[2bigears]

  hello all good AC Gals and gents.  I put a new to me system together as of late. The music is 15% from one channel at start .. that being the one channel is good while the other soft. After an hour, the same and even a few hours.  Leave it overnight and the stereo is singing. If anyone has had this ,, chime right on in.
     The amp is Pass Labs 250x ,,,, pre is VAC mid range with two tubes in main stage. I did switch the tubes around. Stays light on the right channel regardless.  Buying used does have it's drawbacks,,ha.. 

[SteveFord]

Have not had that but bumming a preamp from someone would come in handy.

[thorman]

 Just a guess, maybe a failing Solder. Heats up and expands and works after heating up...Maybe take the top off unit involved and see if you can spot something. Good luck

[Big Red Machine]

swapped the tubes and tried it?

I would guess the preamp. And looking for a poor solder joint is worth a looksee.

How about a cheap passive pre to investigate the amp?

[2bigears]

  yes , thanks.  I'm in a new city so no buddies with stereos.  But if I can bum a pre just to try ,, that would work.   I phoned Nelson and he wasn't concerned about the caps ,, they last a long time ....

[Big Red Machine]

https://www.usaudiomart.com/details/649753701-ci-audio-vpc-1-passive-volume-control/

 

[I.Greyhound Fan]

Schiit Audio makes a passive preamp for $49.

https://www.schiit.com/products/sys

[2bigears]

  option number 1.  Wonder why we pay 5 grand for a pre ? 50 bucks seems more like it ,, ha... 

[Doublej]

Option 3.

Swap the left and right cables connecting the preamplifier to the amplifier. If the problematic channel switches sides, the preamplifier that is faulty. If it stays on the same side it's the amplifier that is having the problem.

You should first verify that all of your cables are good and switch to a different input on the preamplifier to rule out that the problem is with a specific input.

[JLM]

Careful using passive pre-amps, look for low inductance/capacitance interconnects to avoid losing the high frequencies.

Single digital source systems (like mine) don't need a pre-amp to gum up the sound.

[morganc]

Option 3.

Swap the left and right cables connecting the preamplifier to the amplifier. If the problematic channel switches sides, the preamplifier that is faulty. If it stays on the same side it's the amplifier that is having the problem.

You should first verify that all of your cables are good and switch to a different input on the preamplifier to rule out that the problem is with a specific input.

This sounds like a logical next step.

[timind]

Verify proper cable connections first. Then swap left/right cables between amp and pre to determine where problem is.

[toocool4]

As a couple of people have mentioned, swapping the left and right interconnect connection on the Pre or power amp end is the first thing you should do. Only swap at one end not both else you will have undone what you are trying to do.

[FullRangeMan]

+1 on a false solder joint or something on the PS or the rectifiers.

[2bigears]

  thanks all.  I'm gonna let the amp cool in standby state and leave the pre on staying warm. after the amp cools I'll spark it up and try. That would point to the amp I would think if the one channel is weak.  Switching the interconnects is a great idea. I'll try that too. The repair shop Nelson recommended is 6 weeks behind. I think we have a shortage of techs ?   

[2bigears]

  Happy Sunday in Rocktober everybody,,,,  well I found out the heavy amp is ok.  I put it in standby and kept the pre on overnight. Sparked it up and she sang as normal.  The pre is at fault ,,,, dam. I just bought it too from the USA.  Wonder if it's just a tube. But I think I swapped the tubes around already and it stayed on the same channel. I will do it again to be sure. I'm glad the big heavy is ok. She's a big block Chevy that old girl. Ha.