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MoonWatcher
Bronze Member
USA
98 Posts |
 Posted - 08/07/2008 : 19:29:05
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Now granted, this may not be the most elegant solution, and I'm sure that Zentropa will want to run it through his battery of tests, but I think I may have another bleed fix for the SD-1.
Bear in mind that this is in conjunction with the Laurie/Zentropa fix, as I don't have a spare SD-1 with the stock power supply...
Basically, my quick and dirty mod is as elaborate as this:
-Bypass D4 with a 1 meg resistor!
This essentially gives the SD-1 a little less drive than a TS, but obviously the taper of the pot can feel a little weird.
If you need a little more drive, I guess that a 2 meg resistor would work, or you could leave D4 alone, and put different combos of resistors bypassed with D5 and D6. I'm not sure where the actual break point is where the bleed becomes audible, and it probably hinges on how you've modded the pedal, as well.
Just figured I'd throw this one out there for you folks to try! |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 08/07/2008 : 23:20:22
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Interesting... I'm looking at the schematic and can't see quickly why that would be so.
Theoretically... all it shoud do is lower the gain by 3dB. VERY interesting.
On a related topic, the next SD-1 that I mod I'm going to change the L/Z mod a little - use 4k7 resistors for R18 and R19 (selected by measuring with a DMM to be an exact match), and add a 1�F ceramic across R18. Should hold the rail even firmer than the current L/Z mod. Will let you know how it goes. |
Edited by - Laurie on 08/07/2008 23:23:51 |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 08/08/2008 : 04:48:15
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Sounds good.
I plan to tear into a SD-1 tomorrow - maybe I'll try it as well.
They all have the 1 uF monolithic, 100 uF e, and 10K pair already.
Yep - that 3dB must be just enough. Considering that a TS drives the first stage with a 551K load max, I'd have to guess that the upper limit is probably around 620K before the bleed becomes audible (through a solid state amp, with headphones on!).
1 meg across D4 yields about 480K when maxxed. Even a moderately tweaked SD-1 really doesn't need that much. Probably the second easiest thing to do would be to replace the drive pot with a 250K unit. And I'd venture to say that 100K would probably be adequate as well, if you drop all of the 10K, 4.7K, 22K etc. stoppers (a la Eternity mod). You could also bump up the recovery stage as well, and it's actually not too difficult to move the tone circuit after the recovery stage.
Anyways, I'm rambling, eh? |
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zentropa
Gold Member
USA
837 Posts |
Posted - 08/08/2008 : 22:57:07
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i don't have any SD-1's left to mod or i'd give it a whirl.
i'm hoping to find an MIJ PSA SD-1... as i like the sound of those better than the ACA SD-1's.
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SD-1 Bleed Fix - Alternate Solution!
