2. amps-preamps
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I have a weird buzz issue; can you help me solve the problem?

Hi - my integrated amp has a 25db persistent buzzing noise; I need help figuring out how to solve this problem.

Here’s my system:
CODA CSiB integrated amp - custom tuned to produce 25w Class A power before switching to Class B
Lumin T2 streamer/DAC
Dynaudio Focus 380 speakers
Audience AR2-T2 power conditioner w/Audience power cable
Audience AU24 speaker cable
Cardas Clear M power cable
Purist Venustas Luminist Revision RCA interconnect
Synergistic Research TeslaPlex SE outlet
Shunyata Venom Defender

Some background:
I’ve had the CODA integrated for about 5 years. The remainder of my system has come on-line subsequently (I had different speakers initially). Within a few months of purchase, I noticed a buzzing noise coming from the speakers whenever the amp was powered on (bias “on”), but no noise in standby mode (bias off). I took it back to the manufacturer, who plugged the amp into their dedicated circuit and it was dead quiet. I had the same experience taking it to a local audio shop. Thinking that it might be a noisy circuit, the local shop loaned me a lesser priced solid-state amp (I forget which brand) to bring home. I hooked up the shop’s integrated to my system and.....it was dead quiet. Now I was confused. 

A dealer loaned me a completely different system with a tubed integrated, different speakers and cables. There was even a worse buzz coming from this system than from mine. I went back to living with my system and forgetting about the buzz.

Fast forward 4+ years. I have moved to a new house in a new state. Unfortunately, the buzz remains :-( I even tried plugging the system into what the electrician was sure was one dedicated line in the house (it was in the kitchen, so I had to run an extension cord to where my audio system lived). Still, the buzz remains.

I really love the sound of my system, but this persistent buzz is a (ahem) buzz kill (sorry for the predictable and bad pun). 

I would love to get some thoughts on what I can do to get rid of this damn noise. Please help!



mwsl
oldhvymec
5,101 posts
 
You know what is strange, when you had a complete system swap a few years back it was even noiser. How does that play into it..

I'm glad to see your getting somewhere, finally..

For some reason, I keep thinking a variac, would have told you a story.
What can cause it?.. It's just the mechanic in me.  The bias is incorrect, a picky transformer?   Be interesting to know what the fix is.. Not just an amp returned, with no noise..  5 years...is a long time, to put up with noise.

I can't take the noises. LOL,  I never stop until I get the sucker.
I had a few in 45 years of hunting.. oh yea...

Neighbors, wife would use a sewing machine, and caused the problem.. 
Not when using it, all the time. If it was plugged in, the stereo was noisy.
Took two months, until I came over and unplugged the WHOLE house.
Plugged that old machine in and there it was... It was the light on the sewing machine... Turn the work light on, noise, off no noise.. push the peddle, quiet as a mouse. 

It  took two months, and 2 hours to figure it out..


Regards
mwsl OP
52 posts
 
To oldhvymec: 
“You know what is strange, when you had a complete system swap a few years back it was even noiser. How does that play into it?”

I suspect, but do not know for certain, that my previous house did have an AC noise issue. So that when I tried the second system in the house, it too was noisy. 

Yes, I put up with the buzz for a long time. I had a lot of other things going on in my life, but now, with COVID, I have more time to dig into issues that have been put on hold for a while.

Will be calling CODA tomorrow morning.
mwsl OP
52 posts
 
So, here’s a weird one. The input shorting plugs arrived today, so I installed them (for the heck of it). Not only did it not impact the buzz at all, but.......it prevented the amp from generating any sound until I removed them all! Now I know for a fact that I’ve had more than one input connected at one time (I only have one currently), so I don’t get it. 

Can anyone explain this issue? Is it at all related to what might be wrong with the unit?
jea48
4,424 posts
 
@ mwsl

Did you by chance plug the shorting plugs into an output? Inputs only.

.
ptss
1,964 posts
 
I guess the 'solution' will be found by borrowing some gear, including all your wiring and cables, and patiently swapping out til the ugly duckling is revealed. It's not rocket science--just patient organized evaluation )
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