Dod fx86

[Kipper4]

Why oh why oh why.
Told you I was full of stupid questions

What's all the transistors for on the pots at the output. How are they working?
Why run on a bipolar +4.5v -4.5v.
Has anyone built it?
Anyone like /dislike it.
Told you so...........

Link
dod fx86 schematic


Tube here

http://youtu.be/_1jp4IEB3L0

[ashcat_lt]

An actual link to a specific schematic might help.  I can't answer the question about the transistors partly because I'm not sure which ones you're talking about.  I can tell you that a lot of these DOD/Digitech schematics use that somewhat confusing convention of labeling the most positive end of the power supply as 4.5V, the other end as -4.5V, and what we would normally call Vref is ground or 0V.  Don't let that fool you.  If you actually find one with the power supply section included, you'll see that it's just a single ended 9V supply with a voltage divider for Vref like any other pedal.  It's a bit of a reminder that "all voltage is relative", and you can really call any given voltage as ground.

[Mark Hammer]

The transistors...

A number of DOD distortion pedals employ a couple of gyrator circuits for their EQ.  Boss has done the same thing (see the HM-2 for an example).  In some instances, even though there appear to be more gyrator circuits than controls for them, a single pot is used to boost and cut at a few different points.

Also note that DOD pedals use a CD4007 and a few transistors for their bypass circuit.

[bloxstompboxes]

DOD has also used transistors in buffer circuits at the input and output.

[Kipper4]

Sorry Ashcat.
I thought that I had posted a link

Here it is

http://files.effectsdatabase.com/docs/schematics/dod_fx86.gif

[Kipper4]

Gyrators yep Gottya.
Thanks guys
That's me outta questions.

[J0K3RX]

This is one of the better sounding pedals in this class but, before you get on with it check out the Ibanez SM-9..  There is a newer Maxon SM-9 Pro Plus but I like the older version better. The SM-9 is a seriously bad ass pedal but some how not as well known as the FX86. Also check out the DOD FX70C and the DOD Gunslinger mosfet distortion! DOD has a bunch of cool designs worth checking out but the SM-9 is on another level in my opinion..

[Mark Hammer]

There are five gyrator sub-circuits in that pedal; one before and 4 after the clipping.  Two of the post-clipping gyrators are fixed, while two provide adjustable boost/cut at their frequencies.

[duck_arse]

yeah, more gyrations than little egypt.

interesting that the input sleeve (in klipper's selected reference circuit) is connecting to "-4.5V", but the output sleeve is connecting to "-10V", which shows nowhere else on the dia.

[J0K3RX]

This may clear up some questions...
https://dl.dropboxusercontent.com/u/11178619/DOD%20FX86/FX-86%20Rev%20A1.pdf

Probably a better easier to understand schematic hosted here at DIYSB with the addition of the greatly missed gain pot 
http://www.diystompboxes.com/pedals/schems/DODfx-86.GIF

[Kipper4]

That's great thanks. I might give it a whirl when it gets to the top of the list.
I'm intrigued about the gyrators and the way all that's working.
I need to do more homework. There's always more homework.
Thanks again guys