Adcom GDA 600 low level hiss/hum....

Traded an Entech 205.2 Number Cruncher for an Adcom GDA 600 with my friend Cableguy.

He packed it great, of course, couldn't have been done better, but leave it to the shippers to spoil the fun.

When it arrived, the boards inside were rattling around- they had come loose, as the screws that held them down had worked themselves completely free.

!?!?!?!?!?!


Anyhoo, the unit is bolted back together, and there's no visible damage to the boards or caps knocked from them.

However, there's a low-level hum/hiss when I turn it on- my guess is it's the power supply. Not enough to bother most folk, but for some odd reason, my ears are really sensitive to it.



So, where do I look for this hiss? Any ideas what it might be? And are these normally a bit noisy or does this sound like some service is in order? Am I going to need to replace the power supply?

Any help is appreciated. I want to get this healthy, as it was once owned by a few fellas in the hobby I've chatted with, both Rich PA and Cableguy over at Audio Karma. Some sentimental history behind it.

Thanks, fellas.

I'm sorry I can't offer any help as to the source of your problem, but hopefully, once you get it up and running, you'll be as satisfied as I am with mine, It's worked flawlessly for over 12 years, and does a fine job.

My GDA-600 is definitely not noisy, so I doubt that it is common. From my experience hum is usually ground-loop related, and hiss (i.e. raised noise floor) is usually related to other issues which can include out of spec or damaged components. I can't really offer much more advice than that, but I hope you can find a solution to the problems. Once you get the thing working properly I am sure you will enjoy it.

Rob

So Paul, you're listen to two noises?
A hum and a hiss...?! There's a big difference between them.
The hiss issue is not a ground loop problem. Ground loop and PS transformer problems causes 60hz hum, which is something entirely different from hiss. A hisss can be DC noise on the circuit board...

BTW, does your spearkers sensibility similar to both Cableguy and Rich's, or yours are more efficient?

If you talk to Rich give him a big hello from me, will you.

I'm sorry, fellas, let me clarify a bit more.

I really shouldn't have called it a hiss. And it's not coming through on the speakers.

It's a whine, higher-pitched than a hum, and comes from the unit itself.


My bad for not being clearer.

Could be mains transformer buzz, around 60 hz, then.

Try tightening down the mains transformer. If necessary decouple the transformer from the chassis by using rubber or nylon washers / spacers.

So, did you ever get the GDA-600 up and running, and if so, how do you like it?

I've been busy being back at work- matter of fact, just rolled in at 10:54...

So unfortunately no chance yet. Maybe Saturday. I've played it, however, and find it to be a nice DAC indeed. Once I've cured the hum, I expect it to be a bit better, obviously.

I'll keep you posted...