Soulbender differences pre and post august 2001

Started by youngstownguitar, October 01, 2011, 04:18:33 AM

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youngstownguitar

I recently stumbled on this information: 
From Mike  Fuller:
"there's a really cool mod for the SoulBender that invloves changing one of the transistor Bias resistors to a different
value and yanking the 500K volume pot in favor of a 250K, it absolutely explodes notes out of it after this, Carl's is
like this and all post 7/31/01 pedals as well.."
(originally posted here:http://www.musictoyzforums.com/showthread.php?12516-Improved-(7-31-01)-soulbender-questions/page2)

I checked my soulbender (which never sounded as good as others I have played) and it was made in July 2001! One month before he started making this mod routine.

I would like to try this mod as I have made a couple of my own pedals now and I feel like I can safely swap out a pot and resistor.  The problem is that I can't find any info on which resistor to change out.  I know that there are some schematics of soulbender clones here and there but I don't really know enough about this stuff to make sense of them and compare them to my soulbender to see the difference.  Plus I wouldn't know if the schematic is based on the pre or post 8/01 pedal.

I guess what I need is someone with a post 8-01 soulbender to tell me what transistor bias resistors are used so I can compare them with my own.  I don't even know where to look tho.

I think this would be a really neat, kinda unknown project as I dont think this mod is very known.  I'm sure this stuff is childs play for some of you guys but I'm just a hobbyist and any help I could get would be greatly appreciated- thanks!

oh and heres some guts of my soulbender if that helps:





youngstownguitar

Would changing the volume pot and a transistor bias resistor affect the tone? Or would it mostly just increase the volume?

slacker

Changing the volume pot won't make much difference to anything. Changing the bias of one of the transistors could make big changes to the tone and the volume or it could do very little, without knowing what the change it it's impossible to say.

Barcode80

changing the volume pot value WILL change the tone in this case, because of the impedance change...

petemoore

  The potwafer goes from SP to ground ? 500k potwafer reduced to 250k might trim treble slightly more than the overall volume reduction when on 'full', the 250k will make lower settings have less R value for the signal to go through..if the 500k is set at half, that's a 250k resistor in the signal path, set to full that R value is 0 and 500k to ground is higher impedance.
   The bias voltage of Q3C should be what ? What sounds strong or preferred tone...somewhere around/above 1/2 of the supply voltage.
  When setting bias on Ge transistors, the temperature matters, keeping bias within 'good operational' parameters over a temperature range...A thermometer was used to measure the temps, the ice box was used to get the temp to 'low', my thumb/forefinger or blow dryer used to raise the transistor temperature...by picking a range [hardly ever play below 60 degrees, rarely over say 90 degrees. In this way the bias setting may be able to accomodate good operation over greater temperature ranges.
  Measure Q3C voltage as you raise the temperature of the circuit..see what happens.
  That said, if the bias measured at this time = sounds good, leaving the bias set where it is would be an option to consider.
   
 
Convention creates following, following creates convention.