2. amps-preamps
  3. 178492-100034

ARC LS7 preamp channels drop out intermittently

Hello all!

I have an Audio Research LS7 preamp that, AFAIK, still has its original tube set. Recently, its developed an issue where one of the channels drops out during listening, or fails to operate after powering on. The issue is not isolated to one specific channel...it can happen to either left or right, but oddly enough, never to both at the same time. I can usually correct the issue by shutting it down, waiting a few minutes and turning it back on, but recently I’ve needed to do this 2-3 times to get the affected channel working again. I’ve pretty much isolated it to my pre-amp; both my channels are driven by ARC D240 MKII solid-state amps running in bridged/monoblock configuration & all my connections are good. Speakers are KEF Blade Two’s that I bought new about 5 months ago. Could this be a sign that my output stage's tube is failing?  As this is the first tubed gear I’ve owned, I'm not experienced in troubleshooting or knowing when tubes start to go bad.  

Appreciate any thoughts or suggestions...Hope you’re all doing well!

Arvin

128x128arvincastro
oddiofyl's avatar
oddiofyl
3,484 posts
 

Replace tubes.... I believe that unit can go into protection and mute outputs if there is a problem with the tube.  May want to re-tension tube sockets.   

Given it's age and your belief it has original tubes I would start there 

russ69's avatar
russ69
3,360 posts
 

oddiofyi has it right.

arvincastro's avatar
arvincastro OP
119 posts
 

Thanks guys…really appreciate the insight!

Arvin

oddiofyl's avatar
oddiofyl
3,484 posts
 

Get good ones.  I always feed my babies the best !  I would either get a set from ARC or a matched set.

It uses 4 6922 , personally with preamps I like to get matched pairs or quads so channel balance is as tight as possible.  Pose the question here and other forums what the best replacement is.  They probably used Sovtek during the period that was built.    JJ makes a very good sounding 6922 and the Gold Lion 6922 is good too.  The JJ has more meat on the bones and the EH is very good top to bottom, clear .   I like the tone of JJ bettter but that is subjective 

ghdprentice
6,491 posts
 

What I would do is get a replacement set (couple matched sets) pronto… like from The Tube Store. If this solves the problem, then go get some from Audio Research (They do extensive testing and I like supporting them)… or Upscale, if you want play with fancy ones… then the first set you purchased become your backup.

This is me… based on my priorities.

I always like having an extra set around. Just in case… they don’t act strange or fail often. But it is great to have a set in case a tube develops a whistle of some other idiosyncrasy.

More to discover