[FallenAngel]

Quote:

Originally Posted by ferencvaros /img/forum/go_quote.gif I assembled my soha and I have similar problem: but, when I use source, which jacks are grounded (between RCA and AC ground is ~0 ohm), there is not buzz, my soha is dead quiet, but when jacks are not grounded, soha is buzzing loud... case is alluminium hammond with transformer to the enclosure's body are connected: pot, AC ground, other parts are isolated can somebody help me ?

Not sure what you mean exactly.

"RCA to AC ground is ~ 0 ohm" and "other parts are isolated" doesn't make sense unless you're saying that "AC ground" is signal ground on the amp board.

If you mean "AC ground" as in the house ground (3rd prong of power cord) or the transformer center tap? If your case is grounded to the house, don't connect the signal ground to it.

I have my case grounded to house ground. Pot is connected to signal ground just like the RCA inputs and 1/4" output.

It's totally quiet, but when I have no source connected, it humms because the RCA's pick up everything around the area like a little radio antenna. I think that's "normal".

 

[ferencvaros]

case is grounded to the house ...
between the case and RCA jacks (not connected to source) is no connection ..
signal ground is not connected to the case ..

I tried two sources - cd player NAD 541i and sound card Audigy ..

When I connect CD player soha is buzzing, with Audigy is dead quiet ..
I looked for differences - I measured resistance "house ground to RCA jack of CD player" and "house ground to RCA of Audigy" ... Jacks of CD player are not grounded to the house, but jacks of Audigy are ..

It means - when jacks of my source are house grounded, soha is quiet, if not it is buzzing ...

it seems that I have to connect grounding point from http://taihu.bjtzh.gov.cn/~digi01/pic/connections.GIF with house ground ..

yes, it works !!!

 

[FallenAngel]

Quote:

Originally Posted by ferencvaros /img/forum/go_quote.gif case is grounded to the house ... between the case and RCA jacks (not connected to source) is no connection .. signal ground is not connected to the case .. I tried two sources - cd player NAD 541i and sound card Audigy .. When I connect CD player soha is buzzing, with Audigy is dead quiet .. I looked for differences - I measured resistance "house ground to RCA jack of CD player" and "house ground to RCA of Audigy" ... Jacks of CD player are not grounded to the house, but jacks of Audigy are .. It means - when jacks of my source are house grounded, soha is quiet, if not it is buzzing ... it seems that I have to connect grounding point from http://taihu.bjtzh.gov.cn/~digi01/pic/connections.GIF with house ground .. yes, it works !!!

You can create a ground loop through the house ground if another part of the system does the same thing. That's the main (and only) reason for avoiding this.

 

[Zigis]

I don't no about SOHA, but I had on others tube amps buzzing at anything other than full volume, if I forgot conect heater to ground.
Zigis.

 

[ferencvaros]

I have next problem with my soha: my 30VCT toroidal transformer (amveco/talema) is buzzing..

please help me to find why !!!

 

[kklee]

Are saying that the transformer itself is buzzing (versus buzzing induced in the amp by the transformer)? How do you have the transformer mounted? Do you have any pictures of the amp?

 

[ferencvaros]

Transformer is buzzing itself, buzz is not induced into the amp (maybe a little bit only at highest volume).

I have toroidal transformer Talema assembly type H :
http://www.ntmagnetics.cz/index_flas...en&page=montaz

It is mounted using standard screw - but transformer is buzzing also unmounted (not screwed to the case).