Moog Music Forum

Share Ideas and Pass the word

MF101 - modification for separate audio signal to env.fol.

Plug in here for info tips and strategies for your Moogerfooger Analog Effects. Connect more than one for plenty of fun!

MF101 - modification for separate audio signal to env.fol.

Postby JimF » Mon Mar 22, 2010 1:29 pm

Hi everyone,

Sorry about the delay in getting this info up - I promised it several weeks ago.

The question was how to modify an MF101 to accept a second audio signal in to the envelope follower, so that the filtering of the main signal can be enveloped by a second audio signal.

I did this to my MF101 about 10 years ago, after sending a couple of e-mails to Big Briar, and receiving answers from Bob Moog himself with explicit directions. I no longer have the computer on which the e-mails were received, and I have no backups from that time. So the following is retyped from printouts of the e-mails. Points to note:
- these instructions apply to a Big Briar MF101, vintage 1999. I have no idea whether the board and circuit of the current version of the MF101 are the same.
- I haven't got around to taking photos of the guts of mine - sorry...
- these directions are provided under the motto "no responsibility taken" - if you wreck your MF101, that's your problem :-)
- BUT I know that the instructions work - my MF101 has been doing this happily since 2000, when I made the modification.

First e-mail from Bob Moog, 2 March 2000:
"If you're adept at desoldering resistors on circuit board with plated-through holes, you can lift the end of R5 and connect your external signal to it. If you have access to shop equipment, you can drill an extra hole on the back panel of the MF-101, mount a bridging jack in that hole, and then wire the jack up to the R5 part of the circuit."

Several months later, when I finally got around to doing this, I asked for more explicit instructions:
Second e-mail from Bob Moog, 5th October 2000:
"1. DO NOT REMOVE THE CIRCUIT BOARD. Remove the bottom panel and face the jacks away from you. Identify U2 (LM324A).
2. Immediately to the left of U2, starting at the top, are a) two diodes, b) a 270K resistor, c) a 100K resistor, and d) four more resistors. That 100K, right below the 270K, is R5.
3. Carefully unsolder the left end of R5, that is, the end away from U2. Apply your signal to that end of the resistor."

So that's it, folks. It's actually quite easy, and it works like a charm. Like everyone else on this forum, I'm eternally indebted to Bob Moog (may he rest in peace) for his generosity and willingness to help - as well as for the great instruments!

So, have fun!

Cheers,

Jim F.
JimF
 
Posts: 18
Joined: Fri Dec 04, 2009 1:18 pm

Postby Just Me » Mon Mar 22, 2010 2:51 pm

Very cool, I'll have to see if it works on mine!
"Music expresses that which can not be said and on which it is impossible to be silent."
Just Me
 
Posts: 1144
Joined: Fri Feb 27, 2009 11:46 pm
Location: The Great Southwest

Postby latigid on » Mon Mar 22, 2010 4:28 pm

Great mod!
User avatar
latigid on
 
Posts: 1577
Joined: Mon Jan 30, 2006 3:47 pm
Location: Auckland, New Zealand

Postby EricK » Mon Mar 22, 2010 6:25 pm

SO it would function as the original if you multiplied your audio signal and sent it tothe mod and the audio in?

Interesting.
Support the Bob Moog Foundation:
https://npo.networkforgood.org/Donate/Donate.aspx?npoSubscriptionId=4043

I think I hear the mothership coming.
EricK
 
Posts: 5968
Joined: Fri Apr 09, 2004 2:09 pm

Postby DontBelievetheHype » Mon Mar 22, 2010 6:53 pm

Thanks for posting!

EricK wrote:SO it would function as the original if you multiplied your audio signal and sent it tothe mod and the audio in?

Interesting.


I think that it functions as normal when nothing is plugged into the new Key In.. I have/had a few filters with this option and this is how they functioned, and iirc JimF confirmed the same operation of his in the original thread.

Hopefully JimF or someone else with some actual circuit knowledge can confirm.
Synth bass guitar rig including MS-20 filter clone, Paradox TZF, MF101, 102, 103, 107(x2), CP-251 and MP-201
DontBelievetheHype
 
Posts: 148
Joined: Fri Feb 20, 2009 10:19 am

Postby Just Me » Mon Mar 22, 2010 8:32 pm

That is the reason for the shorting jack in the second email. With nothing plugged in, the resistor is back in circuit.
"Music expresses that which can not be said and on which it is impossible to be silent."
Just Me
 
Posts: 1144
Joined: Fri Feb 27, 2009 11:46 pm
Location: The Great Southwest

Postby ColorForm2113 » Mon Mar 22, 2010 11:28 pm

Wow that's seems pretty easy actually. I don't have the equipment for drilling a new jack hole. And my soldering skills are moderate at best. But I will take it to my tech and have him check it out.
My modular so far: Q104, Q106 x2, Q107, Q108, Q109 x2 , Q116, Q118, Q127 w/Q140, Q130, STG Wave Folder, Mixer and Mankato playing with Moog Voyager, VX-351, CP-251, MF-104M x2 ( STEREO!) Volca Beats and Bass, Arturia Beat step
ColorForm2113
 
Posts: 1280
Joined: Fri Feb 02, 2007 2:17 am
Location: Illinois(e)

Postby soundxplorer » Tue Mar 23, 2010 11:23 am

Bob called it a "bridging" jack in his email, but it is also referred to as a "half normal" jack. Plugging a cable in lifts the "normal" connection. Unplugging the cable lets the metal bend back and make the internal connection. You'll need to use one of these to have it work that way.

Image
Gear: Moog LP, Gibson LP, lots of FX
User avatar
soundxplorer
 
Posts: 237
Joined: Fri May 02, 2008 8:07 pm

Postby varice » Tue Mar 23, 2010 4:06 pm

Thanks for sharing this great mod. I had thought about making this type of change to my MF-101 back in 2006 to interface it with my Nord Modular G2X, but I came up with a different solution:

http://electro-music.com/forum/topic-12266.html

Too bad this mod separates the Level LED from the filter audio input, but that’s a relatively small price to pay for greater functionality.
varice
User avatar
varice
 
Posts: 63
Joined: Sun Jul 09, 2006 11:40 am
Location: Louisiana

Re: MF101 - modification for separate audio signal to env.fo

Postby _DemonDan_ » Thu Apr 01, 2010 12:49 pm

JimF wrote:If you're adept at desoldering resistors on circuit board with plated-through holes, you
can lift the end of R5 and connect your external signal to it. If you have access to shop
equipment, you can drill an extra hole on the back panel of the MF-101, mount a
bridging jack in that hole, and then wire the jack up to the R5 part of the circuit."

I don't know what Revision of circuit board Jim had in 2000, but the Rev. D board in
my recently purchased MF-101 is significantly different.

Can anyone definitively say what the new part ID is for that same resistor on a Rev. D
circuit board? (I'm not sure that it's R5 anymore.) And which end should I lift?
_ :twisted: _DemonDan_ :twisted: _
User avatar
_DemonDan_
 
Posts: 1189
Joined: Mon Nov 16, 2009 4:52 pm

Re: MF101 - modification for separate audio signal to env.fo

Postby varice » Thu Apr 01, 2010 1:47 pm

_DemonDan_ wrote:
JimF wrote:If you're adept at desoldering resistors on circuit board with plated-through holes, you
can lift the end of R5 and connect your external signal to it. If you have access to shop
equipment, you can drill an extra hole on the back panel of the MF-101, mount a
bridging jack in that hole, and then wire the jack up to the R5 part of the circuit."

I don't know what Revision of circuit board Jim had in 2000, but the Rev. D board in
my recently purchased MF-101 is significantly different.

Can anyone definitively say what the new part ID is for that same resistor on a Rev. D
circuit board? (I'm not sure that it's R5 anymore.) And which end should I lift?


I would recommend contacting the Moog guys then.

My MF-101 board is marked P/N 11-350C and is layed out as described by Bob. The 100K R5 is connected to pin 3 of U2. The resistor leg not connected to U2 is the one to lift. But, on the D board, U2 might not be the same circuit design...
varice
User avatar
varice
 
Posts: 63
Joined: Sun Jul 09, 2006 11:40 am
Location: Louisiana

Re: MF101 - modification for separate audio signal to env.fo

Postby jeepo » Thu Nov 25, 2010 4:00 pm

I think this has already been brought up, but this mod would be great for the mf-107 too. Has anyone attempted such a thing?
Stage II, MF-102, MF-105m, MF-107, paia theremin, akai s2000, yamaha pss 680, yamaha cp 25, and other stuff
jeepo
 
Posts: 282
Joined: Fri Jul 31, 2009 11:38 pm

Re: MF101 - modification for separate audio signal to env.fo

Postby latigid on » Thu Nov 25, 2010 6:09 pm

jeepo wrote:I think this has already been brought up, but this mod would be great for the mf-107 too. Has anyone attempted such a thing?


Yes :)

It's very cool, the signal at the audio input still interacts with the oscillator (FM, sync and envelope), while the CV signal controls the VCA. Immediately many more things become possible to do with the FB. You can even use the raw oscillator directly and have an ADSR envelope shaping the VCA; a real 'fooger synth!
User avatar
latigid on
 
Posts: 1577
Joined: Mon Jan 30, 2006 3:47 pm
Location: Auckland, New Zealand

Re: MF101 - modification for separate audio signal to env.fo

Postby jeepo » Thu Nov 25, 2010 6:28 pm

latigid on wrote:
jeepo wrote:I think this has already been brought up, but this mod would be great for the mf-107 too. Has anyone attempted such a thing?


Yes :)

It's very cool, the signal at the audio input still interacts with the oscillator (FM, sync and envelope), while the CV signal controls the VCA. Immediately many more things become possible to do with the FB. You can even use the raw oscillator directly and have an ADSR envelope shaping the VCA; a real 'fooger synth!

That's even better, exactly what I wanted actually.
Can you share the details of this mod?
Did you do it, or was it a factory mod?
Stage II, MF-102, MF-105m, MF-107, paia theremin, akai s2000, yamaha pss 680, yamaha cp 25, and other stuff
jeepo
 
Posts: 282
Joined: Fri Jul 31, 2009 11:38 pm

Re: MF101 - modification for separate audio signal to env.fo

Postby latigid on » Fri Nov 26, 2010 1:26 am

Hi there,

I performed the mod myself. It requires just a few parts but will involve cutting a trace on the PCB. I got sent some directions, but "modified" :) them slightly to what I thought was a better method.

I'm not sure if I should give out the details. One condition on receiving the 104 Spillover Mod directions was that I kept the information private. I sent "rosser" at Moog my instructions, which I'm sure he'd pass on to you. I haven't asked, but if he says it's okay I'll post the directions on the forum. It isn't too much different from the 101 mod given above.


Cheers
Andy


P.S. Happy Thanksgiving! :)
User avatar
latigid on
 
Posts: 1577
Joined: Mon Jan 30, 2006 3:47 pm
Location: Auckland, New Zealand

Next

Return to Moogerfooger Forum

Who is online

Users browsing this forum: CommonCrawl [Bot] and 1 guest