dod250 / DeArmond tweaks attempt

[snk]

Hi,
I recently came across a nice looking pedal, the De Armond SquareWave. I found a layout of it, and noticed that it was nearly the same as the Guyatone Loco Dist (and i like this serie of pedals), and the Dod250 (which I already built a couple years ago).
I decided to try to tweak it a bit, so it would not sound exactly like the Dod250, and would allow for more bass, and a subtle tone pot.

I have made a layout (using the Guyatone one as a template), and built it on veroboard.
The problem is that the gain doesn't do anything : i only have the clean signal passing through 
It's such a simple circuit, I have triple-checked my wiring, and everything seems correct.
Would I have made a mistake while drawing my layout?



I am considering remaking the circuit using another layout, but as one of the purpose of the build was to understand the circuit, I would be glad to know if the error comes from my layout or from my build

So, here is my layout :


This is where the inspiration came from :
Guyatone layout
schematic

De ARmon layout
schematic

I have also checked Electrosmash for understanding the circuit and trying to know the tweaks i needed to do...
I also got the bass mod tip from Mark Hammer here : https://www.diystompboxes.com/smfforum/index.php?topic=81235.msg672544#msg672544

[duck_arse]

how can we be sure you have it all in the right spots/values, if you won't show your built thing? how?

[snk]

Hi, Duck Arse,
Yes, obviously  My phone is in charge, i'll take a picture as soon as it's ready.

But maybe I haven't phrased my question the best way I could : the error can be in the build, but it can also be in the layout (as it is an unverified layout i created yesterday). So, does the layout seem correct, at first glance?

[snk]

Hi,
Here are some pictures.
Errh, I must confess that i am quite ashamed of posting such pictures, as this prototype really look terrible and might be a mess to understand for anyone else than me 
The diodes, the 15pF cap are socketed, as well as the Mylar cap for the bass mod (but it is offboard).
As this build is for testing purposes, I haven't put a 3PDT yet (so there is obviously no bypass).
https://imgur.com/a/cvwcixf

[willienillie]

Are those 1S1588s?

[snk]

No,
it's germanium diodes (but not 1S1588). I guess it's 1N60 or 1N34, i'm going to check.

[snk]

1N34As
... and i just tried with 1N60s, and it's the same : i get a clean, unity gain sound, but no distortion. The GAIN pot does nothing.

[willienillie]

I was only asking about the diodes out of curiosity.  Does the gain pot not even affect the volume?

[snk]

No,
The volume pot does lower the volume as expected, but the gain pot does nada.

This is my curse : i often manage to make more complex builds, but struggle on the most simple 

[willienillie]

You have a few stray wire strands, but I can't see if any are causing a short.  You should be able to measure your gain pot's resistance in-circuit.  Does it go from 0 to 500k ohms?

[snk]

Hi,
I measured the pot, and it goes from 0K to 548K (which is roughly within the specification range).

[willienillie]

Yeah, close enough.  So I'm at a loss, basically.  What does the circuit sound like as it is?  Does it seem like the gain is stuck all the way down or all the way up?  Is it gated and weird?

[snk]

That's what puzzles me : the sound is not gated and weird at all : the effect sounds like in bypass (but there is no bypass) : clean signal, unity gain.
Moving the gain pot doesn't do anything, and moving the volume pot makes the sound quieter (as expected).
I changed the diodes, the opamp, it's the same.
I compared my layout with a couple others, and it seemed ok, but i must be missing something obvious like an elephant in the room
I might start again with a fresh build from another layout?

[willienillie]

It's gotta be something simple, but I can't tell you what.  You're not reversing the jacks?  We've all done that once or twice.  Otherwise, I kinda wonder about the bass cap/socket situation.  A bad contact there would cut off your gain pot.  Those sockets are a little loose sometimes, and the cap leads could have tape residue on the very ends.  Spitballing at this point, but everything else I can think of checks out.

[duck_arse]

Hi, Duck Arse,
Yes, obviously  My phone is in charge, i'll take a picture as soon as it's ready.

But maybe I haven't phrased my question the best way I could : the error can be in the build, but it can also be in the layout (as it is an unverified layout i created yesterday). So, does the layout seem correct, at first glance?

phone in charge? NO! we are in charge, not the devices - rise up, people, revolt!

now seeing as you asked - we don't know if your layout is in error or nor, as a) we can't see all the connections [switches, caps etc], and b) we haven't seen your complete circuit diagram, the one you have there that you must have been looking at when you did your layout.

if you put all the information in front of us, we have much less reasons for exasperations and consequent loss of interest. [I can't follow/imagine what you are doing around the top left of your board.]

[snk]

Hi, Duck Arse,
You're right : both the layout and the pictures are a mess 
I was a bit "in my head" and didn't realized that it was not clear and informative enough for someone else to help. I should have taken more time to make the layout clearer (and for the build, well, as it is it's a bit difficult to take in picture where everything is visible and clear enough. I thought it was such an easy build that everything would be troublefree 
I think I will take the evening to make an enclosure for the Causality phaser I built yesterday, and for a Tremulus Lune I built two months ago : It will allow me to take some distance for reflexion... and tidy up my desk a bit so everything will be hopefully less messy.

However, in the meantime, I have updated the layout, which display the way it is now ( = the switch is not a switch yet, just a socket with a capacitor, showing the values i am using right now). I think that the wiring is shown, too.

we haven't seen your complete circuit diagram, the one you have there that you must have been looking at when you did your layout.

I have posted all my sources above : I made my layout using the Guyatone layout as a reference. It happens that this layout is very close to the DeArmon SquareWave which caught my attention some days ago... and both happen to be based on the Dod250/Mxr Dist+ schematic (with a few values changed but no differences in the circuit topology afaik).
I haven't drawn any schematic prior to making the layout, if that was your question, i have done everything using the Guyatone & DeArmon layouts, and the Electrosmash circuit analysis posted above.

Again, I am sincerely sorry if my post exasperated you, as i really do appreciate the help i can get from this forum. I am not a very technical guy (i do nearly everything from layouts, and i am very slow at learning to read schematics), so everything i used was in the links i posted in my first post.

[duck_arse]

hmmmm. well. it would seem that yer board checks out ok [but I still can't fathom those pots/wires]. so - please read to us the markings on the "treble cap". also the markings on the two greencaps on the board. otherwise, I'm at a loss. pull the IC, check voltages on the empty socket pins. then power off, and check resistance measures at the board as you wind the pots, to see if they really connect as/where you think.

[snk]

Hello,
Weird thing... maybe my sockets are crap ?
- I hear the effect of gain better if I remove the diodes... but i hear the gain effect best... when i put my finger on the back of the IC pins !?
- I have tried with several op-amps : LM471 (the original op-amp), JRC4558 (it didn't give better results), 5532 (i got a somewhat louder sound, but again the best sound was when i had my thumb making contact on the back of the IC socket...)
- With diode removed and a 5532, I can hear the gain effect (but it is quite gated, and the volume is very low).
- About the "treble" capacitor : I tried with a 15pF and a 560pF : i couldn't hear a audible change...

So i guess it's not worth spending too much time on this build : something might be wrong and a component may be faulty, so maybe i'd better start again from scratch and try on a new vero ?

[willienillie]

741 is a single opamp.  4558 and 5532 are dual opamps.  They have different pinouts and are not interchangeable without totally rewiring the whole thing.  It's amazing you got any sound through it at all, the supply voltage isn't even going to the right pin.

[duck_arse]

if this was my build, and it wasn't werking, I'd ask for help. I'd present the circuit diagram, or schematic, as I had [intended to] built it - complete with all the modifications and additions and subtractions and substitutions. and I'd provide a layout diagram of some sort. why? well, there are people about much smater then me that can look at a schem and say things like "it won't work as you've drawn it" or loook at a layout and say "yer grey wire is one row low". and that's before the photos.

so I'd provide photos of what I had taken all that time to solder together. why? so's people interested might then be able to compare the schematic [as you intended to build it] and the layout [as you are supposed to have built it] with what you actually built - and these people don't even need to be smarter than me, just interested enough to look. and they might say things like ....

what value is that cap, I can't see the markings? - because you might have misread or misinterpreted the markings ....
is that a 1k resistor or a 1M resistor? .... misread colour bands, bad value "in the bag" .....
you have a short/extra cut ...... like that. they might suggest things like "measure the voltages on the pins, please" because those smart guys, when presented with a circuit diagram and some voltages, can point to the exact spot and say "there!". and they are very often right. just from a diagram! but they need to ask you, because you have the thing, they just have what you allow them to have - information about the thing.

and having the circuit diagram, you will know things like - only a single opamp, so no need to think about any of the dual oppy types, or pnp transistors so no need to try my npn types, backwards or not, and which way the diodes cathode connects, all important stuff.

and - it might turn out that a million monkeys squint for a million hours, each, at all your provided documentation, compare to your photos, and they will scratch their heads and say .... hmmm, dunno, can't see anything. and so then you'd have to go through some arcane practices, like measuring resistances to check connections. because your schematic says this pot connects between here and here, so you'd first check that the pot was the right value, then that it worked to vary resistance, and then you'd measure from two points on the board, say, that are supposed to be connecting to the pot [schem says so, layout shows so] as you work the pot to prove all those things present and correct ....... or not.

same goes with all those switches and jacks, you measure them with your meter to prove they are not the problem. and sometimes, you might try a different tack - prove your circuit works. short the gain pot connections at the board [check your schem] - does the circuit werk? remove that added tone cap, does it now werk? disconnect all the extra stuff like jacks and switches, inject some signal at the input, listen to the opamp output - anything? and by and by, you will eliminate the things that are not causing the issue, until you are left with .........


[please excuse my ranting. also excuse any tying errors - I hate using this keyboard. that is all.]