM
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#2 |
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diyAudio Member
Join Date: Mar 2007
Location: Auckland, NZ
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more info. Schematic with values and measurements at test points.
__________________
Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012 |
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24th August 2010, 03:52 AM
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#3 |
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diyAudio Member
Join Date: Feb 2010
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Schematic attached.
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24th August 2010, 04:20 AM
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#4 |
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diyAudio Member
Join Date: Mar 2007
Location: Auckland, NZ
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coool! OK 1st things 1st - you need to decouple the B+ to the input tube by putting a capacitor (say, 22uf) across the supply AFTER the 680 ohm resistor.
Is your PSU REALLY half wave? Thats gotta hurt! Anyway, no input measurements please - B+ at both tube anodes, voltage drop across both cathode resistors. Measured, not calculated.
__________________
Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012 |
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24th August 2010, 04:48 AM
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#5 |
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diyAudio Member
Join Date: Sep 2006
Location: Pleasant Hill, CA
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Are you sure your 6V6 does not melt yet?
__________________
The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity! |
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24th August 2010, 04:51 AM
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#6 |
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diyAudio Member
Join Date: Feb 2010
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Anode voltage of the 6SN7 is 200Vdc
Testing the anode voltage of the 6V6 makes it go into oscillation. Voltage drop of cathode resistor of 6SN7 is 5vdc Voltage drop of cathode resistor of 6V6 is 7VDC |
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24th August 2010, 04:54 AM
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#7 | |
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diyAudio Member
Join Date: Feb 2010
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Quote:
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24th August 2010, 04:59 AM
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#8 |
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diyAudio Member
Join Date: Mar 2007
Location: Auckland, NZ
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have you put a decoupling cap on the 6sn7 B+ yet?
__________________
Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012 |
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24th August 2010, 05:01 AM
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#9 | |
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diyAudio Member
Join Date: Mar 2007
Location: Auckland, NZ
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Quote:
__________________
Yes, conservatism thrives on low intelligence and poor information. But the liberals in politics... continue to back off, yielding to the supremacy of the stupid. It's turkeys all the way down. - George Monbiot, guardian.co.uk, 6 Feb 2012 |
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24th August 2010, 05:05 AM
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#10 | |
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diyAudio Member
Join Date: Feb 2010
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Quote:
All i had was 15uf. |
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