After designing the Equinox I decided I ought to build a simple PT2399 delay, much like the Rebote or DBD. A lot of people complain about the lack of tails with those two projects, so I added that too. Includes my usual full buffering, electronic switching, and 3dB quasi companding. Heavy filtering allows for useful delay times and the usual analog-ish sound, although above about 300ms you start to hear the digital hiss. You can hear it at the end of the sound clip, when all controls are turned to maximum:
Clip: http://dl.dropbox.com/u/57831278/SmallTime.mp3
PCB layout and all files can be found here:
http://s81.photobucket.com/albums/j207/merlinblencowe/Small%20Time%20Delay/
(http://i81.photobucket.com/albums/j207/merlinblencowe/Small%20Time%20Delay/SmallTimeSchem.jpg)
(http://i81.photobucket.com/albums/j207/merlinblencowe/Small%20Time%20Delay/CIMG6889.jpg)
(http://i81.photobucket.com/albums/j207/merlinblencowe/Small%20Time%20Delay/SmallTime.jpg)
The etching came out better on this pedal than my previous efforts. Name that logo!... :icon_wink:
back to the f..... ;)..cool etch too..
nice one merlin, fantastic, iv'e been dying to get into the pt2399's for a small delay....but with trails is brilliant!!!..thanks for your sharing man. :icon_cool:
could we add a trails on off switch?... ;)
Quote from: deadastronaut on January 18, 2012, 07:37:17 AM
could we add a trails on off switch?... ;)
Of course! I mentioned one method in the Equinox thread. Same thing applies here. Green switch is a 3PDT footswitch, and the red one is a DPDT toggle to select between true bypass and tails:
(http://i81.photobucket.com/albums/j207/merlinblencowe/Equinox%20Reverb/TrueTails.jpg)
cheers man..cool.
son of a bitch, that looks cool.
Will hope for better results than I got with the Equinox :)
Very nice, gonna have to give time one a try. How did you paint the multicolored logo?
Quote from: jimmybjj on January 18, 2012, 09:36:42 AM
Very nice, gonna have to give time one a try. How did you paint the multicolored logo?
With acrylic paints and a fine brush. And patience...
Very nice.
i gather this is not going to fit a 1590b?...125b?... :(
Nice one, Merlin. Coupla questions:
It´s inverting, right? I could make the in buffer an inverting one and so it would be non inverting at the output, right?
What would be a substitute for the J112? That one is not so easy to get for me.
Quote from: deadastronaut on January 18, 2012, 02:58:48 PM
i gather this is not going to fit a 1590b?
Huh? How big do you think it is? It's in a smaller box than the 1590b already!
Quote
It´s inverting, right? I could make the in buffer an inverting one and so it would be non inverting at the output, right?
You could do that, yes. It will be noisy.
Quote
What would be a substitute for the J112? That one is not so easy to get for me.
Anything really, except the J111. J201, or one of the 2SKxxx thingy's, whatever.
Bravo, I'm excited to breadboard this, thanks for the schematic. I love tails! My favorite part of using delay. Nice enclosure!
Quote from: merlinb on January 18, 2012, 05:32:40 PM
Quote from: deadastronaut on January 18, 2012, 02:58:48 PM
i gather this is not going to fit a 1590b?
Huh? How big do you think it is? It's in a smaller box than the 1590b already!
i saw the 56mm pcb, and then looked at the 'eddystone 1590b'
internal width... might go in with a squeeze.. ;)
http://www.tubes.it/27134PSLA.pdf
Quote from: deadastronaut on January 19, 2012, 03:53:48 AM
i saw the 56mm pcb, and then looked at the 'eddystone 1590b'
internal width... might go in with a squeeze.. ;)
http://www.tubes.it/27134PSLA.pdf
Ah. yes. There's room to shave off a millimetre or so from the sides of the PCB. No sweat.
Liking how this circuit sounds. Now, I haven't had a chance to build a PT2399 based circuit yet, but one problem I am coming across in other builds is the PT2399 locking up.
At the risk of sounding like a total n00b, is that a possibility here?
The locking up can happen if the resistance between pins 6 and 4, or 6 and ground, is less than 1k when the power is turned on. In this design the mimimum resistance between those pins is 1k so it shouldn't lock up.
Quote from: slacker on January 21, 2012, 05:07:25 AM
The locking up can happen if the resistance between pins 6 and 4, or 6 and ground, is less than 1k when the power is turned on. In this design the mimimum resistance between those pins is 1k so it shouldn't lock up.
wheee, gonna print out the transfer today so I can build it then haha.
Beautiful... Not just the enclosure, the design also. Man, I'm getting behind on builds.
bob
What is "3db quasi companding"?
Nice project.
Quote from: earthtonesaudio on January 21, 2012, 03:22:05 PM
What is "3db quasi companding"?
It just means that you amplify the signal before it passes through a noisy circuit (in this case the delay line). Then you attenuate by the same amount afterwards. I pinched the term from the Stompbox Cookbook.
Just did a vero layout for this project:
(http://i81.photobucket.com/albums/j207/merlinblencowe/Small%20Time%20Delay/SmallTime-1.jpg)
Nice work!! That is Back to the Future BTW... ;)
Any demos of this design?
I thought it was pretty cool, so I designed a PCB for it, should be here soon. :)
Maybe I'll make a video once I learn how to play guitar haha
Any demos of this design?
First page, first link. ;)
Yes, I've seen that one. I wanted to see some videos with some people twiddling knobs as the demo goes, John. ;)
Ah, ok, gotcha. :icon_wink:
I built one and it's quite nice.
Very tame with no self oscillation as stock
but the sound was nice. No clips though. :-\
Built this today (see Pictures (http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg878905#msg878905) thread for evidence) and I really like it - thanks Merlin! ;D
A small "however"...
I noticed that if I hit a loud note when it's bypassed, signal still gets through to the delay, but very distorted (and pretty quiet). Sounds like the FET is never fully off. Anyone else come across this? Double-checked the circuit vs. layout and everything's fine and dandy. The FET is definitely a J112 (according to the markings on it - and it came from a reputable source) and is otherwise doing its switching duty.
Hey, Merlin, thanks for sharing the design.
Is it possible to add just the tails circuit to other PT based delays?
Quote from: Slade on November 20, 2012, 06:40:24 AM
Is it possible to add just the tails circuit to other PT based delays?
Yes, it's just a generic FET analog switching circuit, so it could be applied to other circuits fairly easily.
Just built one, couldn't get it to delay until I grounded pin 4. Thoughts on connecting dGND to ground?
Interesting. Pin 4 is connected to ground (at pin 3), albeit through a small (~10 ohm) resistor. This according to some handy PT2399 notes prepared by Merlin.
Yeap, I'm aware of that, that's why I was a bit confused.
Quote from: azrael on November 30, 2012, 01:42:50 PM
Yeap, I'm aware of that, that's why I was a bit confused.
Maybe the internal resistor burnt out? Lots of people report weird issues with the PT2399, often attributed to fake parts. I've not yet experienced it myself. Anyway, you can ground both Agnd and Dgnd pins, it doesn't really make any big difference to performance.
I finished breadboarding this last night and although I haven't had a chance to try it at volume it sounds great so far. However, I used the BOM from the vero layout to pull parts and I noticed some oddities between the BOM and the schematic. These aren't showstoppers, but I wanted to note them here for future builders just in case they are ordering parts based on the vero BOM. Only the 3rd item would actually be an issue...
- C9 is listed in the BOM twice.
- C19 is listed as 47uF in the BOM, but as 100uF in the schematic.
- D2 is listed as an LED in the BOM, but as a 1N4001 in the schematic. The graphic for D2 in the vero is correctly shown as a normal diode rather than LED. It also seems to be oriented from +9v to ground rather than inline like it is in the schematic.
hi merlin...
with reference to adding a tails to a TB reverb question..
http://www.diystompboxes.com/smfforum/index.php?topic=95632.msg829073#msg829073
as a dumbass who can't visualize it in the real world... ::)
how would i wire the dpdt?
(https://dl.dropboxusercontent.com/u/7464107/REVERBTAILS1.jpg)
Hey all,
I built this using the toner transfer from merlin's PDF file last night but I still can't get it to work, it only works as bypass as if no signal goes through the PT chip.
Then did a search on google and came across this thread:
http://www.madbeanpedals.com/forum/index.php?topic=5904.0
which probably am facing the lock up as they stated there. I have so far tested with all the 5 PT2399 ICs that I have with me, but all with the same result.
I used J201 instead of J112 since that was only available in my local elect shop.
Now, since all you are super techies here, I thought I'd post here with the hope of having a solution to perhaps fix this on the same
build with minor tweaks/jumper and copper cuts.
Any thoughts?
much appreciated in advance.
maselectguitar
Quote from: maselectguitar on May 24, 2014, 06:20:09 PM
which probably am facing the lock up as they stated there.
Try shorting pins 3+4 together on the PT2399. See bottom of page: http://valvewizard.co.uk/smalltime.html
Hi Merlin,
Thanks for replying. :)
As you recommended, I did solder the pin3 to ping4 but still same result, bypassed signal. I even changed both TL072 and PT to a newer set since I have them socketed.
If this helps, I did the voltage readings for both chip's pins as following, noting that I powered it with a 9v battery.
PT chip:
p1, 5.02v
p2, 2.50v
p3, 0v Grounded
p4, 0v Soldered to pin3
p5, 2.90v ------- > Strangely receiving voltage even it is not connected to anything, probably internally?
p6, 2.50v
p7, 4.61v
p8, 4.61v
p9, 0v Grounded
p10, 0.01v ------- > Is this right?
p11, 0.35v ------- > Is this right?
p12, 4.69v
p13, 2.50v
p14, 0.28v ------- > Is this right?
p15, 2.50v
p16, 2.50v
And the TL072 chip readings:
pin1, 3.56v
pin2, 3.57v
pin3, 3.24v
pin4, 0v
pin5, 3.54v
pin6, 3.54v
pin7, 3.54v
pin8, 7.06
And the voltage regulator am using is L78050v with readings on pin1 = 7.2v, pin2 = 0 Ground, pin3 = 5.02v
Also if this is of any use or a clue that even with the power switch in off position, all pins still show the same readings mentioned above !! :icon_rolleyes:
Appreciate your follow up in advance.
Cheers!
Quote from: maselectguitar on May 26, 2014, 02:08:21 PM
p5, 2.90v ------- > Strangely receiving voltage even it is not connected to anything, probably internally? <<Yes, that's the clock output pin.
p9, 0v Grounded << What do you mean grounded? It shouldn't be connected to ground...
p10, 0.01v ------- > Is this right? << Could be.
p11, 0.35v ------- > Is this right? << Could be.
p12, 4.69v << Should be 2.5V, which is why pin 14 is slammed down to the rail.
p14, 0.28v ------- > Is this right? <<No, it should be 2.5V; see above.
And the TL072 chip readings:
pin8, 7.06 << Looks like your 9V battery is dead... or somethings sucking a helluva lot of current...
Solder bridge? Incorrect component? ???
Hi Merlin,
Thanks again for replying. Much appreciated.
QuoteSolder bridge?
Yabsolutely! Got one on pin9! Even though I checked like a million time for SBs!! this was right on the pin 9 ground bridge as you pointed out that it should not! :D
Still checking further possibilities of SBs, but haven't noticed any so far.
So, now that pin9 SB got sorted, pins 9 to 16 all read as 2.50v!? this should be correct as you mentioned? right?
And now reading for pin7 and pin8 are 0.60v? Is this corrected now? What should the reading be usually? These were 4.61v earlier.
QuoteIncorrect component?
Not sure! Probably not, cause I always get the components sorted with extra care to get them absolute right from beginning to avoid the later hassle, but double checking one more time to be sure.
Quotepin8, 7.06 << Looks like your 9V battery is dead... or somethings sucking a helluva lot of current...
Got a new battery and reading is good on pin8 of opamp at almost 9v. ;D
My apologies for this, could you please help me figure out the POTs pins numbers to the PT and opamp pin number connections? I probably am being terribly wrong with the POTs! They do nothing at all either fully CCW or CW! :icon_eek:
Much appreciated.
Cheers!
Oooooh yeah baby! ;D
Ordered a new pack of 10 from a trusted vendor, got them last week, re-did a new transfer/etch, solder and voila! All awesome and working nicely now!
The batch I got before were cheap Chinese fake parts probably, which I have to throw away. All the new ones were tested and nicely working the same sound.
Thanks a bunch melrin, much appreciate your time and help.
maselectguitar
This might be a stupid question but what exactly does "tails" do? Does it continue echoes even after pedal has been disengaged?
Quote from: BoogiemanX on January 20, 2016, 09:29:16 PM
This might be a stupid question but what exactly does "tails" do? Does it continue echoes even after pedal has been disengaged?
Correct!
I had exactly the same symptom with maselectguitar, I could get only the clean sound. I had 4-5 pt2399s and I found out that only one of them was functioning!!
I have a question,
I would like to ask you how could I add a kill switch to mute completely the clean signal. There are some nice sounds that can be achieved with this.
Quotehow could I add a kill switch to mute completely the clean signal.
see how there are two 10kΩ resistors at the non-inverting input of the second (right-hand) op amp? that's a "summing amplifier"; it allows dry and wet to be mixed together. you could add a SPST between the 10kΩ resistor that is connecting the first op amp's output and the inverting input of the second op amp. that would prevent any clean signal from being summed with the wet signal.
Hi All,
An old thread I know, but...
I recently bought two of the version 3 Small Time Delay PCBs and I was thinking it would be groovy to put them both in the one (1590DD) enclosure with some simple switching options for running them in parallel/series, and for mono/stereo output.
Initially, I thought I would have to devise a third board for buffering/splitting/blending, but after thinking about it, this might be superfluous. The circuit is already book-ended by two op amps.
A question to those with more experience than myself. Is running two of these circuits in parallel likely to work? Or will it cause a feedback, motor-boating, squeal, or other issues like volume drop?
Is there no way to know for sure until I try?
Any advice appreciated.
In parallel, the inputs have high impedance and will be ok joined together.
The outputs "may" be happy. The output circuit is low impededence and two of them will fight each other a bit. The 100R resistor in the output will limit that effect, but I would raise them to 1k. Although this will cut the output level a little, it will be by a trivial amount.
Quote from: anotherjim on May 18, 2021, 04:41:54 PM
... The outputs "may" be happy. The output circuit is low impededence and two of them will fight each other a bit. The 100R resistor in the output will limit that effect, but I would raise them to 1k. Although this will cut the output level a little, it will be by a trivial amount.
Thanks for the reply, I might socket those resistors and try a few values before committing.
Not particularly worried about volume drop, as I already need to put an anti-boost/limiter in front of the Twin that I use for home practice (completely unsuitable home practice amp, but I found it second hand and fell in love). I am worried about treble loss, but I don't think that will be an issue here as increaseing the value of that resistor is really much the same as rolling a Master Volume down a bit.
You could use a blend pot...
(https://i.postimg.cc/ykctBSYD/IMG-20210517-165808015.jpg) (https://postimg.cc/ykctBSYD)
Quote from: merlinb on May 19, 2021, 06:17:49 AM
You could use a blend pot...
(https://i.postimg.cc/ykctBSYD/IMG-20210517-165808015.jpg) (https://postimg.cc/ykctBSYD)
A good idea, thanks Merlin. Although I'll have to think about how it will be wired with some of the switching options I have in mind. Obviously, impedence and blending wont be an issue when in stereo output mode, or when running the circuits in series, but in parallel a blend pot would be good.
Cross feedback is a fun mod to do with two delays in one box. Use a DPDT toggle to send the repeats from delay1 to delay2, and from delay2 to delay1.
Quote from: moosapotamus on May 20, 2021, 12:53:03 PM
Cross feedback is a fun mod to do with two delays in one box. Use a DPDT toggle to send the repeats from delay1 to delay2, and from delay2 to delay1.
Does this create a cacophony?
It can, if the feedback is high enough. But you should be able to turn it down to a level that allows the repeats to gradually fade away. So, maybe somewhere between cacophony and controlled chaos.
Quote from: moosapotamus on May 21, 2021, 03:47:31 PM
somewhere between cacophony and controlled chaos.
That's a reasonable description of this forum, lol :P
Quote from: moosapotamus on May 21, 2021, 03:47:31 PM
It can, if the feedback is high enough. But you should be able to turn it down to a level that allows the repeats to gradually fade away. So, maybe somewhere between cacophony and controlled chaos.
Would this be similar to having a momentary switch contecting pin 14 on board 1 to pin 14 on board 2?
It might be a while before I complete this project, but hopefully I will remember to experiment with some careful circuit bending, and will post results.
I'm sure there might be more than one way to do it. Swapping pin 14 might work. But, I would also try swapping the wipers of the Repeats pots. You could use a momentary DPDT. I used a toggle on my dual Cave Dweller. Another word I might use to describe the effect is "lush."
Quote from: moosapotamus on May 22, 2021, 05:31:34 PM
... Swapping pin 14 might work. But, I would also try swapping the wipers of the Repeats pots.
Ah. Now I get it!
Are there any YouTube videos/soundclips you know of that demonstrate this type of dual delay effect with switched repeats? The search terms I'm useing just seem to pull up advertisments for Strymon (which are not doing this trick).
I'm not aware of anything specific on YouTube. But I can maybe record something with my dual cave dweller within the next several days.
I modified it slightly to include a CMOS audio switch (so I could have pedals that toggled the function) and then designed and made up a PCB for this circuit but I have problems with the operation. It works (after I fitted R25) but the the Repeats pot produces crazy feedback and distortion if I go above anywhere about 1/8 of a turn from fully anti-clockwise.
Any thoughts as to what's wrong or what could fix my issue? I have full lab of sig genes and scopes if you want to suggest tests.
Happy to share design with anyone here.
(https://i.postimg.cc/H8pjY0qS/Reverb1c.png) (https://postimg.cc/H8pjY0qS)
(https://i.postimg.cc/HrJnkkNC/IMG-7371.jpg) (https://postimg.cc/HrJnkkNC)
Running the values of the Multiple-Feedback (MFB) filter around pins 15 and 16 through the useful tool at:
http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm (http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm)
..shows that the filter has a gain of x-1.8. So there's a bit of boost on the way in. I haven't tried the output filter on pins 13 and 14, but if that's similar, that'd probably explain it.
It looks to me like those filter values have been tweaked to ensure that you can get oscillation even with the fairly low cutoff (2.7KHz according to the tool).
HTH,
Tom
Quote from: ElectricDruid on December 20, 2021, 09:39:45 AM
Running the values of the Multiple-Feedback (MFB) filter around pins 15 and 16 through the useful tool at:
http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm (http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm)
..shows that the filter has a gain of x-1.8. So there's a bit of boost on the way in. I haven't tried the output filter on pins 13 and 14, but if that's similar, that'd probably explain it.
It looks to me like those filter values have been tweaked to ensure that you can get oscillation even with the fairly low cutoff (2.7KHz according to the tool).
HTH,
Tom
Thanks, I tried playing around in that calculator and could get the values you saw but that's as far as I got. On the actual circuit, I tried adding a 40k resistor at the top feed into P1 which has made the tails sort of work, the Repeats pot doesn't drive into doom loop tails until I'm about 2/3 round the pot but the tails are not particularly clear - I was hoping to play a note and have it repeat and gradually fade into nothing (with the right settings of course).
Can you make any specific suggestions as to changing component values?
Depending on the delay time setting, the tails aren't *going to be* very clear. This is the PT2399 we're talking about! It's not noted for its fantastic audio quality at longer delays.
The filter values have probably been chosen to limit the crunchiness when you get to longer delays. This also has the often-desirable side-effect of making it sound more like an analog BBD delay, since they frequently used 3KHz filtering too.
Further down the page on the Okawa filter tools is a form where you can do the filter design "the other way around" e.g. instead of putting values in and seeing what cutoff and Q you get, you can put the cutoff and Q in and get it to give you the values required.
Sticking "5KHz" and "0.707" into that gives a first-pass attempt, and tweaking the C values improves things to give us the attached filter. This should cut back the runaway feedback a bit more, and will also open up the sound slightly.
(https://i.postimg.cc/GTkRCV5c/PT2399-Filter.png) (https://postimg.cc/GTkRCV5c)
Of course, "more open" also means "more noise", so try it and see what you think.
HTH,
Tom
When I did my Soft Delay...
https://www.diystompboxes.com/smfforum/index.php?topic=114973.0
...I got a side-effect that with regen just short of "Doom loop" (great name for it) bypassing raised the regen level and the tail would start feeding back.
I do find that having tails isn't all that useful, to be honest. If you just want to bypass to play normal over the tails, they appear to die out too soon under the now dry playing because if not strong enough to cause Doom Loop, they can't help decay in level each time around. You'd need some kind of AGC (*) in the regen to maintain the level of the repeats perhaps?
If you want to stop playing and let the tails fade off - there's no need to bypass.
But, of course, YMMV.
(*) I have an idea to use the AGC in a voice recorder chip (can be used without the recording part) to AGC PT2399 repeats. Not tried it yet.
Quote from: ElectricDruid on December 20, 2021, 11:02:54 AM
Depending on the delay time setting, the tails aren't *going to be* very clear. This is the PT2399 we're talking about! It's not noted for its fantastic audio quality at longer delays.
The filter values have probably been chosen to limit the crunchiness when you get to longer delays. This also has the often-desirable side-effect of making it sound more like an analog BBD delay, since they frequently used 3KHz filtering too.
Further down the page on the Okawa filter tools is a form where you can do the filter design "the other way around" e.g. instead of putting values in and seeing what cutoff and Q you get, you can put the cutoff and Q in and get it to give you the values required.
Sticking "5KHz" and "0.707" into that gives a first-pass attempt, and tweaking the C values improves things to give us the attached filter. This should cut back the runaway feedback a bit more, and will also open up the sound slightly.
(https://i.postimg.cc/GTkRCV5c/PT2399-Filter.png) (https://postimg.cc/GTkRCV5c)
Of course, "more open" also means "more noise", so try it and see what you think.
HTH,
Tom
Tom,
Thanks for your input :D
I changed to the values you suggested and the doom loop effect is totally gone. I can get obvious tails now by cranking P1 fully clockwise. I can make a recording for anyone interested but how do attach that here? Can I upload a .mp3 file and, if not, what's the best practice to share audio or video here?
Updated schematic with correct component values attached.
Ted
(https://i.postimg.cc/06gv5rG4/Reverb1c.png) (https://postimg.cc/06gv5rG4)