increasing the decay on a DOD FX25 autofilter

[littlewing]

hi everybody,

i'm wondering if it's possible to increase the decay time on my DOD FX25 envelope follower. i believe it involves increasing the value of a certain capacitor, but i'm not sure which one.

here's the schematic: http://files.muziq.be/schematics/dod_fx25.gif

my ability to analyze schematics isn't great, but i had an initial thought that C14 might be responsible since it's close to the sensitivity pot. does anyone have an idea?

[expanoncolin]

hi everybody,

i'm wondering if it's possible to increase the decay time on my DOD FX25 envelope follower. i believe it involves increasing the value of a certain capacitor, but i'm not sure which one.

here's the schematic: http://files.muziq.be/schematics/dod_fx25.gif

my ability to analyze schematics isn't great, but i had an initial thought that C14 might be responsible since it's close to the sensitivity pot. does anyone have an idea?

I'm thinking C11 - the diodes and capacitors around there are the AD generating circuitry.

-Colin

[littlewing]

great, thanks colin. i'll check that out as soon as i get a chance.

[jacobyjd]

If this works out, please post an update!

I'm working on pairing up an MXR blue box with an FX25 (rehouse), and I'd love to add a decay switch--both to shorten AND lengthen it

[littlewing]

i surely will.

colin, what's up with the board? why's it been acting so slowly lately?

[expanoncolin]

i surely will.

colin, what's up with the board? why's it been acting so slowly lately?

So it's not just on my computer.... I'm not sure, I think it has something to do with the mysql server of my host (because it's just the board that's going slow).  It's funny because my hosting plan is about to expire with my current company, so they aren't doing a good job of convincing me to renew.  Switching hosts would be a HUGE pain though, not really something I have time for.  Maybe I will just renew for a year and promise myself that I'll sort it out before then.  I will email them about it to see if there's something amuck on their end or if they will blame me somehow.

-Colin

[littlewing]

i concur, it probably is the sql server. when i try to load a page it'll load the top part with the logo and title, but it'll get hung up on all the data that's being accessed from the sql server.

as a side note, the "topic review" on the reply page doesn't show the last post. is that normal?

[expanoncolin]

i concur, it probably is the sql server. when i try to load a page it'll load the top part with the logo and title, but it'll get hung up on all the data that's being accessed from the sql server.

as a side note, the "topic review" on the reply page doesn't show the last post. is that normal?

Yes, I noticed that problem and am not sure what's up with that.  It might not be the SQL server though because http://experimentalistsanonymous.com/blog/ loads with normal speed and also queries the sql server.  Maybe I should just update to phpbb 3 and hope that solves it.

-Colin

[littlewing]

jacobyjd, increasing C11 did increase the decay time. the next largest cap i had was 22 uF which made it really long, must've been 2 or 3 seconds.

you'll have to consult the schematic to find C11 since none of the components are labeled. on mine it wasn't 15 uF like the schematic said, it was actually 10 uF.

does anyone know any other mods for the fx-25? i'm interested in what it's capable of (aside from its normal operation)

[jacobyjd]

awesome--thanks for the info. I'll look into messing with a rotary switch setup for my re-housing project. I don't really know of any other mods out there...there might be a reverse sweep switch mod, but I haven't researched it.

[expanoncolin]

The filter i just a generic LM13700 sallen key VCF, so you could easily swap out the envelope control for an LFO, sequencer, manual sweep, or any CV source.  You can also vary the resonance, or switch the filter range.  Here's a good starting point:



-Colin