sd-1 mid boost....is there a fix?

ode2no1 · February 03, 2009, 06:16:41 PM

i did the keeley mod to my sd-1 and while i think it sounds great i want the mids to be pretty much flat. is there a resistor or cap i can change to lower the midrange? this is pretty much the only thing keeping me from replacing my main overdrive with the sd-1.

kurtlives · February 03, 2009, 06:38:23 PM

Try raising the 47nF cap coming off the first feedback loop to 100nF for a flatter response. (the 47nF cap is connected to a 4K7 resistor).

The nature and success of Tube Screamer's is based around their mid hump....

ode2no1 · February 04, 2009, 10:50:05 AM

that's actually already part of the keeley mod. it definitely flattened out the response but adding some low end but i think raising it any higher might just add too much bass. i guess i'll give it a shot. i compared it to my red snapper and it's pretty close. the snapper sounds a bit more natural, but if i didn't have it there to compare i would have no complaints about the sd-1.

Ben N · February 04, 2009, 10:53:40 AM

These things always puzzle me. Isn't trying to flatten the eq of an SD-1 kind of like saying you like your vibrato, except for the darned wobble? Rather than emasculate the SD-1, why not start from scratch with any number of easy to build flat-eq OD designs?

ode2no1 · February 04, 2009, 11:27:30 AM

well the thing is i bought it just to mod it not knowing what to expect, but i ended up really loving the tone of the pedal. the only thing that would make it perfect is flat mids, and if replacing one more cap or resistor does the trick then why not go for it instead of building up another pedal? i'm not a blues player or anything...i don't need a mid spike. i leave my overdrive pedal on 95% of the time with the gain pretty low so i just want something natural sounding...and the sd-1 is pretty close now.

ode2no1 · February 04, 2009, 11:31:00 AM

also, if the sd-1 was strictly a mid boost pedal, then yes, i would agree with your vibrato example...but it's an overdrive and it can overdrive a signal whether or not it has a mid range boost. isn't the point of modding in general to take something and make it better suited to your liking?

Ben N · February 04, 2009, 02:05:52 PM

Yes, true, but... these things are always subject to the law of unintended consequences. Changing the eq will also affect the distortion quality, in ways you may not anticipate.

kurtlives · February 04, 2009, 03:59:17 PM

Quote from: Ben N on February 04, 2009, 10:53:40 AM
These things always puzzle me. Isn't trying to flatten the eq of an SD-1 kind of like saying you like your vibrato, except for the darned wobble? Rather than emasculate the SD-1, why not start from scratch with any number of easy to build flat-eq OD designs?

Ya that's kinda what I addressed in my first post. Tubescreamer but no mid hump?

wampcat1 · February 05, 2009, 10:19:38 AM

the pedal boosts the frequency at 723hz, clips it, then cuts the frequencies over 723 hz. You can see that there is going to be a big mid hump. lower the frequency at the first stage, raise the frequency at the second stage, or lower it but then make the tone control into a better one.
bw

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sd-1 mid boost....is there a fix?