"Noise Ensemble" - simple PT2399 abuse!

[mongo]

I know this is old but...

I built this and I get a nice fuzz that is affected by the DIN pot. The shambles pot seems dead? I double checked traces, values orientation, no dice. Any ideas on what could be wrong?

Thanks in advance

Andy

Here's a PCB layout. Unverified. Did it real quick so it will need checking by a pair of sharp eyes. The part numbers follow anchovie's stripboard part numbers. I added D1 for polarity protection and C7 for ripple stability. 1590A anyone?

[p_wats]

Hey guys,

Just a heads up, as I've received a few PMs asking abut this, but keep in mind that when I posted any mod ideas a few pages back that I can't seem to count IC pins right! Anything on the right side of the PT2399 was counted backwards, so when I'm talking about pins 11 & 12 I actually mean  13 & 14, etc.

Apologies for any confusion and happy modding!

[blacken]

This seems really cool I been looking for a nice little delay to integrate into a little synth and this might be pretty good.  thanks!

[timd]

Layout (currently unverified):

Has this layout been verified? This thing sounds great.

[kinski]

So I built this bad boy. Pretty fun! Pretty noisy!

It there a way to put a pot (or at least replace a resistor) to control the amount of repeats. When the delay length is set higher, the number of repeats gets a bit out of hand. I'd love to be able to reign it in a bit.

Great build! Thanks!

[kinski]

Nothing? 

[timd]

Nothing? 

Hey, don't feel bad - I posted in October and had nothing but tumbleweed roll by... Typically with any circuit that has the pt2399 chip, the echo control comes off of pin 6. In this case pin 6 is connected to P1 via R1. Breadboard this circuit and alter the size of both R1 and P1. The key is to experiment. When you get tired of that, experiment some more.

[kinski]

Cool, thanks! I'll try this out. I did not have a 22k pot, so I used a 50k.

[timd]

Also, if you haven't already, give this whole thread a read. There's a lot of mods and good info in there.

[drummer4gc]

Hope y'all don't mind me raising the dead a little bit...

I've got a question about PT2399s in general that came to me when breadboarding this circuit. I've got one PT that gives an awesome, nasty, velco gated fuzz in this circuit, and I've got another one with much more sustain - so much, in fact, that it hums/oscillates when notes aren't being played and the guitar's volume control is on 10.

I really am just beginning to learn about op amp configurations and their utilization in our circuits, and I know that there seem to be pretty big differences from one pt2399 to another. I'm wondering if, in the particular case I described, there is a single characteristic of the PT that varies from chip to chip, and if that's the case, if there is a way to sort of tune them into this circuit, like how we bias transistors with trimpots.

Again, my knowledge is super elementary in this area, and I'm reading all that I can. Just thought I'd ask to help me understand and to maybe add some more consistency to this particular project (even though it IS a warbly-fuzzy-echoy-acidnightmare pedal!)

[anchovie]

Attempting to resurrect the associated breadboard memories of this! 

Try different values in place of the 100k resistor between pins 16 & 2 that connects the comparator input to the 2.5V reference - I can't give any hints as to higher or lower! I just have a hazy memory of trying different values before settling on the 100k for the chips that I had. Might need to change the input cap too, but I'd start with that resistor.

[peterg]

Hello noise freaks

I've spent the day playing around with this great circuit (and scaring my neighbours).
I'm workiing with Anchovie's orig scheme and have made the folloowing mods:
-added a 2.2M resist before the out pot to quiet it down
-replaced the 47k resist between pins 6 and 15 to create more chaos
-replaced the 10k resist between pins 13 and 15 to adjust the initial signal and the repeat mix
I'd like to add a fuzz level control. Any suggestions on how to do this? I'm looking for a typical fuzz box control not diode clipping 
Thanks

[peterg]

https://dl-web.dropbox.com/get/IMG-20130908-00316.jpg?w=AAC1WJmqIKMYXTap__qG_vjOYrKRRSLCBOjGfumocbKqnA//

Slight change of plans....
I now have a six pot noise ensemble on my breadboard. I can't figure out how to get good repeat control. The pot marked feedback provides feedback but not the repreats I was hoping for. Any suggestions?

[anchovie]

I can't see your schem as I haven't got a Dropbox account so I don't know what other mods you've done, but with a "stock" Noise Ensemble you won't be able to just add a repeats pot like you would with a regular delay because of that first opamp stage being a comparator. Whatever goes in gets slammed to the full output swing of the opamp with no inbetween, so you'd have to completely redesign that first stage if you're looking for decaying repeats.

[peterg]

http://www.aronnelson.com/gallery/main.php/v/peterg/IMG-20130908-00316.jpg.html

Thanks James

Please try the attached like for the scheme. Any ideas wiring a fuzz control pot? I'm determined to make this a 6 pot pedal!

[anchovie]

You could experiment with making the first opamp a variable gain stage - remove the resistor between pins 2 & 16 and make the input 1uF -> 10k -> pin 16. Put a 10K resistor and a pot in series between pins 15 & 16. I think I messed around with this idea before and found that if the pot value is too high the PT2399 would malfunction as that first opamp isn't totally isolated from the A/D converter that it feeds inside the chip. YYMV though, give the variety of quirks in the PT2399 that forum members have seen. Start with a 1meg pot and see if it functions over the full range.

Input impedance will be really low, so if this is a problem then just have the 10k resistor between 15 & 16 and put the high-impedance variable-gain booster of your choice before the Noise Ensemble to overdrive the PT2399 input.

[peterg]

Thanks James

I don't want to mess with your circuit and Alex's (from earthtonesaaudio) mods  to it (scheme below) too much.

http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43908&g2_serialNumber=2

Alex mentions the additions made to the circuit at pins 14, 15 and 16 are for "less fuzz, nonlinear envelope control and regeneration".

Can anyone tell me what altering the 22k resistor/.1uf cap between pins 15/16 and 14 changes and what altering the 1M resistor at pin 16 changes? I'm subbing with pots and figuring out pot names.

[anchovie]

I think changing the 1meg resistor to a pot would give you a gain control, and changing the 22k to a pot would affect repeats. I'm partly guessing, though.

[peterg]

Thanks James. Adjusting the 1M resistor does affect the gain and deleting it makes the modulation go crazy as per your orig scheme. Adjusting the 22K resistor causes feedback at certain levels.

[peterg]

Working on the envelope control and can't figure out how to make it work. I can't find a large enough resistance pot for it. Can I work with a smaller pot and achieve 0 to about 50M resistance. If not how can I wire a switch to have say 1M resist in mid position (on, off, on switch), 50M resistance (or disconnect) in #1 position and 100k in #3 position?