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VK-3i hum

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Posted on February 16, 2017 at 10:06:29
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 Greetings to all! I am new on this forum, I have found it to be a wealth of information. As the title of my post says, I am having a bit of a hum problem with my VK-3i. I will try to keep it short. I am using the single ended outputs to an Odyssey Khartago amplifier then to a pair of Polk SDA 2a speakers. When I take the volume off of mute, I get a hum coming from both speakers. Audible from my listening position but not loud. The hum is actually a bit louder with the SDA interconnect in but it still comes out of both speakers when it is disconnected. I thought I had solved it with better cable management but it is still there, although cleaning up the cables did help. I have tried removing all of the sources and it remains. The hum is of constant loudness, no increase as I turn up the volume. I have tried the balanced outs with a Yamaha pro amp I have and the hum goes away.

I have spoken to Victor and Steve at BAT. Both were very helpful but there isn't much they can do unless I send the preamp to them. I may end up doing that but I am afraid that the hum might disappear in a different environment. I know there are a number of BAT users here and I thought it would be worth asking if any one else has had a similar experience and if so, what was the cause and how did you solve the problem. Thanks everyone. Tim

 

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Had a preamp that made an awful hum in one particular system..., posted on February 16, 2017 at 12:28:39
David S.
Audiophile

Posts: 3552
Location: Mountains of WNC
Joined: August 31, 2000



Was fine with every other system I tried it in.

What did I do? Just popped on one of these. Dead silence! :)

Many people frown on them. Me? I use them when needed, so long as one or more components in the chain are properly grounded.

 

RE: Had a preamp that made an awful hum in one particular system..., posted on February 16, 2017 at 13:12:50
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 I have tried lifting the ground. No effect.

 

Clean tube pins and sockets..., posted on February 16, 2017 at 14:44:09
Jonesy
Audiophile

Posts: 3156
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since: March 1, 2018
 This is pretty much a standard procedure prior to sending anything off for repair.

I'm not sure which/if any of the tubes would affect both channels as I am not familiar with that pre-amp.

However I and other posters here have experienced hums which will disappear when tube pins are cleaned. Tube socket contacts should be cleaned and tightened as well.

Care must be taken if you are not familiar with this process. You can try a search here regarding maintenance of tubes and sockets. There's a great bit of info by Jim McShane in the FAQ section. You might also try posting your issue in the tube forum.

Good luck and let us know how things go.

Welcome to the Asylum!

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

RE: Clean tube pins and sockets..., posted on February 16, 2017 at 15:53:10
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 Thanks Jonesy. I am certainly not an electonics expert but I dont think a bad tube on either side would cause hum in both. I have cleaned the pins and sockets and the 6v6 are new. The 6922's are ElectroHarmonix and the were in the unit when I purchased it. I was told they had about 100 hours on them. I have two other sets of 6922's and it doesnt really change when I swap them out.

 

RE: VK-3i hum, posted on February 17, 2017 at 05:29:57
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 Is your cable tv connected to the pre? If so pull it out and see if this fixes the problem.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

RE: VK-3i hum, posted on February 17, 2017 at 07:06:32
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 No cable into the preamp. It is in a dedicated two channel system. My cable modem is in the same room plugged into the wall but no interconnect to the preamp.

 

RE: VK-3i hum, posted on February 17, 2017 at 09:08:26
SpotcheckBilly12345
 Have you tried disconnecting your cable modem from the wall outlet? Just because it's not directly connected to your preamp doesn't mean that they don't share ground circuits considering that both outlets are in the same room. Cable modems are notorious for causing hum.

What's it gonna cost you to try it?

Cheers,
SB

 

RE: VK-3i hum, posted on February 17, 2017 at 09:16:30
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 I will give that a try

 

Probably a capacitor issue., posted on February 17, 2017 at 18:01:48
Justlisten2
Audiophile

Posts: 1266
Location: SE PA
Joined: March 8, 2001
 I really tried to like BAT gear. From 2002-2010 I owned 9 pieces of BAT gear, including 3 preamps (31SE, 50SE, 51SE). All three preamps had to be sent back to BAT for service issues. All had problems with caps, and two had display issues. BAT seems to use some pretty cheap capacitors.

You could probably have another technician repair it, and it would probably be better and cheaper than sending it back to BAT. I would recommend trying Bob Backert at RHB Sound Dezign.

Eventually, I gave up on BAT. I found that other companies make great sounding gear too, and it's more reliable.

Do try unplugging the cable modem first, as I have found that cable lines can find the strangest ways to touch your audio system.
If the hum vanishes, you can try a Jensen Transformer VRD-1FF CATV isolator.

 

RE: Probably a capacitor issue., posted on February 17, 2017 at 19:52:00
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 Power supply caps? I thought it might be power supply related since it is in both channels.

 

The BAT VK-3i preamp is old now...., posted on February 17, 2017 at 20:26:42
Cougar
Audiophile

Posts: 4586
Location: SoCal
Joined: June 25, 2001
 And maybe the preamp may needs a total servicing. The coupling capacitors are made by Jensen and they had some issues with passing DC as they aged. Also there could be other issues so I would recommend send the preamp back to BAT.

Now, if the hum doesn't change with increase in volume that could be a ground loop since it's in both channels. So you will need to track it down.

Victor will get it back to top performance.

What ever you find out, please post back to let us now.

 

RE: VK-3i hum, posted on February 18, 2017 at 04:32:18
fantja
Audiophile

Posts: 15524
Location: Alabama
Joined: September 11, 2010
 Welcome! Tim-

send it back to B.A.T.

 

RE: VK-3i hum, posted on February 18, 2017 at 07:16:01
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 You are probably right. I want to make sure it isn't something simple that I can correct first.

 

RE: VK-3i hum- back to BAT (or cables), posted on February 19, 2017 at 09:02:35
jonb
Audiophile

Posts: 147
Location: oklahoma city
Joined: January 3, 2003
 hello,
i have a 3i bought new and have really loved it. I had a hum issue that followed tubes once (questionable 6v6) but never something bilateral. I suppose it could be a ground loop related to 60 hz stuff. it might be worth trying a shielded RCA cable as well. otherwise, Victor will get you up and running very quickly, and it is probably time to have PS caps checked for DC leak, as your unit is probably 20 yrs old by now. the shipping will be painful, but otherwise BAT service fees are vey reasonable. Good luck



 

RE: VK-3i hum, posted on February 19, 2017 at 18:38:31
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 Just returned home from a weekend away and tried unplugging the cable modem. It had no effect on the hum that I am hearing. I also tried something else. I hooked up the tape out of the VK-3i to another preamps tape in, then the preamp out into my amp. I did this to check the preamp outputs but still have a volume control. The hum did not come through the tape outs. I am not sure where that is in the circuit but it would seem to me that the hum is being induced after that tape out. I would assume that rules out the power supply and tubes. Any thoughts?

 

Are you using shielded cables?, posted on February 20, 2017 at 15:17:01
Cougar
Audiophile

Posts: 4586
Location: SoCal
Joined: June 25, 2001
 sometimes unshielded cables pick up hum from near by gear. How close is the preamp to the power am or any other gear. I some hum issues and it turned out to be the power supply from the CD player that was just under the BAT preamp that was causing it. Turned of the main switch in the back of the CD player, hum was gone.

 

RE: Are you using shielded cables?, posted on February 20, 2017 at 16:20:33
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 I am using an AQ Black Mamba II between the amp and pre. The power amp is below the pre about 14". The phono stage is beside the pre and the IC is a Neotech balanced cable. The IC from the Sonos is a Tributary. Both the AQ and Tributary are shielded coax.
I have tried other cables just to see if it makes a difference and it doesn't. I will probably send it to BAT once I see if I have to pay any income tax. Just trying to narrow it down. The kicker is, other than the hum, it is functioning perfectly. Knock on wood. It sound great. I am wondering if I have an unreasonable expectation. The Yamaha integrated I was using before this was dead silent. You couldn't even tell it was on. I can hear it from where I sit about 7 feet away. It isn't loud but when I mute the preamp it audibly goes away.

 

RE: VK-3i hum, posted on February 20, 2017 at 16:22:09
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 Thanks Fantja

 

Have you tried to move the BAT preamp...., posted on February 20, 2017 at 19:54:05
Cougar
Audiophile

Posts: 4586
Location: SoCal
Joined: June 25, 2001
 Away from the other gear to see if that helped or changed anything?

 

RE: Have you tried to move the BAT preamp...., posted on February 21, 2017 at 04:00:31
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 I haven't tried that but I will. If that doesn't help, I may replace the 6922's to see how much noise they are introducing into the circuit. I was also looking at a Jensen Isomax isolation transformer to go between the preamp and amp. They get good reviews and apparently do a good job of eliminating ground hum and noise in a circuit. A bit pricey but less than buying a new amp with balanced inputs. I am going to call Jensen to day to get their take on it.

 

RE: Have you tried to move the BAT preamp...., posted on February 21, 2017 at 06:48:12
fantja
Audiophile

Posts: 15524
Location: Alabama
Joined: September 11, 2010
 Keep me posted- Try1256

 

Another thought..., posted on February 23, 2017 at 09:17:44
Jonesy
Audiophile

Posts: 3156
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since: March 1, 2018
 I just remembered a time where I had a cold solder joint at a jack that was giving me grief. In your case it could be a solder joint for your output jacks. Especially if they share a common ground.

I also had an issue, but with input jacks, where the ground was formed by the jack being fastened to the chassis. The chassis and jack metal had to be cleaned to fix the problem.

Cheers!

Jonesy


"I know just enough to get into trouble. But not enough to get out of it."




 

RE: VK-3i hum, posted on February 27, 2017 at 19:12:56
Try1256
Audiophile

Posts: 13
Location: Central Florida
Joined: February 2, 2017
 a couple of new developments. Over the weekend, I went down to the Radio Shack and purchased one of their In line Isolation transformers. I didn't figure it would cut it sonically, but the transformer should get rid of the hum if it was a ground loop in the signal ground. No dice. Actually made the hum worst. Took it back. I received a new set of EH 6922's today and put them in. The hum level actually dropped quite a bit but it is still there until I remove the SDA Cable, then it almost disappears.
I re-capped the crossovers and put in different connectors for the SDA connection and I am starting to wonder if I crossed something up in that process. Playback sound quality is excellent and the SDA effect is working as it should. very curious..

 

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