dod250 / DeArmond tweaks attempt

[Roland]

The guyatone schematic has an error . Input resistor should be 10k not 1M.

[snk]

Hi,
Sorry for not replying earlier.


So, as I could just not understand what was wrong with the first build, and as @Roland told that the Guyatone layout had some mistakes on the schematic, I decided to start again from scratch, except that this time I followed the DeArmond SquareWave Layout (which is nearly the same than the Guyatone).

1- It works !
2- It sounds good : as you expect, not that far from a Dod250/Mxr Dist+, but it seems a bit more « thick » to my ears.
3- Using a 50K pot after the 10K resistor does indeed act as a smooth TONE pot (I'm glad my little tweak proved to be right this time ). Of course, it isn't a full low pass filter going very down in the frequency range, but i find it very good to tame some harsh harmonics so imho it's a nice addition to the circuit.
4- As I have socketed the 47nF cap, I will report here my findings about the BASS mod (I have played with such « distortion side-chain » capacitors on a Boss DS1, and it can really help shaping your signal further).

Once again, thank you all for your help !

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.

@Duck Arse,
Once again, I apologize if it made you so angry and if you felt my attitude was not « helpful enough towards people trying to help ». I understand what you meant : I was asking for help, but wasn't providing enough information to people with good will (willing to help me).

I do agree that what i provided is not perfect, but i think that i gave every details i could ?
The thing is I really tought it would have been a small & easy build, without anything going possibly wrong.
I didn't draw a schematic myself (therefore I can provide only the ones i found online and the layouts I relied on). I just drew a simple layout on DIY creator, based on the Guyatone layout (from which i gave the link in the first post), without even knowing if it worked (it was just tagged as « verified » on the website i got it).
I just wanted to tweak a couple components (a « bass capacitor », and trying to use a pot along with a resistor after the distortion to see if it can act as a tone pot), and was surprised to see that on such a simple circuit the gain didn't do anything.
If it had been my own design « from scratch », I would have provided a schematic, and much better pictures of my build (because i would have built it since the beginning with that in mind, but here it obviously wasn't the case : it was a quick & dirty build « for internal use »).

Anyway, I will keep the guidelines in mind next time i'll be asking for help

741 is a single opamp.  4558 and 5532 are dual opamps.

@Willienillie
Oops, indeed (insert a « feeling awkward » icon here:)

[snk]

3- Using a 50K pot after the 10K resistor does indeed act as a smooth TONE pot (I'm glad my little tweak proved to be right this time ). Of course, it isn't a full low pass filter going very down in the frequency range, but i find it very good to tame some harsh harmonics so imho it's a nice addition to the circuit.

Further comments about that : In fact, it's not so good.
Well, the thing is that it doesn't just change the tone, it also seems to change the overall gain structure and output level, making it very interactive and quite redundant with the main gain pot.
I think it would be better to use a SWTC instead... or just keep it simple and avoid the tone control.

[eh la bas ma]

I have a similar issue with a dod 250 build, and i suspect the diode clipping to be responsible for the gain loss.
If you are still wondering about this, I humbly suggest to try silicon diodes like 1n4148 and see if you get more gain.

[iainpunk]

have you checked the values of the resistor to ground in the feedback loop, having a too small cap, a too large resistor or just a bad solder joint will take out lots of the gain,
maybe its that

cheers, Iain