[sphinxllama]

Hello,

I finally build my first cmoy and it worked out fine... till I used my EP630 headphone with it.

First of all I used the tangentsoft.net tutorial and this crossfeed (http://www.hifi-forum.de/extURL.php?...sproject2.htm). Now my problem is, that I checked the amp with some cheap headphones because I didn^t have the good ones with me. It worked out all right and sounded really good. Back home I tried and used my Creative EP630 and with the crossfeed out I got some rush. It can be heard at very low volume (build it without a volumecontroll but can adjust with the mp3-player). When I unplug the mp3-player it is still there and gets worth when I tough the mini plug of the interconnection. I thought it is a ground problem but everything seems to be done right and I have on both cannels the same voltage. How can I check for a groundproblem? The rush goes away when i turn on the crossfeed. Don^t know why, but thing because of the higher resistence. With the AKG K81 headphone the rush is not that loud.

Do you have an idea what is wrong with the amp.

Thanks sphinxllama

 

[FallenAngel]

I think the crossfeed is to blame

Not sure exactly how it works, but it looks like it disconnects the output ground from the circuit and I really have no idea why. Perhaps someone could enlighten us both on this, but for now, keep the crossfeed on or take it out of the circuit altogether.

 

[Paragon]

Have not built one, but looking at the pages, output ground should be connected to input ground.

http://www.rock-grotto.co.uk/crossfeedtips.htm for switch hookup

 

[FallenAngel]

Quote:

Originally Posted by Paragon /img/forum/go_quote.gif Have not built one, but looking at the pages, output ground should be connected to input ground. http://www.rock-grotto.co.uk/crossfeedtips.htm for switch hookup

I don't know buddy, I only see signals there.

 

[Paragon]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif I don't know buddy, I only see signals there.

That link was just for the switch to make sure to use a 4pdt switch and how to hook it up.

The Ground should be connected together on the input and output jack.

From the site..
Quote:

If you are using a metal enclosure then it is only necessary to solder the ground to one of the ground tags on the RCA sockets but if you are using a plastic enclosure then it's essential you solder all 4 RCA tags to ground to ensure continuity

 

[sphinxllama]

at first thanks a lot for so many suggestions.

maybe it is really the problem because i use a ON/ON 4p like this one here: http://www1.conrad.de/scripts/wgate/...0&cachedetail=
and i just connected the ground from the 47nF to the ground of the cmoy.

i use a plastic enclosure, so do i understand it right that i have to solder a groundwire from every pin of the switch to the cmoyground?

sphinxllama

 

[FallenAngel]

Quote:

Originally Posted by sphinxllama /img/forum/go_quote.gif at first thanks a lot for so many suggestions. maybe it is really the problem because i use a ON/ON 4p like this one here: http://www1.conrad.de/scripts/wgate/...0&cachedetail= and i just connected the ground from the 47nF to the ground of the cmoy. i use a plastic enclosure, so do i understand it right that i have to solder a groundwire from every pin of the switch to the cmoyground? sphinxllama

Yup, connect all the grounds together

 

[sphinxllama]

but if i solder all the pins from the switch to ground i also connect all the pins...

 

[FallenAngel]

Quote:

Originally Posted by sphinxllama /img/forum/go_quote.gif but if i solder all the pins from the switch to ground i also connect all the pins...

Just solder all the GROUNDS (washers) together, not the pins.

 

[Paragon]

All that should be going to the switch is the signal input and output wires as in the diagram that I linked to previously. That is it.

As for the grounds.. a separate matter.. you have ground at the input jack (or both RCAs), output jack (or both RCAs), ground point on the crossfeed, groundpoint on the cmoy, and ground on the volume potentiometer (one for each channel). These all get connected together.
Now depending on the volume pot you have, you should really ground the outer metal houseing to avoid noise when you touch the knob if it has a metal shaft. You can do this later if you find you need to.