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Old 3rd May 2007, 11:05 AM   #1
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Default UcD400 Gain Issue

I got a UcD400 back from repair a few days ago, hooked it up today, and it has very low gain. I checked all of the gain setting resistors. This is using a SE input, with the - input grounded.

Everything functions perfectly, except it is quite a bit quieter than any other UcD400 I have in house right now.

Any ideas on this? I am stumped after about 2 hours of swapping cables, checking all connections etc.

Thanks,
Paul
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Old 3rd May 2007, 12:40 PM   #2
BWRX is offline BWRX  United States
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Measure the gain of the modules to find out for sure.
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Old 3rd May 2007, 12:51 PM   #3
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Not sure what you mean by that... just input voltage to output voltage....

That I can tell with my ears, around 10dB less on this particular module.

-Paul
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Old 3rd May 2007, 01:00 PM   #4
BWRX is offline BWRX  United States
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10dB is a pretty significant difference!

If they have the same gain setting resistors then they should have the same voltage gain (the modules and power supply are exactly the same otherwise right?). Just use a 1V test tone and measure the output voltage. If the voltage gains are significantly different, which they should be according to what you're hearing, send your information to Hypex. Something clearly isn't right there.
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Old 3rd May 2007, 01:50 PM   #5
Pierre is offline Pierre  France
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Why did they fail? I mean, why did you send them for repair?
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Old 3rd May 2007, 02:35 PM   #6
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Fixed it, lifted the trace on the - input underneath the opamp when I was swapping.

I am not sure why it broke....

-Paul
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