Looking for Hi-Q gutshots of a DOD FX70 Metal X or FX70C Corrosion

[ricothetroll]

Hi,

The DOD Metal X was my very first pedal, I really loved it but it's been stolen a few years ago, and 2nd hand are pretty expensive. It's basically a Metal Zone (MT2) with a different post-distortion EQ, and I've always found that it sounds much better than the MT2.

I'd like to clone it but I know that routing those very hi-gain distortion circuits can be tricky, especially to avoid oscillations. I thought the easiest would be to have some good clean pics/scans of the genuine PCB to trace it and thus clone it.

Would anyone here own this particular pedal, and be kind enough to take some good hi-quality pictures of the copper-side of the PCB ? I'd really appreciate it, and of course I'll share the result here.

I've found some pictures here, but the quality/resolution isn't good enough :
https://www.mikekohn.net/micro/metal_x_fx70.php

... and schemo, with lots of mistakes included, can be found here :
http://rudn.nodevice.com/preview/big/372/372716-1.jpg

Thanx in advance.

Eric

[ElectricDruid]

I can't help with the photos, but looking at the original PCB, you could get the noise lower than they've done by using metal film resistors instead of carbon comp, and decent film caps instead of cheap polyester. Build a "boutique components" version, if you like.

HTH,
Tom

[ricothetroll]

Hi ElectricDruid,

Thanx for your answer !

I will ! I never use carbon resistors anyway, ith the exception for carbon composition for plate resistors (R.G. reprezent )
I thought those polyester caps were actually good for audio use, for example I use MKT (Metallized Polyester) a lot when room is lacking for PP caps, like those ones :

https://www.musikding.de/Arcotronics-MKT_1

What's wrong about them ?

Best regards.

Eric

[ElectricDruid]

Nothing's wrong with those MKT caps, and I'm not advising against polyester itself necessarily. I use those MKT caps too sometimes, although I sometimes get fancier and use MKP polypropylene caps. It's just a question of quality really - and those ones in the DOD pedal look like the cheapest of the cheap to me.

Tom

[ricothetroll]

OK ! I wasn't into electronics back in the 90's, so I didn't know those were low quality. You find them in lots of devices from the 80's/90's, but I guess they're not manufactured anymore, for the best

[ricothetroll]

Hi,

I contacted Mike Kohn from the cited website and he could send me some better resolution pics. I've come to a first version.

I have a question though : it seems that the FET used as switches are not always connected the same way (input on drain or source). Does that matter ? Is there a direction where the FETs behave better ?

Here is what I could do for now (click : download original image for a decent resolution) :




I'll slightly modify the PCB later to fit MKP/MKT caps.

BTW if someone is courageous enough to take a look at the schematic to point out some possible mistakes, I'd be very glad !

Best regards.

Eric

[PRR]

> the FET used as switches are not always connected the same way

Nearly all JFETs, D and S are 99%-100% identical. Makes no difference.

However on the image you linked, I see all inputs on S?

[ricothetroll]

However on the image you linked, I see all inputs on S?

Ow... that's right I had to change the a few times during the tracing/routing process and now they're all the same ! Sorry for this