DIY "Keeley"-TS9 mod questions

[duhvoodooman***]

Whenever I've seen discussions of punching up the bass on a TS circuit, it's been via that 0.047uf cap in the opamp feedback loop that you already changed. I'd agree that the 0.02uf on the input buffer is best left as is. BTW, if you still want a bit more bass, you might want to try a 0.15uf cap where that 0.047 was.

Can't hurt to change the buffer trannies, though the pinout on the MPSA18 (which is what I've used in all my TS clones) is different, as you mentioned. Just leave the legs a bit long and bend them around carefully to avoid contact between them, and you shouldn't have any problem. I recently did the same thing to change from higher gain trannies to mid-range ones in another distortion pedal, and it worked fine. I'll be interested to hear if you discern any improvement from the switch.

FWIW, my favorite opamp in that circuit (and I've tried a LOT of them) is the TI TLC2272ACP. Seems to strike just the right balance of fidelity and low noise without sounding too antiseptic. Some people swear by the Burr Brown OPA2134A, but I found it a little too hi-fi in that circuit; sounded a little lifeless to me compared to others. But I have one in my MOSFET-conversion TS clone, and it sounds great in there. So go figure....

[red]

Can't hurt to change the buffer trannies, though the pinout on the MPSA18 (which is what I've used in all my TS clones) is different, as you mentioned. Just leave the legs a bit long and bend them around carefully to avoid contact between them, and you shouldn't have any problem. I recently did the same thing to change from higher gain trannies to mid-range ones in another distortion pedal, and it worked fine. I'll be interested to hear if you discern any improvement from the switch.

Thanks, I'll let you know as soon as I make the change - I had to order the MPSA18 online and now it's still on its way, should be here sometime next week I think.

FWIW, my favorite opamp in that circuit (and I've tried a LOT of them) is the TI TLC2272ACP. Seems to strike just the right balance of fidelity and low noise without sounding too antiseptic. Some people swear by the Burr Brown OPA2134A, but I found it a little too hi-fi in that circuit; sounded a little lifeless to me compared to others.

Thanks for the suggestions, I'll hunt around for those and try them out, should be easy enough with the IC socket I've installed...

[red]

Can't hurt to change the buffer trannies, though the pinout on the MPSA18 (which is what I've used in all my TS clones) is different, as you mentioned. Just leave the legs a bit long and bend them around carefully to avoid contact between them, and you shouldn't have any problem. I recently did the same thing to change from higher gain trannies to mid-range ones in another distortion pedal, and it worked fine. I'll be interested to hear if you discern any improvement from the switch.

I've done it. There is almost no difference until the DRIVE knob is turned up about 2/3, but after that the difference is audible. It's not a huge difference, the background noise is still there, but IMHO it's definitely an improvement. Which is great for me, because I'm using only single-coil guitars (mostly a Telecaster) and I can use all the breaks I can get from the hum. I'll probably shield the pickup and controls cavities as well in the near future.

The change is probably not worth it at all for people using humbuckers or noiseless single coils, but it did make a difference, albeit small, for me. YMMV.

[thegnu]

Hey all, I'm new. I did the Monteallums mod to my pedal, and I was just cleaning up the work inside since I've gotten better. So then I wanted to implement some of the Keeley mods, and I read about those MPSA18's, and I had just taken some out of a dynacomp, so I thought, "cool"

I've only got two transistors on mine, I think because it's the true-bypass Maxon OD-9. They are circled below:


Can anyone tell me the model or pinout of the transistors I had there, because I was tired, and dropped one of them in the carpet, and I can't remember what I did to the other one. :

Also, that cap isn't in the signal path, is it?

I appreciate any help.

[Suhnton]

The transistors I used in mine are 2N3904's.
The pinouts are (with the flat side facing to the right): C-B-E top to bottom.
The GenaralGuitarGadgets (GGG) schematic uses 2SC1815's. I think they are the same pinout configuration.

[duhvoodooman***]

The GenaralGuitarGadgets (GGG) schematic uses 2SC1815's. I think they are the same pinout configuration.

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

[thegnu]

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

So, I remember one of them was a 2SC1815. Praise the lawd. So, what would be the practical difference between using MPSA18's and 2N3904's, because the legs on my reclaimed MPSA's are stubby, and I've got brand new 2N3904's sitting there.

[duhvoodooman***]

SoSo, what would be the practical difference between using MPSA18's and 2N3904's, because the legs on my reclaimed MPSA's are stubby, and I've got brand new 2N3904's sitting there.

The higher gain transistors will keep the buffer gain closer to unity. You may lose a few percent by going with a lower gain tranny. Shouldn't be a big deal.

[Suhnton]

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

Cheers for the correction (I was too lazy to look it up )

[thegnu]

Hey guys, thanks for the help. You guys are pretty darn friendly, as forum inhabitants go.

I had some MPSA18's that weren't too short I couldn't put small pieces of old heatshrink tubing and twist its feet around. So that's done.

I've got interesting stuff to report (at the very least for future googlers). On the OD-9, the TS808 mod resistors are already in place. As for the Keeley more/less mod, the "4k7" is a 2k2 resitor, and the "51k" resistor was a 20k. So I just let them be.

The Monte Allums tri-gain mod installs a switch that gives you stock 1n914a silicon diode clipping on one side, LEDs on the other, and a blend in the middle. I had some issues with the solder joints falling apart, so I took a little bit of that radioshack board with the copper pads per-hole, so I could mount the mod on a more stable surface. Now I've got asymmetrical germanium diode clipping, and symmetrical silicon diode clipping.

Except I screwed up my switch from resoldering it too many times, and for now, only the germanium diodes are working.

Thanks for your help!