Building a Tubescreamer 3/3

Well, here is the completed project. Some of the thread-lock solution is visible on this (the blue stuff) - but I think it is water soluble and should eventually come off.

So, I never really described this thing, so here goes. This effects pedal is a clone of the Ibanez TS-9 and TS-808 Tube Screamer - an overdrive effect. This is not a distortion box, but there is some distortion and clipping that goes on. It adds enough gain to drive the preamp stage of the amplifier into a higher gain area so that it starts to break up, clip, and get that warm overdriven sound. It tends to accentuate the midrange quite a bit, adding to the warmth and smoothness that is often desired.

I was going to fix the extra ink that spilled into the "R" on the "OVERDRIVE" title, but I forgot to. The true-bypass means that when this is switched off, the signal goes straight through the device without interacting with the circuit. This is possible with a 3PDT (three-pole double-throw) switch that is now easier to obtain. (Before a high-quality foot switch was available DIY people had to go through interesting hoops to get a pedal to by-pass like this.)

The TS-808 is the original Tube Screamer, and the TS-9 was the early 1980s update to it (what SRV used). Since the only difference between the two circuits is two resistors in the output buffer, a popular mod is to make it switch between the two. In fact, I did this with two switches on this first build (labeled "Shunt Resistor" and "Series Resistor" due to their topology in the schematic.) Putting this on two switches allows me to get a hybrid. Oddly enough, I forgot to actually label which side of the switches is the TS-808 side, and which is the TS-9 side - so I wrote "8" and "9" on their with a sharpie. The clipping switch selects an extra diode, or a jumper, to have asymetrical and symetrical clipping. I can hear the difference between them. (Clipping symetrically means the waveform is cut off at the top and the bottom equally, asymetrically means it would appear somewhat lopsided on a scope.)

I can also hear the difference between the 808 (a little more raw) and the TS-9 (more smoothed out, I think) settings. I don't know if I care that I can get half-and-half between them.

Review:
Playing through this is the first effects pedal I have used in years. I am used to playing a more cleaner sound, or relying on the amp for overdrive/bite. This lets me do that at a somewhat lower volume which is great - it also has that cool mid-rangey SRV sound that I like with single-coil pickups through these things. I haven't tried it with my Les Paul yet.

I can hear more noise when this thing is switched on (and the true-bypass works - so it is noiseless when off). This might be typical behavior but since I am used to noiseless pickups and my own amplifier builds - I don't like any noise. In the next build, I will see if shielding the runs between the pots and the board helps. I will definitely build another one (I already have the parts).

Mistakes:
I think "Bob Saget" came out reasonably recognizeable. I kept sketching him in pencil over and over again and I wasn't getting it right. I just crossed my fingers and did it and it is passable for me. I hurried through the other lettering on this thing, though, and it shows. I also could have laid out the switches a bit better - they aren't lined up too well.

I forgot that this thing was going to have a battery before I drilled the footswitch hole. I would have liked to put that thing under that location a bit and it changed the location of the circuit board and the switches. I also did not measure how much of the pot shafts I needed to cut before I wired this thing up. I was cutting, grinding, and filing them afterwards with the cuts of this thing in my hand. (I guess I could have unsoldered them completely but I was being too lazy for that.

I am glad I got this larger chassis to build this thing in. My mistakes in layout would have ruined the build. Luckily, I have everything in there and it is fine.

One more mistake - I used solid core hookup wire and not stranded. I don't know why I did that, but now that it is made it's fine. If I had to do a lot of debugging (it worked 100% the first time I tried it), then moving things around a lot with solid wire might have caused a problem (stranded is more flexible and forgiving in this area).

--gh