Help needed to diagnose preamp channel unbalance.


Hello all. The preamp is a new dual mono linestage with both balanced and single-ended connections. The volume control is an Alps motorized pot. There is no balance control, just a single stereo volume control.

The problem is that at low volumes, there is a channel mismatch resulting in the right channel being noticeably louder than the left. The problem was confirmed to be with the preamp through cable/channel swapping and listening with matched channel test CD's. Correct phase was also confirmed. When the volume is increased to moderate levels, the left channel seems to come fully on-line so that proper balance is restored. This is obviously an unacceptable situation for low level listening.

Has anyone had a similar problem? Is this likely a tracking problem with the volume pot? Is it possible this will improve as the electrical components and volume pot break in, since the preamp is new with only about 15 hours on it? - Thanks
mitch2

Showing 3 responses by 6550c

Is it a tube preamp? I have had this happen when tubes are way missmatched. Just like you said, at low volumes the sound was allot louder in one channel. At higher volume the sound tended to even out.
Is an Alps volume control considered the cheap way? I can't count how many glossy preamp adds mention the use of high quality part like Alps.

BTW, my tube preamp is balanced with multipule gain stages and the tubes are biased by transistors (i think) - 6 tubes in all. So, if I put a JJ in one socket and an EH in the other, it plays loudner in one channel for a while then it seams to balance out. (The EH 6922 is louder). Maybe something else is wrong too?