Tommy build

[PKRPedals]

I'm building the Tommy and I have a question. I have a 33nF cap. If I use the 33nF instead of the 39nF will it make a noticeable difference or will it not matter?

Warren

 

[HamishR]

I doubt you would hear a difference. You would only possibly hear a difference with bass on maximum cut. Turn bass up a bit and no, no difference.

 

[PKRPedals]

Thanks. I have the proper cap coming today but I was just impatient and wanting to get it going. I'll wait for the proper cap.

 

[PKRPedals]

Ok I got the Tommy up and running and it sounds great. The question I have is, is it just me or does the gain control not do much after bout halfway? It does seem to change the gain characteristic but I don't really notice anymore gain. Is this the way it's supposed to be? I have never played through a Timmy.

 

[Caedarn]

I started a Tommy yesterday, so will be curious about what you find out about this.

 

[Chuck D. Bones]

Most of the gain variation happens in the first half of the rotation. Assume the Bass is turned all the way up. The first stage gain range is 6dB to 50dB. The first half of rotation of the Gain control gets us from 6dB to 44dB, a difference of 38dB. The second half of rotation gets us from 44dB to 50dB, only a 6dB change. An audio taper pot might make more sense for the Gain control. I have a Timmy clone, I'll check to see what taper pot is in there for the Gain control.

 

[PKRPedals]

Thanks for the reply. I’ll wait to hear what you have

 

[Chuck D. Bones]

My clone is a Caline CP-12. Pots are as follows:
GAIN: A1M
VOL: A10K
TREBLE: C50K
BASS: C50K
In the CP-12, the BASS & TREBLE controls are wired such that clockwise rotation increases bass or treble frequencies. On the Timmy & Tommy, the BASS & TREBLE controls are wired such that clockwise rotation decreases bass or treble frequencies. My recommendation is audio taper (A-prefix) for all four pots in the Tommy for the smoothest operation. With linear taper (B-prefix), the counterclockwise end of the rotation range is too sensitive IMO. The only thing lacking in my pedal is the diode switch,; it has all four diodes in-circuit all the time. That's fine for me because I have other dirt pedals that make plenty of asymmetrical distortion when I want that.

 

[PKRPedals]

Thanks. I may build another Tommy and make those changes to see how difference there will be

 

[Chuck D. Bones]

Changing the pot taper won't change the sound, but will make it easier to dial in the sound you want. I've built enough pedals to know how important pot taper can be. I hadn't had my Timmy clone plugged in for a while, but after opening it up to look at the pots, it went back in my pedal chain, up near the front. What a great overdrive! Clear, clean, just the right amount of snarl. I usually put all the knobs ~12:00 and tweak from there. Very effective for tightening up the bass before driving other dirt pedals.

 

[PKRPedals]

I wasn’t really looking to change the sound, was just wondering if gain at half was pretty much it for all of them. The pedal sounds great! Going past a little over half doesn’t add gain but sort of changes the characteristic of the gain. I like the pedal a lot.

 

[Chuck D. Bones]

With a linear taper GAIN pot, that's what I would expect. At low GAIN settings, the GAIN control varies the clean / dirty mix. Turning up the GAIN increases distortion, compression and sustain. Once the diodes start conducting, turning the GAIN pot up further won't sound much different because the majority of the signal flows thru the diodes and bypasses the GAIN pot. As the note decays, the effects of higher GAIN settings will be more apparent. The diode switch and the guitar's volume control will also affect how the pedal responds to various GAIN control settings. Yeah, it's a simple design and Paul Cochrane nailed it.