Caiman Output Noise

[chrism]

Oh no!

I appear to have bodged my Caiman since swapping an input cap out and inserting a 10uf tant (I have done quite a bit of trial and error bodging to it so it is my fault as it worked fine a few weeks ago).

Got a slight high pitched whine from my speakers when the Caiman has a signal connected. Tried Spdif from Squeezebox and also USB from PC both the same. As soon as a music source is detected the whine ramps up. It is not volume dependant just there all the time and particularly anoying when the vol is turned down and the signal still connected.

Wondering if it could be some sort of signal break through?

Any ideas greatfully accepted.

Regards

[Reid Malenfant]

Sounds like it could be RF (radio), have you got the lid on it?

[chrism]

Yes have the lid on it although the scews are a little worn!

The reason for the 10uf tant on the input line was to address potential RF(just swapped for a 10uf Silmic as I wondered if the tant was duff). I had on of these big yellow polyesters in before and wondered about putting it back. I have also made a new PSU interconnect recently with a bit of shelded twin core and I ought to swap the old one back just to be sure.

Regards

[chrism]

Mark,

I had built a twin PSU for the Caiman one set at 12v and the other at 5v. I tried to swap out the Murata's and feed the supplies straight in. Had to reverse engineer it though as just could not get it to work.

The 5v supply drops to 4.3v under load (connected in at the same place as the Murata output pin) and I was too scared to up the voltage back to 5v.

The whine was there before I did all this though.

Regards

[Reid Malenfant]

So it's probably nothing to do with the modified PSU If it was dropping to 4.3V then obviously it was having a little difficulty supplying the required current, either that or there was a voltage drop due to resistance in the lead supplying it

12V will be low unless you bypassed the internal regulator, i'm assuming you did this or you'd end up with about 9V to the audio output section which certainly won't help things...

I'm at a loss tbh, i do have a Caiman but i haven't played about with it yet.

What i'd suggest is you take the thing back to as near standard as possible & find out through experimentation which change introduced the noise/whine

[leo]

I'm always weary of strange noises , could be a number of things including instability (going by the whining noise)
You got any pics? usually helps spot possible problems

[chrism]

Ok,

Swapped the PSU and cable out and the whine dissapeared. Unfortunately it then returned a few minutes later after being left on with a signal being fed with zero vol.

I have gone over the Caiman 10 times looking for solder bridges etc - clean as a -------(not using that word!).

May have to take it over to Les next week so that he can tell me what's up with it and also show me how to install the 5v supply properly. I suspect it is an issue with the grounding somewhere.

Regards

Chris

[chrism]

Any one know if when shutting the signal off does the Wolfson chip or something close to it give 3 very tiny pip sounds off (lid off and ear very close to it stuff)? If this is not normal this may be a clue to what's wrong.

Regards

Chris

[Reid Malenfant]

Hi Chris, that'd be the two output muting relays opening

[chrism]

Hi Chris, that'd be the two output muting relays opening

Thanks Mark but the pips are audiable when the signal is switched off not on, they do not make any sound when activated. I don't remember hearing them at all until I bodged it!

Interestingly, the whine reduces when the opamp board is swapped back in.

I thnk that two Caimans are a must when modding - you can always check the standard one out when stuck!

Regards