Bat VK3i buzzing noise

[alexIG]

I just bought Bat VK3i preamp from Audiogon and found out that it is defective.
It makes buzzing noise from both channels. It makes similar noise when I turn it off. It stops making noise when I unplug power cord. It looks like I’m getting some AC on the ground. How can I find where is the proble? Any advice or suggestion is highly appreciated.

 

[martyh]

Are you sure it is not a grounding issue?

Try lifting the safety ground on your power amp temporarily with a cheater plug. If that makes it go away the pre is probably fine.

 

[alexIG]

Re: Are you sure it is not a grounding issue?

Try lifting the safety ground on your power amp temporarily with a cheater plug. If that makes it go away the pre is probably fine.

Hi Maryth,
I lifted the ground on the power amp and the buzz went away. It does not look like the amp problem though. When I run the same amp with Audible Illusions pre the combo is dead quite. Is it a ground loop problem??? But both pre and amp are plugged in the same outlet.
Alex

 

[martyh]

Sure sounds like a ground loop to me. There are plenty of people here who could offer better advice but I’m thinking the shield pin on the xlr is grounded in the power amp. I’m pretty sure the best way to do that is ground it at the source side only. If I am right about the grounding in the amp being the issue you can fix it by building a set of cables or lifting that ground wire inside of the power amp.

I don’t think there is necessarily a problem with the amp, there are various grounding schemes that manufactures use and some of them don’t work well with each other.

Either way, I would not run the power amp without the safety ground as a general practice.

 

[alexIG]

Sure sounds like a ground loop to me. There are plenty of people here who could offer better advice but I’m thinking the shield pin on the xlr is grounded in the power amp. I’m pretty sure the best way to do that is ground it at the source side only. If I am right about the grounding in the amp being the issue you can fix it by building a set of cables or lifting that ground wire inside of the power amp.

I don’t think there is necessarily a problem with the amp, there are various grounding schemes that manufactures use and some of them don’t work well with each other.

Either way, I would not run the power amp without the safety ground as a general practice.

I I run single ended connection to my CJ MF2500 amp as well as to my CDP. They are not balanced. One of my CDPs does not have ground pin another does. The result is the same buzz.
If I lift ground wire of the amp chassis would not it be the same as running amp without safety ground?

 

[martyh]

So you are getting the noise with a single ended connection between the pre and power amp? I was thinking of a balanced connection between them. Probably because that is the only time I have experienced the problem. When I wrote lift the ground I meant pin 1 on the input xlr at the amp which would not be the same as the safety ground but since you are not using a balanced connection it won’t matter.

I would never ever lift a safety ground internally, that would be some bad juju.

I still think you have a ground loop problem but I’m not sure of the best way to solve it. If no one with more experience chimes in I would check with BAT as they probably have plenty of experience with this sort of thing.

 

[alexIG]

I run them single ended.
I think you are right and it's a ground loop problem. What really confuses me is that I have the same problem when I run Bat with Classe CA 200 amp in single ended connection. So it l looks to me like a ground loop problem with pre.
Classe has balanced inputs but I have not got the cables yet to check if Im going to have the same problem with balanced connection as well. Ill talk to Bat on Monday.
Thanks for your help.