buzz/ripple treshold amp

[loviest]

This treshold S/5000e amp does have a buzz on both channel's, but one channel has also high sounding buzz. It's not that loud, but the one channel with tweeter buzz is annoying.
I tried several thing's to elliminate this hum and buzz but still not succeeded.
While starting this amp it will take a minute or so to get stable but in this buzzy state. When then I put my finger on signal mass, it's reasonable quit. One channel is quit without input and the other won't while warming up.
It's a young amp and therefore I don't think there's a bad electrolyth.
I checked balanced/unbal. switches both channel's also.
I'm getting mad by cannot resolve this problem.
I'm very pleased with a schematic or service manual of this amp or even bias settings. There's no DC-offset pot while there's some to set here!
By the way the torroid is making a lot of noise also!
?

[h_a]

When then I put my finger on signal mass, it's reasonable quit.

Sounds like a grounding issue.

and the other won't while warming up.

Sounds like a cold solder joint.

By the way the torroid is making a lot of noise also!

Pretty common, often it's a bit of DC on your mains that saturates the toroid core periodically. A DC-filter could help in that case.

Hannes

[loviest]

Thnx for replying!

Quote:
When then I put my finger on signal mass, it's reasonable quit.
Sounds like a grounding issue.
>I know but this dissapears after the amp warmed up.

Quote:
and the other won't while warming up.
Sounds like a cold solder joint.
>I checked everything and some resoldered indeed.

Quote:
By the way the torroid is making a lot of noise also!
Pretty common, often it's a bit of DC on your mains that saturates the toroid core periodically. A DC-filter could help in that case.
>Yes that's something I wanted to try get the tranny more quit, but does it solve the humming problem in the signal?

I find these amps strange, especially they make a lot of noise when they are starting up and this takes more than a minute! before most hum getting soft. What left is a 50hz hum more in one speaker as the other. When you drive high efficient speakers this a big problem!

Any one experience with these amps?
It's a fully balanced design and gain is maby to much! :-)

[h_a]

but does it solve the humming problem in the signal?

No, a dc-filter will not help much in this regard. It mostly reduces the toroid humming.

What left is a 50hz hum more in one speaker as the other.

This is pretty normal and the quantity of the remaining hum depends a lot on the quality of the grounding scheme. Most commercial amps are designed to be sufficiently quiet with the average efficient speakers and might become noisy with highly efficient ones. But I don't know your unit in particular to know whether this is the case here.

Any additional noise like crackling during warm-up is usually caused by cold solder joints, that occur particularly in the heavy stressed output parts.

Please keep in mind I'm trying to give general advice; it is very difficult to help you in detail without standing in front of your amp

[loviest]

Thnx!
The noise while upstarting is more a lot of hum which get less in a minute or two. Then what's left is the humming noise which irritating especially on the high-efficiency systems.