Echo Base - a new PT2399 delay

[slacker]

nice

[Valoosj]

Slacker, I was wondering if you could show me how to add a second PT2399 in series with the first, so I can obtain a clean delay of about 1000-1400ms?

The schematic on page one, is that the right one, or have there been corrected versions? I read through the topic, but I couldn't find any others.

[Valoosj]

Ok, I got some help from Auke on this.

Can I get double delay time by adding the second PT2399 like in this pedal?
http://buildyourownclone.com/pingponginstructions.pdf

[slacker]

Yes that would give a longer delay. You still need quite a lot of filtering to keep the noise down though so you will probably be able to get about 1000ms of delay but it wont be clean like a proper digital delay.

If you like I'll draw a schematic of how to add an extra PT2399 to the echo base at the weekend.

[Valoosj]

That would be awesome. But you got reasonably clean delay out of 1 pt2399, and that was about 600 or 700 ms, why couldn't you get 1000ms clean with two PTs then?

[slacker]

With 2 chips at 1000ms the sound quality will probably be similar to the longer delays on the echo base, if that's clean enough for you then that's great.
I was really just trying to point out that you won't be able to get super clean sounds, like a digital delay where the delay sounds the same as the original signal. Just making sure you don't spend a lot of time building something and end up disappointed with the results

[Valoosj]

But when I listened to your soundclip in the first post, that was pretty long and clean delay. I thought it would be possible to double that time (and staying as clean as it was) with an extra PT2399. Or am I dreaming now

[slacker]

Here's the schematic for adding an extra PT2399 for potentially double the delay time.

http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/album170/echobasemod.png.html?g2_imageViewsIndex=1

This could be added as a separate board fairly easily, and that's probably the best way to build it because it's completely untested at this point. I did try something similar on breadboard and the basic idea does work.

When the short/long switch is closed the extra chip essentially does nothing, when it's open it adds a preset amount of delay in addition to that selected by the original time pot. The value of the resistor marked XXX determines how much extra delay is added. I did it like this because it's easier than changing the delay time on both chips simultaneously.

Enjoy

[Valoosj]

Thanks a lot Ian!

[slacker]

No problem. I've just realised the schematic might be a bit confusing because the extra PT2399 is drawn flipped vertically. I'll redo it, but if you're following the schematic just go by the pin numbers not the actual drawing and it will be fine.

I think that makes sense 

[Valoosj]

The numbering of the ic is wrong? If you tell me where I should put pin 1 I'm fine.  I guess 1 should be where you wrote 8 right and 16 where it says 9?

[slacker]

The numbering is correct and the components are attached to the correct numbers, but the image is flipped. So the numbers and components that are down the right hand side should be down the left had side and the ones down the left hand side should be down the right hand side.
If you compare it to the original schematic you'll see what I mean. I'll correct it tonight.

[slacker]

The revised version is up now
http://www.aronnelson.com/gallery/main.php/v/slackers-stuff/album170/echobasemod.png.html?g2_imageViewsIndex=1

should be clearer.

[nelson]

I have the vero for this all populated, but nes pas le echo.

I need to debug it.

Congrats on a great project.

[Valoosj]

Thanks Ian! I just need a little switch for that short/long to make it work?
The long delay resistor, what would be the 'longest' clean value? Just to get an idea which values I should get for testing.
You also said something about other values I might need to change, can you clarify that a bit? That way I can get some testing values within a certain range.

Thanks a lot already for this project!

[slacker]

Congrats on a great project.

Cheers   Hopefully you'll get yours debugged.

Thanks Ian! I just need a little switch for that short/long to make it work?

Yeah, when the switch is shut the 100R resistor is connected to ground giving the extra PT2399 has a very short delay which you won't hear when combined with the original one. When the switch is open the 100R and the XXX resistor are connected in series to ground so you get a delay from the extra PT2399 which is added to the original one to give the longer settings.

The long delay resistor, what would be the 'longest' clean value? Just to get an idea which values I should get for testing.

I'd try values between about 30k and 47k.

You also said something about other values I might need to change, can you clarify that a bit?

I'm not sure if anything will need changing but with 2 chips there will be a bit more noise than with one so you might need to change some of the capacitors to filter it out. At a guess the 4n7, 15n or 470p capacitors might need increasing in size, so maybe get some extra 1n, 10n and 22n caps to experiment with.

Like I said this mod works in theory but I haven't actually built it so we might have to figure it out as we go

[Valoosj]

Ok thanks. I'll order my stuff soon and keep you posted.

[omarvolta]

I want to order parts for the echo base, but I only have one question before I do so. This was asked once before(not by me) but wasn't verified. So, Is it possible to make the lfo switchable?? to turn it on and off as one pleases?? Thanks, peace...

[Michael Allen]

you could hook up a spdt switch before the 220R resistor connected mod depth pot. one lug goes to the mod depth pot, other lug goes to ground, middle lug goes to 220R resistor.

[slacker]

Another way to do it is to short out the cap in the integrator part of the LFO, this stops the LFO.  To do this add a switch that shorts out pins 1 and 2 of the LFO opamp.