Boss SD-1 problems

[aran.e666]

Hey guys,

Got a cheap boss SD-1 today and started modding it. First of all, i replaced C3 and R6 with .22uf and 1kOhm. This resulted in some squealing when i stop playing. I think this mod might be the problem although i didnt actually test the pedal before i started modding  .  I'm not sure if this is the problem so i was wondering if the cliping diodes could cause this?

Second, i replaced all the clipping diodes to see if works as a clean boost but it doesnt. It actually lowers the volume.  Can someone tell me how i can use the SD-1 as a fairly clean boost??

Finally, i tried some symmetrical clipping with 4 diodes. It sounds mean and gritty however the low end sounds thin and the mids and high end lose some tone and sustain. What components can i replace to fatten up the low end but brighten the mids and high end?

Thanks guys

~Aran

[robthequiet]

Have you tried backing out the C3/R6 mods and keep the dual diodes? That alone would give you a higher clipping threshold. As far as the hollow sound, usually increasing the value of the input caps gives you a bit more range for the tone. Was the original R6 100k?

Edit: Take a look at this vid and see if it is close or far from what you had in mind?

[aran.e666]

Thanks, What i think i will do tomorrow is like you said back out the input mod that i did. If that causes the same problem I'll still be concerned. As for R6, im not 100% sure but somewhere i saw it was 4.7k. If it is 100k then that is the problem. Also yeah the video is similar to what I'm going for but honestly i love experimenting so i cant say that its exactly what i want.

I'd still like to make a clean boost from it. Any advice would be good because it would save me from having to order more vero to make a boost 

~Aran

[robthequiet]

OK, then my suggestion would be to restore R6 to 100 K or whatever it was, then maybe replace the diodes with 1 green and 1 red LED.  So you're still hard-clipping but with the higher threshold you'll have more level before [clipping diode] distortion. Tuning the tone control is also an option. The C3 change may actually be good, so maybe keep that open to test by itself.

Edit: The 470K R7 controls gain in the first stage  -- It is possible to reduce this to a lesser value such as 250K, more or less, but it would take some experimentation, let your ears decide. The purpose is to reduce the distortion from the first stage.

It is also possible to make C3 even smaller, like .033u, to control the bass if you get a lot of mud in the output.

[Ben Lyman]

If you put the diodes on a switch to break the connection entirely, you get a super loud booster pedal, it's the same thing the Fulldrive II calls "comp cut" on the toggle switch

[aran.e666]

By break the connection, what i did was removed all 3 clipping diodes, soldered 2 wires in place of the outer 2 diodes then soldered 2 wires from the remaining diode location. I soldered them to a DPDT. I then linked two poles and on the pther two, my symmetrical clipping. So in short, either all the diodes were removed OR the center diode (D5) used the symetrical clipping.

What would i do differently to break the connection? I'm assuming what you are saying is i would need to obviously break the link on the switch.

[Ben Lyman]

Clip one end or the diodes and insert a switch to "make/break" connection

[aran.e666]

Gotcha. I suppose my method works the same but im basically breaking both ends of the connection. Il give it a shot in the morning and let you know how it works. Thanks for the diagram

~Aran

[aran.e666]

just an update: i didn't change C3 or R6 yet the horrible noise went away which led me to believe it was the clipping diodes. because i can be a bit clumsy, i destroyed 4 pads on the clipping diodes  this meant i had to solder wires in place of the pads. for some reason, i decided to cut one of the wires and the hissing went away (the hissing was there before the pads broke off) so i have no clue how that fixed it.

as for the boost, i snipped the wire bridging the switch and it works very good.

thanks for the help guys

~Aran