Recent content by BMG123

Hi Sweetbeats and wkrbee (thanks again for the hook-up on the manual) so reading your responses I ran across a video talking about eliminating ground loop noise. this guy suggested a product made by ifi-audio called a ground defender link: https://ifi-audio.com/products/gnd-defender/ It's a bit...

Sweetbeats, I ended up taking the 388 to my buddy's and there is no AC present across the power rails. So at least we can rule that out. But this gets more interesting... With just the Stereo outs plugged into the amp, it's dead quiet. So I figured I'd start adding things and see when hum gets...

Perfect! I think I have a shot at getting my buddy with the oscilloscope to come by here next week. We will review all your suggestions and hopefully get to the bottom of what's going on. Now the hunt is really on, I won't give up till we find and fix the issue. I'll keep you posted on our...

Nope, that other poster is me :) No confusion on your part. I jumped over to this thread after I recapped the power supply. I ended up reading most of the pages in the "388 story" and picked up here. I'll see if I can get those measurements myself. I do have a friend with an oscilloscope but...

Thanks! So this goes back to the original thought that AC current is getting through the power supply, correct? I don't have access to an oscilloscope but was looking on line to see how much they cost. I saw some small versions of "pocket" oscilloscopes for $60 to $80. Here is a link...

Sweetbeats, I know my DMM doesn't have a frequency counter but here is a short audio clip from my phone. You can hear me move from the woofer to the tweeter as I had it in record. Not sure if this tells you anything (besides how annoying this sound is) but I thought I'd try. Brian

Good evening Sweetbeats, sorry for the delayed response. I'm the tech director for a high school and our musical opens in less than a week. I've been overtime getting things ready for the show. Anyways, its Saturday and I'm back in front of the 388. first: set your DMM to DC volts and measure...

Sweetbeats, your description was spot on and easy to follow. I checked resistance from a chassis screw on the Adcom preamp to the ground prong on the AC plug and made sure it was s dead short. Then I attached two wires form that screw and re-tested to the ground prong to the end of each wire...

There is not, I've been looking for anything that has a spot to connect an extra external ground wire and keep coming up short. If your theory is correct, wouldn't the noise stop if I unplug the monitor output? Wouldn't that break the antenna? Because as of now, the noise is present only when...

One final note.... that the volume of the noise/hum is affected by the master fader. Gets louder and quieter as I move it up and down. With the fader all the way down, no noise. Brian

Sorry those pics are so big! I just find it odd that the noise/hum is only when the main stereo outs (either RCA or XLR) are connected to the preamp. The instant I unplug those from the 388, the monitor feed to the headphone amp is silent. With the mains plugged in I hear the hum/noise through...

Thanks Sweetbeats, not that I see. Are are pics of the back of all three:

Good evening Sweetbeats... Had a crazy busy week but finally back in the studio and, as you predicted, the noise is back. If I only plug in the monitor outs to the headphone amp everything is quiet. The minute I plug the stereo out going to the Adcom the noise comes through the monitors AND...

This make sense! The Adcom does have a 3 prong power cord it's model Adcom GFP-815. But working to get the other two to be grounded makes sense. Or at least connected to the Adcom. The phono jack has a threaded ground post..can I tap off that? I'll spend some time with page 31 of the manual. I...

So the gremlins seem to have moved on...I did try exactly what you suggested. The Adcom has six inputs plus a phono channel so I was able to run both the MONITOR and the STEREO outs to the Adcom and had no noise. I went back and tried the initial hook up again AND HAD NO NOISE! I did go through...