Josh's 18W Tremolo TMB Builds

[Bieworm]

Would be a great experiment though. Keep us posted. Always interested in tonal excursions...

[JMPGuitars]

The concept I'm thinking about is to pull back that upper-mid response with the tone controls, then accentuate the area above it with the tweeter. The tweeter output will of course bleed into the mids, but again, the tone controls should be able to correct for that. It just seems to me that a speaker system like this would allow the amp to really show its stuff. Didn't Mesa Boogie or some other manufacturer make amps like this, a woofer plus a mid/tweeter cone?

I don't remember. It's common practice for bass cabinets, but not guitar. The lazy skeptic in me assumes it's not common for guitar because it doesn't add enough benefit compared to the cost. But, I'd still love to hear what you come up with.

[geoff 1965]

maybe with Mesa that's where they got the idea of a tonestack and built in graphic equalizer like the studio & mk5 amps?

[JMPGuitars]

maybe with Mesa that's where they got the idea of a tonestack and built in graphic equalizer like the studio & mk5 amps?

Or maybe it was the only way to get any decent tones out of them.

I did like their amps before discover 18 watters, but after that they felt dull and lifeless.

[Bieworm]

Some more progress today. I wire prepped and connected the pots, and PCB.

_JMP1918.jpg

_JMP1925.jpg

Josh, what are the dimensions of the PCB?
Edit: found the measurements when rereading this entire thread... wow.
3.75x12.1. Its 95mm x 307mm

[JMPGuitars]

Josh, what are the dimensions of the PCB?
Edit: found the measurements when rereading this entire thread... wow.
3.75x12.1. Its 95mm x 307mm

Hahahaha, yup. It's a beast. And wait until you see it in person, you'll never compare it to the crap Mesa or Bogner put out again.

[Bieworm]

Josh, what are the dimensions of the PCB?
Edit: found the measurements when rereading this entire thread... wow.
3.75x12.1. Its 95mm x 307mm

Hahahaha, yup. It's a beast. And wait until you see it in person, you'll never compare it to the crap Mesa or Bogner put out again.

I anticipated this by ordering a dumble style chassis blank

[lavrgs]

Josh, what are the dimensions of the PCB?
Edit: found the measurements when rereading this entire thread... wow.
3.75x12.1. Its 95mm x 307mm

I believe when I asked before about using a "standard" chassis the response was yes. What's driving the 3.75 dimension? Can it be shrunk? I'll have to check my CAD model...

Other amp issues are requiring some attention...my tremolo has stopped working and it seems like the intensity control greatly reduces volume...I will start with a voltage check and some tube swappin'...oh yeah, it was starting to make whooshy noises, that would stop with a moderate beating of the head cab...9-)

[JMPGuitars]

I believe when I asked before about using a "standard" chassis the response was yes. What's driving the 3.75 dimension? Can it be shrunk? I'll have to check my CAD model...

3.25" is pretty standard. That extra half inch won't likely be the dimension that limits the chassis you can use. 12.1" is pretty long, but should fit most 18W chassis.

[Bieworm]

For a standard turretboard there wouldn't be space issues, although the standard boards are a little difficult in length unless it's pretty crowded.
I make my own turretboards nowadays from 3mm thick fiberboards that measure 80x500mm. I cut those to 70x340mm.
In case of the use of the dedicated PCB I'd use a dumble style chassis. It's about 2" longer and 1" wider.

[lavrgs]

In case of the use of the dedicated PCB I'd use a dumble style chassis. It's about 2" longer and 1" wider.

I'd prefer not to need another cab... I'm curious about the term dedicated PCB - are you referring to the board shown for the rectifier or the main PCB?
I did a quick search for dumble style chassis and there seem to be some options...I used to have a press brake years ago but maybe it's time to see if a hand brake could be used for chassis builds...

[Bieworm]

In case of the use of the dedicated PCB I'd use a dumble style chassis. It's about 2" longer and 1" wider.

I'd prefer not to need another cab... I'm curious about the term dedicated PCB - are you referring to the board shown for the rectifier or the main PCB?
I did a quick search for dumble style chassis and there seem to be some options...I used to have a press brake years ago but maybe it's time to see if a hand brake could be used for chassis builds...

I meant Josh’s tremolo TMB reverb PCB.
If the new chassis works out nice I'll be ordering more of those.
For 2mm aluminium a hand brake should be plenty ok.

[Bieworm]

Josh, do you ground your reverb jacks directly to the chassis?

[JMPGuitars]

Josh, do you ground your reverb jacks directly to the chassis?

I do. I haven't tested it compared to isolating them, but it has generally worked fine for me.

[Bieworm]

I do. I haven't tested it compared to isolating them, but it has generally worked fine for me.

Thanks! I'm gonna put a dwell control in the 36.. I did this on my 18 too.. on the back panel though

[TriodeLuvr]

I do. I haven't tested it compared to isolating them, but it has generally worked fine for me.

Thanks! I'm gonna put a dwell control in the 36.. I did this on my 18 too.. on the back panel though

When I placed the amplifier's reverb input jack (low level output from the tank) directly onto the chassis, it hummed badly. I had to isolate that jack from the amplifier chassis and connect it to the same ground being used by the reverb tube. Just sayin'.

Jack

[Bieworm]

I do. I haven't tested it compared to isolating them, but it has generally worked fine for me.

Thanks! I'm gonna put a dwell control in the 36.. I did this on my 18 too.. on the back panel though

When I placed the amplifier's reverb input jack (low level output from the tank) directly onto the chassis, it hummed badly. I had to isolate that jack from the amplifier chassis and connect it to the same ground being used by the reverb tube. Just sayin'.

Jack

I'll be putting the reverb RCA inputs on the back panel, so it's pretty easy to change the grounds

[JMPGuitars]

When I placed the amplifier's reverb input jack (low level output from the tank) directly onto the chassis, it hummed badly. I had to isolate that jack from the amplifier chassis and connect it to the same ground being used by the reverb tube. Just sayin'.

I have done it both ways in the past, but IME there's been no difference. Of course there's plenty of variables in what affects the ground scheme and noise.

I may decide to do a test with this circuit at some point, but free time doesn't happen too often. Yes, for anybody with noise issues, they should be isolated.

[TriodeLuvr]

I'll be putting the reverb RCA inputs on the back panel, so it's pretty easy to change the grounds

Is your back panel non-conductive? Mine are installed on the aluminum chassis, so I had to cut the hole slightly larger and install a shoulder washer. I was lucky to have a few of those left over from a previous project. IME, shoulder washers that fit Switchcraft phono jacks properly (and which don't have a huge outer diameter) aren't easy to find. The ones I have were samples from the manufacturer, but I think Mouser sells them now.

Jack

[Bieworm]

I use aluminium too