Colortone overdrive gain problem

[Steve77]

Hi,
I built a guitarPCB colortone overdrive. Got the kit from mammoth electronics. Seem to go together fairly easily. Ended up with one problem. The gain seems to be crowded to the far end of the pot. I get a clean sound right up the very end then the gain kicks in all the way. I had heard of a similar problem before on a univibe clone, where some had used a reverse taper log pot instead of just a log pot. Also the instructions on guitarPCB state "If you are using one of GuitarPCB’s 3PDT Wiring Boards, pads S4, S5, S6 and D1 would be ignored and R16 would not be installed." I have no idea if I'm using a 3pdt wiring board. Perhaps my problems are coming from having added components that shouldn't have been. All other controls works great. And the gain and boast dispite the lack of control sound awesome. Thanks for any help

[skullservant]

Yeah sounds like you need to switch out your pot. If you are using Log, switch to reverse log and see if that helps at all.

A 3PDT wiring board would be attached to the footswitch itself and extend off of it, you would have to have installed it on the footswitch and the extra parts that they are telling you to leave off would be found on that wiring board instead. But if you didn't put a second pcb in the pedal attached to the footswitch, you aren't using one!

[Steve77]

That would be a drag. The pots being used are the ones supplied by mammoth. The gain pot matches the parts list B10k Lin. The volume being the audio taper A100k. I would suggest the wiring but it's only three wires. Perhaps the pot was miss labeled. I can try getting my hands on another 10k Lin pot. And thanks I understand what they meant now with 3dpt board

[Mike]

I built a guitarPCB colortone overdrive. Got the kit from mammoth electronics. Seem to go together fairly easily. Ended up with one problem. The gain seems to be crowded to the far end of the pot. I get a clean sound right up the very end then the gain kicks in all the way. I had heard of a similar problem before on a univibe clone, where some had used a reverse taper log pot instead of just a log pot.

Even though Mammoth's unfriendly shipping policies have prevented me from ordering from them, I will defend them up on this. The build doc that I found right here (attn GuitarPCB.com, don't make me register at your site just to view your build docs so I can help your customers ) shows the gain pot as 10k Linear. Mammoth shipped what was specified in the build doc. GuitarPCB specified the same potentiometer that was in the original. It should have been obvious during their research and prototyping phase that a reverse taper pot is a better choice. Plus, it has been well known in the DIY community for many years.

Anyway, since the guitarPCB colortone overdrive is basically a Colorsound Power Boost / Overdriver clone, I can tell you with 100% confidence that using a reverse audio potentiometer for the gain control will improve the transition across the gain range. I noted it in the project page for the (second) one I built: "I used a reverse audio taper potentiometer for the gain knob, and I highly recommend this. Otherwise, the fuzz is all piled up in the tiniest little portion of the potentiometer’s rotation."

For the time being, you can use a 10K audio potentiometer wired backwards and think of it as a "clean" knob (more clean to the right, more dirty to the left). You'll need to order the correct 10k reverse audio pot.

Mike

[Dr Satan]

Or you can custom tailor the pot you have to act more like an anti-log pot with a resistor or 2. http://www.geofex.com/article_folders/potsecrets/potscret.htm

[Steve77]

Ok, did a bunch of reading on this. From what I understand your really just imitating a log type pattern on a Lin pot. However most are saying it produces a really smooth sound. To produce the 10k rev log pot I need (if I understand this right)
I need to us a 50k Lin pot with about a 10-12k resistor across lugs two and three.
Does that sound right to anyone. If so, do I just wire it in as normal? One wire off each lug to the corresponding spot on the pcb?

[Dr Satan]

Well, the thing is, a 10K anti log may not even sound right. There is a very large change in sound over a very small set of values. I would grab a couple of jumper/test/alligator leads and just start testing different value resistors to see what sounds right with the pot you have. I know the math doesn't lie, but ears don't do math very well. Look at a Fuzz Face diagram. The gain is achieved in the same way as in your Colortone pedal, and a Fuzz Face only has a 1K pot or something like that and it still has a huge jump in gain on the last quarter turn with relatively little difference in the rest of the sweep. Same for like a Vox Tone Bender or any other pedal that uses a bypass cap to ground through a pot to adjust the gain on a BJT. You can do that with a FET and the gain is a little more linear feeling, but with BJTs it's nothing, nothing, nothing, maybe a little something, ALL THE THINGS! when you turn up the dial.

[Steve77]

I'll try tinkering with it before I order a rev log pot. Do I stand a better chance of producing a smoother gain control with rigged Lin pot.

[Dr Satan]

I think most log and anti log pots are basically 2 linear tapers slapped together. They aren't truly logarithmic to begin with, and unless you have one that is and you sit there and analyze the crap out of it trying to hear the difference, you'll probably never hear a difference. You could even take another pot and tie it in between the center and outer lug that will mimic an anti log pot and tweak it that way then just get a resistor close to the value and solder it in if you wanted. It's not going to hurt anything changing the value of the pot.

[Steve77]

Hey all, been outta town for a while and haven't had a chance to try anything yet. I'm confused though. Many different wiring diagrams show different pots Lin and log used for gain. Granted some are different plans, but even amongst the same plans (colorsound power boost) I'm seeing both Lin and log used as gain. I know with volume you need to use log. Is gain the same? If not, what makes it interchangeable?

[Steve77]

Ordered a 5k rev log. Installed and works awesome. Should have read guitarPCB's site closer. It actually said that the original colorsound power boost circuit suffered from the gain being bunched up at one end. Problem solved and sounds awesome!! Thanks all for the help.

[LPDude]

Ordered a 5k rev log. Installed and works awesome. Should have read guitarPCB's site closer. It actually said that the original colorsound power boost circuit suffered from the gain being bunched up at one end. Problem solved and sounds awesome!! Thanks all for the help.

It is a clone of the Colorsound Overdriver so it is correct for the "gain to be bunched up at the end". For some reason most people seem to be under the impression that the Overdriver is supposed to be some kind of distortion/fuzz pedal, most likely becuse of the word Overdrive in the name. It is actually designed as a powerful clean boost with an active tone circuit that just happens to have a great fuzz/distortion sound when the Drive is turned all the way up.
http://www.kitrae.net/music/Music_mp3_C ... Sound.html