Small Time: PT2399 Delay with tails  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
User avatar
MrJulius
Information
Posts: 5
Joined: 09 Jun 2009, 19:19

Post by MrJulius »

Has anyone verified the vero build? I'm going to tackle it soon.

User avatar
nunomaio
Information
Posts: 8
Joined: 12 Oct 2012, 00:19

Post by nunomaio »

merlinb wrote:
geiristudio wrote:Merlinb, is it verified? I'm desperate for a delay circuit that works. I've gone through a few rebotes that never work (only 1 out of 4-5).
The vero layout is unverified, but thoroughly checked. These delay circuits are very simple- if you've had problems it may be that you're making a systematic error?
What's that footswitch for?
Um...that's the footswitch. You know, the thing you stomp on to switch between clean and FX? It's not true bypass if that's what you mean- it has tails.
I've made a Rebote delay 2.5(3pdt truebypass), is it possible to add tails to it?and if so, how hard is it, is it just a wiring thing, or does it need to add buffering and filtering..or whatever!?thanks man

User avatar
samhay
Information
Posts: 46
Joined: 06 Jul 2012, 10:32
Has thanked: 1 time
Been thanked: 32 times

Post by samhay »

MrJulis - Not sure about Merlin's layout but the SabroTone vero layout is verified, although a few people have had difficulties with it - http://www.sabrotone.com/?p=2785
nunomalo - I built a switchable true bypass/tails version of the small Time. Short answer is that it is just a wiring thing - I can post instructions if you like.

User avatar
bluebunny
Information
Posts: 4
Joined: 05 Dec 2011, 18:50
Location: UK
Been thanked: 1 time

Post by bluebunny »

MrJulius wrote:Has anyone verified the vero build? I'm going to tackle it soon.
If it's any use, here's the layout that I built mine from. So I guess it counts as verified. (It works beautifully!)

Image

User avatar
Pruttelherrie
Solder Soldier
Information
Posts: 248
Joined: 18 Feb 2011, 19:35
Location: The low lands
Has thanked: 46 times
Been thanked: 96 times

Post by Pruttelherrie »

Some time ago I built the pcb version and put it in a 1590B. Works like a charm, but had two minor issues (well, one issue and one wish):

[1] The filtering is a bit strong for highly distorted (wide-band) signals, and since I play mostly (only) high-gain stuff (death/thrash/grind with some melodic and/or lead parts thrown in) this causes the delays to be quite different sounding from the direct signal. Not only analog-sounding, but quite muffled.
[2] In those lead parts, it would be nice to have a bit of a boost so my part doesn't drown in the wall of distortion of the band members.

So I did two small modifications: I decreased the value of the filtercap right before the mix pot and I added a 'boost' pot which replaces the 10k resistor in the dry path when the effect is engaged, the resistor right before the output mixer. I used a DPDT so the second pole switches that R to pot. Actually the boost pot is a fixed resistor in series with a pot to make the range more workable. This works like a charm! I used 2k2+10k so this might need a bit of tweaking still and the cap might need some more decreasing (since the signal is a bucket full of noise anyway I don't really care a lot) but for now I'm fine.

Together this is a one-stop solution to my limited lead-needs: one 1590B takes care of a bit of delay and a bit of boost, I'm happy. :thumbsup

User avatar
euronymous0001
Breadboard Brother
Information
Posts: 86
Joined: 26 Jun 2010, 03:11
Has thanked: 19 times
Been thanked: 28 times

Post by euronymous0001 »

Pruttelherrie,

the filtercap you are referring to would be the 10uF in-between the wiper of the mix pot and the 10k resistor going to the (-) of the last opamp?

TIA

User avatar
Pruttelherrie
Solder Soldier
Information
Posts: 248
Joined: 18 Feb 2011, 19:35
Location: The low lands
Has thanked: 46 times
Been thanked: 96 times

Post by Pruttelherrie »

No, the 47nF across the lugs of the mix pot, left of the mix pot in the schematic. That one shorts a lot of frequencies to ground, decreasing it will let higher frequencies through. You could also decrease the 2.2nF between pins 13 and 14 and the 10nF to the right of that. (The PT2399 datasheet also shows values that are a bit smaller than those)

User avatar
induction
Resistor Ronker
Information
Posts: 276
Joined: 07 Feb 2012, 20:47
Has thanked: 61 times
Been thanked: 116 times

Post by induction »

I finally built this, and I offer unto you my build report. Here's my hybrid TH/SMD vero layout in case anyone is interested.
Small_Time_vero_jfet.png
For SMD, I used size 1206, but 0805 would probably work as well. I swapped the 10k in the repeat path for 6k8 to give infinite repeats, and I added a diode in between the regulator output and the PT2399 power (pin 1) to compensate for dodgy a PT2399. I bought a batch of these chips from China for $0.50/each and wasn't surprised to find them locking up. A tip I picked up elsewhere in the universe suggested reducing the voltage to the PT2399 to ~4.5V, the assumption being that the dodgy chips can't handle the full 5V for some reason. I don't know enough about these chips to say whether that makes sense, but I used a diode to drop the voltage on two different circuits with a several different PT2399's and I can say that it worked on all of them, even after they had locked up previously. I haven't had a single lockup since. If you paid a fair market price for your PT2399, the diode might be unnecessary and you can replace it with a jumper.

Here's my build.
IMG_2536.JPG
IMG_2537.JPG
IMG_2540.JPG
IMG_2539.JPG
I kept the electronic switching because I never used it before. (I used an MPF102 instead of a J112. Works fine.) After seeing it here, I read up on how it works and wanted to try it. The main benefits are the decreased likelihood of popping and the softer feel of SPDT stomp switching. (The latter was unexpected, but very nice.) If you're willing to ditch it in favor of mechanical switching, you might be able to fit this thing into a 1590A, if that's what you're into. (I say you might because I doubt I could fit a Diaphanous Exploder into a 1590A.) I don't like the jumper rubbing elbows with the 10uF cap, but if you insulate the jumper and give it a little slack it should be fine. There's always a price for compactness. It shouldn't pop from DC, but there are several other types of popping that I can't guarantee against.
Small_Time_vero_switch.png
Anyway, thanks for the circuit, Merlin.

User avatar
fersynes
Information
Posts: 14
Joined: 16 Mar 2014, 23:49
Has thanked: 3 times
Been thanked: 4 times

Post by fersynes »

MrJulius wrote:Has anyone verified the vero build? I'm going to tackle it soon.
I made the vero build designed by valve wizard and it does not work, the positive and gnd are togheter in some point that I can´t find

User avatar
Boba7
Information
Posts: 44
Joined: 14 May 2015, 23:05
Has thanked: 25 times
Been thanked: 13 times

Post by Boba7 »

Dirk_Hendrik wrote: 11 Sep 2012, 16:43 Late to the party too.
I'd like to ask for a a pullup resistor to 4.5 volts at the PT2399 side of the J112. In the current case it's unclear if the FET will fully close.
So that’d be at the junction between the fet and the 100n right? 1M to 4.5v, just to bias the fet output right?

I had an issue with this tails switch a few years ago, as I could hear slight wet signal even with the pedal off. Wonder now if a simple resistor could have solved that!

User avatar
soggybag
Resistor Ronker
Information
Posts: 279
Joined: 07 Aug 2007, 23:29
Completed builds: Fuzz Face, Tone Bender, Big Muff, ICBM, Ugly Face, Green Ringer, Super Fuzz, Multiplex Echo, Multiplex Jr, Rebote, Echo Base, SHO, Fuzz Factory, Titan Boost/Octave, Easy Face, Tone Bender MkII, Trem Shifter, Zero Point Mini...
Location: San Francisco
Has thanked: 28 times
Been thanked: 27 times
Contact:

Post by soggybag »

Looks great! Does this use a latching switch? Or is is a momentary? I think it should latching? But it’s a SPST.

I’m working on a PCB at the moment.

Post Reply