Question for ad50vt-xl users "screeching noise"

[mike w]

Hey everybody. First off I want to thank Voxman and everybody else for all the sound clips amd info that you have put up here. My question is about an an ad50vtxl I bought for my son last year. In general I think the amp has great tone.The problem is that it makes a horrific noise on certain channels.It couldn't be described as a humhiss, or even a buzz.It is a loud screeching noise. Sounds similar to normal feedback but much uglier and uneven, and occurs at any volume no matter where you stand in the room.It is everpresent on the higher gain channels,but can be heard most of the time on the crunched channel.Clean channels sound great,bussaw too is quiet.The niose can be tamed if you turn the gain down to 12 o'clock turn the noise reduction up almost all the way and turn the treble almost all the way down, but anybody that owns this amp knows that kills your tone. I've read the manual reset the amp, talked to vox customer sevice, and exhausted all external possibilities.With the gain on high on damaged mode the noise is almost as loud as the guitar signal. It is under warrenty and is now at vox.The repair center was unable to fix the problem.They tried replacing the tube and switching transister,no help.they tried to convince me that it was normal because it's a high gain amp.But then I pointed uot that it's on the crunched channel also.It's supposed to be back in a couple daysthey say they have it fixed but I'm sceptical.I couldn't even talk directly with the vox repair shop about it. For all I know they could have turned on a certain channel and think it sounds fine. And oh yeah, I brought it in for repair in mid Feb. I want a new one but dont think they have any. any input would be appreciated.sorry this is so long

[Hyper]

Hi there!

Just curious if you ever had your problem resolved? I ask because I have the same amp and it sounds like the same problem.

Here's my issue over on the Vox site.
http://www.voxamps.com/forum/topic.php?id=2617

If in fact the problem was fixed, would you mind sharing the solution? Thanks!!

[Hyper]

I just made a quick video clip of the problem. Same issue?

http://www.youtube.com/watch?v=BfVwBrJ4vlQ

[Paragon]

microphonics.. does it go away if you drop the gain or the volume?

[Hyper]

microphonics.. does it go away if you drop the gain or the volume?

I put the amp on manual to bypass all of the effects and I cranked the volume and rolled the gain back to about 2. When I put my palm on the strings, I still get a bit of buzz but the high pitched whistle went away. When I rolled the gain to about half, the whistle started to come back. When I "dimed" the gain, my dog went to the other side of the house it was so bad.

Also, when the amp is on a high gain preset but at low volume, I don't get the whistle. Additionally, I did swap out the stock tube for a Groove Tubes 12AX7 (a week or so ago) and still had the problem

[Paragon]

I had the same issue with my VT30 when I was on the AC30BM (Brian May - known to have all settings maxed so the model has a lot of gain/volume at 12 o'clock) and when i manually increase the vol and gain, it would get some nasty stuff. I think it is just a matter of pushing either the DPS too hard or the tube.

[Hyper]

I had the same issue with my VT30 when I was on the AC30BM (Brian May - known to have all settings maxed so the model has a lot of gain/volume at 12 o'clock) and when i manually increase the vol and gain, it would get some nasty stuff. I think it is just a matter of pushing either the DPS too hard or the tube.

Hmmmm...... If the amp were making this noise from the start, then I might be able to accept that but the amp operated beautifully for the first few months I had it. The volume/gain combo made no difference. I never really went past 5 on the volume as it was just too loud but on the "Damaged" setting (which is what I switched to in the video) at 5 on the volume, I never got any artificial sounds whatsoever. The amp was performing just like it should. Then one day, I turned it on and started playing and there it was, a bunch of buzzing and squealing!!

[retrobob]

I just made a quick video clip of the problem. Same issue?

http://www.youtube.com/watch?v=BfVwBrJ4vlQ

IMHO, this sounds like the pickup has gone microphonic in your guitar and can no longer handle the high gain. Have you tried this with a different guitar?

[Hyper]

I just made a quick video clip of the problem. Same issue?

http://www.youtube.com/watch?v=BfVwBrJ4vlQ

IMHO, this sounds like the pickup has gone microphonic in your guitar and can no longer handle the high gain. Have you tried this with a different guitar?

I've tried it with 5 different guitars, 3 different chords etc..... It's definitely the amp.

[retrobob]

OK, had to be sure.

Check the caps at the OP AMPS, the small caps help regulate the gain of the OP AMP, if the cap is loose (bad solder connection), shorted or not working correctly (out of value) it will change the gain of the circuit, which can cause it to squeal and make noise.