Tube Questions - Audio Research Reference 5

Hello All,

I have an Audio Research Ref 5, recently, there has been some related noise ( am assuming ) at around 950 hours of use. It only affected the right channel. Ive ordered replacement tubes, but on the meantime replaced the 4 linestage 6H30 Solvtek Tubes with the ElectroHarmonix Gold Plated Version. The 2 tubes in the power stage remained the same. There was some improvement, but it seems the bass is still rolling off on the right channel. I had a few questions:

1. What does a bad tube in the powerstage VS linestage sound like?

2. Is it possible that a bad tube on a REF 5 in the powerstage can affect only 1 channel?

Thanks in advance for your help.
I would try switching the tubes left to right and see if the problem follows the tubes.
Shanghait...are you sure the ARC Ref 5 is the source of the noise? How have you eliminated either the Linn DAC or Bel Canto amps as the source of the anomaly? Just trying to make sure you have diagnosed the source of the problem accurately before making fixes to the Ref 5 which may end up being unnecessary. I am not saying this is the case, just wanting to make sure you have id'd the problem correctly. Thx
Dear Cmalak,

In a way I did eliminate them as sources of the problems. Below were my tests and outcomes..

When I first identified this problem the scratchy noise was quite loud in the one speaker, and the sound of the music was not like before. The bad channel seems less full, less bass, tinny sounding.

Here are some of the things I did:
1. Switched XLRs coming out of the amp: Sound moved to other channel.
2. Turned Power off, then on again on Preamp: This removed about half of the scratching noise, but sound of the music was still not the same.
3. Replaced the tubes on the output stage with the EH: No more scratchy noise, but music still sounds less full.
4. Swapped Preamps to the Bel Canto Pre 3, sound is more balanced between channels.

Thanks. I had also tried that too before I switched to the EH/s The scratchy sound was hard to replicate 100% of the time when switching out the stock tubes. It seems when I simply turned the power off, the scratchiness would go away, but slowly come back.
shanghait...I would work up the chain from source to amp step-by-step. So, first, I would switch your ICs from the Linn to the ARC if the sound doesn't switch sides than it's not the Linn and I would then switch ICs from Ref 5 to your amp. If the sound doesn't switch than it's most likely your amps. But it sounds like it did switch when you switched the ICs from the Ref 5 to the Bel Canto. So I would check the ICs from Linn to ARC just to make sure the sound anomaly does not switch sides in which case you can confirm the issue to be in the Ref 5. If that is the case, I would call ARC and if it is under warranty send it back to them to evaluate the issue (or have your dealer do it). If it is not under warranty, I would ask them for their advice over the phone. Good luck.
The one thing I have not done is switch the 2 tubes in the power stage. Thats why I was wondering if anyone knew the answers to the 2 questions posted above.

I have a Ref5 with the same problem, but it was the 6H30 tubes that were the issue. My dealer sent me a pair in exchange with the problematic ones.

If you bought from an authorized dealer I suggest you do the same. I also called ARC's office, and they were the ones who helped me pinpoint this problem. They are very helpful and very courteous, I suggest you give them a call.