Huge voltage drop on PSU
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 27th January 2013, 12:17 PM #31 SjoerdSmits   diyAudio Member     Join Date: Apr 2012 Location: Maarn Ah ok, thanks! I will start with just a wire and see how much current is drawn. Then I'll (try to) calculate the resistor needed. Thank you so much for the much needed help! Kind regards, Sjoerd
 27th January 2013, 01:08 PM #32 SjoerdSmits   diyAudio Member     Join Date: Apr 2012 Location: Maarn Did the work and all is dandy :-) The DC offset is going crazy (back and forth) but no big problems whatsoever.... Question: If you have say +- 30mV DC offset.... what can you do about that? Kind regards! Sjoerd
 27th January 2013, 02:10 PM #33 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK When measuring the offset ensure that you have a shrting plug at the INPUT of the amplifier.
 27th January 2013, 02:13 PM #34 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK Just as a starting point, once the amplifiers are stable and you can measure the DC current being drawn from the power supply. You might be looking to drop approximately 1V across the X3 and X4 resistor. If the two amps are drawing a combined current of say 3A. R = E / I.........so R would be 1 / 3 Ohms = 0R33 P = I ^^2 x R.......so it would need to be at least 3W ...... 5W would be better.
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Join Date: Nov 2011
Location: UK
Quote:
 Originally Posted by KatieandDad When measuring the offset ensure that you have a shrting plug at the INPUT of the amplifier.
That should read SHORTING plug .

 27th January 2013, 02:50 PM #36 SjoerdSmits   diyAudio Member     Join Date: Apr 2012 Location: Maarn The plug results in a DC offset of 0.3mv... thats good I guess... but when I take the plug off, the voltage goes to 3 vdc.... normal?
 27th January 2013, 02:52 PM #37 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK That's normal. With a floating input you will get fluctuating output. If the DC offset is only 0.3mV with the shorting plug then you are ready to carry on.
 27th January 2013, 02:55 PM #38 SjoerdSmits   diyAudio Member     Join Date: Apr 2012 Location: Maarn Ok, thanks! I think it's time to connect some speakers :-)
 27th January 2013, 02:56 PM #39 KatieandDad   diyAudio Member     Join Date: Nov 2011 Location: UK Always try some cheap spare ones first time....
 27th January 2013, 02:57 PM #40 SjoerdSmits   diyAudio Member     Join Date: Apr 2012 Location: Maarn Haha, good point! I'll do that.... I'll let you know how it turns out :-)

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