Engineer's Thumb Redux vC.4 vero

[befey]

I decided to attempt a vero layout of jonny.reckless 8 knob version of the Engineer's Thumb. I've started with just the voltage inverter section.

Full schematic:


The voltage inverter section:


My vero:


This is my first attempt at a vero layout from a schematic, so I'd like to use this thread to post my progress and get feedback about anything that doesn't look right.

I intend to modify the above full schematic slightly by adding a switch for the flat/bright switch. I'd also like to add a switched sidechain input. I think this means I'll need to duplicate the JFET input stage for the sidechain.

[jonny.reckless]

It's quite an ambitious circuit to do as your first vero project. It took me a lot of time and several attempts to build a vero prototype and get it to operate properly without oscillating or humming. I've still got a couple of issue C PCBs left in my project box and can send you one if you are interested, otherwise I'd be happy to share the Gerbers and NC drill files for you to make your own board. Not trying to discourage you, but be prepared for a lot of work 

[Axldeziak]

I'd be interested in the gerber and drill files if your willing to share.

[befey]

It's quite an ambitious circuit to do as your first vero project. It took me a lot of time and several attempts to build a vero prototype and get it to operate properly without oscillating or humming.

Any tips?    Or a working layout to share?

I've still got a couple of issue C PCBs left in my project box and can send you one if you are interested

That's really a kind offer, and I may wind up taking you up on it if this turns out to be beyond my ability. How hard would it be to add the mods I'm looking to do?

Edit: How hard would it be for me to add the mods I want to do to your PCB?

[jonny.reckless]

How hard would it be to add the mods I'm looking to do?

Pretty straightforward with a scalpel, it's a traditional 2 layer through hole PCB, with 0.5mm track and clearance so big enough to work with easily.
I don't have a vero layout per se. I tend to design and build interactively on vero - I don't plan it out in advance, believe it or not. It's a habit I got into as a teenager building fuzz boxes, and I've never gotten out of it. Most of my prototypes are really messy, and I just use them to prove out ideas before I enter them into the CAD and do a PCB layout. I find it's really hard to get grounding right on proto board, and getting the grounding right is so crucial to audio performance, that I always make a PCB, even if it's just for my own personal use.

[jonny.reckless]

I'd be interested in the gerber and drill files if your willing to share.

Altium designer PCB document for Engineer's thumb redux revision C is on my Google drive. You can get a free viewer, and generate PCB fab files from it if you would like. Let me know if you just prefer the Gerber and NC drill files - less flexible, but more universally accepted. Happy to share.
https://drive.google.com/drive/folders/1usNiADluT3tfycfkl7Y7Yo24fzZkVLZN?usp=sharing

[Axldeziak]

I would prefer the gerber,  (or anything that can be loaded in kicad, eagle, or sprint.)
Altium's online viewer chokes on the file. Their old viewers lock up under wine, and you have to sign up to altium for their newest "free" version and well, that ain't happening.

[jonny.reckless]

OK I put the Gerbers and NC drill files in the Google drive folder instead.

[befey]

I've reconfigured the voltage section to tighten it up a little bit.
I also added the JFET input and duplicated for the sidechain input I'm adding. The regular input will go back out to the switched sidechain input jack before one of the two goes on to the sidechain section.





Please let me know if anyone sees anything that's going to be a problem as I keep going. Thanks!

[tubegeek]

Jonny: anything special about BC556B or can I swap with another PNP of similar specs?

[jonny.reckless]

Jonny: anything special about BC556B or can I swap with another PNP of similar specs?

I think you could use any general purpose PNP there. BC556B has CBE pinout so if you use a 2N3906 you need to install it backwards.

[befey]

Here's what I've come up with for the full circuit. I hope people will take a look and let me know if anything doesn't look right.

I'm not sure if I have the switched jack set up right.



DIYLC File here:
https://drive.google.com/file/d/1JUJlE3RKIzI4OkeH-sovNk2sWs0VNNIF

[Kevin Mitchell]

I'm trying to figure out how to attach the DIYLC file.

Put it up on your google drive account and share the link.

-KM

[befey]

Added the link above

[befey]

Removed an unnecessary cut and moved a jumper.

DIYLC File:
https://drive.google.com/file/d/1K3FiR3M2cIuKONAuDtca1ay5LfKEff0V

[jonny.reckless]

Did you get it built and working yet?

[befey]

I haven't yet. I had a few other things on the bench to finish first. I'm hoping to get it started this weekend.

[ficelles]

I have a bare metal Hammond 1590b drilled (by me) for Fuzzdog's ET pcb, going spare as I have now bought a pre-painted Hammond box. Free to anyone who will pay postage or you can pick it up if you are in Devon, PM me.

[befey]

I'm working on wiring this up finally and I think I bought the wrong type of switched jack for the sidechain input.

I bought a switchcraft 13A which has a tip, ring and normally open and normally closed lugs.

I've temporarily wired it in a way that I think will work but it's not ideal.

Normal input > normally closed lug
Tip lug > threshold pot
Normally open lug > board sidechain input buffer in
Board sidechain input buffer out > threshold pot

I'm thinking that this will result in the normal input going to the threshold pot as normal when no jack is inserted.

When a jack is inserted, the unbuffered sidechain input will go to the threshold pot through the tip connection, but the buffered sidechain will also go to the threshold pot from the board output connected there.

This should at least work right?

I'd like to get the right type of switched jack to do this properly but I'm having a hard time sorting through the options and figuring out a source for one. Which type do I need for this?

[befey]

So, I finally got everything together to wire this thing up.

It is mostly working, however I did use electrolytics for some of the 10uf caps.

With a fairly weak input signal and all the knobs full up, I'm getting a high pitched squeal over top of the signal. I don't notice much compression but that may be from the weak signal and the fact that I don't fully grasp the intended workings of each knob yet. The noise gate works perfectly.

Could this be from the electrolytic caps vs ceramic dielectric?

Maybe it would benefit from shielding the input and output wires?

Also, I don't have it boxed yet, so that could be part of it.