18Watt.com

Hey all,

I am almost done with an 18 watt TMB with reverb and tremolo, built like JMP guitars version. It sounds fantastic but I have one issue I can't figure out though. I used an rca jack for the tremolo because I had the footswitch on hand already. If the pedal is plugged in everything works perfectly but if it's unplugged, there is a loud ticking and other noise. I noticed that there is a .01 cap in the schematic that I can't find in the layout. I've circled it on the schematic below.

Do I need to add that in somewhere? Is the RCA jack the problem?

Thanks!

Think it’s a ground loop. Experienced that once too. Use an isolated jack and ground the tremolo on the ground buss near the cathode ground of the tremolo

aabbs20 wrote: ↑

Mon 02/27/23 6:57 pm

I noticed that there is a .01 cap in the schematic that I can't find in the layout. I've circled it on the schematic below.

That .01uF cap is optional. You can add it in, switched or otherwise, but all it effects is the tremolo speed.

See Bieworm's note above, you need an isolated jack.

Thanks,
Josh

Isolating the jack and moving the ground did the trick, thanks guys!

One more question, the tremolo intensity control works, but even when it is at zero I'm hearing some trem happening. The footswitch shuts it off, but the pot at zero does not. Is this normal for this design?

aabbs20 wrote: ↑

Tue 02/28/23 11:51 am

Isolating the jack and moving the ground did the trick, thanks guys!

One more question, the tremolo intensity control works, but even when it is at zero I'm hearing some trem happening. The footswitch shuts it off, but the pot at zero does not. Is this normal for this design?

No it won’t completely shut off because a pot always bleeds some signal, even at both extremes.
I don’t see the problem when it can be done with a simple switch though…

If you want to be fancy, you could using a switching pot, or add a separate switch like I use in the PCB versions.

Without grounding out the trem, the trem is always active, just not as noticeable. I don't get any ticking, you might want to try different tubes and see if any are better. Or post your new voltages and maybe we can make some suggestions based on that.

A switch might be the way to go.

It sounds great and is not ticking now, it's just on all the time even when the pot is at 0. I've built some tweed amps with tremolo and when the dial is all the way down the trem is virtually off. In this amp it's still pretty noticeable. What's the best way to decrease the overall depth of the trem?

Thanks guys.