MXR micro amp pot question

[yeeshkul]

I have an original Dunlop unit and it tends to boost well just at the last two milimeters of the Gain pot turn which is not what i like.
I can see that the pot is 470k C, which probably means reverse-log (i guess ...). So i can't help it this way, there is nothing like "even more reverse".

Can i help it by using just a smaller pot? 100k ... 50k?

[ringworm]

I just finished my build of this from the tonepad layout the other day. I have a 500k log pot wired in reverse and it works like yours with only the last 25% of the turn providing the biggest change in gain, the first 50% stays at unity. I tried a 470k lin pot and it was really bad only about the last 5% had any gain change. I checked on the forum for tips on the pot for this pedal and I think I remember reading that swapping for a smaller pot value only reduced the available gain in the pedal but I may have remembered wrong.

[yeeshkul]

Ah ok, thanks man! So it works the other way. I guess i'll pull out some books on OA and see what i can do.
EDIT: The maximum gain seems to be when the pot value is O. Can i help it with a log pot?

[Thomeeque]

..I guess i'll pull out some books on OA and see what i can do..

http://www.generalguitargadgets.com/diagrams/microamp_sc.gif

Gain = 1 + R4/(R5+R6) = 1 + 56k/(R5+2k7)

T.

EDIT:

Code Select Expand

R5(kΩ)   GAIN
0      21.74074074
50      2.062618596
100     1.545277507
150     1.366732155
200     1.27627035
250     1.221606648
300     1.185001652
350     1.158775163
400     1.139061336
450     1.123702231
500     1.111398448


As you can see, most of the change happens between 0 and 50k, so reversed-log seems to be right choice (and log the worst)..

[yeeshkul]

thanks, that makes sense