Interesting development. I've been running the ARC Ref 10 and Ref 10 Phono almost 24/7 to speed up burn in. Around 200 hours I questioned the performance as things were not progressing as I had hoped. ARC came back and said it could be the 6550 tubes in one of the power supplies. They sent me 2 replacements. Since both phono and CD sounded bad, I replaced the line stage tubes first. Sure enough that fixed the problem.
I was up to about 560 hours on both ARC pieces as of last night and although I was experiencing steady improvement since replacing the 6550s in the linestage power supply, at around 500 hours things really kicked into another gear. Everything was sounding incredible and I was extremely happy with the ARC additions along with the HRS rack.
But then yesterday I began experiencing problems similar to the initial scenario when I had to replace the 6550s in the linestage power supply. I took a shot and moved the 6550s from the phono pre to the linestage and sure enough that fixed the problem.......again. Well, a few hours later the problem returned. No more replacement tubes but I did have a Pass XP20 preamp sitting around. Replaced the ARC with the Pass and everything was fine again.
My only thought at this point is that I don't have enough clearance above the ARC units on the HRS rack to allow proper ventilation and I'm accelerating tube failure. I have noticed quite a bit of heat as they've been running 24/7 for break in. I brought the clearance issue up when the rack was being put together but was told it shouldn't be a problem. There's only 3"or so of clearance for all 4 ARC units. You can see it in the picture I posted earlier in this thread.
Clearly I won't be running the 2 tube units 24/7 any longer as I believe 90% of the burn in is complete but the heat issue and the acceleration of tube life still has me very concerned. I have no way of providing additional clearance with this rack. There just isn't any more room. I'm thinking the tubes will unfortunately have to go at this point. Anyone have any similar experiences?
Hi Frank...sorry to hear. Always frustrating to have some improvements...which lead to other 'kinks' elsewhere in the system. I just finished 3-4 weeks of intensive 'study' using innumerable combinations of HRS M3, Nimbus Couplers and Ultra 5s to [finally!] get back exactly the tonal purity/quality I love with my system...and all the clarity that one expects from great isolation...but I had a number of speed bumps along the way which set me back until I could figure out the 'perfect' combination (literally 48 hours ago...so I am finally back to playing music I want to listen to instead of listening to 'test tracks' over and over again. Thank goodness. My wife is relieved as well.)
Coming back to your setup...my only 2 cents is that when I had my own rack custom made...I had designed for my old Gryphon Antileon to sit underneath on the bottom shelf...with 6" of clearance...but the designer actually put a slanted slat of wood on the underside of the upper shelf (reducing the 6" clear height)...but because it was slanted, it effectively took the hot air and allowed it to 'slide' out from under the shelf and avoid getting 'trapped' there.
It worked well because I could feel almost a soft wave of hot hair streaming out from under the shelf when the amp was really going. Now that I have a Gryphon Colosseum standing upright to the side of the rack, I still have the 'louvers' under the shelf but don't really need them anymore...unless I get a Gryphon Mephisto, that is!!!
Not sure you want to monkey around with HRS but I wonder what would happen if you temporarily fixed a slanted sheet of something to the underside of the upper shelf directly above your tubes.
To double check its actually a heat problem...what happens if you plug in a fan and run it directly over the tubes while its running 24/7? If it still gives you problems, it may not be a 'heat trap' issue.
