MF-101 Envelope Negative Amount and Rate Questions

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facon
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MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Tue Apr 15, 2014 3:04 pm

I've been on a mission to replace the filter section on my EHX Micro Synth. A particular setting that I use often on the EHX is to have the filter sweep rate set slow while sweeping the filter from high to low. I'm trying to get the controls I would need for my MF-101 to accomplish this.

I've noticed that the Moog 500 series module has an amount from - to + 10 and that the - side performs a reverse sweep. I am assuming I should be able to connect the envelope out to my CP-251s attenuator and attenuate to -5 while having the amount knob set to zero. Perhaps connecting both attenuators to get a more drastic sweep. Then back in to the cutoff. Is anybody aware of a mod to the MF-101 that would allow this to happen without using the CP-251? So that the amount knob works the same as the 500 series?

Is it possible to control the rate of the envelope's sweep? Perhaps a mod?

I can find many Moog filter schematics, but can't find any for an envelope that allows for control of the sweep rate and amount.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Alien8 » Tue Apr 15, 2014 10:40 pm

I just went on this quest myself - the same exact one.

To achieve negative amount, I use the attenuators on a CP-251, and it works well, still playable.

Also with the lag processor you can slow down the 'rise' time so that a slower sweep happens.

This almost works to mimic the microsynth. It wasn't good enough for me because I like to set the limits on the EHX. I found the schematic for the microsynth and studied it. With a little help on the muffwiggler forum, I understood how the EHX works. As a result I built a gate generator (Yusynth Comparator) to be used as my low & high voltage source. Using an attenuator from the CP & the lag processor it became identical. I also use the EHX 8 step program for this. It all works quite well with repeatable results.

I finally got my "synth in a box" too, and my rig has never sounded more like a synth. I love it!! The filter is key tho. Together, they sound like a synth, and not just a filtered heavy fuzz.
Vibration emanates from all things, even nothing. Using awareness to translate vibration into "music" is something that I am whole heartedly grateful for.

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facon
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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Tue Apr 15, 2014 11:46 pm

That's awesome! I appreciate the info and am glad to know I'm not the only one haha.

I've been studying the micro synth circuit for the past week and have a good grasp on it all. I'm working on finishing an octaver circuit that is based on the Roctave Divider. It then takes the -2 octave output and goes into a PLL with octaves from -2 to +4. Since the PLL generates signals closer to a sine wave instead of a square fuzz, it should be easier to manipulate. It was recently posted on DIY Stompboxes (sans a few bells and whistles), but still needs some work.

What did you use for your attack delay? I'd love to include a complete ADSR circuit for more options. Especially something with the sustain capabilities of the Philosophers King.

How are you connecting the gate to your signal chain? Are you splitting the signal before the filter, sending the gate output into the lag processor, then shaping the hard on/off to react more like an envelope?

I'd love to just find a schematic of the envelope used in the MF-101 so I could mod it. A low pass with the trigger mod, +/- amount and sweep rate control all built in would absolutely kill.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Alien8 » Wed Apr 16, 2014 12:34 pm

I had thought about going the full ADSR route, but then decided that I just needed a simple sweep like the EHX. I use the lag processor on the CP to turn the square gate signal into a sloped sweep. The 8 Step can do something similar with a glide function, but it's not a musically predictable as the Gate / lag implementation - I do use the 8 step as a two step sequencer with the on / off triggers from the comparator, however it looses sync due to the nature of the whole env gen / comparator / sequencer relationship. You could look up Ken Stone's page to find some simple to complex EG's, and lag implementations. Otherwise, I rely on playing dynamics for envelopes outside of this predefined style of sweep, and if I want to get into extra long sustain I use an EHX HOG freeze & gliss, compressor or looper.

The gate circuit is triggered by the envelope out of the 101. The threshold can be set, and it seems to work well with playing dynamics - similar to the trigger slider on the EHX.

I will check out the DIY pedal, sounds interesting!

As for modding the 101, you could make a daughter board to achieve all of your needs, or an external module. I went external due to power supply requirements and not wanting to re-engineer the whole thing.
Vibration emanates from all things, even nothing. Using awareness to translate vibration into "music" is something that I am whole heartedly grateful for.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by hieronymous » Wed Apr 16, 2014 1:57 pm

This is a cool discussion - can I ask what instrument(s) you folks are using?

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facon
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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Wed Apr 16, 2014 2:08 pm

hieronymous wrote:This is a cool discussion - can I ask what instrument(s) you folks are using?
I'm using it mostly for guitar and bass. But it does see the occasional studio use as a filter for drums, synths, samples, etc.

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facon
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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Wed Apr 16, 2014 2:13 pm

Great info. Thanks again!
Last edited by facon on Wed Apr 16, 2014 8:04 pm, edited 1 time in total.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Alien8 » Wed Apr 16, 2014 6:44 pm

Instruments: bass & guitar mainly. Some post processing as well, but I'm really focused on playing it the way it should sound, with only tone assistance at mix down and stereo separation.

I should add that I mostly play in an improv jam scenario for fun and creative release. That's all that time affords at the moment.
Vibration emanates from all things, even nothing. Using awareness to translate vibration into "music" is something that I am whole heartedly grateful for.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Wed Apr 16, 2014 8:43 pm

Envelope -> Attenuator -5 -> Cutoff did the trick when the Amount was set to 0.

I've contacted Moog for some help with the mods. Hopefully it is possible. I'd love to save the space from my CP-251 as well as use the envelope out (with ADSR) to control a volume swell circuit.

EDIT: Well I opened the MF-101 to start figuring out the circuit and it looks like Moog decided to change over to SMD. That's a big disappointment!

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Alien8 » Wed Apr 16, 2014 10:19 pm

That's how I started - volume swells. The whole synth pedal idea was cool but I wondered if I needed to automate that part, and decided that it would be fun to plan to. As synchronicity would prevail, Moog released the MF boost, also known as the VCA :). I will own one but not soon, I'm having too much fun with what I have.

Eventually I arrived at the idea I posted in the 109 thread - really would love to see that pedal made. Will likely make one myself someday, unless Moog does it!
Vibration emanates from all things, even nothing. Using awareness to translate vibration into "music" is something that I am whole heartedly grateful for.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Bryan B » Thu Apr 17, 2014 8:48 am

You could trade somebody for an older version maybe?

I noticed the change to SMT as well. I had all of the older ones and sold them. Now that I am buying them back I wanted to see if they changed inside and they surely did. The pedals still act the same as far as my memory goes, so this change never bothered me.

SMT is a wise move for Moog, since it brings the cost down and parts will be available for longer than the older style. the only complaints I have heard from manufacturers are that the capacitors leak sometimes.
MemoryMoog Plus (with Kenton Midi Upgrade Kit) MF-101 Lowpass Filter, MF-102 Ring Mod, MF-103 Stage Phaser, MF104M Delay, MF-105M MIDI MuRF, MF-107 Freq Box, MF-108M ClusterFlux and CP-251 Control Processor.

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facon
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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Sun Apr 20, 2014 11:59 am

Well, it's pretty obvious that I confused an envelope follower with an envelope generator. So now the gate makes a lot more sense to me. It's clear why there are no ADSR controls. I was also having a difficult time finding the sweet spot for the follower with my single coil guitars.

The Yusynth modules look great, but rather than dealing with +/- 12v, I may build the guitar to gate circuit on musicfromouterspace.com.

Also, the negative amount will work if you use the negative output of the mixer section as well. This is nice since you can still grab the positive easily.

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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by Alien8 » Mon Apr 21, 2014 10:36 am

I used the power supply from MFOS to power the comparator; tag-boarded the whole thing; put into a plastic box. I saw the guitar to CV schem, but would really like to avoid adding extra circuits in my audio path - I'm really picky this way.

101 env out -> comparator trigger in -> Gate out -> CP attenuator In -> CP attenuator out -> Lag In -> Lag out -> 101 Frequency In works nicely. I found that you really need to be a clean player, to keep the envelope from triggering. Maybe a little tweaking on the threshold of the comparator is required, or an audio gate to help. Noisy pedals going into the 101 cause all kinds of problems for me; random triggers all over the place.

101 env out -> comparator trigger in -> Gate ON & OFF Trig out -> CP Milt -> EHX 8-Step CV in -> 101 Frequency was neat too - it allowed some on / off triggering of the 8-step.

I'm finding that this comparator / gate box was missing from my life for a while now. There are musical uses all over the place that I'm enjoying so very much! Well worth the build time!!
Vibration emanates from all things, even nothing. Using awareness to translate vibration into "music" is something that I am whole heartedly grateful for.

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facon
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Re: MF-101 Envelope Negative Amount and Rate Questions

Post by facon » Mon Apr 21, 2014 11:33 am

Sounds like a great addition. It's definitely my next project. I've also been thinking about a signal splitter and trigger input on the 101. That way fuzz can still go before it, but there will always be a clean signal. I've noticed that my Big Muff makes the MF-101 completely useless, but would sound much better placed before it if the envelope would work.

I think an MF Boost would make a great addition for that setup. I'm imagining it could be used for Slow Gear type swells, a compressor, a trem/vibrato unit and obviously a clean boost :)

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