LPD Pick Attack Modifier (PAM)

[Groovenut]

So a friend who does laser etching for me had let me know about this Tel-Ray pedal that he had used "back in the day". He was disappointed that his had been stolen and that if and when he could find them, they went for silly money on eBay. I told him I'd have a look into it.

The orginal pedal was a volume pedal that doubled as an attack control. The foot pedal set the release time in attack control mode. It used 4 LED/LDRs in the circuit and operated on 15 volts. I made several adaptations to allow for 9 volt operation and considerably reduce current draw. The operation principle is the same as the original.

Here's a demo of the breadboarded circuit I came up with

Part I Short Release Times

Part II Medium Release Times

Part III Long Release Times

Part IV Note Tracking with faster release times

I have as yet not been able to find any video demos of the original circuit to compare my circuit performance to.

So I am waiting on my friends opinion of the demos to see if I got close to what he remembers his pedal behaving like.

The small cable I am holding in my pick hand is connected to the circuit and provides a very small control voltage that engages the circuit as it touches the strings.

At first I was skeptical that having to use such an interface would be worth the trouble, but the amount of control, accuracy and dynamics available definitely make it worth while.

My goal is to make the final layout small enough to fit into the guitar control cavity along with a 9 volt battery. My circuit draws 1.75mA and should allow a battery to last fairly long. Installing an 1/8" jack in the pick guard to plug the control wire/metal pick into is an option as well as some kind of true bypass toggle.


Thoughts?

[thermionix]

The sound is very cool.  The logistics will limit its appeal.  Not too many folks like metal picks, or extra wires.  There's got to be a more practical way to achieve the same effect.

[Groovenut]

The sound is very cool.  The logistics will limit its appeal.  Not too many folks like metal picks, or extra wires.  There's got to be a more practical way to achieve the same effect.

I agree with the logistics argument. Most players will probably skip trying it based on the need for a special pick/connecting wire, which is too bad. The amount of control the player has over the effect in this configuration is a huge selling point, not to mention the combination of sounds only available with this set up, ie when using hybrid picking ( 1 ducked note in combination with 1-2 unducked notes). Plus the effect tracking and the way it handles chords. Being able to use it as a stutter effect, etc.

I was pretty skeptical myself when my friend was going on about how cool it was to play this effect, and then I spent an hour playing it and I can understand his enthusiasm.

I'll see if I can put together another demo of just the unique things the arrangement will do.

Thanks for the input!

[Ben N]

Would make a great built-in effect, maybe along with a Fernandes-like sustainer for a kind of super-dynamic guitar. If the wire only has to go as far as the body of the guitar, that makes it a lot easier to deal with.

[Groovenut]

Would make a great built-in effect, maybe along with a Fernandes-like sustainer for a kind of super-dynamic guitar. If the wire only has to go as far as the body of the guitar, that makes it a lot easier to deal with.

Hey Ben!

Yes that was part of my goal of installiing it in the guitar control cavity. The control cable would then only need to be 6-8" long, maybe less. I envisioned using an eighth inch stereo jack/plug that would be wired to both power and activate the circuit when plugged in (deactivate and bypass when unplugged). One could even use an alligator clip on the end of the control cable so that any object of conductive material could be used as a pick (I'm just using the alligator clip as the pick in the demo clips).

[R.G.]

Neat effect. I've heard several similar things, and I like the effect a lot.

The fundamental issue with this kind of effect is deciding when a pick attack happened. The metal pick and wires is one way, and a more direct one.

The other versions look at the signal and do some variations of looking for a sudden increase in signal level. These are much more convenient to use as you don't need a metal pick and wires, but have worse performance, as the circuits really have to guess when a pick attack happened. There is a wide range of pick attacks, of course. Sensing an unambiguous metal contact is more definite.

Changing the pick attack dynamics makes the guitar into a different-sounding instrument. I've often speculated on a setup that would do this by having at least one channel that compressed the devil out of the signal to get an almost uniform signal level, and a dynamics setting channel that would be fed either the normal guitar or the compressed version, with a dynamics sensing channel that tried its best to find pick events and silence events from both the dry channel and compressed channel, then imposed either attack modification or full ADSR on the audio.

So many designs, so little time... 

[Groovenut]

Neat effect. I've heard several similar things, and I like the effect a lot.

The fundamental issue with this kind of effect is deciding when a pick attack happened. The metal pick and wires is one way, and a more direct one.

The other versions look at the signal and do some variations of looking for a sudden increase in signal level. These are much more convenient to use as you don't need a metal pick and wires, but have worse performance, as the circuits really have to guess when a pick attack happened. There is a wide range of pick attacks, of course. Sensing an unambiguous metal contact is more definite.

Changing the pick attack dynamics makes the guitar into a different-sounding instrument. I've often speculated on a setup that would do this by having at least one channel that compressed the devil out of the signal to get an almost uniform signal level, and a dynamics setting channel that would be fed either the normal guitar or the compressed version, with a dynamics sensing channel that tried its best to find pick events and silence events from both the dry channel and compressed channel, then imposed either attack modification or full ADSR on the audio.

So many designs, so little time... 

I've mucked about with most of the pick envelope sensing designs that have come to light (dsp and analog), Boss Slow Gear/AxeFx as an example, and was never very impressed with the dynamics of their control (although I have not yet tried Kippers most recent swell effect). As you stated RG, it's a difficult thing to nail down because of the nature of the guitar signal envelope. Sometimes, hardware is the answer 

I do find this setup at least highly controllable albeit somewhat inconvenient. Nothings free eh.....

[Mark Hammer]

Reliably identifying the "start" of a strum on a guitar is one of the major hurdles in a great many effects, not the least of which was guitar synthesis for the longest time.

The traditional strategy was to distinguish the "start" by the difference in amplitude between picking and not picking.  But that meant that a soft strum could not be reliably detected.  One would have to set a threshold that was high enough for the circuitry to distinguish between noise, note decay, and note onset, and that meant you always had to pick hard.  It was a bit like playing a piano where a note would only register if you pounded the keyboard; it would work, but cramped one's musical expression in the process of trying to expand it.

The Morley approach made it possible for the act of picking to be differentiated from the intensity of picking - no small achievement.

Wouldn't it be great if a person could fade in effects in a reliable and controllable fashion, using a system like this?  So, strum a chord, and modulated delay fades in to accompany the dry signal as the chord decays.

[Groovenut]

Wouldn't it be great if a person could fade in effects in a reliable and controllable fashion, using a system like this?  So, strum a chord, and modulated delay fades in to accompany the dry signal as the chord decays.

You should be able to achieve this by using the control mechanism of this circuit to control the level of say an effects loop return as apposed to the main dry volume I would think. Just a matter of rerouting the control elements.

But now we are talking about something that needs to be in a pedal and not on the guitar itself. Which brings a host of new challenges

I suppose you could use a stereo cable from the pedal. One conductor for signal, one for control voltage.

[Kipper4]

Awesome Lawrence.

[Quackzed]

+1 awesome!!!

[R.G.]

I got it. A pick containing a piezo crystal to generate a signal from the impact with the strings, then a bluetooth module to spit out pick hits.

Not exactly no wires, but perhaps a palm-mounted widgie instead of a long wire.

[R.G.]

Just as I hit "post" I realized that my fingerpicking friends would then insist on piezo adapters for fingernails.

[thermionix]

How about a foot-operated pedal, that looks like a wah, where the player can control the volume swell of each note or chord as he/she sees fit?

[Groovenut]

You may be on to something there ^^

[Tony Forestiere]

Just as I hit "post" I realized that my fingerpicking friends would then insist on piezo adapters for fingernails.

Surgically implanted by sharks with lasers.

But now we are talking about something that needs to be in a pedal and not on the guitar itself. Which brings a host of new challenges

I genuinely like the effect. It is not something one would use constantly, nor is it something I feel a need for, but is a very salient proof-of-concept for a fast-acting trigger in a one-off, body installed situation. Build it into a guitar only meant to be used for this purpose. My personal opinion about the "gimmick" wired metal pick as the trigger, and the subsequent tight tracking, is that is a vastly different and more precise approach than standard envelope followers. (I most assuredly do not mean 'gimmick" is any despairing manner).

Neat effect. I've heard several similar things, and I like the effect a lot.

The fundamental issue with this kind of effect is deciding when a pick attack happened. The metal pick and wires is one way, and a more direct one.

The other versions look at the signal and do some variations of looking for a sudden increase in signal level. These are much more convenient to use as you don't need a metal pick and wires, but have worse performance, as the circuits really have to guess when a pick attack happened. There is a wide range of pick attacks, of course. Sensing an unambiguous metal contact is more definite.

Nice job, but I wouldn't try a pedal format. Stick with the on-board thing. 

[Mark Hammer]

So which Tel-Ray/Morley was this based on?  Here's the schematic for the Pik-Percussion.

I did manage to find several other Youtube demos of something similar.  This one would seem to be a homebrew circut.

This one is a Morley unit, although the video would seem to be from when 320x240 was considered good resolution.  I gather the exaggerated hand movement are just the player's style and not an operational requirement

Your circuit doesn't actually need to be built into the instrument, although that would clearly permit a cleaner interface.  Depending on the current requirements, a simple little plastic box, velcroed to the top of the guitar, could be serviceable and locally powered.  Run a short pedal-board type patch cord from the normal output jack to the add-on box, and then your guitar cord from there.

[R.G.]

How about a foot-operated pedal, that looks like a wah, where the player can control the volume swell of each note or chord as he/she sees fit?

Hmmmm... like a kind of volume pedal?

One of the guys at the office plays whale songs with a distortion, a chorus and a volume pedal.

[Groovenut]

Mark

That schematic is one of the ones I found when I did a google search. The other was a bit more simplified but both are still more complex than the circuit I came up with. I think one used opamps and the other discrete transistors.

I'll see if I can find the other schematic I saw.

My circuit draws 1.75mA so 9 volt battery whould last a long time. Having a toggle switch for bypass makes sense to me, though the unity gain amplifier circuit sounds really good and should be able to drive long cables pretty easily. I think I'll be able to get it on a 1" x 1" pcb and mount it via the release pot. I'm still working on that part.

The only issue I can forsee with your idea about the box and velcro to the front of the guitar is having to have the cable from the amp running to the top of your guitar. I suppose looped through the back of the strap would keep it out of the way though.

Those demos where...well.... I guess I could tell what the effect was supposed to be doing. 

[Groovenut]

Well of course now I cant find the other schematic....

In essence, it had a series of BJTs and a Darlington to produce the control signal via grounding to the strings with the metal pick, this was fed to a Darlington and RC network that drove the LEDs and controlled the release time. I think there were 4 LDRs in the circuit, which seemed like overkill to me. I only use one. The volume control pedal was connected to a bulb shade that progressively blocked the light falling on one of the LDRs to control the release time. Also, they chose to connect the LDRs in such a way as to not take advantage of their naturally slow release and attack characteristics. Which was a head scratcher...

In any case, I've finished the proto layout and as soon as I have a finalized set of component values, I'll post the schematic/layout.

Thanks everyone for the interest!

Law