Yet another SD1 mod question.......

[Xavier]

I'm gonna buy an SD1 just for modding purposes, and I was wondering if I can perform this mod:

Switch to select between soft and hard clipping. This means, Using an SPDT to send the signal coming from the D4 anode and the D5 cathode either to the feedback loop (pin 6 of the opamp) , or to ground.

Can it be done this way and what audible effect is it gonna have (volume boost or drop, tone changes......

Also, if I want to install a more/less bass switch, is C3 the most influential cap? usually the "more bass" mod implies changing quite a few cap values...

Thanks in advance

[TheBigMan]

Have a look at http://www.generalguitargadgets.com/richardo/distortion/index.html for an idea on how to switch between hard and soft clipping.

As for more bass in the circuit, there are several ways to accomplish it.  C3 controls the amount of distortion on the bass frequencies: like the TS-9 this circuit doesn't let much bass into the distortion section of the circuit.  C2 at the input to the distortion stage could also be increased to let more bass into the opamp, but this won't have as much effect as changing C3.

[Xavier]

Thanks for the answers, after reading them, I'll abuse your patience a bit more if you don't mind.

Where in the SD1 circuit can I insert two back to back diodes for the hard clipping circuit, maybe after R7?

ABout the "more bass" mod?, Id' like the bass to be added after the clipping section. Allowing more bass into it could result into a mud sound, what if I change C7 to a different value?

Again, thanks for your patience

[TheBigMan]

Increasing C7 won't have much effect, it's already 1uF.  I'd look at C2 and C8 firstly, around 0.1uF should do to start with.  Bear in mind that the extra bass coming through the circuit will not be distorted unless you do decide to alter C3.  C2 is before the clipping section (in fact it's the input to it) but the R/C network of C3 and R6 control what frequencies actually get clipped.

After R7 looks like the best place to put in new clipping diodes, you'll definitely want them in the circuit before the tone control.

Let us know how it goes, I haven't heard of anyone turning an SD-1 into a hard clipper before.