SD1 more gain questions?

sevenisthenumber · January 08, 2008, 03:13:02 PM

I was wondering how to get more gain out of my SD-1. It already has the (x2 gain mod, asymetrical clipping mod, germanium transistor in the diode section and burr brown). I love the tone I just wish the gain went to 15 or 20. I love the character of the overdrive and dont want a distortion. I just want more gain. Could i change the gain pot to a higher value?
Any help is appreciated...

Melanhead · January 08, 2008, 06:52:56 PM

what values do you have in there for r6 and c3 ?

sevenisthenumber · January 08, 2008, 07:27:25 PM

C3 is stock and R6 is 2.2k and the stock on a toggle.

wampcat1 · January 08, 2008, 11:22:32 PM

I think the most you could squeeze in there without oscillating is probably a 800ohm-ish in r6, move c3 up in value to keep the same frequency range (off the top of my head, maybe a .25 uf or so?) A little larger on C3 if you want more bottom end.
bw

sevenisthenumber · January 08, 2008, 11:26:53 PM

Thanks Wampcat!

so i can max the r6 at around 800ohm's....?
Does c3 have to be moved up? What if it stays the same. Whats the result?

wampcat1 · January 08, 2008, 11:49:20 PM

Quote from: sevenisthenumber on January 08, 2008, 11:26:53 PM
Thanks Wampcat!

so i can max the r6 at around 800ohm's....?
Does c3 have to be moved up? What if it stays the same. Whats the result?

Looking here: http://www.muzique.com/schem/filter.htm , if you keep the same value for c3 ( .047), and move r6 down to 800 ohms, you are going to boost and clip 4.2khz and up or so. Not only will this be thin sounding, it probably won't sound like much gain was added. You need to move c3 up in value to compensate. Stock r6 is 4.7k I believe (723hz with c3 being .047uf). Move r6 to 1k and c3 to .22uf for the same frequency and more gain. I'm guessing 800 ohms is about as low as you can go without oscillating... you might try a 470ohm just to see though.
So:
r6: 470 ohm, c3: .47uf
r8: 800 ohm, c3: .28uf or so.

For more bass, make c3 larger values (see http://www.muzique.com/schem/filter.htm for exactly which to get the desired frequency).
Hope that helps!

bw

Khas Evets · January 09, 2008, 05:49:00 AM

Are you looking for more gain or volume? The suggestions above will increase gain, but the clipping theshhold is still the same. I find the stock SD1 could use more of a volume boost after the clipping stage.

Melanhead · January 09, 2008, 06:38:56 AM

Quote from: wampcat1 on January 08, 2008, 11:22:32 PM
I think the most you could squeeze in there without oscillating is probably a 800ohm-ish in r6, move c3 up in value to keep the same frequency range (off the top of my head, maybe a .25 uf or so?) A little larger on C3 if you want more bottom end.
bw

+1 ...

brett · January 09, 2008, 08:12:35 AM

Hi
I think that maybe the low headroom associated with the Ge diode might be giving the impression of low gain. It will certainly limit the slew rate a lot of the time. The 51pF cap has the same effect.

I would first reduce the 51pF cap to 10pF and try it out. Next step would be to try 3 x LEDs for that classic high-gain "crunch" tone.
cheers

sevenisthenumber · January 09, 2008, 08:51:15 AM

Thanks guys!! I will lower the resistor/change cap and see what i can get from that!
Like ive said before.... I have a germanium transistor in d6 (2N3440) and a 1n4002 in d5.
I love what the germanium does to the feel of the pedal! What could i add to that clipping stage for more gain (distortion) besides the 1n4002?

wampcat1 · January 09, 2008, 09:37:55 AM

Quote from: sevenisthenumber on January 09, 2008, 08:51:15 AM
Thanks guys!! I will lower the resistor/change cap and see what i can get from that!
Like ive said before.... I have a germanium transistor in d6 (2N3440) and a 1n4002 in d5.
I love what the germanium does to the feel of the pedal! What could i add to that clipping stage for more gain (distortion) besides the 1n4002?

whoops, I overlooked you had the germ. tranny in d6. You aren't going to get alot more clipping with it in there by itself IMO - if it was me, I'd connect another 4002 in series with the one in d5, then add 2 more of them in series in place of d4.

bw

JDoyle · January 09, 2008, 10:58:00 AM

To get the most gain possible from a feedback clipper, take the gain pot out entirely.

sevenisthenumber · January 11, 2008, 04:53:37 PM

hey wampcat1,

i did the diode changes and they really added a little extra kick!!!
Only prob is now the led is barely on when in bypass? I moved r30 to a 1.1 to make the led brighter. It wasnt doing it before though???

thanks!

wampcat1 · January 11, 2008, 10:08:45 PM

Quote from: sevenisthenumber on January 11, 2008, 04:53:37 PM
hey wampcat1,

i did the diode changes and they really added a little extra kick!!!
Only prob is now the led is barely on when in bypass? I moved r30 to a 1.1 to make the led brighter. It wasnt doing it before though???

thanks!

odd... I've never had that happen before... I would put the stock value back in and just put in a brighter LED.
bw

sevenisthenumber · January 11, 2008, 10:19:35 PM

I dont think i was clear. my fault.

I already had the LED resistor changed way before I wanted more gain. Ive used the pedal for months and it never had an led prob. It started when i changed the clipping arrangement.
Thanks.

wampcat1 · January 11, 2008, 10:27:21 PM

Quote from: sevenisthenumber on January 11, 2008, 10:19:35 PM
I dont think i was clear. my fault.

I already had the LED resistor changed way before I wanted more gain. Ive used the pedal for months and it never had an led prob. It started when i changed the clipping arrangement.
Thanks.

The diodes aren't really associated with the on/off led at all though... my first inclination would be to double check all the solder joints in the area. Then, make sure you didn't accidentally change D2 instead of the clippers.
bw

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SD1 more gain questions?