[Sathimas]

Hello,

after lots of sweat and fear, I had my SOHA running perfectly and was amazed by the sound.

For my test setup I used only one RCA input, connected to the board through a source selector switch.
(2pin 6 positions, I do not switch ground, thats permanently connected.)

Now I added the other two inputs and the SOHA started making problems.
It sounds like if I was listening to the radio while the reception wasn't perfect.
Some sounds, especially loud notes, distort/buzz - no matter if its some synth or a guitar,
it happens over a wide frequency range.

I'm totally clueless where the problem might be,
I've already desoldered the ground of the additional inputs - no change.
I'll desolder the other inuts completely this afternoon.

I hope somebody has an idea or hint where my problem might be.
I'm a total noob in electronics, the SOHA is my very first DIY project...

Greeetings from sunny Germany
Sathimas

 

[Sathimas]

Ok guys, since none of you had any idea about my problem, I had to find out myself ...

Yesterday evening, the distortions where gone when I connected the amp to my CD Player.
Today - they where BACK !

I was about to go crazy... Just 10 minutes after I finally finished the case the amp started making problems again...

Then I began to simply undo anything I did before I reconnected it.
Only 5 minutes later I had the solution:

I'm using a Y-adapter from my CD Player to my Onkyo Receiver and the SOHA,
because always plugging and unplugging the cables bothers me.
If the receiver and the amp are connected I get distortions, if the
Onkyo is not connected - I've got perfect sound!

Now I'm wondering how to get rid of this problem, since I'm still not willing to
steadily change the cables - this disturbs the perfect order behind my receiver

 

[ericj]

distribution amplifier, switch box, tape loop output on your onkyo . . . .

 

[Sathimas]

Well, my Onkyo got a tape in and a tape out - maybe you could explain what you mean by "tape loop" ?
Goal is to keep the receiver off, since it consumes lots of power even in zone2 mode (about 85 or 90 Watts, my Soha only needs 5)

Switchbox and distribution amplifier cost money, which I do not want to spend.
The SOHA and a couple of other audio related things already exceeded my planned budget somehow

I think the problem is, that the Onkyo can't be turned off completely.
It simply stays in standby...

 

[jbloudg20]

Don't want to spend money? Keep plugging and unplugging.

 

[tomb]

There are such things as a ground loop breaker. This sounds like a classic case. If your receiver's fm antenna is grounded, that may be causing it. Parts Express has one pretty cheap:
Dayton VIT-1 Video Isolation Transformer

just a guess ...

 

[Sathimas]

Ok, I just tested some things ...

Unplugging antenna - no change, still problems
Disconnecting receiver from AC - no change, still problems.

Seems like I'll have to build a switch box ...

This will have to wait until my next holidays in February/March next year anyway.
Til then, I'll keep plugging and unplugging ...

 

[ericj]

if you're sure it's the ground loop, unplugging the receiver won't solve the problem because it's still coupled to other things that are plugged in.

Ground loops suck that way.

 

[tomb]

Yep - Eric's right. There are also ground loop breakers that are made to connect into RCA patch cables, but I couldn't find an example on short notice. I have one that's integrated into a vinyl-to-digital conversion box, but nothing separate.

 

[ericj]

Yeah, the ground loop breaker / isolator is basically a 600ohm:600ohm audio transformer, sometimes with a capacitor in front of it to prevent DC from damaging the transformer.

since you're in germany i dunno where to tell you to get one. Car audio stores and Radioshack carry them in the US. I forget if you still have tandy stores in germany.

 

[Sathimas]

Thank you for your advice, I think I'll build a switchbox in my next holidays.
The switches are rather cheap, cables too and the wood for the case is for free from my grandfathers workshop

(See the pictures of my SOHA in the "Post pics of your builds" thread

)

The strange thing is that I'm also using a y-adapter on my NAD PP2 Phonopreamp.
No problems here