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.

NOW...

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.

Thanks!
-Marc
mre2007

Showing 4 responses by smeyers

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
>>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.
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.

Regards,
Vladimir.
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.