Boss switching network...

[GonzoFonts]

I was wondering if anyone knew how to remove the switching network of a Boss pedal.

For example, let's say I want to breadboard a Boss DS-1 but I don't want to breadboard the switching circuit.

Also, from a few other Boss schematics that I have, the switching implementation is a little different for each pedal meaning where the circuit is bypassed is in a slightly different location.

Maybe if someone here can post an example of a schematic (it doesn't have to be a Boss DS-1, I was just using that as an example) showing the switching network and another example without, it would make more sense to me.

Thanks in advance.

GF

[phillip]

Here's a good example of the removal of the JFET switching.  Here's the complete schematic of the Boss OD-1, the predecessor to the SD-1, with the JFET switching:

http://axiseffects.home.att.net/misc/OD1.gif

And here's the same circuit, but with the JFET switching removed:

http://axiseffects.home.att.net/misc/OD1_noswitching.gif

Hope this helps some!
Phillip

[Coriolis]

Ooh...very useful!  
Thanks for that one Phillip!
And thanks for asking, GonzoFonts...

[GonzoFonts]

Phillip,

Thanks for posting the schematics.

The removal of the switching network is as I suspected however, I would have left in R2 and C6 because from the looks of it, they look to form some type of feedback.

Since you removed them, they are obviously part of the switching network.

Can you please explain the purpose of R2 and C6.

Thanks in advance.

GF

[cd]

R2 biases the input transistor, C6 is the "clean" (bypass) path.  You can remove C6 but you have to leave R2.

[phillip]

R2 wasn't removed from the no JFET switching schematic...it's still between the base of Q6 and Vbias.

Phillip

[GonzoFonts]

I think there is some confusion...

In the schematic that shows the switching network, there are two R2 resistors.

The first R2 (470k) is at the base of Q6 tied to 4.5V.

The second R2 (1M) is between C6 and the drain (?) of Q2 and it's also tied to 4.5V.

When I asked "Can you please explain the purpose of R2 and C6" I was referring to the R2 that is 1M.

Thanks.

GF

[phillip]

Whoops!  I didn't notice that second R2...I'll correct the schematic ASAP

EDIT:  The schematic of the OD-1 with the JFET switching has been corrected.  The second R2 that's attached to the JFET Q2 is actually R11.  That one isn't needed without the JFET switching since I think that it provides power to the JFET to operate.

The real R2, the 470K resistor on the base of Q6 (input transistor) is needed to bias it properly.  If you were to build the circuit, I would crank up the value of that resistor to 620K or so for more input impedance.

Phillip

[GonzoFonts]

Phillip,

Thanks for the info.

I was just thinking, I have all the parts to build this (a nice Sunday afternoon project) except for the 2SC732 transistors.

Since all the local surplus electronic stores are closed on Sunday (), I’m stuck with Fry's. I just called and all of the Fry’s in town are out of NTE199 which is the NTE equivalent to the 2SC732.

Any possibility of using a good 'ol 2N3904?

Thanks again.

GF

[phillip]

2N3904 or 2N5088 would work for the input and output transistors.  2N5088 might be a little better since it's higher gain...I've heard that some people like to use 2N5089 or MPSA18 since they're low noise.

Phillip

[GonzoFonts]

Phillip,

Thanks again for the info.

I bread-boarded the circuit and it works. It has a nice natural organic sound to it. However, there does not seem to be enough volume or overdrive even with both pots maxed out.

It’s probably because I’m using the 2N3904. I’m off from work tomorrow so I’ll pick up some of the transistors you mentioned (along with a few of the 2SC732/NTE199s) and experiment.

Thanks again for your help.

GF

[phillip]

I would try using a 100K audio taper pot for the "level" control instead of 10KA.  I would also mess around with that 4K7/0.047uF series (C3 & R6) on pin 2 of the IC.  If you half the resistor and double the capacitor, you'll have more overdrive available.  R6 could be 2.2K or 2.4K, and C3 could be 0.1uF or so.  If you make C3 even bigger you'll get more bass reponse.

Phillip

[GonzoFonts]

Phillip,

WOW!!! After making those changes (100k pot for level, R6 = 2.2k, and C3 = 0.1), the pedal came alive. I’m off work today so I’m running of to the surplus electronics store to buy the transistors you recommended.

A BIG thanks for all your help.

GF

[Jay J]

How about DOD switching? For example the one used in this compressor?

http://www.muzique.com/schem/dod525.jpg

Are the parts in upper right-hand corner (after LED) plus FET J113 in lower left-hand corner unnecessary?