Tube amp hum - Coincident Dynamo 34SE


Hi everyone,

I am the new owner of a Coincident Dynamo 34SE tube amp. It sounds wonderful except for a very noticeable hum both at the amp and through the speakers. It's noticeable anywhere in my listening room. I had been using a Musical Paradise 301 tube integrated with no hum problems, so it's clearly something related to the Coincident. I haven't changed any cables or sources.

Any thoughts? RIght now I'm using the stock tubes, and I don't know if changing them out for something else might have an impact. I'm a bit worried - as I read more reviews of the Dynamo I see that every reviewer has had some type of issue with it (blown tubes, hum, defective, etc.), but they all say it sounds fantastic. I agree it sounds great, but I hope that I can solve the hum problem.

Thanks for any help you can give me.

Best,
Scott
smrex13
Some quick troubleshooting tips.

Disconnect the inputs so only the speakers are hooked up to the amp. Disconnect anything on that same breaker from the power. Does the amp still hum?

If it does, and if it's possible, doing the same as above, try moving the amp and speakers to different areas in the house to see if it's doing the same thing on all outlets. Then again, if it's possible, take it all to a friends house. If it's doing it everywhere, it's probably going to be an amp issue and you should contact Coincident.

You can try a cheater plug also to see if that does something but using one long term is not something I'd recommend...just do it for a troubleshooting measure. If the cheater plug fixes it, then it's probably not an amp issue, but something going on with things connected to your power.

Dimmer switches, fluorescent lights, sometimes appliances, cable tv boxes...at some point I've read that all these have caused hum in a system.

Good luck, hum issues can be maddening. There are others here far more knowledgeable than me. Hopefully they'll chime in or correct any issues in my post.
Smrex13,
Here is what to do: first, read Tim Smith's review in 6 Moons online. Tim had some hum and here is what he said: I eliminated that tiny hum by connecting the Dynamo to my $99 Emotiva CMX-2, a handy little device that removes DC offset from your power line. I too, had some hum and I followed Tim's suggestion and bought the $99 Emotiva CMX. Hum busted, gone for good. You can purchase this device on Amazon. It absolutely does the job.

Tim's review is a thorough, well-written piece on the Dynamo. A couple of
suggestions. You can elevate the already good sound by rolling some tubes. The Rectifier should be changed to something like a Mullard 5AR4 for about $85-100, or other compatible rectifier. Next, change the front 6SL7 something like the Sylvania 6SL7 Military WGT model (also about
$85-100), or RCA Red Base 5691. These recommended by Tim are stellar as I also use various combos of these tubes. Of course there are others to consider. And last, I'd recommend the Shuguang Black Treasure 6CA7
Power tubes from Rachel at Grant Fidelity. For the other tubes mentioned, Brent Jesse, Jim McShane and Andy at Vintage Tube all provide excellent service. Good luck and enjoy. I love my Dynamo!
Mikirob - did your hum come through the speakers, too? I did order the Emotiva gizmo figuring it's going to be useful at some point. I'll wait to see what Coincident has to say about servicing it. A local service shop told me not to use the amp because the problem may be a bad filter cap.

I hope Coincident is proactive in solving this problem.

Thanks,
Scott
If it's new, talk to your dealer, he should be willing to help you. If you have the hum at the amp as well as the speakers, it could be some sort of transformer hum, which should be addressed by the manufacturer.
The hum did seem very slight at the speakers, also slight at the transformers. The Emotiva completely took care of it. Yes, the best thing to do is talk to Israel Blume; but I think the problem is likely similar to Tim Smith experience as well as my own. Hopefully it is that simple. Best.
Smrex13,
Please keep us posted on your progress/results.
Will do. I'm going to try the Emotiva power strip before returning it just to see if it works. I'll have to send it back to Coincident if it doesn't solve the problem.

I'll keep y'all posted.