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I'm trying to reduce the noise from my guitar to an inaudible level. So far I've done a few experiments. It gets low when I'm touching the strings-tail conduit... but not when my dad touches it or when connecting the tail to the 1/4 socket with a spare string... which baffles me. It gets low turning off a tone knob. Turning off the light does nothing. When I'm grounding with my hands the waveform pattern is the same at a lower volume. Btw, the lights on my powerbars flicker.
 
Spikes at 120hz:
 
 
Add spikes at 75hz (vscan) at close range to monitor:
 
Oscar Schmidt:
 

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Boswell Wed, 08/31/2011 - 09:22

I don't think the AudioBuddy is any way grounded through the transformer, but there should be an adequate ground connection through the Audiophile card and the PC. I'm assuming your PC is a desktop with a proper grounded power lead that has a 3-pin mains connector.

What type of cable and connectors are you using between the AudioBuddy and the Audiophile 192 card?

CaleyMcKibbin Wed, 08/31/2011 - 10:07

Boswell, post: 375743 wrote: What type of cable and connectors are you using between the AudioBuddy and the Audiophile 192 card?

I tried 2 different standard 1/4" patch cords. The waveform is a bit different, but the level is the same (-45 to -35). Unplugging the guitar drops the level a bit. Unplugging the cord from the input drops it down to -66 to -60. Using a different guitar it's the same.

It is a desktop PC.

CaleyMcKibbin Sun, 09/11/2011 - 08:48

I also tried wrapping the pre-amp like a gift in tinfoil with no inputs plugged, which showed no noise difference with the gain all the way up. Looking at the spectrum analyzer again in log view on a recording with the sample rate bumped up to 192khz the noise becomes well defined as multiples of 60. I wasn't seeing it at 96kh. Having the patch cord and guitar plugged in is just amplifying that. The SM58 on the mic slot produces virtually inaudible noise. I also learned that grounding was not working because the outlet I was using is not grounded. So, the level goes down to around the same as the SM58 on the XLR gets, -60db, when I run a guitar string from the ground part of any of the jacks to a ground slot in a different outlet.