Monolithic Fuzz Oracle

[rocket88]

I just came across this pedal on youtube, and it sounds badass. It's supposed to be similar to a MK 1.5 tonebender, but more lows. I cant find a schematic, but on Monolithic's site there is a near perfect gutshot, and figured someone more knowledgeable then me can create a layout easily.

Here's a description of the pedal from Monolithic.

[GSoave]

I've found this project at turretboard.org. Take a look, maybe that's what you want. ;)

[rocket88]

Oh man that's awesome. I'm usually on turretboard checking for new things, so I'm surprised I missed it. I'll try to make a vero layout, but I'm not so good at it yet. Hopefully someone better than me can turn the turret layout into a nice compact vero one.

[mojo321]

Its easier working from the schematic, but as hard as I tried, I couldn't find the schematic that that tagboard claims to have been built from...

[mojo321]

Hmmm...the ground routing on that layout is trippy.  It looks like they use shielded cable to get ground to the board.  (see little yellow wire that pops out of the thick wires with blue cores).  

[johnk]

mojo321 wrote

Its easier working from the schematic, but as hard as I tried, I couldn't find the schematic that that tagboard claims to have been built from...

http://www.freestompboxes.org/download/file.php?id=3171&mode=view

[rocket88]

Awesome. Thanks John.

[mojo321]

Cool, John thanks! i have the vero done on paper.  I'll get it posted tomorrow after I get off work and have a chance to CAD it. Pretty small 12x14ish...

[johnk]

yeah, I drew one up too. mine came out to 16 x 9 with no standup resistors.

[johnk]

here's mine. I haven't built it yet so it's not verified:

[johnk]

I've checked my vero a bunch of times so I think that it matches the posted schematic but I built it and it doesn't work properly. it's fuzzy but super gated / sputtery, and the gain and tone controls do almost nothing. i'm starting to question the schematic. it also says hfe 112/304 but OC76's are usually around 40-55.

[johnk]

okay, I found a 'corrected schematic here:
http://www.freestompboxes.org/download/file.php?id=3171&mode=view

so, I grounded the 2k2/680R reistors & 6n8 cap junction and it works just like the video now.

so here's my verified vero:




as on the original pedal, the B1M gain/density control is basically useless, so i'm going to mod mine in that area. it appears that the designer tried to simulate a volume control on the guitar but it really doesn't work that way the way that the circuit is wired.

[IvIark]

Excellent, nice one guys!

[johnk]

and here's my modded version with a variable gain control:

[mojo321]

Dang John, you killed it!  You even built it to verify!   I have one question though, why DPDT on the switch?  Isn't it just an SPDT on-on that toggles the resistor value from 100k to 12k?  

Thanks for the updated schematic.  

[mojo321]

The schematic could have just connected the 100k and 12k resistors together, not switched them.  the single switch on the other end of the pair is plenty.  

[johnk]

mojo321 wrote

The schematic could have just connected the 100k and 12k resistors together, not switched them.  the single switch on the other end of the pair is plenty.

yes, it could've been done that way. I just drew mine up according to the schematic.

[rocket88]

damn john. I can't believe you built it, verified it, and modded it to make it more usable. I just had time to look at the schematic and nothing else. You are the man. Btw, where/how did you find the right germanium transistors that aren't leaky as could be? When I saw that in the schematic and the tagboard layout I thought that was wrong.

[johnk]

rocket88 wrote

damn john. I can't believe you built it, verified it, and modded it to make it more usable. I just had time to look at the schematic and nothing else. You are the man. Btw, where/how did you find the right germanium transistors that aren't leaky as could be? When I saw that in the schematic and the tagboard layout I thought that was wrong.

I have several hundred ge transistors on hand. the ones that work the best for me in this one are AC128's with an hfe of around 95-110. low hfe ones (45-60hfe) barely work at all.

[rocket88]

SEVERAL HUNDREDS!!!!! (Jaw Hits Floor). That's incredible. Did you make both transistors the same? What other transistors did you try, cause I'm going to have to get some since I don't have much PNP Ge transistors. BTW, is this a PNP circuit or NPN circuit?