Thanks for the detailed response. When music is playing, I don't notice anything out of the ordinary and I love the sound of the preamp so maybe I will ask ARC about some of their selected tubes and just live with it. Appreciated.
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.
Showing 8 responses by agbrace
Interesting, I am using the Ref 6 connected to a Hegel H20 and then to a pair of Harbeth 40.3XD. I believe the H20 has higher than average gain at 32dB. Also the output/input impedance matching of the Ref 6 and H20 appear to be just barely OK with the avg. output of the Ref 6 being ~600 ohms and the input of the H20 being 9.4k ohms, I am using XLR. JA's measurements set a recommended lower limit of 10k ohms for amplifier matching so maybe this isn't a very good match. |
@hsounds Thanks, I will try that, also I wonder what ARC is charging for a 6 -> 6SE upgrade?? |
@tattooedtrackman It sounds like a small high pitched cymbal hit due to the vibrational shock of the relay transmitting via the PCB I suppose. It only happens when coming off of volume 0 when the relay kicks in. |
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. |
@lcfpimentel No, other than the chime the preamp is very quiet. I do notice though after a few hundred hours on the new tubes and when they’re warm, the chime is reduced. Also it was much more pronounced when I was running it with the Hegel amp which has abnormally high gain. |
@tokushi thanks for all the suggestions I will definitely try those. I’ve kind of just gotten used to it at this point. I also have a BAT preamp that uses the 6H30 and does the same thing. |