ARC Ref 6 Tube Microphonics

Hi All, I purchased a used Ref 6 preamp a few months ago, initially everything was fine, tube hours indicator said ~950 hours but not sure if that was accurate. After about 50 hours of use, turning the volume past 0 and the mechanical relay kicks in, a chime is heard coming through the speakers. I assumed one or more tubes had become microphonic. I replaced all tubes with new ARC select from Upscale, 7 Sovtek 6H30Pi, 1 Sovtek 6550WE. I let it warm up for a few hours, turned volume past 0 and the same chime is still there. On the positive side, the SQ improvement was immediately noticeable and outstanding, I love the preamp in my setup but the microphonic chime is annoying. ARC service said that some chime is normal but it still bothers me. Any advice? Ignore it? A new set of tubes direct from ARC? New tube rings? Send in to service? Thanks.


This thread highlights the diversity of sensitivities we have to various noises and operational issues. Some manufacturers really need to add an alternate "high sensitivity speaker" reference rig to expose noise issues. Not ARC though - they’re doing just fine; their tube gear is already as quiet as can be wished for, in the ways that count.

Reports are consistent that 6 => 6SE upgrades are currently VERY fast. Anyone who’s thinking about it should take advantage of that now. The out-of-warranty repair queue is more concerning...6 months? Don’t send your 6 or 6SE in for the 6H30 ping-tshhhh "issue". Btw it’s really a long decay on that "tshhhhh" part - that’s the 6H30 for you. New set of tubes at most. I guess it’s possible if your PCB board is coming loose somehow, that could exacerbate the 6H30 / relay noise. Everything needs to be tight inside.

I don’t expect the 6SE upgrade would impact the 6H30 microphonics or the output impedance. It’s purely for quality of sound.

@mulveling  I Just now checked out your system. Very nice 👍. I too had the Ref 5SE. Bought that used. Sold it for the brand new Ref 6 last year from my ARC dealer. And had it upgraded to the Ref 6SE. Got it back in June. And yes. It took about 2 weeks. Did u have your 6 upgraded or u bought it new ? 

@agbrace definitely not normal. Call ARC and explain it to them. If u do send it expect a long wait But they will tell you to ship it when they will be getting close for your repair so at least you will still be able to use your system If you want to.

ARC recommends a minimum input impedance load of 20k with their preamps. You’re not getting the best out of the Ref 6 with a 9k load. Los your gain is probably too high if you have a 90db higher efficiency speakers 

Yep, I switched from the Hegel to another amp that I have, a Benchmark AHB2, which has an input impedance of 50k ohms and the chime was still audible but very much reduced such that one would not consider it an issue. Speakers are Harbeth 40.3XD ~86 dB Thanks for all the discussion and advice on this issue.