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
rwortman's avatar
rwortman
41 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. ( : 
imhififan's avatar
imhififan
2,204 posts
 
Many higher end components are designed by barely competent engineers.
Eric Lauchli?
mwsl OP
52 posts
 
Ordered grounding plugs for RCA and XLR inputs. Should arrive in a few days. Will try this experiment as well as the one with the breaker and report back early next week. I’m expecting that none of these will solve the issue and that I’ll need to send the amp back to CODA. I hope to be pleasantly surprised.
oldhvymec
5,101 posts
 
Shorting plugs are real good for Point To Point, cross talk.. That I do know..Buzz, Hum.. It would be a new one, but not to expensive to try.

I been reading back through the post, a couple things. A goner posed speakers? something about powered speakers. Point is, unhook ONE speaker and see if the noise goes away. Just one. Hook it back up and do the other side.

If it goes away with one but not the other,  you're CLOSE!

If the speakers are bi ampable? PULL the jumpers, ok Bear with me..

Again one at a time. First top (highs) then the bottoms 

I'm noisy, bare with me.

Clean the jumpers, get zip cord, I don't care BUT change the jumpers
clean the post all of them

If none of that works. Cost nothing, right.


The Second a Variac, you happen to know anybody with one?

You need to have a variac, though.
It didn't dawn on me to try.  It's kind of second nature for me, tinkering to use a variac.. I've had transformer noise, and speaker noise, and stopped it with a Variac. It WAS NOT the cure but it lead to one. A pair of filter caps, and a cheap pair of mismatched bridge rectifiers. They acted up with 120 VAC but shut right up at 110 or so.

You would start at say 101-5, and really start listening and paying attention.  Again ya never know.. and it doesn't cost a dime, just time.

Gee! tough one for sure.. Plane ticket time... I'd like to try, just to see what the mystery was.. 2 hours..Tops.. I bet we could figure it out ..With a  DMM, couple wires, clips and a variac.

Happier hunting.. you'll get it...Eye of the Tiger... all that stuff..

Regards..
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