PT2399 delay with modulation - PCBs for sale

[Taylor]

Here's another PCB designed more in the format of guitar stompboxes, but which would be quite useful for electronic musicians of all types. This is a PCB for the Echo Base, a PT2399-based delay with an LFO controlling delay time. It does excellent analog-ish (it's a digital chip) delays up to 700ms (or up to several seconds with more noise/more filtering necessary), vibrato, chorus, pseudo-ring mod. It's a great-sounding unit.

This is a professionally manufactured PCB with blue soldermask, silkscreened component legend, plated-through holes, etc. Very nice quality boards.

There's a build document here with BOM, schematic, wiring diagram, etc.:

http://musicpcb.com/documentation

Boards are $14 each, plus shipping. I've set up a little website to make ordering easy:

http://musicpcb.com

I do ship internationally, to any country on the planet. Make sure to buy international shipping.

[Danno Gee Ray]

Order sent for 2 PCB's.

[Funky40]

I'm very interested, but need a CV input instead of the onboard LFO.
can i connect a external CV to pin1 of the PT2399 ? any additional parts needed ?
A little schematic for the mod would be very great

[Taylor]

Pin1 is power, so definitely do not do that.

I think you could do this by leaving out all the LFO parts the left of the depth pot (on the schem), and inject CV to the rightmost pad of the depth pot (on the board).

[DGTom]

Looks really good. Seems like it could be modularized quite easily by mounting the "Mod Depth" pot off the board. Tap into the internal LFO (an extra LFO is always a good thing - one with an on/off switch even better!) & add an external CV in

Its a shame that extra 4066 block isn't used for the "Bypass" switch, with the tails mode this would be a very cool sequencing option in a modular set-up.

[Taylor]

[DGTom]

If I understand the schem. (big IF) when the bypass switch is open & the base of the transistor is not connected to ground the effect is on.

So, this is the "wrong way round" if we wanted to turn the effect off with an external gate, but, if U4B was placed across the bypass switch we could turn the effect off with a positive gate to that switches Enable pin.

That way a sequencer could be used to switch off the effect & with the "tails" mode you'd get some really cool stuff going with looping sequences.

... not sure if I havn't confused myself now
& I don't totally "get" how the bypass works as is...

[Taylor]

Hmm, I see. I'm not really versed in modular stuff so I hadn't thought about that. I think you are right in your assessment. I believe it wouldn't be too difficult a mod if you just lift pin 5 of the 4066 from the socket and solder your gate input there, then wire pins 3 and 4 across the bypass pads.

[slacker]

So you want a "high" input to turn the effect on and a "low" to bypass it? That should be a simple enough mod, leave it with me.

For an explanation of the "bypass" switching have a look here http://www.diystompboxes.com/smfforum/forums.html?topic=60662.0

Note I got my open and closeds the wrong way round, but hopefully it makes sense.

[DGTom]

actually the other way round; "low" on the 'bypass' gate input would turn the effect on & "high" would bypass it.

Dunno if that seems wierd, but, it seems more intuative to me if you want to sequence the delay being off; most of the time you want the delay on, except for a few notes in a sequence, which is where the tails come in.

[slacker]

That's how it works already, connecting the the base of the bypass transistor to ground turns on the effect.
So to control it with a gate signal all you need to do is add a diode with its anode connected to the base and the cathode connected to your jack. A low gate signal will then pull the base low through the diode turning it on, a high signal from the gate will reverse bias the diode and the 220k pull up resistor will turn the effect off.
If you did want the opposite response you can just replace the NPN transistor with a PNP and then it will be low = off.
If you want to you can also access the control pins for the CD4066 directly, via the pads for the "tails" switch, so if you wanted you could have gate control that would give you "hard bypass" or bypass with tails. You need to make sure your gate signals don't go negative though or you risk killing the CD4066.

If I get chance later this week I'll try it out with some synth modules and post some notes about interfacing it with a modular.

Just to avoid any confusion the PCB is all Taylor's work and other than giving him my permission to do it, I've had nothing to do with it, so I can't answer any questions about that. I'll do my best to answer any questions about the circuit its self though

[Taylor]

I should point out that Slacker is the designer of this circuit, so he understands it much betetr than I.

[rosch]

will they be available for a while? i just ordered 1 but might need more soon.

[Taylor]

Yes, I should have more for a while.

[ericcoleridge]

[Taylor]

The delay time is modulated by the LFO. In the PT2399, delay time is set by a resistor to ground. So you can't just plug a voltage in there. That's why the transistor/resistor network is there on pin 6, because you need a varying resistance, not a voltage.

So the base time is set with the time knob, and the LFO creates a slightly asymmetric triangloid wave that modulates it from there.

I'll be doing a much more complex delay PCB in the future which includes everything on this one, plus a second delay chip for double time or parallel delay, with tap tempo with variable divisor on each delay (so you can do tap tempo and have 2 parallel delay lines with a 3-to-4 time ratio for example).

[slacker]

[ericcoleridge]

[Taylor]

Here's the thread:

http://www.diystompboxes.com/smfforum/forums.html?topic=81668.0

It'll probably be a while as the design became more complex than originally planned. I do plan to have it done in the next couple of months.

[ericcoleridge]

[Taylor]

It should be fairly simple to inject your LFO into the point where the onboard LFO would go. The tap tempo works by way of a momentary SPST to ground, so if your controlling device can send a "low" state in time with the beat you want, you'd have external tempo control that way as well.

[rosch]

Shruti-1 + Echo Base by rosch

Shruti-1 with the Echo Base delay (all temporary on cardboard)
2morepics

[adambee7]

Yeah, i like that. Good stuff.

[Taylor]

Cool sounds Roger! I hadn't heard of the Shruti-1 before now, but it's very interesting. Too bad they're not making them anymore.

[Peake]