King Dubby PT2399 x 2 delay, momntary dub/oscillation switch

[Nocentelli]

Here's a variation on the deep blue delay; two PT2399 chips and a current mirror delay pot give around 2200ms delay, although beyond 700ms gets pretty lo-fi. There are two points where a momentary SPST can be used: Either to briefly connect the input to the delay input on select phrases (dub mode), or to bypass the repeats feedback resistor for self-oscillation on demand. I use a DPDT toggle switch to choose dub or oscillation mode using a single momentary footswitch.

king dubby_schem_nocentelli.jpg

I've also done a vero, but won't have a chance to build it for a week so it's not verified yet:

King dubby_vero_nocentelli.gif

I recorded a basic video while I was testing the switching arrangement on a breadboard:

https://m.youtube.com/watch?v=ioN-4r8J9 ... 6744232-35

[storyboardist]

Working on a PCB layout of this and one question: are the emitters of the PNPs connected just to each other or do they go to 9v or 4.5v?

[Nocentelli]

They're just grounded, there's no significance to to different symbol.

[Dirk_Hendrik]

I may be mistaken but fail to see how those PNP's conduct in this arrangement The sudden use of a different ground symbol is confusing indeed.

[Nocentelli]

I may be mistaken but fail to see how those PNP's conduct in this arrangement The sudden use of a different ground symbol is confusing indeed.

It's lifted straight from the rebote 3 with no changes. The rebote 3 schematic shows the emitters connected to pin 4 (i.e. digital ground) but I always link pin 3 and 4: The different symbol IS confusing, I apologise again, but I copd thedelay section from the rebote schematic where a different symbol is used for digital ground.

[Dirk_Hendrik]

I see what you mean. I'd say the Tonepad orientation of the transistors is wrong (someone reversed a top view and bottom vieuw) and the schematic was drawn from the layout.

[storyboardist]

Here's my go at a layout for this thing.



Dimensionally it could fit in a 125B, but if it were me...

[rock soderstrom]

Hi Nocentelli, I really like your King Dubby Delay with the momentary footswitch and I ask myself if I can do the same with the Multiplex Echo Machine? What do you think, is there any problem if I do the the same around IC2? cheers

[Nocentelli]

Because the multiplex has that 3P3T switch that gives either one PT, two PTs in parallel, or two PTs in series, i think you'd need to put the momentary switch for dub/punch-in between the output of the first opamp and SW1A.

[rock soderstrom]

Because the multiplex has that 3P3T switch that gives either one PT, two PTs in parallel, or two PTs in series, i think you'd need to put the momentary switch for dub/punch-in between the output of the first opamp and SW1A.

Thanks, I will test it tomorrow.

[Sirppi]

What transistors did you use? I built this using the first pair of pnp's i encountered in my transistor bin, and the time pot doesn't act very linear.

[Nocentelli]

No, it's not very linear. I started off using a dual gang pot for time, but switched to the current mirror because I reasoned many diy-ers won't necessarily have duals kicking about in their parts stash. I can live with the 'reverse log' action of the pot, as it spreads the shorter (more useable?) times 80-500ms over the first half of the rotation where you might want more precision to match time to tempo, and the longer 500-2000ms, sample rate reduced graunchy repeats are restricted to the latter half of the rotation (I have three tap tempo digital delays to choose from if I want a much longer beat matched delay). If you reference the top of the time pot to 5v instead of 9v, you get a shorter maximum time, but it *seems* to respond slightly more smoothly.

I used BC559s for the pnps, I don't know if a different part would respond differently, may be worth trying.

[Nocentelli]

Sadly on hold. I built a vero and it didn't work but I had no time and little appetite for debugging. It's currently sitting on my kitchen sideboard giving me occasional venomous glances. I'm not keen on posting a vero that is not verified by me (although I am fairly sure it's sound and I just screwed up the build and can't see it), but i'll post it in projects in progress so maybe some kind soul would lend another pair of eyes to check it over.

[aishabag23]

FWIW... I know this is an old thread, but I have built Storyboardist's PCB layout and it works beautifully.

[Pedal Jerk]

Hi there. If I wanted to whip up one of these, but I wanted to use a dual-gang pot for the Delay Time rather than the current mirror configuration, what value/taper would you recommend for the pot? And do I just wire up each gang as a variable resistor from pin 6 to ground on each chip? I want to have a really smooth time control, and preferably limit the delay time range from 40ms to a little over 700ms on this unit. I have no need for super long, degraded delays. Thanks for any replies!

[bsoncini]

Just built one of these from the tagboard site layout. Worked first try. Thanks for the circuit.