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Indyguitarist
Copper Member
USA
18 Posts |
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cctsim
Silver Member
United Kingdom
418 Posts |
 Posted - 09/11/2008 : 21:23:47
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I think your fix uses a different concept where, while in bypass mode, the J201 + capacitor are connected to the feedback path of the opamp.
Correct me if I am wrong, but it seems with your fix you are trying to reduce the gain of the opamp.
The fix I suggested (copied from DS1) prevents the signal from reaching the opamp in bypass mode. Here, J201 will not let enough signal pass through when the pedal is engaged because the IDDS range is to small. |
Edited by - cctsim on 09/11/2008 21:36:06 |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 09/11/2008 : 22:18:47
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Here is a simulation of bw's bleed fix:
In bypass mode, it seems the opamp gain becomes approx. 1 across the frequency spectrum, which also means some clean signal might bleed unnoticeable through Q1. This might be a bit of a problem if you have a distortion pedal before the SD1.
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Edited by - cctsim on 09/11/2008 22:37:24 |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/11/2008 : 22:22:43
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Yes - this fix is comparable to what Keeley and Analogman are now doing.
An update - if using an AVX style cap, you can cement or hot glue the JFET to it. The hot glue is actually wonderful for keeping the tranny pins from moving around and snapping off. I feed the S under the cap, and bend one cap lead in to solder to. I route the G around the side of the cap. And the D is oriented to be in roughly the same space as one cap lead.
My digital camera stinks for closeup pics, or I'd post one.
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bitsandvolts
Copper Member
1 Posts |
Posted - 12/20/2008 : 23:30:37
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Hey folks, I wanted to thank all of you for your contributions to this thread (especially cctsim's pictures). I was able to perform this mod with an MPF102 I got at Radio Shack. It worked *perfectly* and I am no longer experiencing any bleeding...
...and let me say, the bleeding on my SD-1 was driving me absolutely MAD!
So thank you!!!
-Frank |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 12/21/2008 : 04:14:54
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Hi bitsandvolts
Welcome to the forum from Australia.
And thanks for your comments.
Regards Dr. Bob |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 12/22/2008 : 20:35:38
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I may have yet another solution, but I have yet to assure that it works (with my tried and true method of using a super clean solid state amp with headphones plugged in).
If you don't find yourself maxxing the drive knob, you can cut down C3 and bump up R6 - just make sure you use an R/C calculator to zero in on your optimal HP filter shelf. I tend to prefer .027uF/10K or maybe .033/10K, as the reduced drive diminishes the possibility for unacceptable intermodulation.
The best part is that you can then bring it full up on the drive knob without it being too much. I'm going to try a 6.8K for R6 to try and fine tune it a bit more.
If you've ever had the chance to play a pedal like the Barber LTD, this is exactly what he does - .027uF/13.3K R/C network. One sweet sounding pedal, IMO. |
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cctsim
Silver Member
United Kingdom
418 Posts |
Posted - 12/23/2008 : 04:56:44
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Hi bitsandvolts,
Welcome to the Forum from the UK.
Nice to hear that you found the bleed fix mod useful.
Best Reagrds
cctsim |
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Topic |
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One component SD1 Bleed fix
