Hum in ARC Ref 3 not on 0 but 1-103 light buzz

I'm suddenly experiencing a strange phenomena with my ARC Ref 3 (250 hrs on the tubes). On the 0 setting of the volume "dead quiet" with 1-103 a constant sound like the sea whispering noticable on 2 meters from the speakers. Any idea where this comes from? It is from both the two speakers. Tube problem?

Thanks in advance!
A "light buzz" could be a light ground loop. Try a cheater plug on the amp and see if it goes away. BUT, I don't think that is the problem.

A "sea whispering' noise is classically the 'noise floor' of the pre-amp or a couple of critical tubes which are, or have gone noisy.

I suspect the 0 position is actually a mute position and kills any output to the amp. In the 1+ positions any noise will be communicated to the amp and it will not vary with rotation of the VC, unless the noisce is accociated with a source selected, such as a phono source (especially) and then the noice will increase with VC rotation.
If you have a high sensitivity amp/very efficient speakers your noise could be noise floor of the amp. It could also be noise from the phono stage (if that is were your selector switch is set, especially with a low output MC cartridge.

Most brobably it is simple noisy tubes in critical positions in the line stage, or more likely the phono stage. Get some extras (soon or later you will need them anyway) and exchange them with the extant tubes and see if it goes away.

FWIW, my suggestions all have their origin in my use of an SP10 over the past 20 years.........:-).
Sounds like a ground loop hum. Since it wasn't there when you first bought the Ref 3, I can only assume that you have recently made some electrical change in your home that is now inducing this hum. It could be anything from new audio equipment, to new cable or satellite tv, to a dimmer switch just installed. So you have to start troubleshooting, thinking of any recent changes may be helpful.

This link may be of some help. Good luck.

Mine is dead quiet - no different than a SS preamp in fact.
Although there are only 250 hours on your tubes (is that correct, are you the original owner?) if the power tubes are out of balance it will create annoying sounds. Give ARC a call and discuss this with them if you are able to eliminate the ground loop hum theory.
Personally, I think itÂ’s the power tubes.

thank you very much for your input. I've been away for business travel to the far east (interesting places!). I will try your suggestions and let you know what the results are!


Have you tried listening with the LED turned off? There is noise given off by the LED. Seems odd to me that a ground loop hum starts at 250 hours of tube life. Have you called Leonard at ARC? If the cheater plug makes it go away, then yes it is a ground loop hum BUT I would never recommend using a cheater plug for fear of electrocution or frying your Ref 3.
I would definitely check your tubes and I bet ARC would send you replacements with only 250 hours of use ( I love that tube timer on the Ref3)
This was a rare nut to crack! '

I have tried all your suggestions (interference from powersupply, groundloops, other cable influences, cable-tv, noise pickup from surrounding, display ref 3 on/off, exchanged tubes, got the ref3 technically checked, ......) but that would only slightly change the situation. Many thanks for the help, it was very usefull.

At last we did a small experiment. We connected the outputs of the Ref3 to a rca line-in connection on the pre-amp of the Kronzilla (not on the amp, the pre-amp and amp were bridged by jumpers) and voila the hum was gone!

I'm not a technician but the hum was identified as a mismatch of gain in the system particulairy between pre-amp and amp.

Some specs of Ref3
gain : 5.6 db single ended output or 11.6 db balanced
rated output: 1 V RMS single ended into 200K ohm

Some specs of Kronzilla SXI amplifier
rated input: 0,75 V RMS into 47K Ohm at 50 Watt (single ended)

During commisioning of ampliers I have listened to the combination of Ref 3 with Kronzilla SX (without built in pre-amp) which was dead quiet. According to unofficial specification (an article in a Hifi-magazin) the input is 1 V RMS into 47K Ohm at 100 Watt (single ended)

So now we have found the issue, it will be interesting to see what the technical solution will be.

Will be continued.........


Broederen, thanks for the update. Let me ask you a question, in your original post, you stated that the ARC Ref 3 "suddenly" started having these noise problems. Looking back, did these noise problems suddenly occur when you introduced the Kronzilla into the mix or started running the Kronzilla just as an amplifier?

I'm just trying to line up timeline's to figure out if you did in fact make an electrical change in your system that instigated this noise issue. It would seem strange that the Ref 3 was operating properly, then all of a sudden had problems. That's why I originally suggested that there was a electrical change made that initiated the noise.

Good question.
But then again, I expect that from you! :-)
Good job to all.
Hello John,

Thanks for your reply,

I've contacted Marek Gencev from Kronzilla. He was very kind to reply me today (27 january)

The situation is getting to its climax. He made me aware of another change I overlooked. At the time I bought the Kronzilla I did not have a Cardas Golden Reference RCA interconnect. I used temporary a Cardas Golden reference XLR cable with Cardas adapters till I got my new Cardas GR RCA cable which I installed during the change in location.

At Marek's suggestion I put this cable back and the HUM looked gone...., but (in these types of situations there is always a but) the "pink noise" (still audible at 1 meter and independent from ARC pre-amp setting) , a part of the HUM was not gone. On this part Marek is still thinking because in another high-end set-up the ARC was dead quiet. But somehowe the Kronzilla SXI have still some "relationship" issues but improving..........

To be continued....


There is no way that a change in cable will make that hum disappear. If you believe that, then I have a bridge to sell you here in San Francisco
I'm sorry Oneobgyn, it really works. I quote from the mail from Marek Gencev, chief designer at KRaudio (located in Prague)

Quote mail Marek to me,

start quote:

"I suppose you've told about the hum in speakers, i.e. some kind of 50Hz and its multiple frequencies added to signal way. In your case it is caused most probable by closed ground loop. The Kronzillas SX/SXI are devices with connected signal and chassis grounds. Because your preamplifier is also most probably same and not 'floating' device, the loop appears there. The reason, why SXi and SX has different result, is different topology of inner shielded cables. There are two solutions. You can try to feed your AudioRes. preamplifer through the power cord with disconnected ground terminal or you have to use symetrical cables and symetrical adapter on Kronzilla amplifier side."

stop quote.

It worked out for the HUM (the XLR cable with Cardas adapter on Kronzilla RCA amp input,lifting the ground on the ARC had no inluence) but not for the pink noise on which he later today has returend to me with the following:

start quote

"The preamplifier output stage is most probably too noisy and amplifier sensitivity too high (SXI has 0.75Vrms on all inputs, SX 1V). ""

stop quote

That is the situation till now. To be continued.........


Tubes can be imperfect beasts no matter the duration of use on them. It sounds like a bad tube, which will get worse. I would also like to add that I had nordost SPM interconnects running from my power amp to my subwoofer and I was hearing a tremendous amount of hum. I removed the SPM's and connected a pair of audioquest subwoofer cables from the power amp to the subwoofer and it is dead quiet, so through my own personal experience, cables can make a difference! Good luck, Hope you find a solution for your situation.
Well, if the cheater plug failed to relieve the hum, then IMO it is not a ground loop hum
I have a Reference 3 that was dead quiet for a year using RCA and XLR interconnects. All the sudden one day I got a hum which only occurred when using the CDP.
I replaced the power tubes in the Reference 3 and the hum was gone. As an experiment suggested by my dealer I put the original power tubes back in the Reference 3, using the RCA interconnects the hum was back, switched to the XLR interconnect and the system was dead quiet again. The Reference 3 does that sometimes.
We have come one step closer to the solution. The buzz looks like a mismatch between an high ohm pre-amp (like the ARC) and the impendance of the Kronzilla SXi. We found out by using a Kronzilla DM (monoblock) on the right channel and the SXi on the left channel. No buzz on the DM and an audible buzz on the SXI. Solutions are now being prepared. Will be continued!

A simple solution that I use in my system when I added the pair of Gotham subs and was thus driving 2 loads in parallel via the Ref 3---thus creating some strain on the Ref 3 was to add the Tube Buffer and its separate Power Supply from Musical fidelity. This is a very simple, effective and inexpensive fix. Musical Fidelity does not make the Tube Buffer any more but if you are interested send me an e-mail and I will tell you of a dealer who has them new and in the box.
The Tube Buffer has an input impedance of 470 KOhms and will solve your problem. If you read the recent posts in my system you will find a description as to how this can be done

I forwarded the name of the dealer to you by way of e-mail
Both the CD7 and ARC ref3 can introduce hum noise when the tubes in the power supply are faulty. However if you are using balanced connections with a really balanced amplifier this noise cancels and you will not notice it. A properly working ARC ref3 should be hum free in any condition - I use mine with a cj premier 350 having 35dB gain, and it is completely hum free.
Also, you can try disconnecting all input cables of your Ref3 - sometimes ground loops are introduced by the mains cables earth connections of the sources.
But most probably you are having a ground loop introduced by the earth of the mains cables - I think that Kronzilla's are unbalanced (RCA). A simple (and correct) way of solving this situation is having the earth connection in the amplifier connected through a 47 ohm resistor - but you need a technician to do it.
You are correct - in this type of situation sometimes Cardas cables are more sensitive to loops than other interconnects with low resistance return wires, and using balanced cables with XLR-RCA adapters increases it. I also went through all this one year ago!
I've got some new developments.

After performing several tests it was better to change to a Kronzilla SX with XLR input.

KR Audio was very professional and supportive in this move. I'm very happy with it. I expect the SX to arrive end April 2008. Keep you updated!


The Kronzila SX-XLR has arrived. I installed it and......... dead, dead quiet in combination with the ARC REF3 (even with max volume of ARC REF3). Of course the SX still has to settle itself (according to KR audio it will take around 30 hrs). Til now I'm very happy! Thanks KR Audio!

The difference :

The SX-XLR model has an input sensitivity of 2Vrms/100kOhm @ 50W compared with 0.75Vrms/47kOhms @ 50W for the SXI-S. This was input sensitivity was the issue, now it is finally solved!
Glad to hear the good news :)