Small Time: PT2399 Delay with tails

[maselectguitar]

Oooooh yeah baby! 

Ordered a new pack of 10 from a trusted vendor, got them last week, re-did a new transfer/etch, solder and voila! All awesome and working nicely now!

The batch I got before were cheap Chinese fake parts probably, which I have to throw away. All the new ones were tested and nicely working the same sound.

Thanks a bunch melrin, much appreciate your time and help.

maselectguitar

[BoogiemanX]

This might be a stupid question but what exactly does "tails" do? Does it continue echoes even after pedal has been disengaged?

[Groovenut]

This might be a stupid question but what exactly does "tails" do? Does it continue echoes even after pedal has been disengaged?

Correct!

[fatecasino]

I had exactly the same symptom with maselectguitar, I could get only the clean sound. I had 4-5 pt2399s and I found out that only one of them was functioning!!
I have a question,
I would like to ask you how could I add a kill switch to mute completely the clean signal. There are some nice sounds that can be achieved with this.

[garcho]

how could I add a kill switch to mute completely the clean signal.

see how there are two 10kΩ resistors at the non-inverting input of the second (right-hand) op amp? that's a "summing amplifier"; it allows dry and wet to be mixed together. you could add a SPST between the 10kΩ resistor that is connecting the first op amp's output and the inverting input of the second op amp. that would prevent any clean signal from being summed with the wet signal.

[Radical CJ]

Hi All,

An old thread I know, but...

I recently bought two of the version 3 Small Time Delay PCBs and I was thinking it would be groovy to put them both in the one (1590DD) enclosure with some simple switching options for running them in parallel/series, and for mono/stereo output.

Initially, I thought I would have to devise a third board for buffering/splitting/blending, but after thinking about it, this might be superfluous. The circuit is already book-ended by two op amps.

A question to those with more experience than myself. Is running two of these circuits in parallel likely to work? Or will it cause a feedback, motor-boating, squeal, or other issues like volume drop?

Is there no way to know for sure until I try?

Any advice appreciated.

[anotherjim]

In parallel, the inputs have high impedance and will be ok joined together.
The outputs "may" be happy. The output circuit is low impededence and two of them will fight each other a bit. The 100R resistor in the output will limit that effect, but I would raise them to 1k. Although this will cut the output level a little, it will be by a trivial amount.

[Radical CJ]

... The outputs "may" be happy. The output circuit is low impededence and two of them will fight each other a bit. The 100R resistor in the output will limit that effect, but I would raise them to 1k. Although this will cut the output level a little, it will be by a trivial amount.

Thanks for the reply, I might socket those resistors and try a few values before committing.

Not particularly worried about volume drop, as I already need to put an anti-boost/limiter in front of the Twin that I use for home practice (completely unsuitable home practice amp, but I found it second hand and fell in love). I am worried about treble loss, but I don't think that will be an issue here as increaseing the value of that resistor is really much the same as rolling a Master Volume down a bit.

[merlinb]

You could use a blend pot...

[Radical CJ]

You could use a blend pot...

A good idea, thanks Merlin. Although I'll have to think about how it will be wired with some of the switching options I have in mind. Obviously, impedence and blending wont be an issue when in stereo output mode, or when running the circuits in series, but in parallel a blend pot would be good.

[moosapotamus]

Cross feedback is a fun mod to do with two delays in one box. Use a DPDT toggle to send the repeats from delay1 to delay2, and from delay2 to delay1.

[Radical CJ]

Cross feedback is a fun mod to do with two delays in one box. Use a DPDT toggle to send the repeats from delay1 to delay2, and from delay2 to delay1.

Does this create a cacophony?

[moosapotamus]

It can, if the feedback is high enough. But you should be able to turn it down to a level that allows the repeats to gradually fade away. So, maybe somewhere between cacophony and controlled chaos.

[ElectricDruid]

somewhere between cacophony and controlled chaos.

That's a reasonable description of this forum, lol 

[Radical CJ]

It can, if the feedback is high enough. But you should be able to turn it down to a level that allows the repeats to gradually fade away. So, maybe somewhere between cacophony and controlled chaos.

Would this be similar to having a momentary switch contecting pin 14 on board 1 to pin 14 on board 2?

It might be a while before I complete this project, but hopefully I will remember to experiment with some careful circuit bending, and will post results.

[moosapotamus]

I'm sure there might be more than one way to do it. Swapping pin 14 might work. But, I would also try swapping the wipers of the Repeats pots. You could use a momentary DPDT. I used a toggle on my dual Cave Dweller. Another word I might use to describe the effect is "lush."

[Radical CJ]

... Swapping pin 14 might work. But, I would also try swapping the wipers of the Repeats pots.

Ah. Now I get it!

Are there any YouTube videos/soundclips you know of that demonstrate this type of dual delay effect with switched repeats? The search terms I'm useing just seem to pull up advertisments for Strymon (which are not doing this trick).

[moosapotamus]

I'm not aware of anything specific on YouTube. But I can maybe record something with my dual cave dweller within the next several days.

[Gandalf_Sr]

I modified it slightly to include a CMOS audio switch (so I could have pedals that toggled the function) and then designed and made up a PCB for this circuit but I have problems with the operation. It works (after I fitted R25) but the the Repeats pot produces crazy feedback and distortion if I go above anywhere about 1/8 of a turn from fully anti-clockwise.

Any thoughts as to what's wrong or what could fix my issue?  I have full lab of sig genes and scopes if you want to suggest tests.

Happy to share design with anyone here.

[ElectricDruid]

Running the values of the Multiple-Feedback (MFB) filter around pins 15 and 16 through the useful tool at:

http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm

..shows that the filter has a gain of x-1.8. So there's a bit of boost on the way in. I haven't tried the output filter on pins 13 and 14, but if that's similar, that'd probably explain it.

It looks to me like those filter values have been tweaked to ensure that you can get oscillation even with the fairly low cutoff (2.7KHz according to the tool).

HTH,
Tom