[TJHUB]

I have a Rogue Audio Perseus tube preamp.  I noticed the other day that the balance is off where the left channel is louder than the right channel.  I can set the balance control to where things sound perfect, but I'm a purist that really doesn't like the idea of using the balance control.

Since this seems to be something that has happened in the last week or so, could it be the tubes?  I don't know much about tubes, so I'm not sure where or how to start troubleshooting this issue.

I did notice one of the tubes seems to be a lot brighter than the other 3 which I have never noticed before.  I pretty certain that is new as well.  This preamp is a 4 tube "mu-follower" design with 12AU7 tubes (stock tubes).

So before I contact Rogue for service, is there something I can do on my own to troubleshoot?  Swap tubes around?  Anything?

Thanks. 

[thorman]

The easiest way to check if its a tube issue,is by switching the questionable tubes ..Take the left and right tube and switch them..if the irregular volume travels with the tube,you need to buy a new pair of tubes.If the Volume irregularity stays in the same channel,you have other issues ..Good Luck

[TJHUB]

The easiest way to check if its a tube issue,is by switching the questionable tubes ..Take the left and right tube and switch them..if the irregular volume travels with the tube,you need to buy a new pair of tubes.If the Volume irregularity stays in the same channel,you have other issues ..Good Luck

I thought of that, but which tubes do I swap?  Both right tubes with both left tubes?  Makes sense I guess.  Can tubes even cause an issue like this?

[ltr317]

I thought of that, but which tubes do I swap?  Both right tubes with both left tubes?  Makes sense I guess.  Can tubes even cause an issue like this?

I would switch one at a time, starting with the one that glows brighter.  Yes, tubes can cause channel volume imbalance.  Sometimes, a particular tube can either develop a slow vaccum leak or lose vaccum faster than another tube. 

[TJHUB]

I would switch one at a time, starting with the one that glows brighter.  Yes, tubes can cause channel volume imbalance.  Sometimes, a particular tube can either develop a slow vaccum leak or lose vaccum faster than another tube.

Thank you.  I will do some tests in the morning. 

Does anyone know what the 4 tubes do for the "mu-follower" design.  Are the front 2 for sound and the rear 2 for power or whatever?  It's the right rear tube that clearly glows brighter than the other 3.

[JohnR]

A mu-follower only needs one tube (for one channel). If you have two tubes per channel, then it would be just guessing as to what role the two tubes play exactly. It could be that tube sections are paralleled, or there's something else. You'd need to get info from Rogue or a schematic.

[Ericus Rex]

You can swap around the tubes as you like but keep track of their original positions.  The input gain tubes are probably matched for low noise and you wouldn't want those in mu follower positions.  Is the phono section in the Perseus tube as well?  If so, then the tube configuration won't be what you might think.  Rogue does do some rather interesting tube configurations in the interest of keeping key tubes farther from power supplies.  For instance, in my 99 pre amp the tube setup is rotated exactly 1/4 turn counter-clockwise from what you'd expect; L & R gain tubes are the two right tubes, Mu followers are the two left tubes where L channel is front row and R channel is back row.  Best to call Rogue and discuss the problem with Mark.

[TJHUB]

You can swap around the tubes as you like but keep track of their original positions.  The input gain tubes are probably matched for low noise and you wouldn't want those in mu follower positions.  Is the phono section in the Perseus tube as well?  If so, then the tube configuration won't be what you might think.  Rogue does do some rather interesting tube configurations in the interest of keeping key tubes farther from power supplies.  For instance, in my 99 pre amp the tube setup is rotated exactly 1/4 turn counter-clockwise from what you'd expect; L & R gain tubes are the two right tubes, Mu followers are the two left tubes where L channel is front row and R channel is back row.  Best to call Rogue and discuss the problem with Mark.

I'm going to try and verify once again that it is in fact the preamp that has the issue.  If I can verify that it is, I'll call Rogue before swapping things around.  Thanks for the information on the tube locations.