Fluctuating volume in one channel: Part II


I posted a few days ago about my left channel volume fluctuating from time to time. I got advice saying that it was most likely either the tubes in the preamp or a bad solder joint on an interconnect.

I switched the tubes in the preamp from left to right and right to left and the problem stayed the same (left channel fluctuating). Then I switched the ICs between the preamp and the amp from right to left and left to right. The problem stayed the same (left channel still fluctuating).

I did not bother switching the ICs from the cd player to the preamp because the problem remains even if I listen from a different source.

What is next in line for me to test? If you would like to see the other thread, it can be found here:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1087439704&openusid&zzKetchup&4&5#Ketchup
Forgive me for starting another thread, but I know old threads don't always get read.
ketchup
Hello Ketchup,

I have a similar problem. I have Classe CAM 200 mono's. I have narrowed the problem down to one of the amps. In my case the volume doesn't entirely cut out, but when it goes, it goes down to about 1/4 of the normal amp's volume. It just started a few nights ago, and doesn't always happen (sometimes volume and quality are just fine from the amp). I was wondering what model you had, and what had happened with your repair.

thanks, Bill
Good news!
I got my ca-200 back from Classe a few days ago. Including shipping time it was gone for about 2.5 - 3 weeks, but I figure Classe only had it for about one week.

I called them to find out exactly what was done to the unit because it's been working perfectly for the past few days and even seems to sound better.

They went over the whole amp and did necessary repairs.
One problem was the shield wires, which connect the input boards to the main boards. A third party used to terminate them and apparently weren't doing the best job, so they were replaced (this is now done by Classe). They also replaced the RCA jacks (probably due to normal wear) and made some updates. The updates included changing some output resistors, 2 caps, and a few diodes. The updates were, according to Classe, intended to improve reliability and stability.

They did the repairs at no cost and even sent it back to me free of charge... that's at least 50 bucks right there. I was very impressed with the whole experience and am now putting Classe up there with Thiel for unsurpassed customer service. I should also mention that I am not the original owner of the amp and it's warranty had already expired.

Bill, that's how my problem started... slight volume level changes now and then followed by more drastic level changes more often. I would call Classe and ask for Arman in tech support. If you can be helped he will help you.
Ketchup,

thanks for your reply. Good to hear that everything worked out with Classe- it is nice to know that they stand behind the product!

In my case I am using the XLR inputs, not the RCA's. I suppose the input board/shields that you mention are common to both RCA and XLR. My units are 2 1/2 yrs old.

I'll be darned but the amp has been running great for the past 48 hours. As soon as it acts up again I will be giving Classe a call.

thanks, Bill
Just an update . . . I sent in my amps to Classe via my dealer, and just got them back. So far so good after one night of listening. Armin mentioned replacing the shield wires, and replacing a resistor and cap, which he said wouldn't affect the unit sonically. Everything is sounding great once again!

Bill
gnobber, that's great! i hope it wasn't too painful being without your amps for tha time. it sounds like the switched the same things in our amps for the same reasons... they must be very similar inside.
i'm glad they're working well again. enjoy some music!