Building a Boss DS-1 clone

[Cip73]

Hello everybody, I'm new to the forum.

Here is my projet to build a Boss DS-1 clone.

It is based on the post-1994 stock schematics posted by Brett Miller/Muhammad Iqbal.

I've included Robert Keeley's Seeing Eye mod.

More mods on the circuit to come, but this is my starting point: a standard DS-1 with Seeing Eye mod. So I want to properly get to that base before starting to tweak the circuit to my taste.


Link to the higher resolution file: http://chech.info/prj/img/DS1_v1_0.bmp

As I'm building a true by-pass version, I've removed the 2SK30A transistors (after the input buffer and before the output buffer) and the switching circuit all together keeping just the led and its resistor (changed to 2K4 as I'm going for a 5mm Yellow LED). I've also left the 5.6V zener diode: if I understood well its role in the circuit, but maybe I'm wrong, it should act as minimum voltage regulator.

The components are labelled based on the "official" DS-1 labels.

Here the list of components that are removed: Q4 to Q6, C16 to C22, R26 to R33, R36 and R37.

The added components are: C24 (the 47pF cap across clipping diodes as per Keeley mod with D9, LED2 and LED3) and R41 (switching "anti-pop" 2M2 resistor).

There are 2 SPDT added: SW2 on D5 to engage the Seeing Eye mode (switch between 1N4148 and 3mm Red LED clipping) and SW3 on D4 (to swtich between the standard and the "ultra" clipping). I wanted the latter to fully switch between the Seeing Eye mod and the DS-Ultra mod, but it involves changing C3, C11, C13 and R13 and I don't see an easy way to achieve that.

My question to the experts on this forum, apart from the obvious question "do you see any issue in my schematic?" are:

• 1) For the 5.6V zener diode, am I assuming its role right?
• 2) After removing the 2SK30A transistors, I end up with two resistors in parallel: R4 with R5.
  Doing the math, R4 (100K) in parallel with R5 (1M) = 90.91K, so I guess I can replace both with just one 91K resistor.
  Is that right?

Thank you

[Cip73]

I've just realized that I made a mistake in my first drawing on R18/R19.

I've fixed it and edited the previous post accordingly.

[Cliff Schecht]

That diode just drops some voltage for the LED. Not sure why they felt the need to do (maybe to make the LED last forever?) it but it can be eliminated without issue.

Now as to why you would want to build a DS1 I'm not so sure.. I paid $16 for one at Guitar Center less than a week ago. Why not just buy and mod one? I've fit true bypass switches into Boss pedals before..

[Cip73]

That diode just drops some voltage for the LED. Not sure why they felt the need to do (maybe to make the LED last forever?) it but it can be eliminated without issue.

Thanks for the reply

Now as to why you would want to build a DS1 I'm not so sure.. I paid $16 for one at Guitar Center less than a week ago. Why not just buy and mod one? I've fit true bypass switches into Boss pedals before..

Yes, I know that buying one and then do the mods it's a simpler solution and probably make more sense.
Could be that one day I'll end up doing so... but now I'm in "experimentation mood": I want to understand and rebuild the circuits of effects I like and then mess around with components and values on that prototype.

It's for my own experience, and I think it could eventually help me to take the right directions the day I'm going to modify a real one.

[Andr3as]

I think you can drop the zener without any problems, usually there's only a resistor in series from V+ or ground to the LED.

What software did you use for the schematic?

[JRB]

The zener acts as a low battery indicator the LED will lower its brightness when the battery gets low.

[Cip73]

I think you can drop the zener without any problems, usually there's only a resistor in series from V+ or ground to the LED.

I think as well that I can drop it, but I'm trying to understand its role and the possible advantage to leave it or remove it.

What software did you use for the schematic?

I've used ExpressSCH, which is part of the free ExpressPCB package.

[Cip73]

The zener acts as a low battery indicator the LED will lower its brightness when the battery gets low.

Thank you for the info!

Regarding the resistors, R4 (100K) in parallel with R5 (1M), is it ok if I replace them with just one 91K resistor?