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I suddenly have a weird buzz issue; can someone help me solve the problem?

Hi all,

 

To provide some background, My system is as follows:

 

A “headless” Mac Mini as Roon core (my hands are tied with respect to using the MacMini, as I use Theoretica Physics BACCH4Mac cross-channel cancellation software/filtering to achieve "true" 3D sound, and this requires the player/streamer be a Mac device), outputting USB to a BelCanto RefLink USB-to-SPDIF converter, outputting SPDIF to a Mojo Audio Mystique v3+ DAC, which feeds a custom-built Dennis Had LP-2030 preamp, which outputs to a custom-built Dennis Had Inspire KT88 FireBottle SEP amplifier (max output, depending on tubes, is 12 WPC). Speakers are Coherent Audio GR-15 Neo Signatures.

 

All components are plugged into a Puritan PSM156 conditioner. I also have a GoldenEar Forcefield powered sub (amp is like 1200 watts) that is plugged directly into a dedicated outlet.

 

About a week ago, I became intrigued with the idea of powering my system completely off the grid, as even with the Puritan, I still noticed my system sounded markedly better on certain days and at certain times of day than others.  Also, there was some hum/buzz from the system, which I assumed was still AC-related, as it seemed worse at certain times of day than others.

 

I followed the guide from Ric Schultz here:

http://tweakaudio.com/EVS-2/Inverter_Power.html

 

All necessary components arrived, and I got them all hooked up.  Everything except the powered sub is plugged into the Puritan, which is now being fed by the Giandel inverter.

 

Interestingly, when I powered everything up, the previous hum noise is gone (yay!), and the sound is glorious when music is playing, but I now have a buzzing sound coming from my speakers (when nothing playing) that increases as I turn up the volume on my preamp. I tried installing cheater plugs on all components, lifting everything from ground, as I thought it could have something to do with the sub being plugged into the wall and the other components all going though the Puritan and the Giandel inverter, but this made no difference at all.

 

I would be very grateful for any advice/suggestions on what I can try.

 

One thing I noted is that the inverter is putting out 122 volts. I am wondering if the preamp is “unhappy” with this slightly high voltage and would prefer something closer to 115-118 volts, as read on another forum that this may be an issue and that one can test this by using a Variac, but I don’t know enough about electrical things to know whether it is a valid point or not, and I don’t know if I can plug a Variac into the inverter or not to test this possibility.

 

Thanks so much,

Chris

cporada
pennfootball71's avatar
pennfootball71
274 posts
 

Try a spare solid amp and pre

if there is no hum it’s your tube stuff 

if there is a hum you have dc on the line and need to install a dc blocker in your house power box 

jriggy's avatar
jriggy
562 posts
 

This may or may not be useful… I recently demoed a new preamp. I’ve had a silent system for years and years, with many component changes but the new preamp brought a hum with it like you describe. The culprit ended up being the Puritan 156 or so it seemed. Tried one balanced transformer power conditioner and tried a passive Furutech power filter strip. Both had not issues. Went back to the Puritan and there was the hum again. BUT a cheater plug on the DAC solved the issue. 
 
Both the preamp and the Puritan have ‘special’ builds so they say, with a quite different and powerful, U.S. patented, power supply on the preamp (called GreenForce) and the multiple filtering stages of the Puritan, evidently being ‘special’ and not seen from any other company, made us feel there was simply a mismatch somehow between the 156 and the new preamp’s power supply. 
 

cporada OP
36 posts
 

Thanks all, for the additional suggestions. @pennfootball71: I don't think it should be DC, because the Puritan has a DC blocker and because I'm running the system off a battery and pure sinew wave inverter. I have an old SS preamp that I can try, though, since the buzz/hum does not appear with just my tube power amp - that's a great idea!

@vinylshadow and @jriggy - I will try cheater plugs. I don't think it's a ground loop, as I installed cheater plugs on all components and the buzz/hum remained, but I did not try installing the cheater plug on one component at a time, so I will give that a try.

@jriggy: that's quite interesting about the weird interaction of your preamp and the Puritan, but that putting a cheater plug on your DAC solved it. I will do some testing with the cheater plugs one at a time. I'll also try plugging everything into just a piece of junk power strip in lieu of the Puritan and see what that yields.

Thanks!

Chris

davidrolon's avatar
davidrolon
39 posts
 

Longshot reply here. Had persistent buzz/hum. Called Steve at Decware. Thought it might be the amp. I started listing the numerous components in the system. He told me to shut up. He asked if there was a WiFi router near the components. I said yes. He said move it. I did that. Noise gone.

wolf_garcia
6,695 posts
 

I recommend the song, "I'm through with Buzz" by Steely Dan. That should fix it.

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