Lower gain in left channel.

Could be the tubes. Make sure all the other connections are tight. If the amp has auto biasing or some other user method you might change tubes--side to side (left with the right)--Driver tubes as well;see if the problem stays on the left. If it stays on the left--change side to side--the tubes in the pre amp.

Does it happen at all volume levels, or is it only noticeable at very soft levels?? If it only happens at low levels, it could just be the natural effect of the volume control not being able to match precisely...that's natural and it happens with many stereo volume controls. If it happens at all level, then follow the above suggestion and swap tubes side to side. They may not have been a matched pair, one may be older, etc.

It happens at all volumes, so I'll experiment with the tubes.

Jond; I've had the problem you describe for years, and it's why I always use a pre-amp with channel balance control. My left channel output volume is higher than the right channel, so I always have to dial in about 3-5 dB (biased to the right) of volume to achieve good channel balance and proper imaging. I CAN get good imaging by slightly biasing my listening position-- which is then slightly off center.

I've blamed my room, my speaker set-up, my hearing etc, but in 4-5 years in my present room have yet to figure out why this is the case. I've also changed tubes in my pre-amp several times and it has made no difference. Sorry I can't help. I'll follow this thread with interest. Craig

I'm experiencing the same problem. I was getting a constant hum from the right channel of my OTL amp. I took it in for repair. Apparently one of the capacitors (there are 2 per channel on my amp) on the right side had gone bad and needed replacement. After replacing the capacitor the hum went away but, I started to notice this ever so slight loss of gain from the right. I tried the tube switching but without success. What could be causing this? Hope someone can shed some light on this. I know it's not my preamp because I was able to try a different amp last night -- there were no loss on right channel.

I would suggest narrowing the problem to a particular piece of hardware. Maybe you've already done so, but I would swap the cables between preamp and power amp, and swap speaker cables or speakers whichever is easiest. I had a similar problem with a pair of electostatics and it turned out to be the crossover in one speaker was bad. Oddly enough it was the speaker that was loudest that was the culprit.
Jim Robinson

Some music is recorded that way, you'll notice a difference on some recordings from song to song...

Jwrobinson - I tried switching cables (ICs and Spkr cables) but the problem persisted. What it looks like is the right channel of my amp. Wondering what could the repaire man have done to it while he replaced the capacitor, if anything. Or is it possible that a new capacitor could function slightly differently (breakin etc) from the old ones.

Pops - I considered that. I thought it was the recording at first so I tried several cds. They all displayed the same problems - right channel slighty quieter than the left. For a while I thought it was my hearing, especially since I mostly use my left ear to answer phone calls etc. I thought I might just hear slightly better on my left ear. But when I switched amps (a friend's amp) the problem went away. Unfortunately my preamp does not have a balance or separate left/right gain controls. Man it sucks!!!

Thought I'd pass this along -- just spoke to the distributor of my amp. While speaking to him I realized one other variable in this problem. The power tubes (2 pairs of 6C33C-B) in my amp are not a matching quad. This could potentially be a problem. My distributor suggested, instead of buying matching tubes now (expensive proposition) I should try an bias one channel slightly higher than the other to see what the impact is. I will try this next when I get home from work. I'll keep you posted...

I'm having a similar problem with my 'phones. Both channels operate, but right is clearly "louder" than left. They are HD600s, run off of the tape out of my pre to a Headroom Home. Same problem from both headphone jacks, problem remains the same when input cables to Headroom are swapped, so I'm guessing its the headphone amp. I'll call Headroom tomorrow, but I have noticed a similar (but to a lesser degree) problem with my overall system. Could it be the CDP (CAL CL-10)? Hard to imagine that could be the case, but maybe I'll try swapping the outputs from the DAC, or running the analog output from the CL-10 internal dacs direct to the pre. Maybe its due to coriolis force; anyone down under have reverse problem?;>).

Update - just wanted to report that ALL IS WELL once again...the loss of right gain is NO LONGER. It might have been a "newbee" problem. I've only had 1.5 year of experience with my tube amp (first tube gear). Upto now I've only been resetting the bias but not the "offset". The owners manual (4 photocopied pages in all) does not discuss bias or offset at all - very odd. Must be a language problem, the amp is made in Italy or I did not receive all documents from the dealer. All I can say is, after resetting the bias and the offset, the sound appears to be completely in balanced. I'm a happy camper! Best of luck to you all...