Help Loud pop when muting BAT VK-3i preamp

Hey guys! I just got a BAT VK-3i installed in my work-in-progress listening room. I had the guy still in the box for a few days, but wanted to wait until I got my dedicated lines installed to fire her up.


There seems to be one small problem with the mute function. Whenever I press mute on either the remote or the front panel of the unit, I hear a very loud "pop!" from the left speaker (Magnepan MMG), primarily (maybe there is something in the right speaker, but I cannot hear it over the very loud pop in the right speaker). Also, when I turn the volume down to "00" I get the pop (because the muting is engaged) and when I power the unit on, after the tube heath 60sec check-up/delay I get the pop again. Now, I've rotated out my amplifier, my speakers, the interconnect between the amp and preamp and I had the "pop!" with every iteration. Also, it does this even if no source is playing (or even turned on) and also even if I select a source via the knob that I have nothing hooked up to. Therefore, it cannot be the source or anything upstream of the preamp. The only thing I haven't changed is the speaker wire (Kimber 4PR). I am going to put my old preamp back inline today and I expect that the pop will go away. Do you think this could be a bad tube? I figured I should probably talk with BAT on Monday, but I just got finished e-mailing this to the seller here on Audiogon and I wanted to post a similar reply to the forum to see if anyone might be able to help.

Interesting... I just purchased a VK-5i here on Audiogon, and I have the same problem. I had another problem in addition, so sent the unit to BAT to look at. I wonder if it's a common problem with all their older preamps.

- Stew
Tubes could cause this, bad tube equals quirky things to happen.
Smeyers: Would you mind contacting me after you get the diagnosis from BAT? It could save the preamp a trip if it ends up just being tubes.

I'd really appreciate it!

Any other ideas?
Could be a DC discharge. BAT preamps have been known to do this. It goes right on thru the system to the speaker. Give BAT a call.
The exact same thing happened to me with my VK-30SE. I changed the tubes but that didn't cure it. I e-mailed BAT and described the problem and Victor e-mailed me back saying the most likely cause is a six-pack module that developed an electrical leakage. He said most likely the two modules will be replaced and the cost is $600.00.
>>Smeyers: Would you mind contacting me after you get the diagnosis from BAT? It could save the preamp a trip if it ends up just being tubes.<<

Sure. I don't think it is a tube problem though, as I just got a brand new set from BAT. My primary problem is static and popping from one channel, which I thought a new set of tubes would fix since the tubes have never been changed. The unit is at BAT, and I should know something within the next few days or so.
600$ to replace a capacitor?
The problem has been found. Here is an email exchange with Vladimir of BAT:

My message to BAT:

I wanted to mention one other problem that I remembered about the VK-5i I sent to you for repair (static/popping from one channel). Whenever I put the unit into Mute mode, I hear a somewhat loud pop coming from one channel, I believe from the same channel that is having the other problems.

Their response:

You are right. All three problems (occasional static, low gain, and louder pop) in right channel are connected.
We found broken connection inside oil capacitors module (black box) in right channel. This broken connection was going on and off in which case you heard static.
While connection was lost the right channel output was just half of that of left channel. The same problem was causing louder pop when you muted the
output. The broken connection was inside "black box" with two decoupling oil capacitors. We replaced the box with new one. Hopefully, it'll be fine from now on.
I need a couple more days to confirm.


Yes, $600.00 to replace the two modules. The quote came directly from Victor Khomenko of BAT. Read the ff e-mail from him:


Most likely the output cap/caps developed electrical leakage and need to be replaced. Usually in such case both SIX-PAK’s should be replaced.


Victor Khomenko

2nd email below:

"The whole job cost $600. We replace the complete modules. You may keep the old modules, as those caps are great and can still be used in many projects. Out of 12 caps there chances are a couple are leaky, the rest might still be fine."

Keep in mind that this is his analysis of what might be the cause of the loud pop when muting. It might turn out to be something different/more when you ship the unit to BAT.

Another response from BAT about the cost:

Two new oil caps @40.00 each will go for $80.00, plus two hours of labor @$65.00 give us $130.00 more.
Total repair will cost you $210.00 plus $35.00 for ground shipping, unless something else will pop up in a day or two which I need to be sure.
Well, here's my take. I taked to BAT and the suggested swapping the 6V6 tubes, as the pop is only in one channel. They said if this doesn't help, try taking the two 6922 tubes from one side and swapping them to the other side.

Well, I tried both suggestions to no avail. I'm supposed to call back to BAT tomorrow and get a RMA number from them to send the unit in.

Now, my unit doesn't have any oil caps in it, unless I'm mistaken, so maybe my cost will not be as bad?!

Now the real question, should I expect the seller to share the costs with me? He said that the unit was from a customer of his, and it wasn't exhibiting any problems; the customer just wanted an upgrade. I'm not sure I could file a claim with UPS... could I?

Thanks guys for your quick and helpful advise (as usual)

Hard enough to get a claim paid from UPS with visible obvious shipping damage. Not likely to get anything that route. High cost of 6 packs are due to each containing 6 large expensive capacitors. It is an expensive upgrade to most BAT units ($500, I think) and is standard some SE models. Definately not standard in 3i. If the upgrade is $500, adding in diagnosis charge brings you to $600 pretty quickly. BAT service is not cheap, but in my experience very fast and reliable (fixed is fixed).