Envelope Filter Recommendations?

[Mark Hammer]

Not against it, but I'd like to think for ~$100 I'd be able to find something that sounds good out of the box.

Any mods on deck for the DOD FX25b?

Yeah. I hotrodded a clone I made of an FX-25 for a bass-playing buddy. The stock FX-25 can be easily modded to have a lowpass output (usually bandpass only) which is much better for bass. I also gave it a much faster decay time, which makes bass sound more synth-ey, as well as more resonance, and more touch sensitivity. Get your hands on an FX-25 or 25b and I'll talk you through every mod.

[uvacom]

The neutron looks interesting to me, but mouser no longer stocks the listed header w/ cover for the LDR/LED. I searched mouser but could not find any suitable replacement header which had a cover. Does anybody know of one?

[mt_spiffy]

Thanks!

FYI, I'm a guitar player, if it makes a difference re: the mods

[uvacom]

The neutron looks interesting to me, but mouser no longer stocks the listed header w/ cover for the LDR/LED. I searched mouser but could not find any suitable replacement header which had a cover. Does anybody know of one?

NM, after a little searching I found them at digikey.

PN# A107-ND and A102AE-ND, if anybody is interested.

[roughcut studios]

Neutron PCB

Here is a ready to solder PCB for the Neutron,

General Guitar Gadgets - Neutron RTS PCB (Mutron III Replica)

[Mark Hammer]

The impact of any envelope filter will depend on:

a) the amount of harmonic content you feed it (it has to filter something, right?)

b) the alignment between the harmonic content and the action of the filter.

So:

i) Faster filter decays will appear to have a more pronounced effect because most of the harmonic content "lives" near the start of the note. Filter sweeps that occur long after the initial attack will be attempting to remove frequency/harmonic content that simply isn't around any more. There is a critical range for "acceptable" decay rates. If a decay is quick, but not fast enough, the player will hear a sort of gurgling as the note/chord dies out. This results from envelope ripple and inconsistencies in the envelope/control signal driving the sweep. You can fix it by increasing a capacitor value but that simply makes the decay much slower. If you can make the decay a little faster, however, the sweep will have completed before that point in the note where that gurgling starts to be audible.

ii) Bass-oriented envelope-filters will have the filtering action situated an octave or so lower in the audio spectrum, since the critical harmonic content to be removed (or emphasized) for bass is lower than that for guitars.

By far, the favourite envelope filter for bassists, over the years, has been the Mu-Tron III and all related variants (rebranded versions like the Fernandes/Melos/Univox "Funky Filter" Univox MU-1500 Funky Filter | DiscoFreq's Effects Database, or the Ibanez AF9: Ibanez AF9 Auto Filter | DiscoFreq's Effects Database ). The reason is that:

1) Bass needs to be solid-sounding, and that means holding the bottom even as the sweep is going on. Where a great many other filter units in the early days were bandpass type, Mutron offered a lowpass filter setting that let you always keep the "meat" of the bass.

2) The sweep of the Mutron was particularly wide, which made it seem to sweep fast (it covered a lot of ground in the same time that other filters covered less), producing a very pronounced percussive effect; something that works well for bass.

3) The Mutron had two sweep ranges, one of them better for bass.

Now, while lowpass sounds great for bass, that doesn't mean it sounds "bad" for guitar. If you crank up the resonance/peak of the unit, such that the shifting corner frequency of the lowpass filter has a lot of emphasis, that moving resonant frequency is noticeably louder than the part of the spectrum below it (which is flat), so you get something that sounds like a bandpass without losing the "meat" of the instrument. I noted that I had hotrodded this FX-25 for bass purposes, but it sounds pretty decent for guitar too.

[mt_spiffy]

Thanks! I will bookmark that link.

Mark, point taken.

As of right now I ended up ordering the Funk Filter out of curiousity. We'll see if it sucks.

[mt_spiffy]

I stumbled upon a cache of DOD FX25b's NIB. I am still looking for a better pedal, but in the meanwhile I will use (and maybe mod) one of these.

The rest I am offering up for sale. $50 each plus shipping.

Anyone interested?

[Mark Hammer]

The 25B includes a Blend control which allows you to mix in clean signal with filtered signal. That accomplishes some of what lowpass filter mode does, with the exception it also includes clean content above the filter resonant frequency, whereas the lowpass filter does not. In view of the inclusion of bass content, via the blend pot, I will ignore the conversion from bandpass to lowpass mode here.

The schematic can be found in several places, but we'll use this one for reference: http://www.experimentalistsanonymous...OD%20FX25B.gif

Mods to the FX-25B which will "improve" it in a number of ways are the following:

1) D5 provides rectification of the signal envelope permitting only one hald of the signal waveform to pass, thus providing a unidirectional indication of the present signal amplitude. Unfortunately, it requires at least 500-600mv of signal before it conducts. That's not necessarily "punitive" or prohibitive, but you'll miss out on some of the touch sensitivity. Replace it with any germanium diode, like a 1N34a. This will conduct at voltages as low as 200-220mv in some instances (generally not higher than 300mv), permitting it to respond to subtler picking, and a little earlier in the note's attack.

2) The 100k "Range" pot controls the resonance/emphasis of the filter. It also tends to shift the centre frequency of the filter downward as resonance is increased, which is probably why they called it Range. Increases in the resistance of that pot increase resonance/emphasis. Replace it with a 250k pot, and you can achieve some more synth-like resonances. If the 250k at max setting is too much (and you will know that because it whistles), stick a 680k-1M resistor in parallel with the pot to keep the max resistance down.

3) The decay time is partly set by R30 and C11. On the FX-25, the equivalent of C11 is 22uf, which produces an even longer decay/recovery time than the 15uf used on the FX-25B. Pretty much what you would expect from something designed for guitar rather than bass. Replace that 15uf unit with a 4u7 unit (making sure to orient it properly) and the decay time will shorten, yielding a more synth-like sound; particularly when used with higher resonance settings.

That's it. Try it out and let me know what you think.

[mt_spiffy]

Thanks! I wont have a chance to try any of these any time soon, but I will eventually. Especially the first one.

[Cactus]

Mutron and MXR

I fall over when I try to use a cry baby so I use a Mutron. It was found in the back of a old F Twin, it looks real old. There is a loose Capasitor rolling around inside that I don't know where it belongs but the pedal still works great. The other day a budy gave me an old MXR Envolope pedal he said didn't work. It was just missing the battery terminal. It's not as fat as the Mutron and distorts a bit which is OK if you want that. Any of the modern versions I've tried like Digi tech are not even close.
Closest I ever got to the Mutron was using the one in Native instruments Guitar Rig 3. Because my laptop is old school it has latency issues I cannot use it live.
My son in law has a Funky Box. Its an excellent atempt but still can't replace the old Mutron.

[mt_spiffy]

Someone eMailed me to buy one of the DOD's and I replied, but didnt hear back. Then they sent me a PM and I replied to that as well . . . if you're reading, I *AM* trying to contact you back.

I will definitely be trying Mark's mods on one of the DOD's.