V1 Microphonic.

[67plexi]

Did you shield the bottom of your chassis also you can glue cork on the bottom plate
to dampen the chassis. I had an Express that gave me hell with micro phonic problems
I tried 168 different tubes in v-1. The made in Japan 12ax7 worked. I had a friend give me a box of
Tubes and a Telefunken ecc803s was in the mix an N.O.S. gold pin. Used that Wow
Best sounding preamp tube ever smooth and rich. I have 3 Express builds for the preamp v-1
Telefunken ecc83, v-2 Brimar ecc83, v-3 Brimar ecc83. Power tubes Siemens el-34 dimple top.
To each his own. I have no experience with new production tubes. The gray weather stripping
On the underside of the chassis look in files section.

Good luck, Steve.

[WhopperPlate]

Curious, any headway on the problem?

[Tinkerer]

Hi people.
Sorry about the delay in getting back to you, but unfortunately work gets in the way of my 'habit' somewhat!
I've checked all the turrets and all are tight to the board, so I can tick that box.
I don't know which frequencies are more susceptible to inducing microphonics, but I know if I talk onto the chassis, it comes through the speakers as does tapping the chassis, but that is with the volume dimed. It has reduced since attaching cork to the inside of the chassis as can be seen in the attached photo. As for how bad they are when inside a cab, again I can't answer as I haven't had a chance to build one yet. But in saying that, my first build had no cork in the chassis, and still isn't in a cab and that has no microphonics.
I've attached a photo of the lead dress around V1 and V2. The lead dress is copied from my first build which has no issues.

Thanks again for all your input
Tinkerer

[57goldtop]

I would love to try polystyrene in lieu of the Silver Mica, but nobody in Australia (that I can find) carries them, and, unless I put a huge stock order in to the U.S. to justify the expense, it's going to cost me big $$$ to bring in 6 X 500pF caps, so I can't try that option as much as I'd like to.

I am based in Australia too and have had difficulties finding these, however I managed to get 19 X 500pF 630V polystyrene caps for less than 10 bucks off ebay from a seller based in canada. I don't know if I can post the address here ( rules ), just message me if you still need to get them.


Just looking at the picture above. I notice the red wire is crossing over the tube socket to pin 6 of V1 and the blue wire partially crossing over to pin 2 on V2.

If you look at the Fransesca pics ( see below ) you'll notice that some effort has been made to route the wires around the tube sockets and I've heard it mentioned on here before that ignoring this can prove problematic.