DOD FX-10 Bi FET PREAMP

[sevenisthenumber]

Ive owned a couple of these and they are amazing. Great as a booster or even for an acoustic guitar to warm it up. Does anyone know where a schematic or layout for this is. In my opinion this is one of the most underrated pedals ever commercially built.

[Caferacernoc]

I like mine too. I wish I could find a schematic and I've looked. What the heck does bi-fet mean? Is it a jfet or bipolar, haha?
I really think it's similar to a MXR micro amp with a BMP tone control added on IMHO.

[tcobretti]

Apparently it was designed for acoustic guitar

http://filters.muziq.be/model/dod/fx/fx10

[Ben N]

You've got mail.

[MikeH]

I'd like to see it too!

[comfortably_numb]

I'd like a copy of this schematic please.

Thanks.

[Ben N]

PM me your email, but I probably wont get to send it out until Sunday.

[aron]

It's great. $10 before the vintage craze it.

[aron]

Maybe this is close?

http://img366.imageshack.us/my.php?image=dod410studiobifetpreamp4bb.gif

[frank_p]

Maybe this is close?

http://img366.imageshack.us/my.php?image=dod410studiobifetpreamp4bb.gif

That would make sense since it is a JFET input opamp. 

[wampcat1]

Maybe this is close?

http://img366.imageshack.us/my.php?image=dod410studiobifetpreamp4bb.gif

I can't find the schem now, but IIRC it was a pretty basic non-inverting opamp into a baxandall eq stage.
bw

[ironman28]

The schematic in the link http://img366.imageshack.us/my.php?image=dod410studiobifetpreamp4bb.gif for the 410 is almost correct. There are two parts missing as drawn.
The later FX10 BiFET (bipolar output/ FET input) Preamp uses a similar but slightly different circuit. The EQ behaves like a tilt type with bass boost+treble cut/treble boost+bass cut. It is very useful to fatten up single coils or clean up a humbucker.
Look at the tone control section of the FX53 or other DOD distortions and that is the FX10 circuit. The other components in the FX10 are for the FET bypass and buffering. The 410 uses a TL081 and the FX10 uses a TL062. The high input impedance brings out the high end nicely for both guitars and basses. I will draw a corrected 410 schematic and post it.

[ironman28]

http://i232.photobucket.com/albums/ee168/ironman-28/dod%20410/dod410.jpg

Here is the 410 schematic with a snippet for the FX10 type tone control. I like the 410 better than the FX10. Maybe it's because the 410 is bare essentials with no buffer or FET's in the path. I'll take a stab at a vero layout later this week end.

[sevenisthenumber]

This is great stuff! Thanks ironman. Cant wait to see a vero on this!

[Ben N]

Thanks for the update on the 410, Ironman. It's been a long time since I traced that, and I was never sure if I got it right. I emailed everybody who PMed me with the FX10 schemo. The description is correct, except that there is no separate buffer stage, just some interesting switching to set the gain stage to unity in "bypass" mode. Besides the TL062 there is a 4007 controlling the switching through jfets.

[aron]

Wow, great! I might make another with this new info. Thanks!!!!!!

[George Giblet]

Thanks for schem Ironman.

I'd drop that 220k (R2) to 10k or less.  I can only see it adding a lot of noise.

[ironman28]

Thanks for the update on the 410, Ironman. It's been a long time since I traced that, and I was never sure if I got it right. I emailed everybody who PMed me with the FX10 schemo. The description is correct, except that there is no separate buffer stage, just some interesting switching to set the gain stage to unity in "bypass" mode. Besides the TL062 there is a 4007 controlling the switching through jfets.

Thanks for the correction...I never have traced the FX10 completely so I assumed  it was a standard bypass buffer. I'll have to take a look at it again.

[slacker]

The original bypass is possibly done by disconnecting the bottom of C2 and maybe C5 from ground using fets. That would give the stage a gain of 1 making it into a buffer.
The DOD graphic equaliser uses uses a similar method.

[ironman28]

http://i232.photobucket.com/albums/ee168/ironman-28/dod%20410/410.jpg

Ok here is the first attempt. I have not built this yet so consider it unverified. I did not include the off board components .
I'll do another one with the FX10 tone control later. The 410 tone control is "backwards" so you may want to reverse the tone 1 and tone 3 connections.
The 410 has CTS 100k pots both the volume and tone. I dont know the taper but I will check. The FX10 tone circuit uses a W taper pot. A linear one will work but you may want to use some tapering resistors to get the right feel.