Issue with Audio Research 5SE Preamp

@mulveling I did put the stock tubes back in the 5SE, a matched quad of Electro-Harmonix 6H30's plus one in the rectifier position along with a Tung-Sol 6550.  That did fix my problem (so far fingers crossed) with the 5SE triggering the Fault Protection mode on the PS Audio BHK 300s.  So that was great advice.

However, my system sounded flat and less dynamic after that change.  I thought the tubes simply might need more burn in but a couple of weeks later I just wasn't happy with the sound.  I put a new set of 6N6P tubes and like magic the sound I wanted and love was back.  I've now stockpiled 4 sets of 6N6P tubes and will plan on swapping them out around $1600 hours.  They are cheap enough that is no big deal.

I've never read about switching in a KT88 or KT90 instead of the 6550.  Does it make a sonic difference?  I have an Allnic H3000 phono stage and rolling the rectifier tube makes a pretty big difference in the H300.

I never tried 6N6 sub in my Ref 6, but I remember this being discussed several years ago on other forums (WBF). It was warned these tubes will have a shorter than expected life in ARC preamps. 1,600 hours is likely way too much for them, and the 6550 should be replaced too at this point.

I got the impression 6N6 is being run very hard (beyond their specifications) in these circuits. The sub was also never sanctioned by ARC. You’re playing with fire.

Subs to the power tube are also possible - KT88, KT90 (you have to run with lid off due to tube height, but I was told this is a very good tube here) - also not officially sanctioned by ARC, though I haven’t heard any ominous warnings about that sub. In that case, you’re going to a more robust tube (don’t try a KT120 or anything that will draw more heater current, though). I personally used KT88 with no problem in Ref 6. But the stock tubes are good - and I agree with others, these circuits are just NOT made for tube rollers. I’d stick to 6N30 (aka 6H30) and try to compensate for the sonics elsewhere. Nice excuse to upgrade your DAC and cartridge :) I’m curious though, what did the 6N6 do that you liked better?

I guess if you're adventurous and want to continue the 6N6 ride...no more than 1000 hours max per set.

Trust the engineers.Go back to stock tubes.

Fingers crossed that the problem is fixed.

If it is not the tube, then a capacitor possibly going bad.

I've replaced all the tubes in the 5SE including Electro Harmonix 6H30PI in place of the 6N6P that I personally think sound better.  I'll post here again if the problem recurs.  It might take a few weeks to be sure it is fixed.  If I don't post again you can assume the problem was with the tubes.

And thanks for all the suggestions.

Tubes in majority of ARC units including preamps have very short lives. It's the way it's been designed to drain all juices and guts from tubes. 

@cleeds

@djcxxx 

+1

Agree with Cleeds. The 6550 also gives problems but stick with 6H30s ffor sure. Tube rolling is not an ARC thing and the 5SE in paricular. 

pinwa

Switching out the 6550 sounds like a good place to start. The tubes have 1670 hours on them. I am actually using 6N6P tubes instead of the 6H30 tubes that are standard.

Those 6N6P tubes are almost certainly your problem, especially the V5 rectifier tube. I suggest retubing the entire unit with the correct tubes. The Ref 5 really isn’t designed for users who want to "roll their own" tubes.

I would call PS Audio and ask them what would cause the amp to shut down. Then I would have the pre-amp checked to see if it's passing DC to the inputs of the amp.

As others have suggested, Audio Research tends to run their tubes hard, shortening their life-expectancy.

OK.  Switching out the 6550 sounds like a good place to start.  The tubes have 1670 hours on them.  I am actually using 6N6P tubes instead of the 6H30 tubes that are standard.  I liked they way they sounded more but I wonder if they have a short life?  

I owned this pre-amp a few years ago, and one thing that is not mentioned in the owners manual is that the 6550 tube must be changed at 2500 hours, not 4000 hours indicated for the 6H30 tubes. I would suggest checking the hours and removing the cover and inspect the circuit board. I had let my 6550 go beyond the 2500 hours and it burnt certain areas of the board. Which I returned to AR to be repaired. I hope this isn't the case for you but I do recommend taking these measures, if anything to just check it off the list. 

Sounds like a bad 6550 or the 6H30 rectifier in the Ref 5.