MXR Dist + ?

[Arn C.]

Howdy!

I was wondering in the original is the distortion pot linear or log?


Thank you!
Arn C.

[jasperoosthoek]

I don't know about the original but a log pot will be a very poor choice. A linear pot works but a reverse log pot is a better choice. This will spread the distortion range more evenly when you rotate the pot. With a linear pot only the rightmost part has much effect, a normal log pot will be unusable.

Linear or reverse log won't sound different. I recommend getting a reverse pot from small bear which is slightly more expensive. What's in the original is not really important, only economics is important .

[Arn C.]

Thanks for the response!   I have both kinds of pots.  I believe the original must have been linear.  But I do agree about the reverse audio pot being the better choice.

Peace!
Arn C.

[jasperoosthoek]

That's my guess too. Reverse log pots are usually more expensive due to their limited use. Better than linear ones but they eat a small part the company's profit margin, which becomes large when big quantities are sold. These type of circuits with the pot connected in the feedback path have a gain of 1/R or 1/(1+R) which makes a reverse log pot a better choice.

Have fun building!

[Mark Hammer]

It's reverse log.  Do the math to calculate what the gain is at various settings/resistances of the gain pot, and you'll see why.   It needs to hurry past the first couple hundred Kilohms of pot resistance. and stretch out the last 50k.

[tubelectron]

Hi,

I have an original 1980 block logo MXR Distortion + :



The distortion pot measures 577K full, 53K half, and 0 min, it's a 500K-RA (reverse audio = reverse log)

The output pot measures 55K full, 6K4 half, and 0 min, it's 50K-A (audio = log)

A+!

[Mark Hammer]

This is why I constantly suggest that Dist+ builders, unless going for meticulous historical accuracy, are just as well off with a 100k or even 50k gain pot.  Nothing particularly interesting happens until you hit the 50k gain pot mark anyways.

The original was intended to fulfill a sort of dual function as both distortion and semi-clean booster, and the choice of gain pot value/taper served that goal.  Of course precious few players in the 70,s and early 80's would have had a clean booster as part of their arsenal, so there was sort of a need for that kind of thing.

[Arn C.]

Tube electron:  That is the same one I have.  Not that good of shape tho.   I am repairing it for someone else and the pots were already there, I just didn't know what kind they were.  I also got similar readings.

Thanks Mark for the explanation.  Yes, I needed to keep it original for the owner.

Peace!
Arn C.