SOLVED 'CrabVerb' (Equinox II) - PT2399 vero build [new enclosure + demo]

owlexifry

Well-known member
i've never built a reverb or a PT2399 based circuit before. this is my first time dipping my toes into this wild territory... built heaps of drives, but nothing fancy like this yet..

the idea behind this build was inspired by howard moon, well, this scene:
IMG_3640.JPG

i wanted to build a circuit for my friend inside a crab. i was hoping he wanted a distortion or something, but he asked for a reverb 😅
i didn't really want to spend on a belton brick, and I wanted to to give these chips a go, so i thought this 2x PT2399 based circuit would be cool:

IMG_4465 2.PNG
followed this layout:
IMG_4463 2.PNG

built it (there's much work to be done yet)
IMG_5903.JPG

IMG_5902.JPG

works great with the 'reverb' control turned all the the way down, the dry/clean signal is passing crystal clear, no worries.
but as soon as i turn up the 'reverb' control' there is an awful oscillating low frequency noise, gets louder the more you turn it up. makes no difference whether effect is switched on or bypassed. [and boy howdy that noise - frightened my partner in the other room, thought the aliens were arriving to take us:alien:]

voltages looked ok. regulator putting out a healthy 5.02V. (8.99V to the TL072 with my DIY 9V regulated power supply.. full voltage list below).

whipped out the audio probe to trace the signal, not real sure what's happening with this circuit, so i thought i'd see what happens when it goes to the PT2399 ICs, couldn't really find anything profound or indicative of something wrong, except the signal is clear until it passes this 10K resistor:
Screen Shot 2022-11-20 at 12.04.12 am.png
with the audio probe, before the 10K resistor, signal is clear, once it passes and meets the 15n cap, the oscillating noise is there. not sure if that means anything or is useful.
IMG_5901.JPG

i bought the PT2399 chips from tayda. reading that these can be hit and miss, i've tried 3 different pairs (from my purchase of x8), but nothing changes.
could the chips, if faulty, be responsible for this noise?

full voltage readings:

IC2
1- 5.02
2- 2.516
3- 0
4- 0
5- 3.016
6- 2.463
7- 2.5 <-> 2.8 (oscillates up and down)
8- 2.5 <-> 2.8 (oscillates up and down)

9- 2.521
10- 2.517
11- 2.517
12- 2.489
13- 2.49
14- 2.498
15- 2.516
16- 2.516


IC3
1- 5.02V
2- 2.51
3- 0
4- 0
5- 2.475
6- 2.331
7- 2.5 <-> 2.8 (oscillates up and down)
8- 2.5 <-> 2.8 (oscillates up and down)

9- 2.513
10- 2.511
11- 2.510
12- 2.517
13- 2.51
14- 2.51
15- 2.509
16- 2.51

IC1
1- 4.49
2- 4.49
3- 4.07
4- 0
5- 4.47
6- 4.51
7- 4.49
8- 8.49

not sure if those pins 7+8 on IC2+3 are supposed to oscillate like that...

i'm stumped at this point and don't really know what else to look for.

i would greatly appreciate some advice with this circuit, i really hope i can get this to work.
thanks :)
 
Those voltages all look normal. Pins 7 & 8 will move up and down a bit as the signal level changes. It's hard enough to troubleshoot my own Vero boards and doubly so with someone else's. None of the components have ref designators, so it's hard to talk about the schematic. That circuit does not have a "bypass" mode because it has tails. It has a "kill the input to the delay chips" mode. That means that the delay chips are ALWAYS in the circuit driving the output, except when the MIX control is at zero. There is a fixed amount of feedback around both delay chips to give repeats. It's possible that one or more of the resistors in the signal path thru the delays and the feedback are the wrong value and are providing too much feedback. There's a 22K resistor in the feedback path. Try lifting one end and see if the oscillation goes away. That will at least confirm whether we're getting too much feedback . Have YOU checked the Vero layout against the schematic? I have to ask that because I have seen too many layouts that are lableled "verified" but have errors in them. You also need to inspect everything for wrong connections, incorrect component values, shorts, etc. You have capacitors on the board that are too big for the layout and they might be shorting to something, it's impossible to tell from the photos.
 
Those voltages all look normal. Pins 7 & 8 will move up and down a bit as the signal level changes.
thanks for commenting on the voltages.
never played with PT2399 before, so it's difficult to know what to expect or how to troubleshoot with these chips.

It's hard enough to troubleshoot my own Vero boards and doubly so with someone else's. None of the components have ref designators, so it's hard to talk about the schematic.
absolutely, definitely not asking anyone to find an error in my vero build based on a quick photo, that'd be silly... photos provided more for context.

That circuit does not have a "bypass" mode because it has tails. It has a "kill the input to the delay chips" mode.
indeed, the layout i'm following eliminates the JFET switching seen in the schematic, and instead uses a DPDT switch to control the signal (pins 4+5).

That means that the delay chips are ALWAYS in the circuit driving the output, except when the MIX control is at zero. There is a fixed amount of feedback around both delay chips to give repeats. It's possible that one or more of the resistors in the signal path thru the delays and the feedback are the wrong value and are providing too much feedback. There's a 22K resistor in the feedback path. Try lifting one end and see if the oscillation goes away. That will at least confirm whether we're getting too much feedback.
ahhhhh yes. many thanks for the tip! I will have a look at this and see how it goes.

Have YOU checked the Vero layout against the schematic? I have to ask that because I have seen too many layouts that are lableled "verified" but have errors in them. You also need to inspect everything for wrong connections, incorrect component values, shorts, etc. You have capacitors on the board that are too big for the layout and they might be shorting to something, it's impossible to tell from the photos.
not entirely.
i sourced this layout from:
there does appear to be a handful of folks that have successfully built this supposedly verified layout.

but you do raise a good point.
i've made plenty of build errors before, and it's highly likely i've made some here 😵‍💫 many thanks for the tips!
 
there does appear to be a handful of folks that have successfully built this supposedly verified layout.
That still doesn't guarantee success because I have seen people claim "verified" on broken layouts. Sometimes these guys fix problems in their build and don't report it, so the layout on the website remains broken. You have to read every comment because in some cases that's the ONLY place you'll find corrections to the layout. If you don't check it yourself, you'll never know for sure. I usually breadboard stuff I find on the internets before I commit to making a Vero or buying a PCB.
 
That still doesn't guarantee success because I have seen people claim "verified" on broken layouts. Sometimes these guys fix problems in their build and don't report it, so the layout on the website remains broken. You have to read every comment because in some cases that's the ONLY place you'll find corrections to the layout. If you don't check it yourself, you'll never know for sure. I usually breadboard stuff I find on the internets before I commit to making a Vero or buying a PCB.
fair point.
well, i checked the layout vs schematic and couldn’t fault the layout.
checked everything over and over, again and again.
could not find any errors.
was going mad.
and then i considered maybe the soldering just wasn't good enough. i did this a few weeks ago with my old iron, it was dying, and it was a bit of a struggle to flow properly (when it shouldn't be).
i’ve since had a new iron for a while, so tonight i whipped out the flux gel, went ham and reflowed every single solder joint on the board.
was a pain in the arse to clean off, cos i used way too much flux, but now the soldering looks a lot better and well guess what, it actually works too!
perfectly.
🤟🏻 so stoked.

many thanks for the responses @Chuck D. Bones ✌️

evidence:
here's a quick lil demo running direct to DAW:

IMG_5936.JPG

flux gel. it's magic.
IMG_5933.JPG
 
Roe Roe Roe your Crab,
Gentle undersea-verb
Vero-ly Vero-ly Vero-ly Vero-ly
Verified is superb



I'm always on the lookout for creative enclosures. 🤿
L💗VE the 🦀 idea.
technically it was the mighty boosh' idea, but i had to make this tomfoolery a reality.

now i have the challenge of figuring out how to fix/reinforce the board+jacks inside the crab. i wonder how far i can go with hot glue.... 🤔
(unfortunately 2 pak resin/epoxy is stupidly expensive)
 
Well, there are FV-1 1590A reverbs if you decide to scuttle the vero, I've got the BYOC one, decent Hall type verb.

However, I did enjoy your take on the Equinox II — as Chuck said, looks and sounds great. First time I've listened to a demo of it and your build & demo moved my Effects Layouts Sonorus* up the build queue quite a few notches.


(*Sonorus is a sorta modded Equinox, but I don't know if it'd be any smaller than your vero)
 
now i have the challenge of figuring out how to fix/reinforce the board+jacks inside the crab. i wonder how far i can go with hot glue.... 🤔
(unfortunately 2 pak resin/epoxy is stupidly expensive)
Hot glue is flexible, probably won't be strong enough unless you fill the entire crab with it and that's not practical. JB-Weld is extremely strong. The challenge you will face is that the crab body itself is weak and unless you reinforce every square mm of the crab, it will break just outside the reinforced area because the stress is concentrated there.
 
Well, there are FV-1 1590A reverbs if you decide to scuttle the vero, I've got the BYOC one, decent Hall type verb.
1590A would certainly fit better.
if i wanted to make this easier on myself i could have just bought a small easy reverb PCB, load it up, done. heck i could have even bought a cheap 1590A $20 reverb pedal on amazon, gut it and use that - even less cost than what i've done here.
but where's the fun in that?
idk, i much prefer the challenge of trying new things (PT2399 circuit) and seeing how far i can go with vero.

FV-1 hasn't really piqued my interest just yet... just cos it's a bit expensive and difficult to source (at least in australia, none of the local online suppliers have it, tayda doesn't have it, and shipping charges from the US ain't friendly)

keen to see what more i can get out of PT2399 circuits though, still got x6 of them left to play with

However, I did enjoy your take on the Equinox II — as Chuck said, looks and sounds great. First time I've listened to a demo of it and your build & demo moved my Effects Layouts Sonorus* up the build queue quite a few notches.

(*Sonorus is a sorta modded Equinox, but I don't know if it'd be any smaller than your vero)
ayy cheers, ill take that as a compliment✌️
quite surprising that it sounds as clean/good as it does at the moment, with zero shielding and spaghetti dinner lead dress...

Hot glue is flexible, probably won't be strong enough unless you fill the entire crab with it and that's not practical. JB-Weld is extremely strong. The challenge you will face is that the crab body itself is weak and unless you reinforce every square mm of the crab, it will break just outside the reinforced area because the stress is concentrated there.
true.
well, ive just ordered an orange 125B.....
 
UPDATE:
the crab's guts have now been enclosed in a 125B 😄

IMG_6089.JPG
IMG_6088.JPG IMG_6090.JPG IMG_6091.JPG

was a bit tricky getting the wiring resoldered to the board and i even managed to get the switch leads wrong and had to redo it, but very glad to have this one working and done now.

what a silly build hahah 🤣

so with the board now in a real enclosure, here's a new demo:

 
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