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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
imhififan's avatar
imhififan
2,180 posts
 
I also like to add that something like a cold solder joint can caused intermittent problem like this, that explain why the amp was dead quiet when plugged into the mains at audio store and the manufacturer.
mwsl OP
52 posts
 
Thanks imhififan. Given that you have a dead quiet amp, and mine has been “noisy” in two separate homes, I have to think that despite it being quiet at manufacturer and audio store, something is likely amiss with the amp itself. I will try your experiment, and then contact CODA for repair. 

Just out of curiosity, did you have CODA bump up the amount of Class A watts?
imhififan's avatar
imhififan
2,180 posts
 
Just out of curiosity, did you have CODA bump up the amount of Class A watts?
I wish I could, but I need most of the class B power to feed the power hungry Thiel.
rwortman's avatar
rwortman
40 posts
 
If your amp is humming or buzzing with nothing connected either it is broken or you have noise or DC offset in your AC line.  You could try an isolation transformer.  Or you could just sell the amp and but something with a design that isn't susceptible to such things.  Many higher end components are designed by barely competent engineers.
pjr801's avatar
pjr801
192 posts
 
Had a problem with an earthing hum years ago. It ended up that I had sent my TT arm away as it had a bearing issue. The bearing was replaced and shortly after a hum developed in my system. After quite a few expensive repair shops saying they had fixed it (they soldered a wire onto the deck of the TT  to create a ground when it was plugged in) it didn't work. I finally found someone who knew what they were doing. The bearing repairers had pinched the arm cable creating an earth hum. The specialist repairer I sent it to left town with my turntable and I never saw it again. Back to your problem. Get back to Coda the changes they made seem to be the genesis of your problem. It may be intermittent (the worst kind )and when you had them test it the movement may have temporarily given the problem a short term reprieve. If there is anyone from Coda on this forum they may be able to help. If Coda is a good corporate citizen I'm sure they may be able to assist you with this. My story reflects the fact that sometimes you have to find the right person to diagnose the problem as plenty of technicians go for a quick easy fix to get you out the door. It really is a job for someone that has the proper understanding of amplifier circuits. Even though it has been five years I'm sure if you rang CODA you might find someone with a sympathetic ear. As for me, I'm still tracking down that turntable and one day I might find it. If anyone has seen a Logic DM101 with a Datum 2 arm and a Garrott  P 77 cartridge let me know. ( : 
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