Check out earlier posts to learn more about this device and see and hear demos. I can’t say enough about how happy I am with this design! The only surface mount part is the MAX 7401 IC which is a SOIC8 and easy to solder.
Go to the link below to download the express pcb file. You can use this, modify it and have the board produced quickly by www.expresspcb.com at a reasonable cost. Check out there site for more detail if you are not familiar with the service
link to zip file with schematic and layout info:
https://www.adrive.com/public/PeAeX9/PT2399%20delay%20files.zip
Here is a picture of the layout to scale:
The Board Layout can easily be altered add PCB Jacks, or resize, etc. Currently it is sized to fit in a 1590B type stomp box.
Circuit Salad 
Just a question, are there connections on the backside of this board? i mean is it supposed to be a double sided pcb or no? thanks! 😀
yes the board is double side using the back as ground plane and a few connections
Hey! Really love the design! I am really interested in your comments about the 0.47uF cap between pins 9 + 10. You said it provides “significant increase in the delay output but the noise remains at the same level”. I don’t know the internal structure of the PT2399, but do you know by how much the gain is increased? Or is it perhaps just the noise is reduced because it is filtered away, and makeup gains elsewhere are giving the impression of a hotter signal (due to better s/n ratio)?
Anyway, any thoughts much appreciated!
Yes that’s a good question. I did not test accurately but – I think its about 6dB-8dB gain – the digital noise increases less, but then I attenuate both the delay and noise back down to unity with the R2 and R12 being larger. So the noise gets companded downward. Pins 9 and 10 are across the pins of an op-amp intended to be an integrating filter. To be honest, its not clear to me completely what is going on (why the gain increase) – The data sheet is suspect and so there is some thoughtful guessing going on here. I believe the ADC is a 1 bit delta modulator oversampling type.
Aha! so very interesting. And the reason I asked is because I’m thinking of squeezing the absolute best noise performance by running your delay with an actual compander around it. I’m using the NE570 (amazing chip, often misunderstood). If your 0.47uF cap results in non-unity gain, I’ll need to adjust the expander section accordingly. My favorite part about your design is the the switched cap filter. I’m thinking about making a variable clock to drive it too!
Hello there! Thanks so much for the site. Very excellent info. I am going to try to build the delay circuit (beginner here) and am kludging through the schematic, but if you ever felt like posting a BOM that would be super cool. Either way, thanks again so much. Amazing job.
If I can help let me know. As far as the bom… I will try and reference to digikey parts you can easily get that are not clear. The resitors for example are all standard 1/4 watt jobs you can get even at radio shack. Some of the Capacitors may be confusing regarding physical size so I will post those. Should be able to build this on perf board or bread board pretty easily to get a feel for how it works.
Hi there! Is any alternative available instead of the mcp1804t? Will a simple lm7805 do the work? The pcb file it’s not available anymore! Can you fix this? Thanks!
the original post has a working link now:
https://www.adrive.com/public/PeAeX9/PT2399%20delay%20files.zip
let me know if you have any issues
yes you can use any 5Volt regulator you want….I am going to figure out what to do about all of the bad links this week.
Thanks!
Thanks for your good job! I really want to try this circuit out! Two questions.. Pin 4 is not connected to the ground on purpose or is the schematic wrong? and one more, this circuit will work for mic too, or i have to make some adjustments?
It should be grounded..if I remember correctly you may not actually have to, but it is grounded on my layout…so I am grounding it. Not sure why I left it that way? I need to go back and review. It will work with a MIC but if it is a balanced output microphone you will need to convert to unbalanced output to go into the input of the effect.
Hi,
Very interesting read about the PT2399. And I’ve been reading your blog for about an hour now… the ring mod looks amazing… 🙂
So just a quick question if you have the time.
I just built another PT2399 based delay that I really like (Multiplex Jr by 1776 effects), and I’m wondering about modding it a bit. If I change the cap between pin 9 and 10 for a larger one and then reduce the overall volume at the output opamp (changing the resistor between pin 6 and 7), it should do the trick right? Or am I missing something?
Thanks a lot!! 🙂
I assume the pin 6 and 7 are of a standard dual op amp which is connected to the PT2399. If you increase the cap on the PT2399, it gain is greater than unity so you have attenuate it some…I do that with the 56k resistor R2. So with respect to your circuit you need to adjust the level down at your wet/dry mixer – which is probably an op amp. If it’s not clear, the PT2399 has two utility op amps on it which you can use any way you like. So I outboarded the filter and did the mixing on the leftover PT2399 op amp.
Thanks for the super fast answer! It is very clear, and I’m gonna try something on the circuit I just built. I’d love to build your circuit at some point, I’m very curious to learn more about it, tweak it, and see how it sounds. And I believe it could work well with a taptation circuit, which would give it tap tempo and modulation… Could be quite an amazing delay!
Thanks again!
The switch cap filter IC really gets the part count down and allows easy adjustment of the filter knee. The max 7401 is about 8 bucks which make builders shy away from it.The MAX7410 is more in the $3 range – its a 5 pole filter and will work well also. Others who have built it have had very good results.
Thanks!
I just put a .33 in my PT2399 build, and changed a couple values regarding feedback and wet signal mix, and the result is just great! It seems that the larger the cap is and the more it acts as a high pass filter, cutting some low frequencies. Maybe it’s just in my circuit though. .47 was too much for me, but .33 sounds great. Definitely improves the noise and gets a longer usable delay.
Thanks a lot! If I want to build another PT2399 delay, yours will be first on the list!
Interesting ..I found the gain and sig to noise ratio improved but not so much a tonal change. When I went higher than. 47 it definitely became unstable. Your .33 may work better. With the circuit I created .47 has worked very well with about ten units I have built. I can get 600 mSec delays that are useable and not overly grainy.
Well maybe I’m imagining it. I should try again. I did finally put the .47 and it sounds great. With the tone rolled off (I have included a tone pot), as dark as possible, I can almost get to a second without some overpowering noise. Definitely better than the standard .1 cap!
Neat, I often change values on my pedals. Nothing ever sounds right twice! I think the PT2399 isn’t about perfect replication – it about colorful abience and reinforcement – I just don’t like the grit
Yeah I actually really like its character. And with this new way to tame it, it’s just great. 🙂
I have two questions:
All capacitors are ceramic except for C1, C2, C4, right?
Some are not electrolytic but polarized, what did I miss?
im so confused!
So the schematic makes clear where I used electrolytic caps…having said that in many places it doesn’t matter very much as long as the value is correct. Assuming you are confused by the PCB layout footprints..some of those are footprints for tantalum electrolytic caps not standard cylindrical aluminum caps.
I think I understand, maybe..
Where the cap is polarised i need to use a electrolytic or a tantalum?
is this what you mean?
yes both are types of electrolytic that I used and have different layout pads but where I used a polarized cap, that designation is shown in the schematic and on the layout silk screen
ok so i need to use tantalum caps! thank you!
hello. this is a nice design, very clean… but why are you using the pt2399 internal opamp? that’s a lot of headroom compromise, isn’t it? if you got a hot signal, you are going to clip easily. and that’s a problem because here even the bypass is passing through the 5V pt2399
yes but if I use the part anywhere in the signal chain it still has this issue…so what does it matter?
hello. this is a nice design, very clean… but why are you using the pt2399 internal opamp? that’s a lot of headroom compromise, isn’t it? if you got a hot signal, you are going to clip easily. and that’s a problem because here even the bypass is passing through the 5V pt2399
The entire part has the headroom issue so using other op amps with higher supply levels doesn’t help.. The system level headroom is defined by the lowest headroom in the system.