DOD FX32 Meatbox

[tomk]

schematic here:
http://freestompboxes.org/viewtopic.php?f=1&t=8570&hilit=meatbox

thanks!

[Jorge Moura]

I look forward to this scheme.

It's a fantastic pedal and there is no replacement currently. It seems that the problem lies more in one of the IC, which is not easy to find / replace.

[Geiri]

You can find the ICs on eBay but they're not super cheap

[Hozy31]

Still can't find a vero of this. Would love to give it a go. Anybody up for the task?

[Emil]

Hi!

I attempted to draw up a schematic of this minus the switching. Does it look OK?
Maybe there's a few to many cap+resistor pairs around the Level pot + Q5 in my schematic? Wasn't too sure how much to remove from the J-fet switching sections.

Also, small note, I couldn't get the IC-symbol for the M51134 to work quite the way I wanted it to. I had to move pin 9 to IC2A instead of IC2B in the original because of this.

Edit: Updated schematic, see post below.

[Alex]

C30 and R33 can be eliminated.
I've started drawing a layout and then realized V Ref from the original schematic may not be V Bias but they should be connected together. I think V Ref comes from pin 11.
Any idea?

[Emil]

Alright!

Oh you're right. I assumed Vbias and Vref were the same. But looking at it, it basically follows the datasheet "Test circuit" connections . Pin 11, 3, 15 and 16 are connected there. Speaking of pin 15 and 16: I was a bit unsure what the VCA CV labels meant, but it should mean that they are connected there I think.

Updated the schematic!

[Alex]

Cool.
Also Flank 2 & 3 are not connected.
The layout came out quite large.

[Emil]

Oh, thanks :). Changed it again.

Cool, yeah I suppose it was inevitably going to be pretty big :).

[Emil]

BTW, noticed this diy-project based on this chip, that looks a bit slimmer.

http://www.diystompboxes.com/smfforum/index.php?topic=101580.0.

[Alex]

Here it is.
I'm pretty sure it matches the schematic but any extra help would be appreciated.
I'll move it on the main page once the layout has been confirmed as correct.

[Hozy31]

Amazing Alex, nice one. Will give it a go next weekend.

[Sphere80]

"C30 and R33 can be eliminated. " ̶D̶o̶ ̶y̶o̶u̶ ̶m̶e̶a̶n̶ ̶R̶3̶4̶ ̶o̶n̶ ̶e̶m̶i̶l̶p̶a̶u̶l̶s̶r̶u̶d̶'̶s̶ ̶s̶c̶h̶e̶m̶a̶t̶i̶c̶,̶ ̶t̶h̶e̶ ̶1̶0̶0̶k̶ ̶o̶n̶ ̶t̶h̶e̶ ̶s̶a̶m̶e̶ ̶l̶a̶n̶e̶ ̶a̶s̶ ̶M̶e̶a̶t̶#̶1̶ ̶o̶n̶ ̶t̶h̶e̶ ̶l̶a̶y̶o̶u̶t̶?̶ ̶ ̶T̶h̶e̶n̶ ̶a̶d̶d̶ ̶a̶ ̶j̶u̶m̶p̶e̶r̶ ̶f̶r̶o̶m̶ ̶t̶h̶e̶ ̶b̶a̶s̶e̶ ̶o̶f̶ ̶Q̶5̶ ̶t̶o̶ ̶t̶h̶e̶ ̶1̶0̶0̶o̶h̶m̶ ̶l̶e̶a̶d̶i̶n̶g̶ ̶t̶o̶ ̶t̶h̶e̶ ̶o̶u̶t̶p̶u̶t̶ *nevermind, that part of the schem. was correct*

[Hozy31]

It says at the top of the schematic post "Edit: Updated schematic, see post below." So i presume he has removed them already and renumbered the schematic.

[Sphere80]

Oh, no I see, (on the layout) the top of the 100k needs to be brought down a row so it goes to ground. Level#1, not Meat#1.

There is a larger concern, let's refer to the original schematic on the 1st post on the FSB link.  Emilpaulsrud, Q2 is the switching jfet, but you also got rid of Q1.  Your Q1, the 2n5088 that's called Q3 on the original, is part of the switching I think.

 I'm only able to get sound if I connect my input directly to Meat #2, bypassing all the remnants of the switching/buffer section.  I don't have the 51134 yet, but both low and sub EQ pots work as they should, with no effect at noon, but cutting/boosting either way.  

[Emil]

Yeah, that's right. Changed that already and renumbered.

[Alex]

You are right. 100K goes to ground and I think there's the Input's J201 missing.
I'll correct it later but we had problems with DOD's "fake" schematics before and I don't know if this one will work or not. That's why I didn't put it on the main page yet.

[Emil]

I see. So, like this? Should Q1 (the 2n5088) also be removed? Anything else?

[Alex]

I think C7 is not needed and C8 goes to Vbias instead of ground.

[Sphere80]

I fixed C8 by moving it up two rows (removed CLR) and fixed the 100k from yesterday. I have sound but... you tell me:

https://soundcloud.com/user-562468024/alexsez-meatbox-2017-03-24-01a-test

This is a drop A tuned guitar direct. First loop is dry, second with rump and flank at noon, third with them on full. They're low frequencies so it's not very noticeable here, but in the room, and especially with distortion, they're powerful.

Is this the octave working, or is there some heavy low pass happening on the final stage? I ask because I bypassed the input buffer and went directly to Meat #3 with the dial all the way to the right.  That's the OUTPUT of the M51134.  How is it getting signal in? No sound if I remove the M51134.

 I can't seem to get a nice blend happening with the meat pot, and I tried two B100k's.  We'll have to get that input section squared away.