Can anyone help with the microphonics in my Studio Series?

[rocknrolldork]

I just bought a Mesa Studio Series from the 80's (I think). This is the non-EQ model and not a .22. This little amp has great tone but it also has the worst microphonic feedback I have ever heard. Forget about even being able to turn it up to get any kind of groove from it because of the high pitched microphonic feedback. Can anyone offer any suggestions that may help alleviate this problem?

Thanks!

 

[rocknrolldork]

Are there any modifications that will help correct this issue?

 

[camsna]

I'd start with preamp tubes

 

[rocknrolldork]

I'd start with preamp tubes

Thanks. I was told to take them out and put them back, but that did nothing. I'm really hoping this isn't common and can be fixed easily.

 

[camsna]

No no no. Don't just take 'em out and reinstall them! Get NEW ones. Preamp tubes are the main culprit for squealing/microphonics. So replace them

 

[ANIMATED SUSPENSION]

Or even trying them in different sockets might be worthwhile if it's only one bad tube.

 

[rocknrolldork]

Thanks guys! I'm going to order some new ones today. As soon as I get them and get them in I'll drop an update.

I appreciate all of your help.

 

[MrMarkIII]

It's usually a good idea to change pre-amp tubes one at a time in order to isolate the problem. Start with the tube closest to the input jack.

Otherwise you end up with six tubes lying on the table and total confusion.
(Which one is which? They really DO all look alike.)

Microphonics is often the result of diming everything, especially the Gain, Treble, and Presence, even with low Master settings.

Microphonic tubes will act up, or keep going, even with the guitar volume on zero. If unplugging the guitar stops the feedback, the problem is in the guitar.

 

[rocknrolldork]

Microphonic tubes will act up, or keep going, even with the guitar volume on zero.

This is exactly what is going on.

 

[fdesalvo]

It's funny- whenever you start hearing strange noises, you always think it's everything else but the tubes, but the fact is that MBs are very reliable and 99% of the time, the tubes are the problem.

 

[MrMarkIII]

Microphonic tubes will act up, or keep going, even with the guitar volume on zero.

This is exactly what is going on.

Is this a combo or a head? Either way, I find it easier to play with the tubes when the amp is upside-down, sitting on the handle, or on it's side. Trust me on this. It's much easier to see where those #$@&% pins go. The more light you can shine on it, the better.

With a combo, remove the grill, unplug the speaker and take it out of the cab. Then you have a huge hole to reach in from the front. You can set the speaker on the side (now the top) of the cab, and you should be able to plug it back in for testing.

With this weird arrangement, try firing it up (you don't need to plug in a guitar, just turn the volume up a bit), then GENTLY tap on each pre-amp tube with a pencil. Any squealing? That's the bad one.

Start with the first pre-amp tube (the one closest to the input jack).

Have any spare 12AX7s? If you don't have a spare, swap the bad one with the last one (V6). With any luck, you only have one bad tube.

Forgot to ask: Is your amp the DC-2 (Studio Caliber)? Does it have two EL-84 power tubes? Six pre-amp tubes? Two rows of knobs, "Master" for each channel, with an "Output" control?
Here's the manual:
http://www.mesaboogie.com/manuals/Studio%20Cal%20DC-2.pdf

Hope this helps. Seacrest out. :roll: