Pots in MXR Envelope Filter from Tonepad?

[jdjonsson]

Hi everyone,

I built the MXR Envelope filter from tonepad, with the reverse sweep mod, and the emphasis control mod. I also made some of the gain improving mods from the build reports. And it seems to Wah pretty well, but the adjustment of the pots leaves a lot to be desired.

The plans just say "500K Pot" for the parts, and I started using linear taper. Well, those just don't seem to work right, and I got much better results from the emphasis pot when I put in an audio log taper. I tried audio log for the other two (Attack, Threshold) in testing, but no matter what I do, particularly for the threshold pot, I seem to get all my adjustment in about 1/4 (less with audio taper)  of the knob's sweep. That lead me to believe that I might need a reverse audio taper for that, so I ordered some from smallbear. I can't figure out how to adjust the attack with either audio or linear. But I've heard that's tricky even on the factory pedal.

I know Francisco and Matt sometimes read this board, so, do they, or anybody have a quick answer for what I should be using here?

[Mark Hammer]

You can actually use 1M for both the Attack and Threshold pots for a little extra range, though for many people 500k will be fine.   If you would like even slower attack, though, and need to be able to fine-tweak sweep width with hot input signals, conider 1M pots for one or both those functions.

Personally, I've never really paid much attention to the taper of the pots, and I've owned 2 and built 3 of these things.  The ideal taper would really depend on what aspect of the range needs finer gradations given your needs.  For instance, if you tend to have ultrahot input signal levels, then clearly you'll want the most tweakability around the 7:00 to 11:00 range of the Threshold pot, whereas if you're the kind who feeds a nonboosted lipstick-pickup equipped guitar directly into the EF, then chances are pretty good the zone you play with most is around 3:00 to 5:00 and if you could use pot taper to spread that out over the 12:00 to 5:00 range that would be a blessing to you.

Fortunately, both the attack and threshold controls are wired as variable resistors, and both easily conceptually reversible.  That is, it would not be as confusing to have an attack pot that went from fast to slow (instead of slow to fast) as it would be to have a volume pot that went from full to off (instead of silent to full).  That goves you the freedom to try wiring a log pot in either "direction" (i.e., rapid resistance changes hard left or hard right), as it suits you.

Make sense?

[Fp-www.Tonepad.com]

I built my MXREF without the mods, but I'll update the pdf with any info you might have.

Fp

ps: Mark, I thought you'd have some comments on the MaestroFSH1, since you like envelope filters so much

[Mark Hammer]

Francisco,

If I had the time to tackle it, I would.  At this point, I'm about 10 weeks behind where I ought to be with projects, some of which I essentially "owe" people.  The only thing I might suggest without hands-on treatment is that a 5k attack pot might be a little over-zealous.  Personally, I woldn't go much over 1k.  Not because slower attack isn't pleasing or useful, but because in the half-wave rectifier context you quickly run out of sweep width when sticking in a series resistance that big.  You CAN compensate by cranking the gain of the gain stage that feed the rectifying diode but over the range of series resistances needed to achieve a wide range of attack times, you'd have to switch/adjust the gain differently for one end of the attack spectrum vs the other.  Far better, perhaps to just stick in a different smoothing cap and make it switchable for slower/faster response.  That cap (4u7 in stock form) affects not only the decay/release time but the attack time as well.  So, putting it together, a 1k pot and a parallel switchable 22uf cap might be the ticket.

Forgot to add....many thanks for the LM13600 redesign.  I'm sure many will appreciate your efforts.

[moeburn]

Francisco,

If I had the time to tackle it, I would.  At this point, I'm about 10 weeks behind where I ought to be with projects, some of which I essentially "owe" people.  The only thing I might suggest without hands-on treatment is that a 5k attack pot might be a little over-zealous.   Personally, I woldn't go much over 1k.

You mean 5m and 1m, right?

I'm going to build one of these pedals, and I'm a fan of tweakability.  I'm wondering if someone knows all the mods I can use on this pedal?  Whats the volume fix for, is there something wrong with the volume of the pedal?