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Update on my Coincident Dynamo 34SE

Hi everyone,

A while back many of you gave me guidance on some hum issues I had with my new Coincident Dynamo. I ended up sending it back to Coincident for service. They said the filter caps were the problem and replaced them. I got it back today, plugged it in, and….the hum started up right away. It is not only just as bad, now it's equally bad in both channels (it was worse in the right channel before). I have to imagine that the techs listened to the amp after changing the filter caps, so perhaps this level of noise is normal?

I'm somewhat new to single ended tube amps, and I know that there is some hum associated with them. However, I can hear the hum from 20 feet away. It makes headphone listening impossible. It's also not going to work for near field listening at my work desk. From about 8 feet away in my listening chair, the hum is audible during very quiet passages and between songs. I guess it's just not meant to be...

I guess this falls under the "live and learn" category.

Scott
smrex13
mapman's avatar
mapman
15,679 posts
 
perhaps before a roadtrip to see if a change of location helps....

What does Coincident have to say about it at this point?

Assuming all was well when they shipped it as was indicated, there is still possibility it was damaged again in some way while in transit.

Or there is something about the ground still currently that is causing a problem.

Or something in your source device perhaps? Have you tried an alternate source device for comparison? With different ICs?

Always gotta switch everything possible in and out for comparison in order to isolate a problem best.

It is three prong plug right? Did you try the cheater?

No sense testing anything with things disconnected really. It only matters when all parts are connected. Plus you avoid potential to cause more problems running devices in isolation that might not be designed to do so.
smrex13 OP
423 posts
 
Coincident says it's bizarre and that it was working well when it left their shop. I told them I'd try it in another system at another location to see what happens.

No matter what I try (different sources, different ICs, different outlets, different rooms, headphones, speakers, etc.) the hum is exactly the same in all cases.

Frustrating!
audioman58's avatar
audioman58
1,219 posts
 
I spoke with my friend who is a tech.
The Coincdence amps use the Excellent Star grounding scheme
Which grounds at several avenues. This IMO is a excellent way to go.
If there still is a hum then another item in the chain needs the ground to be lifted . With the ground lift box from emotiva try plugging that into other equipment.Possibly just plug the amplifier in
Seperately. Since it only has one volume pot for a pre . If using a preeamp
Then hook up through rca and turn volume to full on the Dynamo and just back off slightly ,
plug both in same circuit. I run dual isolated circuits from the breaker box
With Audiophile Copper,Gold sockets. Please remember unless you are using a Regenerator which is the best - New power, then any factories in your area as well as noise from lights frig can sometimes dirty a signal
Bleed into the house circuit.
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