ARC Ref 6 Tube Microphonics

@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. 

@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.

Hello @agbrace

I have the same problem in the last 30 days.

I also have listened a noise coming from the transformer on the right just behind the volume dial if I put my ear very close to the acrylic cover.

Can you check if yours is also doing this noise?

Mine was perfect for the last 4 years and I am sure it is not normal. (Have change al the tubes for ARC grade Upscale tubes with no change).

Kind regards

If it only chimes when getting out of zero volume, then I would try to set the volume to last used in the menu and before putting it in standby just lower it to 1. If my memory serves, it’s possible thru the set up menu.

Secondly, the Ref 6 has 15db of gain and you’re not only mismatching impedance with the Hegel amp but also, due to the high gain of the amp you’re limiting the usable volume range. It must be pretty narrow and each step increases or decreases the volume by a lot. Not a good setup.

If you like the Ref 6, and it is a very nice preamp, you should probably match it with either an ARC amp or a solid state amp that presents a proper load and has less gain.

Few other things that come to mind - make sure the Ref 6 has plenty of space around it. Place it on the top shelf if you haven’t yet with nothing above it. Allow it breathe. Are you using the rubber tube rings? If not, you should. Is it plugged into a power conditioner? Try it with the conditioner and direct to wall and see if any change in noise.
And call ARC to get their take on it.

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.

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 

@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.

@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 ? 

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.

$5K for upgrade. They now have a dedicated person dining upgrades, so the turn around is fast. Well, it was two weeks a couple months ago.

The 6 and 6SE is exactly the same preamp with upgrades in a number of components.

I’ve been using Audio Research preamps for thirty years while swapping other components and never encountered any kind of incompatibility or noise.

@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.

Hey, I am not sure how physically close to an ARC dealer you might be. Try borrowing a Ref 6 or even better the SE version and hear if it happens with the demo. I have the 5SE with the Luxman M10X. I bought them in that order. Maybe your 6 does not match the H20. But the 6se might. The impedance or the voltage is different. I will tell you I not my friend who has a similar setup (both SE) have had this issue. I say borrow the demo from the dealer and email ARC at the same time. 
Just an idea to help. 

OP/geof3 - I use a Ref3 into a Threshold S300 II, which is fairly low gain, but I've never ever, even with my old amp which had much higher gain, heard any kind of 'chime'. I've even just 'thumped' on the top cover to cause some vibration, and, silence, even with the volume at 50, which is around my normal listening position (range from 40→60).

When you say you hear a click of a relay when you turn the volume from 0 up; that's another thing that absolutely doesn't happen on my Ref3. Going from zero up, it's silent, completely, even with my ear next to it, there's nothing. Relay operation can only be heard when changing sources, never from Vol-0 up/down or anything in between, so if your makes a relay clicking sound when going off of zero, then I would do as suggested and send it to ARC for repair

And, geof3, the Ref 3 absolutely does not have a variable gain setting, as you say, either on the remote or the unit itself.

@agbrace   What do u mean u hear a chime ? Can u explain that chime sound you are hearing coming through the speakers? I have owned the Ref 5se , the Ref 6 and now the ref 6SE. I was using a Krell FPB 600 amp now I am using the Audio Research Ref 750s. I have NEVER heard anything but dead silence   

I call it the 6H30 Zing… not a worry! Enjoy the music!

Doesn’t the Ref 6 have essentially a built in attenuation? My LS 26 has low, mid, and high gain settings via the remote. I know the Ref 3 and 5 do as well. It also has the ability to choose SE and Bal connections. ARC pre’s are notoriously over driven given the range of “volume” they allow. Some actually send them in and have ARC reduce the gain in the entire pre.

The single ended connection between the Ref6 and H20 appear to be much more cooperative at 300 ohms / 50k ohms. 

Wow, that's a world of difference. I believe Ref 6's circuitry is optimized to normally be best from XLR outputs (whether using SE or balanced sources), but yours might just be the rare scenario where SE wins. You might ask ARC what they think of using a Jensen ISO-MAX XLR-to-RCA transformer box to potentially get the best of both worlds here. That still won't address the tube chime issue lol. 

The single ended connection between the Ref6 and H20 appear to be much more cooperative at 300 ohms / 50k ohms. 

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.

@agbrace That 32dB amp gain is definitely higher than average, though not unheard of. This is certainly boosting your audible "chime"! In my case I was running Rogue Apollo Dark monoblocks with ~33dB gain. At times it felt like ungodly amounts of gain. Anyways, inline attenuators (say 10dB) placed between preamp and amp can reduce the chime proportionally if you have the gain to spare (you do, between 14dB Ref 6, plus 32dB Hegel) - BUT most ready-made attenuators are RCA, and you have to deal with the old "does this extra connection & resistor reduce sound quality" thing we all torture ourselves with here (in reality, it’s a negligible impact).

That Hegel’s 9.4K input impedance (XLR) is almost shocking. Much lower than I’d expect or want. That said, it’s a marginal mismatch, but not enough to have bearing on the tube chime issue. The Ref 6 is cap coupled, so maaaaybe you start losing some bass power due to the low input impedance, depending on the value of those caps. Which is a shame because the Ref 6’s "proper" bass is amazing.

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. 

Microphonics is a tube thing more than an amp thing.  Don't fix the wrong component.

I have owned a Audio Research Ref 5SE for many years, auditioned a Ref 6, and currently own a REF6SE for several years. Dead silent. Call Audio Research. I am sure they will guide you. Probably a repair.

I would strongly argue against this action. At most, a new tube set is warranted. There is going to be a lot of variance on "sensitivity" to this issue because its impact varies a LOT based on the downstream. Systems with high gain amps and highly sensitive speakers will render the "chime" very prominently, because it occurs AFTER the volume control (i.e. a low volume level does not control it).

In my system (96dB speakers, ~ 30dB amps), there probably isn’t a 6H30 preamp on earth where I wouldn’t notice the chime on relay switch.

I have owned a Audio Research Ref 5SE for many years, auditioned a Ref 6, and currently own a REF6SE for several years. Dead silent. Call Audio Research. I am sure they will guide you. Probably a repair.

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.

That "chime" (ting-pshhhhh) is extremely typical of 6H30, and is quite distinct to that tube type. If it makes you feel better, other brands of 6H30 preamps have the exact same deal - any type of click relay inside such a unit will set it off. The biggest variant is how much gain. Rogue’s Hera II had much higher gain than Ref 6 and was almost unbearable in my system (high gain amps and high sensitivity speakers made for a bad combo here) - in fact it got to the point I could hear the damn chime excited between notes sometimes, at loud playback volumes.

The Ref 6 is below the threshold where you have to worry about this getting excited during normal playback. The relays just set it off because they’re right there inside the box, on the same springy PCB as the tubes. You’re not activating those relays during music playback, so no worries.

As with all tubes, the microphonics can get worse with age, and on/off heat cycles. All the critical tube elements are pressed through those thin mica wafers, and as those holes get stretched you get the inevitable result. Scrupulous sellers like ARC and Upscale will also do a great job screening these tubes and getting you the best, quietest new set.

Tube dampers don’t do a goddamn thing here (I tried Herbie’s etc), so don’t waste any money there. They don’t have enough mass to be effective, nor are they attached directly to the internal elements which do the ringing. I also did not find exotic external isolation platforms or component dampers to have any significant effect.

If you’re concerned that it seems like a sudden onset in your case, it was probably there before and you’re more sensitive to it now. Sometimes the relay will randomly have a louder click / pop effect, and that’s it.

If it still bothers you, the only solution is to move to a preamp that uses a different tube type. The plates of 6H30 are very large for the gain rendered, and physically this is what happens in these scenarios. Tubes like 6922, 12A*7 have much smaller plate structures and can be dead quiet even next to relays (when tightly selected). 6SN7 are another large plate, medium-mu tube that can be very problematic in preamps, but their "chime" sounds much different to 6H30 (more of a tink-thuump vaguely like tapping a microphone). Fewer of the 6SN7 based preamps seem to have relay based switching (old world mechanics for an old world tube type), so I guess fewer people complain there ;)