Build Your Own Clone Message Board

I know there is madness for analog delay, and for good reason, but sometimes I'd like a pristine slapback. Is there any way to add a pot or such to the circuit to adjust the amount of roll off? I'm a total build newbe (but mechanically inclined-I'm a pipefitter by trade) so explanations need to be dumbed down accordingly. Thanks-d

By "amount of roll off" you mean treble roll off right?

You need to mod a few cap values. We haven't decided on the best set of values yet.

Skiraly017 were about to test a mod... maybe he'll report back.

K

From what I've read so far, you will never get pristine repeats from a PT2399. It's just not what it's designed to do. I picked up an used BYOC delay from cheap that I can tear apart and modify as needed, so I will report back.

Now for the public apology. Kahel was kind enough to help me ID the caps that needed to be swapped. Not only did I accidentally delete the PM once, but I've now deleted accidentally a second time!



Kahel, if you would be so kind...

_________________
Resistance is futile (if < 1ohm).

I do mean high end roll off & as I re-read the title/body I realize I wasn't quite clear enough. You all picked up on my meaning though.-d

Ha ha!

Well, you probably didn't delete them on purpose, the're a very low cap on our PM inboxes, and old messages are deleted automatically. I think Matt is worried about total board bit size vs hosting costs...

So, to recap -

The BYOC delay is based on the Princeton PT2399 chip, and in the datasheet of that chip there's an application circuit called "Echo". If you go to http://www.tonepad.com and look for the "Rebote", you will find 3 different versions of that "echo" circuit. The first one is a direct translation of the Princeton Echo app circuit, the Rebote 2 is a modified version will more filtering and roll off, and the last one is called Rebote 2.5 and has more pre/post filtering but a little less roll off.

The BYOC delay is based on the Rebote 2 version. I've been planning to post a mod taking the BYOC delay to Rebote 2.5 spec, but haven't had free time to work it out yet, and there are several minor changes to the filtering before and after the delay chip.


But to answer the question, there are two caps that are important in setting the amount of treble roll off, and that's the two .0027's just left of the IC, below the .082's.

My suggestions are:
Change the upper one of these to 1nF (.001uF).
Change the lower one to 560pF.

Four wires and a DPDT to make it switchable.

This should give you delays with more treble presence. Just remember, the PT2399 is a "consumer" chip not intended for long/high fidelity delay. The roll off was probably added for a reason (noise reduction), so ths mod may only be useful for fast range delays.

K