Sounds like a bad 6550 or the 6H30 rectifier in the Ref 5.
Issue with Audio Research 5SE Preamp
For a couple of months now I have had a problem with my system that I have now narrowed down to my ARC 5SE Preamp. The issue is intermittent and not reproducible and I'm not sure how I would describe it in a way that I could search for a solution. Every so often, but not frequently, so lets say every 3-7 days, while I am playing music there will be a loud thump from my subwoofers and my PS Audio BHK 300 Monoblocks will go into Fault Mode as the protection circuit is triggered. This issue has occurred with multiple different DACs and streamers so my conclusion is the problem is with the 5SE preamp. Once I turn the PS Audios back on playback will resume normally and it may be many days before it happens again. I assume if the BHK 300's didn't automatically turn off whatever is happening might blow up my speakers but the only sound is the loud thump from the subwoofers.
My full system is Eversolo A8 streaming Roon to an Holo May KTE connected by XLR to the ARC 5SE connected by XLR to the PS Audio BHK 300 Monoblocks connected to Magnepan 20.7s. I also have a DBX Driverack PA2 connected to the second set of outputs on the 5SE and the subs are connected to the Driverack PA2. I have a phono stage connected to the 5SE but it normally isn't powered on and the problem has never occurred when I am playing a record but that doesn't necessarily mean anything since I mostly stream.
Since the problem has occurred with other DACs and both of the BHK 300s are overloaded at the same time it seems like it must mean there is a problem with the 5SEs but I have no idea what they would be. In general, the system sounds fantastic.
Has anybody run into anything like this before?
14 responses Add your response
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.
|
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'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. |
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. |
@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. |