Penfold Dynamic Tremolo

[calpolyengineer]

I was wondering (hoping really) that one of you would be so kind as to post the schematic for the dynamic tremolo from penfold's book. Thanks

-Joe

[RaceDriver205]

What is this dynamic tremolo?

[calpolyengineer]

It varies the rate of the tremolo based on how hard you strum the guitar. Pretty amazing stuff. I'm working on making one now and I just need some "pointers" from Penfold cause I know he made one.

-Joe

[RaceDriver205]

That'd be cool if you could make it and contribute the layout/pcb etc.
Im working on tracing the PCB from the Penfold Active Ring Modulator (light metal) article. This guy sounds like he knows his stuff.

[StephenGiles]

What you need is a Pluck Follower, which produces a control voltage proportional to the speed of plucking the strings. Craig Anderton designed one of these for the AMS 100 in Device, to be found in Mark Hammer's site here:
http://ampage.org/hammer/files/Device1-11.PDF
I have not seen Uncle Penfold's circuit, but I suspect LM 13600 is to be found lurking in there somewhere.

[Mark Hammer]

What you need is a Pluck Follower, which produces a control voltage proportional to the speed of plucking the strings. Craig Anderton designed one of these for the AMS 100 in Device, to be found in Mark Hammer's site here:
http://ampage.org/hammer/files/Device1-11.PDF
I have not seen Uncle Penfold's circuit, but I suspect LM 13600 is to be found lurking in there somewhere.

Not necessarily.

The Pluck Follower essentially represents the "note density", not the picking strength.  It sums trigger pulses, not envelopes.  Pick a lot of notes in a short period of time and the pluck follower voltage goes higher, but it doesn't care whether you caressed the strings or hit them with a ball peen hammer.

I think what is requested here is something akin to what was included in the E-H Polyphase in analog form, and is included in the Line 6 Tap Tremolo in digital form.  That is, an LFO whose rate  can be momentarily accelerated  by harder picking/strumming.  A fairly standard envelope follower can be used to achieve this, assuming that the oscillation rate depends on a single varying resistance.

The big difference in this application, however, is that where an envelope follower is most often used to map some change onto the course of a single note's lifespan (as in the case of an autowah), here one is trying to produce a change that will be apparent over the course of several cycles of an LFO.  To do that it has to have a much slower attack and decay time than might be appropriate for a filter sweep.  Think of a Leslie switching from fast to slow speed.  You want to create the sense of the oscillator or "motor" slowing down or settling down.  If you have a 200msec decay time in there you may not even hear the change or it may be unpleasant or grating.  The change in speed has to feel like something breaking out into a gallop, and slowing down to catch its breath.  To do this, I'd suggest kicking up the value of the timing cap a notch or two.  So, if you have a 10uf cap in the envelope follower, try 47uf or maybe even 100uf instead.

[hank reynolds 3rd]

would something like the envelope section of the mcmeat/mutron etc work using the led to affect an ldr in place of the speed knob??? 

[Mark Hammer]

Absolutely.  Just keep in mind the attack and decay constants for the Mutron are set to be fast.  I think you'll need to increase that 4.7uf cap to 33uf or so, maybe even higher.

Given the Mutron rectifier/follower design with the upward/downward drive, you have the possibility to have the tremolo speed increase OR decrease as you play harder.  Note that would, theoretically, let you strum gently for tremoloed rhythm and essentially suspend the tremolo modulation for a bit with a few hard picked notes.  In effect, the tremolo enters when you're not "trying so hard".  That would be an interesting effect.

By contrast, having tremolo rate increase with picking strength adds a little more emotion with increased volume because the quiver in the modulation conveys a kind of nervousness, as if one's voice is cracking from tension.

Both musically valid effects.  Just keep in mind that the ideal rise and fall times for each direction might not be identical.  I don't know about you but I find that I usually like a downward swept filter to move a little slower than an upward swept one.  Part of the reason this is so is because the note itself changes over time.  Both frequency content and note amplitude change once you pick it.  Sometimes you want the envelope-controlled device to wait until some change has happened, and sometimes you want it to act before some change has occurred.

[hank reynolds 3rd]

'Given the Mutron rectifier/follower design with the upward/downward drive, you have the possibility to have the tremolo speed increase OR decrease as you play harder.  Note that would, theoretically, let you strum gently for tremoloed rhythm and essentially suspend the tremolo modulation for a bit with a few hard picked notes.  In effect, the tremolo enters when you're not "trying so hard".  That would be an interesting effect.'

That's what I was thinking. the Mcmeat envelope seems like a really good candidate, as you have control over attack and decay of the CV going to the LFO,aswell as the intensity (soft to hard trem??)....

[Steve Newton]

Scan deleted to save my bandwidth.

[Ge_Whiz]

This guy sounds like he knows his stuff.

Yes, he always did. Sometimes, there is even a suggestion that he built the circuits he published!

[RaceDriver205]

Sometimes, there is even a suggestion that he built the circuits he published!

lol, that fills me with confidence 
The 'light metal' ring mod article does however give indication that he actually built it, he talks about the sounds it makes etc.
It better work! Ive already got 4 other FX that dont work yet and I dont need another!

[RaceDriver205]

Oh, and do you have any more interesting Penfold articles, Steve?
Im interested to know what else this guy made.

[Paul Perry (Frostwave)]

Sometimes, there is even a suggestion that he built the circuits he published!

This raises a pet peeve of mine, magazines that publish DIY articles without having someone else rebuild them USING THE ARTICLE before it is published. Buggered up circuit diagrams & layouts have probably led to more people quitting DIY than any other reason. Some Penfold circuits included (not his fault, he used to design stuff for magazines & some got wrecked by the publishing staff).
Penfold's little Circuit Sourcebooks 1 & 2 are better than others of their kind.

[Dan N]

Thanks Steve! I have that circuit in a book (somewhere), but my book does not have the perf or parts layout. What is the title please?

[calpolyengineer]

WOW

This thread has gotten a lot of attention since I last checked last night! I had a final this morning followed by a 6 hour car trip to go back home for break.

Anyway,
StephenGiles I am well aware of the pluck follower and I do believe that would be a really cool effect. I was however actually looking at using your envelope generator. I just had one question, what is that track that splits of of the first 324 chip? I just assumed it was buffered dry signal.

Thank you all for posting ideas here, I will have my design up soon, hopefully it will be the god among mere mortal tremolos. Thanks especially to Steve Newton!

-Joe

[Steve Newton]

Thanks Steve! I have that circuit in a book (somewhere), but my book does not have the perf or parts layout. What is the title please?

One thing with Penfold designs is that they tend to get repeated in various magazine articles and his books. The book I scanned for this one is  - Electronic Projects For guitar
ISBN 1-870775-31-7 . It's saving grace for some would be complete perfboard layouts. Suggesting at least that they have been made at some point

[StephenGiles]

WOW

This thread has gotten a lot of attention since I last checked last night! I had a final this morning followed by a 6 hour car trip to go back home for break.

Anyway,
StephenGiles I am well aware of the pluck follower and I do believe that would be a really cool effect. I was however actually looking at using your envelope generator. I just had one question, what is that track that splits of of the first 324 chip? I just assumed it was buffered dry signal.

Thank you all for posting ideas here, I will have my design up soon, hopefully it will be the god among mere mortal tremolos. Thanks especially to Steve Newton!

-Joe

Which envelope generator are you referring to?
Stephen

[hank reynolds 3rd]

maybe the Royal Filter ?
I've thought of using this Env Generator for a couple of things ,just need the free time ,dammit!!! 

Seems like a good candidate for this env controlled trem idea,as I was thinking of the mutron/mcmeat envelope generator maybe having ripple (although this might be a good effect if it can be controlled a bit, where the royal one,I'm thinking,won't display this...

[calpolyengineer]

It was the one you posted here: http://www.diystompboxes.com/smfforum/index.php?topic=36221.0

-Joe