Seppuku kompakt kassette/broken tape delay style pedals?

[jimladladlooklike]

Just wondering if there are any existing layouts for such a thing? Cheers!

[patrick398]

You can get somewhere pretty close using a pt2399 delay with a really short delay speed and an LFO modulating pin 6. Random step LFOs work very well for this. From the demo i just watched it sounds like it could be using an envelope to modulate it too

[jimladladlooklike]

You can get somewhere pretty close using a pt2399 delay with a really short delay speed and an LFO modulating pin 6. Random step LFOs work very well for this. From the demo i just watched it sounds like it could be using an envelope to modulate it too

I see. Thanks for the explanation. I'm definitely going to get the breadboard out for this one at some point. Apparently, the delay effect (specifically how mangled/warped it sounds) is controlled by the input signal from the guitar. I'm guessing this has sonething to do with pin 6 too? Would it be a case of putting the input signal through an envelope then the output of said envelope to pin 6?

Cheers!

[patrick398]

Apparently, the delay effect (specifically how mangled/warped it sounds) is controlled by the input signal from the guitar. I'm guessing this has sonething to do with pin 6 too? Would it be a case of putting the input signal through an envelope then the output of said envelope to pin 6?

Cheers!

That makes sense, sounded like there was some kind of envelope involved. Difficult to say without the schematic for the specific circuit but yes i suspect you could get somewhere pretty close or at least equally as mad with an envelope on the input.

Maybe have a look at the envelope section of the tremulus lune, or the Depth Charge tremolo which i believe Kipper from this forum put together and used to control tremolo speed with input envelope.
If you're using a LED/LDR set up i think you could probably get away with taking the output from the LDR straight into pin 6, bypassing the usual transistor as variable resistor, though you might need some resistors to set minimum and maximum delay times so the pt2399 doesn't completely loose it's shit...although i quite like that effect. I think there's a potential for problems with chip latch up but i've never run into that.

Breadboard sounds like the way to go with this. I'll be following with interest!

[jimladladlooklike]

Awesome, thanks for the advice!

What's chip latch up?

[patrick398]

I'm not sure on the specifics of it but basically if the resistance between pin 6 and ground falls below 1k-ish it can cause the IC to stop working properly, you can usually reset the chip by turning power off and on. I think to resistance between pin 6 and ground has to be above 1k when the chip starts up though otherwise it can damage it irreparably. I think with a resistance of 1k between 6 and ground you get basically the shortest possible delay time anyway so there's no benefit of reducing it anyway.

[jimladladlooklike]

Right-o! Noted. Cheers again!!

[BluffChill]

My shagpile and shagpile deluxe are essentially delay pedals with the pin 6 modulated by an attack envelope from the guitar's input, thread with schematic is here:

https://www.diystompboxes.com/smfforum/index.php?topic=122139.0

No vero layout yet but I'd like for someone to try one

[jimladladlooklike]

That's cool as shit. I'm not great at vero layouts, but maybe someone else here can have a crack at it.....

[sergiomr706]

If someone else wants to check this layout this would be great. I think this might work. Thanks to BluffChill Devices for his great work

[BluffChill]

Nice work! Looks good but you need a track cut on the 9v rail otherwise you chuck 9v straight into VREF at pin 2  of the PT2399 

[rankot]

I have also designed envelope controlled delay, but still have no enough time to breadboard and test it. Hopefully soon

[sergiomr706]

Thanks for detecting the mistake. This could have been downsided 2 rows but I prefered to have a little more room for the resistors, if someone wants the DIYL I can upload it for them to play with.

[jimladladlooklike]

Ayyy nice one with the layout. Cant wait to try and make one of these! I did notice however that on rev 2 of the layout the ICs aren't labelled.

[BluffChill]

It's just a dual op amp (LM358 is my fave) and a PT2399, and a 78L05 regulator.

[jimladladlooklike]

Hey guys! Finally got round to building this. I love it! It's gonna have a place on my board for sure.

A couple of issues I think I've found with the vero layout were:

-The anode of the 1n4148 needs moving up 1 row
-I swapped round the 100nF and 100uF with their legs connected to rows 11 and 12, then I realised that I couldn't find the 100nF on the schem (please point this out to me if I'm wrong) so I omitted it entirely.
-I think the misplaced 100nF is the cap that's meant to be in series between the input and the 47k resistor, as per the schem. To fix this I made a cut at 9 down and 5 across (between 10k and 100k resistors). Then added a jumper from 8 down 3 across to 9 down 3 across. Then placed the 100nF cap between 8 down 7 across and 9 down 8 across.

Once I did all this it seemed to work, although it makes some weird noises when I stop playing suddenly. Hopefully it won't be as bad once I screw the enclosure cover on.

[BluffChill]

Glad to hear it! I'm afraid the weird little noise does stay after you stop playing. I've since updated the layout with more aggressive filtering from pin 12, using pins 13 and 14 too, which minimises it a bit. But it's something to do with the envelope follower finishing up and pin 6's VCO resetting itself through the resistor to ground, I think.

Some people have also suggested not linking pins 3 and 4, as doing so dumps a lot of digital noise straight to analog ground, but I've tried unlinking these and I don't think it made much difference.

I'm also working on a more accurate transistor controlled VCO modulation which allows modulation at shorter delay speeds. In fact, I've already produced a pedal version of it with no controls except an envelope strength adjust, and I call it the Wax Ether:

[jimladladlooklike]

Ah I see. I'd be interested to hear the results. Might even have a go at modding mine at some point.

And the Wax Ether is also very cool! Would love a crack at that too if there's a schematic you're willing to give up...

[abram]

good work there, BluffChill! i'm definitely a fan of the weird lofi delays achieved by the PT2399. i did a number of experiments with modulating pin 6 a number of years ago, but i've been doing some re-designs in the past few weeks after reading over this article on ElectroSmash (https://www.electrosmash.com/pt2399-analysis). similar to what they had shown, i just used a single opamp oscillator to modulate the base of a 2N3904 connected to pin 6 on the PT2399. it definitely made for some tape-warble like delay. anyone interested in the results of that experiment can see it here:

hopefully, i can pick this project back up over the next few months. i'd love to get the bugs worked out of the circuit and get it into an enclosure.

[jimladladlooklike]

So... I'm hoping to revisit this idea and get to the breadboard soon. I've been reading up on envelope filters for guitar fx, Mark Hammer's article over on geofx has been super helpful: http://www.geofex.com/article_folders/ecftech/ecftech.htm

From what I can gather, there are two elements of an envelope controlled filter that are most essential (leaving out the input buffer stage): The envelope detector/generator and the filter. The guitar signal is fed into both of these in parallel (I think?)

The envelope generator harnesses the guitar signal to create an envelope, which then triggers the filter section to react: So for example, if using an LED/LDR setup or a vactrol, this would be what links these two parts of the circuit. The envelope generator lights up an LED, which then changes the resistance on an LDR, the LDR being the "control element" of the filter section and causing the sweep of frequencies. I hope I'm understanding this correctly.

My next question is, do I need the filter/control element part of the circuit at all? Or would the envelope generator do? From what I gather, the filter is only necessary if attempting to get that auto-wah sound... and I just want to manipulate the amount of current flowing from pin 6 of the PT2399.

I found this attack release envelope schematic on synthnerd and wondered if I could use this as a starting point?