Making a generic envelope follower

[Transmogrifox]

I really wish this didn't suck the way it does, but thats the nature of the beast

No kidding.  I think we need to start working on the non-causal system.  A device that can determine what you're about to play before it even comes through your fingers could sell for a lot of money in the psychic/fortune telling circles.  A lot of DSP enthusiasts would be writing home about it, too.

[Paul Perry (Frostwave)]

The closest I know of to 'precognition' on guitar controllers, is the use of neural networks to predict what note a person is playing, while the initial transients are still there.

"Yamaha Corp. has developed a more versatile sound-synthesis system by tapping neural network technology. Unlike conventional digital signal processing methods, the new system can predict a signal's waveform even before its full cycle of data is known. This capability is expected to accelerate the information-processing speed of guitar waveform-synthesis components. Yamaha's G50 pitch detector for electric guitars uses neural learning algorithms to reliably predict the pitch of a signal from the characteristic shape of its beginning transient. When the neural network was trained on thousands of guitar sound samples, it learned to detect frequency within a half cycle four times faster than conventional systems, which need two full cycles to reliably detect pitch"

[A.S.P.]

information lost...

[R.G.]

The 'double rectification' technique really does not help with a guitar input. The typical guitar wave has one large peak, and two smaller peaks of opposite polarity. Rectify that twice and the extra peaks you WISH would fill in the gaps simply won't. They are sure to be below the main peak and won't help at all with the ripple. Another  good-idea-on-paper.  It seems to work on a sine wave, but even then the extra peaks are way too thin to deliver much extra charge to the filter cap.

I suspect that may be true with single-string signals. But the double rectification does seem to work at least to my ear on more general signals - like two or more strings at a time. And it's a notable help on generic audio. I guess like all signal processing, it depends on what signal you're processing.

On the icons:
Have you tried turning off display of images in your browser?

[Arno van der Heijden]

REQUEST : Please, can anyone tell me how to abort the animated emoticons on the posting
page. Its costing me ONE SECOND per letter... I can't get much done. Is there a text-only page available

Harry,

This works for me: If you're using MS Internet Explorer, go to 'Internet options' => 'Advanced' => look for the 'Multimedia' header and uncheck 'Play animations in web pages'.

Good luck!!

[Dave_B]

Just a thought before coffee: What if you used a fast noise gate on the guitar signal that actually gated the EF?  Would that get you there?

[R.G.]

Here's a bit of simplification - I think I figured out how to make this thing self clocking. More later.

[Mark Hammer]

Harry,

What a pleasure to see you here!  Warmest regards to both you and Dana.

Mark

[Joe Kramer]

I would like to see the NE570/571 envelope can anyone point me to a schematic?

Soggy: If no one else here can post this circuit, I can take a digital pic of what I have and email it to you (sorry, got no personal webspace).  Let me know. 

BTW, on simpler rectification-type envelope followers for guitar (similar to Soggy's first draft), I've found germanium diodes help a lot with initial attack sensitivity over silicon.  My 2 cents.

Joe

[J. Luja]

REQUEST : Please, can anyone tell me how to abort the animated emoticons on the posting
page. Its costing me ONE SECOND per letter... I can't get much done. Is there a text-only page available

if you press Esc after the page has loaded it should stop the animations

[A.S.P.]

information lost...

[H^)harry]

Hello All.

Thanks for the tips on the smiley faces. I have them stopped now. its still pretty slow but I
can live with it.

Greetings (returned) to Mark Hammer :^P

(RE: RG)  The double rectification technique has 'some' benefit on a generic signal. The problem I'm describing
is documented in some Electronotes issue, where they did some work on DC restoration to make sure that the
peaks do match in amplitude. It gets pretty complex as well...

(RE: Paul Perry)   The Axon converter is siad to use 'neural network' techniques as well. In reality it tries
to match the shape of the attack transient as it reflects from the bridge and the fret. It can give a 'so-so'
guess of the pitch in the first half cycle, followed with a traditional pitch ocnversion for accuracy.

I'm using the actual string to generate waveforms. I get some horrible distortion for a single cycle... but you cannot hear
that easily. At least it does something in 'real time' so the perception of delay is not bad.  Presumable even if the Axon
or Yamaha guesses wrong for 1/2 cycle you will not be able to tell exactly that anything was wrong.

H^) harry

[johngreene]

Actually, to stop the animations just hit the 'stop' button on the explorer bar. That way you don't have to permanently disable them if you don't want to (for other sites).

--john

[soggybag]

A couple of questions

I have been trying to get this work with no luck. Can anyone give me any pointers? I hooked my guitar directly to input, should I add a buffer? It looks like the Base is at about 1.9v. I have an LED connected as shown and I'm expecting it should light up as a I play?



Also I have been working with the enevelope follower I posted originally. It seems to work but it is not sensitive enough. I have the output connected to an LED. As a play the LED lights up, but only when I pick hard on bass notes or hit a chord hard.

[GFR]

Now if you extract the envelope with a PIC, why not using the PIC to output a PWM'ed envelope to make a controlled filter, or phaser, or a compressor, or ...

[Mark Hammer]

Okay, here's an idea.

One of the problems inherent to envelope-tracking a guitar signal is the sub-audio, or almost sub-audio, volume fluctuations, that can come from a variety of sources like beats between strings, beats within strings (when their worn), finger vibrato, and so on.

I'm wondering if something akin to how Joe Gagan uses an alternate cap and variable resistor to adjust how much bottom comes in his various Fuzz Face derivatives (well, their more than that, but you know what I mean) might be of use in nailing a more ripple-free envelope voltage. Smoothing at the other end certainly helps, but it is really lowpass filtering of the envelope.  I'm suggesting here that both highpass AND lowpass can help to complement each other and achieve an envelope output that ignores some of th usual sources of error.

[moosapotamus]

I have been trying to get this work with no luck. Can anyone give me any pointers? I hooked my guitar directly to input, should I add a buffer? It looks like the Base is at about 1.9v. I have an LED connected as shown and I'm expecting it should light up as a I play?

I would try adding a buffer in front. In the circuits where I have seen this follower work, it's input gets fed by the circuit's input buffer, i.e. uglyface.

Also I have been working with the enevelope follower I posted originally. It seems to work but it is not sensitive enough. I have the output connected to an LED. As a play the LED lights up, but only when I pick hard on bass notes or hit a chord hard.

Sounds like you just need more gain. Take a look at Tim's most recent version of the uglyface... LM386.

~ Charlie

[Joe Kramer]

Soggy,

I could be seeing this wrong, but the diodes on your output (op amp version) look backwards.  I have a similar circuit that works okay, but with those diodes reversed and with +V connected to where you are showing "CV."  FWIW.

Joe

   

[soggybag]

Thanks for the reply Moose (can we call ya Moose?) I will try a few things with this this weekend. I'm not the most electronically inclined, it's all like alchemy to me. One day I may see the light. I hope at that point that it doesn't loose the fun.

I keep thinking that you should be able to light an LED with a simple transitor fed by the signal from your instrument. I had been thinking to use a FET. It seems that if the LDR had a little lag that might smooth out the on off of the audio going through the LED. Maybe a cap in there would help?

Joe: There may be an error in there. I took the envelope section from Jack Orman's Dr Quack and added a non inverting op-amp buffer to the front of it. I figured that would make it self contained and able to drop into a wider variety of situations.

[soggybag]

No one seemed to express any sentiment either way about posting a page from Stompboxology. So here's a link. The image was too large to post in the frame here. This page shows several envelope followers, the wave forms they create and some notes about the use.

Number 3 looks promissing. I tried to build it with a TL082 and it didn't work. But the notes say it must be 358 or 324 type op-amp. I didn't have a 358, which is why tried the 082, but I do have a 324 so I will give this a try next. I'm clear on what the difference is here?

Stompboxology was a really nifty publication with a lot of good stompbox ideas. Too bad it isn't around any more. Does anyway know how many issues are out there? I have a few, but I'm guess there were a lot more.