[2bigears]

  hello all good AC'ers.  My system makes pretty good sound 'once very warmed up' .  One channel is near none audible till like a good 10 hours or so.  I really don't know what could be the trouble.  The pre is an older VAC with two main driver tubes I have switched ,, so I don't think that's it. The amp is an old Pass x250. I leave it in stand-by near all the time.  Not sure how to figure this out ? I just moved to a new place to live and have no audio buddies to bum an amp from ?  Anyone have any ideas ? 
       Thanks for any help. 

[Wayner]

The tubes are only responding to what is being fed to them. The problem might be in the actual circuits powering their grids or passing signal thru them. Swapping tubes is a great way to determine if its the tubes or not (problem would follow the tube, if it was the tube). Power supply problems or other issues sound like the cause.

Wayner

[2bigears]

  thanks Wayner.  Amp or pre power ? I will phone VAC and Pass ,,,, see what they say. 
      Both these big old units are a pain to ship. Good lord. Cheaper to buy new now a days.   

[FullRangeMan]

Try the PASS with other préamp tô see what happens.

[Doublej]

I take it that you have ruled out it being a cable (interconnect and speaker) issue by swapping around cables.

If your gear will not blow up with the following suggestion I would try this:

Take a single channel (Left or Right) from the VAC and feed it to single channel (Left or Right) of the PASS. Note how it sounds. Now switch the input to the other channel of the PASS. If both times it sounds good or bad, it is the VAC that is broken. You can confirm this by repeating the test with the other channel of the VAC. You should get the opposite result with both channels of the PASS.

If sound goes from good to bad or bad to good when you feed the same channel from the VAC to different channels of the PASS, it is the PASS.

Alternatively, you could feed the analog output of a computer (headphone jack) to the PASS. If the VAC is broken, both channels will now sound good. If the PASS is bad, then the bad channel will still sound bad and the good channel will still sound good.

[2bigears]

  ahhhhh. Correct. Run mono testing both sides From the pre. If both sides sound good , it's the big 100 pound amp. I thing that's what your saying. Will have to do this once it cools down for a day or two. 

[charmerci]

I take it that you have ruled out it being a cable (interconnect and speaker) issue by swapping around cables.

If your gear will not blow up with the following suggestion I would try this:

Take a single channel (Left or Right) from the VAC and feed it to single channel (Left or Right) of the PASS. Note how it sounds. Now switch the input to the other channel of the PASS. If both times it sounds good or bad, it is the VAC that is broken. You can confirm this by repeating the test with the other channel of the VAC. You should get the opposite result with both channels of the PASS.

If sound goes from good to bad or bad to good when you feed the same channel from the VAC to different channels of the PASS, it is the PASS.

Alternatively, you could feed the analog output of a computer (headphone jack) to the PASS. If the VAC is broken, both channels will now sound good. If the PASS is bad, then the bad channel will still sound bad and the good channel will still sound good.

Always start from the source and work your way component/IC/input/output by component/... down.

[2bigears]

  it needs to warm up for a day so it's big whatever it is. It's not a cable or source. 
       I will call Kevin at VAC , he is a good guy and just might have so insight.  But cold start in mono switching left to right with  a cable might be the ticket.  Thanks 

[FullRangeMan]

it needs to warm up for a day so it's big whatever it is. It's not a cable or source. 

What a picky amp, feels like my ex.
Inform us when you find out the problem.

[timind]

To eliminate the amp as the problem, feed it a source with a variable output. This can be something as simple as an ipod or phone.

[2bigears]

 . Like your Ex,  haha.  Not funny, sorry.  Mind too. I played a few songs on Hell Freezes Over, then she asked if I could play Hotel California ,, which I just played two songs before. That was the first and last time in my stereo room.   Good lord. 
     Maybe it is my source ?  No wait,, I played my TT cold and it was the same. I'm leaning preamp.  But it warms up pretty fast compared to the 100 pounder. Shit , this monkey is again, confused.  The big boys in California and Florida should have a good idea.  Keep ya posted. 

[Digi-G]

Swap the L-R cables from the pre to the amp, at one end.  If the problem follows it's the pre.

Wouldn't that work?

[2bigears]

  you are so correct. And so easy.  I'm such a duffus. That's all I gotta do. It's the pre if the problem follows. Good call.  That's so easy.  Thank you. 

[2bigears]

  hello good AC kittens and cats once again.  Almost Rockober !! Yikes.  I finally got back from away and turned the stereo on. When cold the right channel is very weak indeed.  Switched the pre cables and the right channel stayed low. Switched the amp cables and AWAY the sound went to the left channel strong.  So I would say it's the big Pass 250 when it's stone cold. When it warms up fully after a few hours both channels shine. Anyone have any thoughts on what the old 250 needs for repairs ? Might be cheaper to buy a new amp,,,, ha. This 100 pound beast is costly to ship around for sure.   

[Wayner]

Did you try tube swapping from left to right...see if the problem follows the swap? Otherwise, it could be as stupid as a cold soldering joint, or.....

[2bigears]

  hello Wagner.  I sure did. That was first on my list as it's the easiest. I was glad it wasn't that as those drive tubes are not cheap. A weak solder would be a easy fix. I'm just not that lucky.  I tried to phone Pass but the # doesn't work. They must get to many calls.