Colorsound Overdriver question about gain pot / build report

[joelap]

Hey guys, last night I finished a Colorsound Overdriver using BC109's and the layout found on this page: http://homepage.ntlworld.com/s.castledine/greenfuz/overdrv.html

I cant take pictures now as I'm late for work, and I'll try and find a way to record some clips too.  At first messing with it, I've got a few observations I've made:
This is an extremely versatile circuit.  The words "clean to mean" come to mind, but in this case actually ring true.  The bass and treble controls are very flexible, not hard to get a nice sound of out them, but can be tweaked to almost infinity it seems.  And man, does this thing friggin' BOOST!  I was setting it up last night with my guitar into the Dr. Boogie, then into the Colorsound, then into my Vox AC30CC and DAMN, this thing will almost definately be my solo boost pedal.  Nice and loud and up front.  And the good part is, should I ever be in a gig and my Dr. Boogie goes down, I can always use the Colorsound as my distortion unit too.  Great unit.  Only gripe is that that layout only has one connection for ground, yet the Volume pot, gain pot, in jack, out jack, 9V adaptor, and 3PDT all needed grounds.  I really dont like having to connect the grounds together like connecting the pot grounds to the jacks and then the jacks to the board ground, but I cant really complain since someone was kind enough to post their layout for guys like me to follow anyways.

Pics coming soon, hopefully clips soon as well.  I dont have an interface to record with so I cant garuntee them 

My only question is this: I used a 10kLog potentiometer like the schematic calls for, but in my build, there is very little effect in the first 75% of the gain knob... its barely noticable.  Then once the knob gets past that 75% point, all this gain quickly shows up.  I have about 30 degrees of useful knob placement for some reason... for you guys who have built this, is this normal?  The circuit calls for Log, is this a sign I should switch to linear taper?

[GibsonGM]

Sounds like a need for a REVERSE log taper, to me.  My Dist+ is like that.  You sure the pot is wired up correctly?

If I'm not mistaken (not familiar with the circuit) the ground issue is solved by running only 1 ground from the board to a spot on the enclosure (or at the input jack, using the switching trick to engage the batter -).  If you don't use an insulated jack, the enclosure is now grounded.  Pots and the output jack ground themselves to the enclosure that way (being sure they have continuity with the enclosure, of course).   This is close to star grounding, and is a good way to keep ground at the same potential for quieter operation.   

[joelap]

Hmmm... I may try tha treverse log taper.  At the moment, I'm using it for a solo boost and setting the EQ for are more "focused" sound, so its not too big of a deal, but I wont call the project "complete" until its fixed.  I'm pretty sure the gain pot is wired correctly... I will take another look tonight with a fresh pair of eyes  and see if maybe the jumper for the two lugs might have came off.  If that checks out ok, I might just grab a 10k Reverse Aud from smallbear and see if that does the trick.

[slacker]

Unfortunately that's just how the gain pot works. If you search for colorsound overdriver there's a few threads about the gain being bunched up and a few possible solutions. Great pedal though, I use mine as a treble boost as well as a full on fuzz.

[MartyMart]

Try a linear taper, you'll get more change earlier in the sweep then.
I'm pretty sure that's what i used in mine.
MM

[Bernardduur]

He, I have an original and it has the same issues with the gain pot........

I just got used to it

[joegagan]

He, I have an original and it has the same issues with the gain pot........

I just got used to it

SEE, this is why this forum is so great. it is priceless to know that an original does the same thing!

[makenxero]

Hi, I just built my copy of it and I definitely notice the gain pot issue as well.  For me however, the gain knob doesn't do anything and then it gets into full out distortion. Also the clean sound doesn't get too loud, only when it is into distortion. At the time I bought my parts, the guy at the surplus store didn't have bc109s and gave me a few NTE123As which he said were a replacement. I have a feeling that this is the problem and I've ordered some bc109s, but I was wondering if anyone has had any experience with this.

[Mark Hammer]

He, I have an original and it has the same issues with the gain pot........
I just got used to it

THAT is where your chicken-head knob comes in handy; for making adjustments with poorly-chosen pot tapers.  The wider radius of the knob, and pointy aspect, allow the user to more easily achieve small increments/decrements.  And you thought they were just for looks!

[makenxero]

Try a linear taper, you'll get more change earlier in the sweep then.
I'm pretty sure that's what i used in mine.
MM

Yes, I just popped in a 10k linear and definitely helps.

[MartyMart]

Try a linear taper, you'll get more change earlier in the sweep then.
I'm pretty sure that's what i used in mine.
MM

Yes, I just popped in a 10k linear and definitely helps.

Probably a reverse log pot would be even better, glad that it's working a little better though

[joelap]

I've pretty much just been using mine lately as a solo boost, with the pregain set clean and the volume set for a boost.  I can't get along with the distortion characteristics of it.  I might try 2n5089's to get more sputtery gating effects, unless someone decides they want to trade me for the colorsound of course

[petemoore]

  The schematic is HUGE, but I pin/haystacked through it...looks like that 10k connects to ground, works like a volume pot.
  It takes me a minute to put a stop resistor on a pot wired like that, or many hours of debugging when a pot like that shunts all signal to ground [as in CCW position].
  I never use a gain knob to turn a circuit all the way down.
  I generally leave gain settings above 1/2 way up.
  a 4k7 or 5k2 stop resistor, along with a 5k pot...whatever adds up to about the same max resistance as the pot in a schematic, then all the below 1/2 gain settings are gone, the 'R+pot 'fine tune' adjusts between 5/10 gain and 10/10 gain.
  Or use series resistor across 1/2 or all of the gain pot wafer, thereby reducing it's value and altering it's taper, add the lost back resistance with a stop *resistor between lug */ ground.
  Sometimes you can go with a 100k, other times the value of the potwafer is part of the bias network...I could get resolution to see blur or 1/20th of schematic.

[makenxero]

I'll try the reverse log when I get a chance to visit my local electronics surplus again