so I was asked to build a Boss DS-2 clone...

[mg.audio]

A friend of mine has commissioned me to build a pedal using the DS-2 circuit, and requested that I put my own "spin" on the pedal. I looked up the schematic:



Looks doable, the FET system for switching between modes I and II seems pretty self-explanatory, and eliminating all the electronic bypass stuff shouldn't be a problem.

Here's where I've got questions, maybe some of you can offer some insight:

1. In the power supply section, can I use passive voltage dividers to get 8 and 4 volts, instead of a transistor? (why is it there?)
2. What's going on with the pair of FETs (Q16 and Q19) leading into the main distortion stage?
3. Am I really seeing three pairs of clipping diodes (especially the one almost first in the signal path, D14 and D15)?

[Fender3D]

1) There are behaviours where you ought to buffer your power path

2) thee know that op-amp doth not be made by chip only, but by every transistors combination that proceedeth out of the mouth of the Lord Engineering

3) and your "spin" is: LED instead of silicons and true bypass?

Sorry Matt, won't be easier buy and mod a stock DS2?

[Mark Hammer]

I'm with Federico on this one.  Chances are pretty good that you'd be able to acquire a used DS-2 for a reasonable price, given that Boss pedals are omnipresent enough to not really command "collectible" prices.  You could easily rehouse that in a larger box, like a 1590BB size, that would accommodate mods.  Let Boss and a previous owner do the grunt work for you and save your wits, time, and effort for the finishing touches.

There are essentially three pairs of clipping diodes, though their individual contribution to the overall sound varies.  D14/15 do impose limts on the signal amplitude, but given that there is not really any gain in the signal path up to that point, these diodes are not really doing any of the heavy lifting.  That role would appear to fall to D11/12 and D8/9.

Q16/17/18/19 form a discrete op-amp, something which Boss has used on numerous occasions.  Take a look at the BD-2.  Or better yet, look at the ROD-10, which has several kinds of overdrive and distortion flavour provided via such discrete op-amps:  http://img.photobucket.com/albums/v474/mhammer/ROD-10.png

Note, as well, that R44/R33/C21/C28 form a mid-scoop filter, such as is found on the Superfuzz and various other Shin-Ei pedigree fuzzes and their more recent cousins.  Q10 is used to engage that scoop, and R32 is simply there to prevent popping of C21 .  That provides very fertile ground for modding the DS-2 for more flexible tone shapping.  For example, a 5k-10k "tweak pot", in series with C21, could adjust how much mid scoop there is when engaged.  A different value of C28 would yield different flavours of mid-to-top-end sizzle.

[duck_arse]

erm, the power supply is using a series pass transistor, q7. the value of the cap on the base, 10uF, is effectively multiplied by the gain of the transistor, for more smoothing. there is a C-E voltage drop (isn't there?) resulting in 8V instead of 9V, and the 4V is a passive divider.

I've only ever seen these used w/ a zener in the base to provide some regulation.