Vintage HiFi Audio Forum

Audio Discussion => CARVER => Topic started by: treos33 on December 09, 2012, 01:31:38 PM

Title: C-1 channel imbalance
Post by: treos33 on December 09, 2012, 01:31:38 PM

Has anyone noticed this with other C-1s? At low volumes there is a significant volume imbalance with the left channel being much lower than the right. It evens out at about 1/8 rotation of the volume knob but my speakers are efficient enough and amp powerful enough that this is quite loud.

Do you think some deoxit could fix this or is this just characteristic of the volume pots Carver used?

Title: Re: C-1 channel imbalance
Post by: Kingman on December 09, 2012, 01:33:17 PM

I would think oxidation.

Title: Re: C-1 channel imbalance
Post by: Slim-Shaddy on December 09, 2012, 05:21:12 PM

I had a problem similar to this and it turned out to be a dirty speaker switch on the amp.

Title: Re: C-1 channel imbalance
Post by: OCCD on December 11, 2012, 05:19:02 PM

Most of the time it is dirt. 

Title: Re: C-1 channel imbalance
Post by: treos33 on December 11, 2012, 07:38:00 PM

Alright, I'll try some contact cleaner this weekend. It could possibly be the amp, still need to change the speaker relays on my NAD 2200 but that problem manifest differently. Thanks for the replies.

Title: Re: C-1 channel imbalance
Post by: treos33 on January 16, 2013, 08:24:19 AM

Tom, after some reading this seems to be a known issue with the Carver volume pots. If you and Anders can't fix it with some contact cleaner then don't worry about looking for a replacement pot.

Refer to:

http://www.audiokarma.org/forums/showthread.php?t=55854 (http://www.audiokarma.org/forums/showthread.php?t=55854)

Specifically:

"According to a service bulletin put out by Carver in 1988 there were numerous complaints about non-linear tracking and preamp noise(hiss) at lower volume knob setting, say below the 8:00 position. For example: my C-1 would lose volume on the left channel before the right channel when trying to listen to it at very low volume levels, say late at night when everyone was sleeping and I didn't want to disturb them. At the other extreme, It would play at unbelievably loud levels at ~10:00 on the volume control. I would guess that it would max my amp out at ~12:00 volume setting.

In order to correct the problem it was necessary to lower the gain of "MAIN OUT 1" (which is programmable) in order to get away from the non-linear portion of the volume control and also to operate the preamp away from its noise floor. This would also allow the end user to get the best possible signal to noise ratio at normal or optimal listening levels."

Title: Re: C-1 channel imbalance
Post by: treos33 on January 16, 2013, 10:28:45 AM

I found the service bulletin so I'm just going to change the resistors myself to reduce the output gain on Main 1. Don't even bother opening it up.

If anyone is interested in this mod, the service bulletin can be found on the last page of this PDF:

http://thecarversite.com/manuals/mandir/Carver%20C-1%20service%20manual.pdf (http://thecarversite.com/manuals/mandir/Carver%20C-1%20service%20manual.pdf)



P.S. Tom, looks like it was the volume pot itself, so suck it.   O0

Title: Re: C-1 channel imbalance
Post by: OCCD on January 16, 2013, 11:57:24 PM

lol  you prob broke that cheap ass pot... >:D >:D >:D >:D >:D