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QRV-08 hum

Started by CapRock, February 01, 2011, 03:52:46 AM

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CapRock

So I wired it up today and tested it and it works.  there is no buzz/hum until the last 2 steps of my attenuator and it is almost not audible, so it is very low.  LED's are still dark though.  I tried to adjust the bias trimpots and they have no effect on the voltage across R1/E1.  E1 was reading .006VDC and R1 was reading .022VDC.  The sound is good and it stays tight and clean even when very loud.  I have to leave the jumpers on though because when I remove them the sound was crackling and distorting.  Any Idea why the trimpots wont work?  Also, as I said before I am not very familiar with oscilloscope's, so what is it exactly that you would like me to measure and how do I measure it?  I'm  sure my friend that owns the scope will be able to help me though this, thanks.

peranders

The reason why the LED's not are on is that the input voltage is too low, assuming that the regulators are correct.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff

CapRock

since my voltage is not high enough do you think I am still not hearing the full potential of the amp?  If it is worth it I will continue to search for the problem.

peranders

The amp will most likely work properly but the power supply rejection isn't so high so clean supply is essential but as you have noticed a small of hum will slip through. It would be interesting to see how your raw voltage look like. Depending how it look you can disable the LM317/337 preregulators. By this you will "earn" 2-3 volts but it could be tricky if you don't have the right tools.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff