Random idea for Mu-trons and similar

[Mark Hammer]

I was listening to an older Jeff Beck concert, and when Rhonda Smith played a brief solo with what was obviously a Mu-Tron or equivalent (Q-Tron, etc.), it occurred to me that the pedal had the right degree of responsiveness/sensitivity, but dammit it was sweeping much too high to suit the mood or intent of the solo.

The standard configuration in Mu-Trons is that the LDRs are each placed entirely in parallel with a 220k fixed resistor.  As the LED lights up in response to picking, the combined parallel resistance of the fixed resistor and LDR goes low, and the filter sweeps upward (well, as long as the direction is up).  How high it sweeps is a function of picking strength, sensitivity setting, and also the value of the resistor/resistance.

So what if you want the thing to respond to more than heavy picking, but just not go quite as crazy when it sweeps?  You could always add resistance in series with each LDR/220k pair, but then that would change the overall corner/center frequency range of the filter.  What I'm aiming for is for the filter to go "woh" rather than "wah".

So here's what I came up with.  Split each 220k into 2 resistances in series.  Let's say 200k and 20k, in that order (subject to change, but used here as an illustration).  One end of each LDR is at the "incoming" end of the 200k.  The other end of the LDR half goes to the common of a DPDT toggle.  The toggle connects the "free" end of each LDR to either the junction of the 200k/20k OR to the far end of the 20k.  What you end up with is a situation whereby the combined parallel resistance can go as low as your picking and sensitivity setting dictate, OR can never go below 20k.

Another way of doing it is to get yourself a dual-ganged 100k pot. replace each of the 220k fixed resistors with 120k, wired in series with a section of the pot.  The "free" end of the LDR goes to the wiper of the pot.  This would allow for continuously variable upper sweep point, dictated by how much of the pot resistance is placed in series with the LED/fixed-resistance, and how much is placed in parallel.

Again, the net outcome would be that you could crank the sensitivity all the way, such that it would respond to the nuances of your picking/strumming, but it would sweep more modestly.  The nice thing is that all stock sounds would still be preserved, and the high/low ranges would still be in effect.

Whatcha think, folks?

[digi2t]

Would this be like a poor man's version of running a compressor/limiter in front of the Mutron? 

(Probably not, right?)

[Kipper4]

You mean as in R10 R12 here Mark

http://www.sabrotone.com/?attachment_id=3192

I experimented with changing the above values and also the 220ks in my latest SVF.

[Mark Hammer]

You mean as in R10 R12 here Mark

http://www.sabrotone.com/?attachment_id=3192

Actually, no.  The 10k may be in series with the LDR, but it is still in parallel with the 220k.  So, say I drive the envelope-extractor crazy with a ridiculously hot signal and the LDR magically drops down to 0 ohms.  We still have 10k in parallel with 220k which is 9.56k.  If that 10k was, say 47k, combined parallel resistance, if the LDR reached the magical zero, would be 38.7k.

From where I stand, the more straightforward thing to do is to have the LDR in parallel with varying portions of the full 220k, such that one can more easily calculate, and set, the maximum corner frequency point, using the non-paralleled resistance and feedback cap value in the calculations.  The Sabrotone variation gets you most of the way there (and it is smart), yes, but I think what one wants to do is be able to say "HERE is how high I'm going to let it sweep at most".

[Kipper4]

So maybe replace the // 220k with a
220k+100k pot wired as a variable resistance. Dual 100k pot.
There's always the possibility of wiring one of the variable resistors the opposite way.
This isn't helping is it?
Sorry not thread jacking.

[Mark Hammer]

No, I'm honoured I've got you thinking about it.  For purposes of being easily able to replicate stock settings/sound (and the Mu-tron didn't become popular because it didn't sound quite good enough), I think 120k in series with half a dual-ganged 100k is optimal.  The pot half always functions like a fixed 100k in series with 120k to provide the stock sound, but can be reconfigured to provide something with a lower "ceiling".

[pinkjimiphoton]

Would this be like a poor man's version of running a compressor/limiter in front of the Mutron? 

(Probably not, right?)

sorry for the momentary highjack... but i found if ya put a compressor before an autowah and crank the attack time real low and the decay/sustain long it will sweep the filter for ya automatically on held notes. it's kinda cool.

related, if ya do the compressor with a noise gate after it, and do the same with a high threshold level on the gate, at one point with your guitar volume backed down to the right point, there's a "sweet spot" where the gate and comp will fight each other and it starts sounding like you're playing backwards. <<<actual stupid pedal tricks

i had peeps used to ask me how i got that "backwards" sound live, well... that's it.

back to your regularly scheduled posting!!

mark, that idea sounds wicked wicked cool.

effectively, you can dial in the "range" of the filter sweep with it? have you tried it yet?

[digi2t]

What if those two 220K resistors were LDR's as well, and reacted dynamically to the picking as well? Have another dual Vactrol, LED driven by the envelope detector side, with an intensity control (only word I could think of right now) to range between high and low?

[Kipper4]

I still have the sabrotone on the breadboard when I get home after work I'll try the 120k -100k pot combo Mark.

[Mark Hammer]

Would this be like a poor man's version of running a compressor/limiter in front of the Mutron? 

(Probably not, right?)

sorry for the momentary highjack... but i found if ya put a compressor before an autowah and crank the attack time real low and the decay/sustain long it will sweep the filter for ya automatically on held notes. it's kinda cool.

related, if ya do the compressor with a noise gate after it, and do the same with a high threshold level on the gate, at one point with your guitar volume backed down to the right point, there's a "sweet spot" where the gate and comp will fight each other and it starts sounding like you're playing backwards. <<<actual stupid pedal tricks

i had peeps used to ask me how i got that "backwards" sound live, well... that's it.

back to your regularly scheduled posting!!

mark, that idea sounds wicked wicked cool.

effectively, you can dial in the "range" of the filter sweep with it? have you tried it yet?

In the late 70's that was similar to how I would get backwards-tape sounds.  Univox Compressor -> MXR Envelope Filter -> MXR 6 band
The filter was set for slowest attack, and the compressor made that even more gradual.  The lower three sliders on the EQ were pulled way down and the upper three sliders were dimed.  The filter sweeps from low to high, so when it starts its upward sweep, the output level is much much lower.  As it sweeps upward the part of the spectrum that the EQ gooses gets louder.  And since the old 6-band provided too much boost for its own good, it would begin to clip at the top of the sweep.  That would mimic what happens with a plucked string, providing more harmonic content at the beginning, except in reverse.

I haven't done that in over 35 years, so between my memory, and what reverse digital delays have made us more accustomed to, I suspect it didn't sound as great as I remember.  But given that this was well before digital delays, it was as close as we could get at the time, so we thought it sounded amazing. 

[pinkjimiphoton]

i first discovered it in my old boss me5.
i had limited parameters on it, so i'd set the compression attack at the lowest setting, the decay at the longest, and boost the treble with it. then i'd crank the noise gate up most of the way.. and just above the spot where the guitar would cut out, you'd get these ridiculous backwards effects. add a little delay or reverb and it was really really cool. i discovered patching an autowah in made it even cooler... doctor q worked perfectly for it. as the comp sustained it would sweep the filter open while the noise gate fought it all in one glorious hot mess of a sound.
kinda swelling in and out at the same time, and you could ride the effect and control it's sensitivity fromt he guitar volume. turn up, and you play normal guitar. turn down, and suddenly it's the 60's and you're spinning beatle disc backwards listening for turn me on, dead man

so even 35 years later mark, yeah, it's still a cool sound. i'm not sold on "reverse" sounds from digital effects. they aren't the same and you can't use them in real time the same way.

it seems to me this idea and dino's and scruff's all tie back to that envelope stuff i asked about a week or two back.

if you can make your pick attack "trigger" different things that could be really cool... this is the stuff i love about this forum.

[pinkjimiphoton]

What if those two 220K resistors were LDR's as well, and reacted dynamically to the picking as well? Have another dual Vactrol, LED driven by the envelope detector side, with an intensity control (only word I could think of right now) to range between high and low?

more genius!!!
this is the stuff i was trying to describe a couple weeks ago. i mean, you should be able to put almost any parameter under envelope control, right?
and being able to sweep the "range" where the sweet spot is would be a great addition to many existing fx

[digi2t]

more genius!!!

Someone who comes up with the occasional good idea = lucky (me)
Someone who comes up with good ideas on a consistent basis = genius (Mark, R.G., Gus, PRR, etc. Too many to name, no particular order).

[pinkjimiphoton]

hell, i can't even come up with a good idea, lol, every time i do it's already been done a thousand times over, and better.

that's why i always say i'm standing on the shoulders of giants... so many of them... mark, rg, jc, paul, merlin, d'astro,you, gus, lucifer, scruffie, mictester, kipper.... and all the million other guys who come up with so much stuff that it blows my mind.

when you think about it, aron too... especially... for having the vision to make a place that could set the musical world on fire like this. that's why i get so pissy about the guys that come here just to brain pick these geniuses and don't give anything back (close to an apology as i get).... i have spent years trying to make one stupid little thing worthy of contributing and my best pales in comparison.
i AM a monkey with a breadboard. nothing more.

i think the only original thing i've come up with is using a GE transistor in the feedback loop of an opamp as a semi-powered diode. to this day, i still haven't seen THAT one other than in the flying spaghetti monster.

most of my other shit has been either collabs with guys here or fsb, or the occaisonal "rediscovery" of something someone again far smarter than me already did.

i am proud to stand on these shoulders. and i am not too proud to get down and shine the shoes of these giants wherever possible and give props and respect where it's due. i am humbled by the majority of the people here, sharing, and teaching and guiding each other to the ability to make the ultimate gift... being able to help YOU realize the weird noises in your head. nothing but respect.

i won't go off about guys lifting other peeps circuits and calling them their own... i won't i won't i won't...

if ya post it to the interwebs at all, guess what? it's now FREE.

thank god for people still willing to share their minds and experiments and even failures with us. cuz without these giants to stand on, we'd all be scratchin' our nads lookin pissily at non working fuzzfaces

[Mark Hammer]

i first discovered it in my old boss me5.
i had limited parameters on it, so i'd set the compression attack at the lowest setting, the decay at the longest, and boost the treble with it. then i'd crank the noise gate up most of the way.. and just above the spot where the guitar would cut out, you'd get these ridiculous backwards effects. add a little delay or reverb and it was really really cool. i discovered patching an autowah in made it even cooler... doctor q worked perfectly for it. as the comp sustained it would sweep the filter open while the noise gate fought it all in one glorious hot mess of a sound.
kinda swelling in and out at the same time, and you could ride the effect and control it's sensitivity fromt he guitar volume. turn up, and you play normal guitar. turn down, and suddenly it's the 60's and you're spinning beatle disc backwards listening for turn me on, dead man

so even 35 years later mark, yeah, it's still a cool sound. i'm not sold on "reverse" sounds from digital effects. they aren't the same and you can't use them in real time the same way.

it seems to me this idea and dino's and scruff's all tie back to that envelope stuff i asked about a week or two back.

if you can make your pick attack "trigger" different things that could be really cool... this is the stuff i love about this forum.

I like the sound of reverse delay, jimi, but agree with you wholeheartedly that it is not the sort of things one uses for impromptu solos, if the intent is to have something that builds.  "Swell" effects are much better for that since the notes come out in the order you play them.  At the same time, swell effects generally miss the mark, tone-wise, since they don't increase treble content over time.

While slow sweeps are possible, the thing is that most envelope-controlled filters use envelope-detectors that are too simple to yield long swells.  They can do prompt and twitchy envelopes, and "lazy" envelopes, but not slow ones.  Steve Giles will likely pop in here any moment and tout the virtues of the start/stop envelope generators used in a variety of older EHX pedals and percussion circuits.  And he's probably right about that.  But this is about a simple and useful mod to a Mu-Tron / Q-Tron / Neutron.

Dino,
Take heart.
History is the one who decides genius, not us.  We just give history something to chew over.

[pinkjimiphoton]

thanks mark,
i was just trying to digest your idea and dino's... both should be able to work on any number of circuits i'd imagine.

this is kinda like where i was trying to go a couple weeks ago when i asked about envelope control of threads..

i was kinda picturing it as a filter sweep (or phase, or phlange, or....) where if you play legato (i think that's the term... like, pick one note but play many others) it would sweep, but if you hit it with a strong attack it would start the sweep with each attack. still trying to figure out how to describe it well... but it seems there's myriad uses for this kind of control, and that your idea for "ranging" it could be implemented in most of them.

btw, the thing i was talking about with the me5 was good also in that as it was quieter, less treble. as it got louder, you DID get more treble so it's actually almost doable.

i like the digital things, especially the ones that sample what you play then throw it back at you reversed, but to me, reverse delays and reverbs just aren't controllable enough to cut the mustard... they seem to be lacking that analog midrange "gutsiness" of a real signal.

and if i'm trying to get that backward "feel" and sound live (which is where i do this the most, believe it or not) digital is hard to work with.

analog comp and filter and gate you're working with the actual signal itself, and you can manipulate it even more... in real time, with your real tone generators... your fingers.

the digital stuff "sounds like" it, but to me, the hard way with the analog stuff just sounds more real, and you can do it live. once you learn to phrase stuff so it sounds backwards, it's all moot anyways cuz ya don't need the smoke n mirrors as much.  it's a "feel" thing.

tell ya what... when ya suddenly start sounding backwards live the people hip to that sorta stuff take instant notice.

do you have dropbox? i think i still have your email, love to send ya a couple tracks with some backwards stuff... and some FAKED backwards stuff.

rock on... sorry to hijack the thread.

i think your idea for the mutron is awesome, and i believe it could be used in any kinda circuit that uses envelope controls.

[midwayfair]

edit: derp.

[Kipper4]

Excuse my french.

[Kipper4]

[Kipper4]

Time for bed said Zebedee.