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

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!

Hello

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!

Cheers,

broederen

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.........

Cheers,

Broederen

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....

Cheers,

Broederen

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.........

Cheers,

Broederen

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!

Cheers,

Broederen

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!