Reverb with more than two PT2399

[seedlings]

I want to build a non-digital reverb pedal.  I like Merlinb's designs, but would like just a bit more lushness - something that probably isn't in my realm of ability...  My quad of PT2399 chips came in and I've been trying to familiarize with them.  Breadboarded a Sea Urchin delay that worked right off.  Right now have breadboarded two stock-from-the-datasheet PT2399 echo circuits.

The principle of a reverb is multiple (nigh, an infinite number of) delays working simultaneously.  I see that Merlinb put one chip in the 'effects loop' of the other chip, how will that differ from, 3 delays in series or 3 delays in parallel, set to different (short) times?

I've been searching for a reverb using 3 or 4 PT2399 chips, but can't find one. Now that I reflect on that, it may answer my question.

CHAD

[deadastronaut]

apparently the belton brick btdr 2-h is made from 3 pt2399's...under the goop.

so i guess its diy possible...sounds interesting.

[induction]

I want to build a non-digital reverb pedal...

The PT2399 is digital.

[Kesh]

The principle of a reverb is multiple (nigh, an infinite number of) delays working simultaneously.  I see that Merlinb put one chip in the 'effects loop' of the other chip, how will that differ from, 3 delays in series or 3 delays in parallel, set to different (short) times?



CHAD

If both chips get to delay each other's delays, a more complex delay pattern is formed than if each are independent (parallel) or one just gets to delay the other (series). Also, one should "detune" the two delays' times for a more natural and richer reverb to build up.

[psychedelicfish]

The one problem I have with Merlin's designs is that there is an audible "repeat" when you play a sharp note. What they need more attenuation of the wet signal and a slower decay, and they'd be great. It would still be interesting to try more than two PT2399s though...

[artifus]

not built the circuits and have only really glanced at the schematics so excuse my ignorance but how do they differentiate between flat, in tune and sharp notes before deciding to output a noticeable repeat? i'm not sure i understand.

attenuation of signals could be achieved with resistors, no?

just got a couple to play with - what do folk recommend beyond reverb/delay and chorus? i don't mind a bit of freaky noise.

[gcme93]

By 'sharp' I'm fairly sure he means 'strong' 'staccato like' rather than pitch-sharp

[artifus]

ah - like bleed thru whilst in bypass?

[gcme93]

The "repeats" is about the fact that for a pure reverb, you wouldn't hear an echo from a louder note, just a louder point for the sound to decay from. However, when we make a reverb out of several deliberately unsynchronised delay chips, it still emphasises a little echo from playing a louder note. I guess this is pretty unavoidable unless you use several chips. It would be really interesting to know exactly what's in one of those Belton Bricks...

[artifus]

gotcha. i'm sure someone mentioned the belton having an lfo employed somewhere, perhaps to smear the pre delay. or slight modulation of each stage maybe. think merlin or earthtone have posted about it.

[deadastronaut]

Ive often wondered about using 3 or 4 to get a long delay by doing something i did years ago with a few delay pedals wired up
so that the delay is "accumulative" ..... E.g .  Each pedals delay time is added to the next etc. This gives a really long loop like delay.
and would be quite clean too. Ill have to try and remember how i had them wired up....cant remember off the top of my head, but it was pretty cool.

[seedlings]

I want to build a non-digital reverb pedal...

The PT2399 is digital.

Touché.

The one problem I have with Merlin's designs is that there is an audible "repeat" when you play a sharp note. What they need more attenuation of the wet signal and a slower decay, and they'd be great. It would still be interesting to try more than two PT2399s though...

Yes.  This is what I'm hoping to avoid, but may have to go the FV-1 route.

Thanks for the input. Right now I'm fighting some trouble on the two breadboarded delays.  Eventually I'll experiment enough to come to all the conclusions many have already experienced.

CHAD

[psychedelicfish]

I wonder if feeding the wet signal through a simple compressor would help with the repeat? could be interesting to try...

[Kesh]

Stand somewhere echoey and clap, you will hear sharp, individual delays as well as reverb.

[stevie1556]

apparently the belton brick btdr 2-h is made from 3 pt2399's...under the goop.

It is, and I built a Rub-A-Dub reverb from 1776 Effects using one on the long bricks. Sounds great, really really really nice reverb, possibly my favourite one yet.

[deadastronaut]

thought so, yeah i built a reverb using that btdr 2-h too..

and a few of us have modded it, bright/warm switching, wet/dry mod etc..very nice.

http://www.diystompboxes.com/smfforum/index.php?topic=101126.msg917324#msg917324

here my first build..without wet/dry/ and volume mods.

http://www.youtube.com/watch?v=wt9t80alsDI

[gcme93]

This is quite a cool reverb build:



I'm referring to the room which is in the Southampton Institute of Vibration Research and it's designed to have every wall at an angle to create close to perfect reverb around the whole room. I've stood in there and it takes for ever for any noise to die away! It just keeps bouncing around...

[deadastronaut]

cool, i could have fun in there..

[merlinb]

Yes.  This is what I'm hoping to avoid, but may have to go the FV-1 route.

Three PT2399s is enough to get you a really good reverb sound, after all, the Belton does it. Presumably four would be even more convincing; the sky's the limit really. I just wanted to see if you could do anything even remotely convincing with two chips, and it is just barely possible. Using an LFO to modulate one or more of the delays is definitely the way to go if you want the fattest, most realistic sound.

You can see the Belton circuit here:
https://patentimages.storage.googleapis.com/US8204240B2/US08204240-20120619-D00007.png

Basically it is two delay lines in parallel, both feeding into a third one which is modulated a bit. They all have feedback too, of course.

[deadastronaut]

^ nice one merlin, never seen that before .

so can we expect a 4 x  pt2399 reverb soon then?.