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Old 30th September 2012, 11:03 AM   #51
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Trying the attachment again...
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Last edited by linuxguru; 30th September 2012 at 11:11 AM.
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Old 1st October 2012, 12:10 AM   #52
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Some measurements of DC offset voltage at the output, with various opamps installed:

OPA2134: < 7 mV
JRC4580: < 4 mV
LF02 (with LT1361 installed): ~ 30 mV
LF03 (fully discrete dual): < 9 mV

Last edited by linuxguru; 1st October 2012 at 12:29 AM.
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Old 1st October 2012, 01:09 AM   #53
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NE5532 (TI): ~20 mV
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Old 1st October 2012, 09:12 AM   #54
AndrewT is offline AndrewT  Scotland
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does the output offset at each 3886 outpin vary when the opamps are swapped?
Do the two 3886 offsets always match and to what discrepancy/tolerance?
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Old 1st October 2012, 10:09 AM   #55
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Quote:
Originally Posted by AndrewT View Post
does the output offset at each 3886 outpin vary when the opamps are swapped?
Do the two 3886 offsets always match and to what discrepancy/tolerance?
I can't easily swap left and right opamps since it's a dual DIP8 - the only way to do it is with 2 SOIC8 opamps on a Brown Dog or similar. However, for any specific opamp type (say OPA2134) the variation seems to be no more than +/- 50 per cent or so.

The variation between channels can be large - with the JRC4560, one channel shows about 4 mV, and the other about 0.8 mV. However, this could be due to external resistors, etc.
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Old 1st October 2012, 10:18 AM   #56
AndrewT is offline AndrewT  Scotland
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I thought you had a parallel 3886 set up.
I am referring to the voltage differences, if any, between the two halves of the parallel.
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Old 10th October 2012, 01:08 AM   #57
kmibb is offline kmibb  United States
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Do you have any objective or subjective data to give on this? Still very interested.
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Old 10th October 2012, 04:47 AM   #58
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Other than the static output offsets posted earlier, no measurements yet. The good news is that it is stable or could be made stable with a fairly wide representative sample of dual DIP8 opamps, with very minor tweaks. I have a very similar 2nd prototype in the assembly stage with LM3876, instead of LM3886, for comparitive testing. I hope to audition both shortly.
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Old 14th October 2012, 06:31 PM   #59
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Default Congratulations!

Congratulations for your design.Keep up the good work.
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Old 16th November 2012, 05:43 PM   #60
kmibb is offline kmibb  United States
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Any news?
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