my new delay, over the top PT2399's

Stompboxes circuits published in magazines, books or on DIY electronics websites.
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rocklander
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Post by rocklander »

tbp will stuff up/override trails (just like the echo base).. cos it's true bypass (so no effect, ergo 'trails', can have an effect on the signal.. it's bypassed.. truly).. but that doesn't mean you're not allowed to ask.. I use the echo base purely as tbp as my main gigging delay at the moment... I don't miss the trails.
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Post by ALDOUSCROSS »

rocklander wrote:tbp will stuff up/override trails (just like the echo base).. cos it's true bypass (so no effect, ergo 'trails', can have an effect on the signal.. it's bypassed.. truly).. but that doesn't mean you're not allowed to ask.. I use the echo base purely as tbp as my main gigging delay at the moment... I don't miss the trails.
thanks rocklander. im trying to design this one on Cadence Allegro 16.3. I hope I could finish this one.

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Post by frequencycentral »

Just a couple of thoughts to ponder on multiple PT2399 delays:

- it would appear from recent reseach that pins 3 and 4 are connected internally by a low value resistor. If you look at the example circuits on the PT2399 datasheet, the delay pot is connected to digital ground. So maybe connect the delay pot between pins 4 and 6, with no direct connection between pin 4 and ground. Might help with sound quality.

- it would further appear from recent reseach that the PT2399 dumps a load of hash into the 5v supply rail, so the 5v supply rail should not really be used as a convenient vref for other stuff (not that cpm has done this). So, as the PT2399 is dumping hash - would it not make sense in a multiple PT2399 delay to use a seperate 7805 for each PT2399, thus further isolating and reducing hash?

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Post by ALDOUSCROSS »

frequencycentral wrote:Just a couple of thoughts to ponder on multiple PT2399 delays:

- it would appear from recent reseach that pins 3 and 4 are connected internally by a low value resistor. If you look at the example circuits on the PT2399 datasheet, the delay pot is connected to digital ground. So maybe connect the delay pot between pins 4 and 6, with no direct connection between pin 4 and ground. Might help with sound quality.

- it would further appear from recent reseach that the PT2399 dumps a load of hash into the 5v supply rail, so the 5v supply rail should not really be used as a convenient vref for other stuff (not that cpm has done this). So, as the PT2399 is dumping hash - would it not make sense in a multiple PT2399 delay to use a seperate 7805 for each PT2399, thus further isolating and reducing hash?
yup FC you're right. this pin is a digital ground. tried it on my ReboteDelay 2.5 design. and compared it with the ones i didn't isolated. and yeah at high volume/gain setting of my amp and dirts it can be heared. and this one here sounds a bit silent. and the delay is ambient IMO. here it is. i tried putting a lower value resistor. to alter it.

Image

purple is my DigitalGround and gree is my AnalogGround
this alteration of grounds is also used on CPU motherboards. and mobile phones, which uses Digital and analog circuits.

I forgot, about using separate 7805s in this one i think wouldnt affect anything if you properly bypassed each power pins.(putting a bypass/filter capacitor at each IC's power pin.). and the current of course.
Last edited by ALDOUSCROSS on 17 Nov 2011, 22:37, edited 1 time in total.

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Post by Barcode »

If I'm not mistaken Brian (madbean) also utilized digital ground on his Mad Professor Deep Blue Delay boards for that exact reason.

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Post by rocklander »

Barcode wrote:If I'm not mistaken Brian (madbean) also utilized digital ground on his Mad Professor Deep Blue Delay boards for that exact reason.
perhaps that's why audioguy noted some noise with my layout here?

[edit] oops.. that was vol drop, not noise.. ignore me... :oops: [/edit]
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Post by muzboz »

That is a really fantastic sounding effect. Big ups! I am a real fan of the WEM WAtkins Copicat tape delays, and your pedal has some of that lovely modulation going on, often only found in the high end boutique pedals. Very cool!

- Murray

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Post by Yonatan »

I found this thread while going through the DIY designs and am so impressed by the sound that I'm considering building it, but some of the concepts in this project are new to me and I have a few questions:

1. To start with, I want to put together a list of parts, but I couldn't tell a couple of things from the schematic:
- What part should be used for the photocoupler, something like VTL5C10? I haven't used one before in any project.
- Are the 2 footswitches, SW_BYPASS and SW_FBACK_2 both momentary switches, or latching?

2. I haven't used the PT2399 in any project yet and don't understand how the ground connections work here:
- What is the difference between AGND and 0V? Do they just eventually connect to each other at DC_AGND (and is this the negative terminal of the battery )?
- Where does DGND eventually get connected to? Does it connect somehow/somewhere to AGND?
- Where do the audio input/output grounds (and the enclosure itself) get connected to, AGND?

I realize that this project wasn't intended for noobs, but aside from the huge numbers of components, I think that the rest of it is fairly straightforward for me.

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Post by cpm »

Yonatan wrote:I found this thread while going through the DIY designs and am so impressed by the sound that I'm considering building it, but some of the concepts in this project are new to me and I have a few questions:

1. To start with, I want to put together a list of parts, but I couldn't tell a couple of things from the schematic:
- What part should be used for the photocoupler, something like VTL5C10? I haven't used one before in any project.
- Are the 2 footswitches, SW_BYPASS and SW_FBACK_2 both momentary switches, or latching?

2. I haven't used the PT2399 in any project yet and don't understand how the ground connections work here:
- What is the difference between AGND and 0V? Do they just eventually connect to each other at DC_AGND (and is this the negative terminal of the battery )?
- Where does DGND eventually get connected to? Does it connect somehow/somewhere to AGND?
- Where do the audio input/output grounds (and the enclosure itself) get connected to, AGND?

I realize that this project wasn't intended for noobs, but aside from the huge numbers of components, I think that the rest of it is fairly straightforward for me.
1)
- The optocoupler is not critical here, doesnt need to be very low resistance, nor linear. It can be whatever LED and LDR combo which is cheaper. The LED should be an efficient one (high brightness, clear lens, and such), because there are two in series feeded with a 1/2Vcc drop. One is for the LDR and the other ir mounted externally as indicator.
- Bypass switch is momentary, and can be as simple as SPST (two contacts). The latching is made with the cmos 4027 ic. The Feedback switch is intended to be momentary, but also can be latching to get that effect locked. I designes the switching to use silent momentary switches, which i particulary like and have around.

2)
- "AGND" and "0v" is a method to separate digital from analog ground on the schematic software. They should be joined, usually the DC suply or main filter cap, sort of "star ground"
- DGND is the label for the 1/2 rail, which is buffered by the opamp. This is reference voltage for biasing several stages.
- External ground, and chasis should be connected to the most stable ground, which sould be the DC supply or the filter cap.

Hope you get some things clearer now.
this is a nice sounding delay and a rewarding project. Not for begginers, but not as difficult as first may seem. Good luck!

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Post by Yonatan »

Thanks for the info. These components are all new for me, but I'm slowly starting to piece together the control flow.

Just checking if I understand:

For the bypass state, the 4027 stores the bypass state (based on the event of momentarily closing the SW_BYPASS pins), and its output is routed to one of the controls of the 4053 (to control the path of the input signal).

For the feedback state, it is stateless (doesn't use the 4027), and depending on whether the pins of SW_FBACK_2 are open or closed, it sends a different voltage (low/high) to one of the controls of the 4053 (to control the feedback path).

So question: The only reason that the 4027 is needed in this circuit is to support a momentary bypass switch? If a latching switch was acceptable, then the 4027 wouldn't be needed to be used? Though I see the elegance of using a momentary switch (more easily operated? less mechanical components to break? cheaper maybe?)

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Post by cpm »

Yonatan wrote:Thanks for the info. These components are all new for me, but I'm slowly starting to piece together the control flow.

Just checking if I understand:

For the bypass state, the 4027 stores the bypass state (based on the event of momentarily closing the SW_BYPASS pins), and its output is routed to one of the controls of the 4053 (to control the path of the input signal).

For the feedback state, it is stateless (doesn't use the 4027), and depending on whether the pins of SW_FBACK_2 are open or closed, it sends a different voltage (low/high) to one of the controls of the 4053 (to control the feedback path).

So question: The only reason that the 4027 is needed in this circuit is to support a momentary bypass switch? If a latching switch was acceptable, then the 4027 wouldn't be needed to be used? Though I see the elegance of using a momentary switch (more easily operated? less mechanical components to break? cheaper maybe?)
yes yes & yes :wink: every point is spot on

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Post by Pokfor »

Many thanks to the author of the scheme for publishing it.
I made some modifications. It turned out such a scheme.
Atmosphere Delay.JPG
That's how my pedal sounds.
https://youtu.be/ZnOBRurM14I

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Post by rocklander »

Pokfor wrote:Many thanks to the author of the scheme for publishing it.
I made some modifications. It turned out such a scheme.
Atmosphere Delay.JPG
That's how my pedal sounds.
https://youtu.be/ZnOBRurM14I
this is lovely indeed. do you have the layout file available?
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Post by Pokfor »

The project on my materials is published on the Russian-language website.
http://guitar-gear.ru/2018/at_delay/
There are all the necessary materials. I hope with the help of an interpreter you can translate the entire description correctly.

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Post by rocklander »

Pokfor wrote:The project on my materials is published on the Russian-language website.
http://guitar-gear.ru/2018/at_delay/
There are all the necessary materials. I hope with the help of an interpreter you can translate the entire description correctly.
what programme do you use for the Atmosphere Delay.lay file? can you export to JPG or PNG? thanks :horsey:
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Post by Pokfor »

I used the program Sprint Layout
You can easily download it on the Internet
With the format jpeg you will not work poorly. It will be necessary to make a description with an explanation. This is english language for me is difficult.
I made a similar project on the Russian site and gave you a link. If you really want to collect this pedal then all the data I have already given there.
Attachments
Atmosphere Delay_PCB.pdf
(59.39 KiB) Downloaded 43 times
Plate_2.JPG
Plate_1.JPG

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Post by BetterOffShred »

This is a super dope project!! I am excited to maybe make one of these soon. Thanks so much for sharing!

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Post by Barcode »

So are these two boards stacked somehow?

EDIT: Never mind, just read the linked page :oops:

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