Another stupid idea - using echo --

[Lurco]

So, I breadboarded Maarten's Autoswell circuit, and found some sweet spots on the response time/swell effect during the testings.
After all, I found it to be very difficult to get stable 'effects' out of it. 
Additionally, no clean effect, no. Actually a very raw fuzz sound was present. I don't mean to underrate that circuit. It just isn't the one, that is needed in this project.

Before I take the final step, and build that Slow gear clone, I'll go to the very basic level.


The circuit above shows the simplest form of the 'one shot' -circuit, that I'm aware of. Meaning, when the voltage source is connected to that circuit, Led flashes only once, no matter, how long time the voltage is applied.  Question is, how to reset that bugger?

Once that electrolytic cap will be charged all the way with the wrong polarity, it might shoot once and will jump out of the circuit. The light will dim then. Can take some thermal related time though. I.o.w.: the cap symbol is correct, but that plus-sign is on the wrong side. What gives?

[woody alien]

Lurco, my bad .

Corrected one:

[Lurco]

Lurco, my bad .

Corrected one:

plus-sign is on the right side now. Conventional symbol for the cap is wrong though!

[woody alien]

Now, at this stage, I'm ready for the tar'n'feather treatment.

But in the meantime, I managed to make a third, updated version of that pesky circuit:
 

It actually provides the effect, that I'm after. Components(values) are just the ones, that I have at hand.

Replacing the voltage source with a comparator's output is the next thing.

[woody alien]

...Replacing the voltage source with a comparator's output is the next thing.

Mission accomplished, although there is always room for... refining the circuit.

At first, I was looking for a 4066(quad switch IC) to work out the needed switching actions.
But it was like trying to make a DPDT(Double pole, double throw) switch out of discrete push buttons.

I have some 12V miniature DPDT relays on my shelf, so one of them made its way to the breadboard.
After some fiddling, I got the 'logic', figured out, and had, and still have, a solid switching block.

I have omitted the details of the comparator circuit, that I use, as there may well be better signal sources, to feed the actual transistor-relay based circuit.

When the (guitar) note or chord is played, it goes through the comparator(in this case), which provides narrowed, but still irregular pulses in length.
Resulting circuit provides the trigger/reset sequence, which makes the Led to flash only shortly(depending on the timing capacitor).
Meaning, that the Led is on only for certain time at a time, no matter how irregular pulses the comparator puts out.



It actually works very well, so I literally get that 'tick', when plucking a note or a chord on a guitar. 

[~arph]

Ah so the goal is to mute the initial attack of the plucked note?

This is pretty hard as you need to have a immediate response to the note played. Any small delay will mean that you will still hear a bit I the attack. So using led and ldr's to control the muting is a no go. Ldr's are too slow. A relay takes some time too. One option is to delay the playback signal and use the non delayed signal for triggering.

[woody alien]

Ah so the goal is to mute the initial attack of the plucked note?

Yes, exactly. LDR may be slow, but how about a phototransistor? I'm going to test both, if necessary, as the process moves ahead.
Also the relay may be slow, but it sure doesn't sound like it is...

Anyways, slow or fast, the audible effect is what counts. Can't say more about it, before the testings. 

[woody alien]

Well, the project is moving along, and, although I've had some difficulties to record sounds to my laptop, I managed to make a short demo, which
shows exactly the opposite effect of 'swell'.

Why do I present that first? Because it hopefully provides the insight, of how the circuit responds. Also, I haven't explored other options yet .

Ultimate sustain killer: www.kolumbus.fi/kz1706/echo/Sustain_killer.mp3

Diagram of what is in use:

[~arph]

That sounds really cool! Was that intentional? I think we can swap the relay contraption with two transistors. I'm going to breadboard some of this.

[woody alien]

Intentional? Can't tell, as I was only picking notes, without any palm muting. I guess that it's just the way the circuit works.

But, ~arph, it would be great to have a solid state version of that relay thingy! I have looked for a solid state relays, but there seems to be no DPDT -versions available. Or is there?

Using transistors to perform the switching would make a lot more durable/reliable solution. If I only could handle that much logic...
Anyways, thanks for the interest, ~arph!

[jk-fm]

If you switch R and LDR, will it work in reverse?

[~arph]

you can replace the relay with a pnp to switch to gnd when the comparator output is low and a npn to switch power when the output is high.

[woody alien]

Jk-fm, yes it works, sort of.. and at this point, the rise/fall factors step in. Meaning, that the Led needs to have more specified control signal, than just on/off pulse.
That very on/off signal needs to have a separate controls for both, rise and fall times. Simple thing, I guess. But I haven't figured it out yet, how to accomplish that.

In the meantime, here is an updated diagram of the current circuit:


I used the tube driver to emphasize the 'thump' -effect, that the plain on/off switching has to offer:
www.kolumbus.fi/kz1706/echo/relay_thing.mp3

~arph, thanks for the suggestion, although I still have no clue, of how to replace that heinous dpdt relay with transistors.

[woody alien]

I finally built the GGG Slow Gear: http://www.generalguitargadgets.com/projects/19-filters-envelope/110-slow-gear

It provides nice swell effects without doubt(no shitty solos this time). But it also has one severe drawback: Device's overall output level decays abruptly
at the same rate, as the input signal does. Is that really the way this device is designed to work?

Or maybe I'm doing something wrong. The circuit itself should work as it is, as I triple checked it for possible solder
bridges, and wirings, before connecting it to the power supply. What comes to testing, I used straight guitar signal to feed the bugger.

Before that, I tried some transistor and jfet circuits, to achieve the trigger/reset sequence, that was, and still is, available using that stinky, tuned comparator-relay contraption.
Simply too much challenge for me.

ADSR(Attack-Decay-Sustain-Release) generator is the next step, as the one, that I'm building, has separate pots for all four factors. Who knows, what the results are.

[woody alien]

I've been without an audio interface for some time, since my beloved Zoom 9002 deceased. So not much of a chance to perform aural testings.
Today arrived the replacement, Zoom G3.  

The only reason, why I mention that new Zoom device here is, that it has an effect, called 'Trigger Hold Delay',
which pretty much produces the effect, that I was after, when I started this thread.

Main thing is, that it doesn't sound like I thought it would, at all. But, that's just a part of learning process, I guess.

What comes to that 'comparator-one-shot-relay' -thing, it has grown too much already, to be a dirt simple device.
After all, I'm positive, that it will, some day, produce an adjustable swell effect, having rather good tracking(which it already has).

ADSR circuit, that's involved: http://www.yusynth.net/Modular/EN/ADSR/index_new.html