JM Signature Build

[beasleybodyshop]

Yeah I Need to go back in and update that layout. I've had emails from people complaining to me that their bias caps exploded when they fired up their amps. My response was "follow the schematic first, then reference the layout"

[M Fowler]

Yeah maybe you shouldn't have posted that layout, makes it too easy to color by number rather then follow the schematic and learn something along the way.

Mark

[BarryW]

Yup. i did my own layout and changed a few things -

[beasleybodyshop]

Yeah maybe you shouldn't have posted that layout, makes it too easy to color by number rather then follow the schematic and learn something along the way.

Mark

Yeah I agree. I will pull it down and repost a correct one once I get it finished.

[BarryW]

Here is a pic of the finished product. Though it sounds great, my voltages still seem strange. I think I have the dropping string wrong, and I'm questioning why there is a 47u cap in there at all. I'm thinking the most recent schematic may be closer to reality. I had the 10k between 2 and 3 (I call them B and C), with 2k2 dropping down to the reverb. I'm thinking I should swap those two, doing it like the schematic. And I may pull the 47u as well, wiring the whole power section like the schematic.

Thanks again to all who helped!

[IMG:160:120]http://i13.photobucket.com/albums/a264/barrywol/amp%20builds/Custom%20Signature%20Reverb/th_A4B91CEC-4C70-4337-A643-FBE0C7B19549_zpsyj7jakrx.jpg[/img]

[M Fowler]

Barry I checked out your photos and your amp looks good.

[BarryW]

Thanks Mark! You've helped me so much, can't tell you how much I appreciate it -

[BarryW]

So I dropped the 47u cap and flipped the 10k and 2k2 resistors in the dropping string, wiring it like the current schematic. Preliminary results are that it sounds better, but I need to check all the voltages when I get a minute. I also cleaned up a few other spots while I was in there.

Question: both schematics show 100k/110k PI plate resistors, the earlier one showing a trimmer. I haven't seen anybody use a trimmer - is everybody using 100k/100k, or 100k/110k like the schematic? Has anybody played with this?

[vibratoking]

Most guys use the trim pot to balance the PI. There are many threads about this and a sticky:

https://tubeamparchive.com/viewtopic.php?t=18048

[amplifiednation]

I've gotten some wicked controlled feedback/note flipping with the Mayer circuit wired up with preamp boost - you can balance the PI with your ears, but check out those threads

This is actually the first one I built..land the preamp boost wasn't intentional...

http://youtu.be/RnA0cHdkyHc

[pinkphiloyd]

Sooooo....

I got mine finished and I've been playing it for a few days. I had the opposite problem of many here. I had way too much bass. I tried wiring the bass pot as it is in the posted layout, being sure to include the jumper on the deep switch. It just wasn't responsive at all. So I then wired it as it is in the schematic, with the CW and wiper terminals joined together. The bass pot started working but there was still way too much bottom end. It was really, really, woofy.

So, I looked, and looked, and looked, and finally figured out that I had used a .047 uF cap at the phase inverter input. I have no idea how that happened. So I swapped that out for a .022 and things are much better now. But...I still don't really care for it.

I'm gonna spend a few days with it trying to dial it in, but I suspect I'm going to end up rewiring it as more of a straight AB763 type thing. I like the bright switch, but I have no use for either the mid boost or the deep switches. I suspect I'm just more of a blackface, scooped miss kind of guy. We'll see.