2. amps-preamps
  3. 1061393832

Help Troubleshoot - Left Ch. Louder than Right Ch.

I need your collective troubleshooting assistance.

I just put together a new system (comprised of used gear, of course) and hooked it all up last night.

Unfortunately, the left channel is considerably louder than the right. Or - it could be that the right is much QUIETER than the left. Not to be facetious, but in actuality, the left channel seems more "appropriate" all things considered.

The amp is an Antique Sound Labs AQ-1002 (50wpc) and the preamp is a Counterpoint SA-1000. Unfortunately, I don't have any additional components to swap out and determine which piece is the culprit. Can you guys think of any other techniques that might help determine what's causing the problem?

Also, if the amp is not biased properly, could that cause one channel to play louder (or quieter) than the other? There are no Gain controls on the amp that I can see.

I need to figure out what's wrong so that I can either fix it, or seek recourse from the seller before too much time has elapsed.

Thanks guys!
gullahisland
12 responses Add your response
kotta's avatar
kotta
649 posts
 
Your source equipment could also be the cause. Also, the loudspeaker.(Depends on how close of a tolerance the manufacturer used w/ the drivers.)
josephaud
41 posts
 
Try swapping the left and right input cables on the back of your amp ( power it down first)
Then listen and see if the louder sound is on the same speaker or if it moved.

If the other channel is now louder the problem is in your preamp or before. IF the same channel is louder it's in the amp or speaker

Jeff
gullahisland OP
83 posts
 
Jeff, you're a genius!

I'll give that a try this evening and report back tomorrow.

If it turns out to be the amp...Does anyone have an idea of what might cause such a thing? Could it be as simple as the bias?

Thanks!
marakanetz's avatar
marakanetz
5,473 posts
 
It could even be simplier than bias: bad tube!
gullahisland OP
83 posts
 
Well,

I switched the interconnects and the problem stays in the right channel. I switched the speakers as well, just to confirm that there's not issue with them and, again, the problem stays in the right channel.

Marakanetz - Should I just switch the placement of the tubes and see if the problem follows the tubes? The amp uses two 6550s for each channel. Is it safe to just switch them? I'm a tube novice and don't want to do anything catastrophic.

Thanks again.
newbee
4,756 posts
 
Try switching the drive tubes first - you don't have to worry about the bias settings on these.
gullahisland OP
83 posts
 
Newbee - Please forgive my ignorance, but I assume by "drive tubes", that means the 6550 output tubes? On the input side there are 4 12AU7s.

Thanks again everybody.
newbee
4,756 posts
 
No, I was referring to the small tubes, the 12AU7's. It is not unusually at all that when small tubes die that you start to loose volume before they go dead. The 6550's are usually referred to as the power output tubes.
piezo
304 posts
 
I have a transient problem with my VTL 185s that sounds kind of similar and i was wondering if this could be a tube thing as well. One amp will suddenly get louder and then start to hum, or will just start to hum without the volume surge. Toggling the on off switch gets rid of it...no need to let the sound die, just hit the switch. same problem with different ic's and in two different houses. Used to be i could toggle either power amp or the pre amp and the hum would quit but now seems to only work on the afflicted amp. doesn't happen often enough to spend the money to ship it to VTL, where it would probaly work fine. any ideas?
gullahisland OP
83 posts
 
A quick update:

I went home for lunch today and tried swapping the placement of the the 12AU7s and an interesting thing happened. The balance now seems normal. I also listened closely for distortion or other signs that the tube(s) are failing and couldn't really tell.

My kids were taking a nap, so I couldn't really "listen", but as best I could tell, the problem seems to have gone away.

Now I'm more baffled than ever. Could one of them have just been loose? Is it possible that one of them is failing and the problem will be intermittent until it finally goes out?

This raises another question. I hear about people "testing" their tubes. Where could I take them to find out if they're any good or not? I don't want to just replace them all if I don't have to. It's not a huge investment, but I'd be looking at around $150-175 to re-tube the amp.

Are there any places in the SF Bay Area that will test your tubes for you and or sell new ones?

Thanks so much!
newbee
4,756 posts
 
You may have just had a pin on the tube in poor contact with the socket. If it were me, I wouldn't look a gift horse in the mouth - but what I do, so I won't get upset when tubes die, is keep a pair of spares for emergencies.
gullahisland OP
83 posts
 
Thanks everybody. I'm guessing that Newbee is right. All I know is that after swapping the placement of the input tubes, it sounds spectacular.

I couldn't be happier and I sure appreciate the assistance.

Good listening!
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