Basic Audio Scarab Deluxe

[aelling]

Thanks to Sphere80 for asking me to clarify some things of my original one of these, I looked inside and I saw a few things off. A few pot wirings where off like Fat 1 & Bias 1 are not connected, a 2n2 cap between Base & Collector of Q2 and only a low pass filter in the tone circuit, I drew a schematic so I'll include that. The layout is a little bigger than I wanted but it'll make do for now.

New compact layout with in/output on board not verified yet.  EDIT: 23/10/2018 moved Q3 so it didn't sit between 2 caps. Still not verified.


Original compact layout not verified yet


Schematic

[Sphere80]

Thanks for your work, aelling!  The 2n2 clears up that mystery and glad to have the fat pot wiring finally fixed too.

[aelling]

No problem, thanks again for bringing this up. Hold off on the layout though, I have one that is smaller coming up, just going over it one last time.

[aelling]

Okay, I added the compact layout, deleted the old one so I hope nobody started from that.

[HamishR]

I have a Basic Audio Scarab Deluxe and love it, and recently built a Pitbull Fuzz from a kit by Fuzzdog in the UK.  Looking at these schematics at seems that there are a lot of similarities although the pedals do sound quite different.  I have been meaning to build another Pitbull with more low-end to get a bit more sludge out of it and this circuit has given me a few ideas.

Maybe I should draw up a vero version of the Pitbull - unless someone already has?

[Sphere80]

   Very nice layout, aelling.  Thank you for the very quick response. It's about
the same size as the old one on the main page and has the protection diode and LDR.

   For anyone else who already built that 2014 one, I fixed mine by tacking a 2n2 on
the back of Q2 and corrected the bias and fat pot wiring. You may have to jumper a
connection or move a component up a row for the fat pot. You want the 10n to always
be on and blend the 10uf in. You aren't mixing between them like some older layouts
and schematics showed.

  HamishR, with some jumpers, and a few omitted parts, you could build the Scarab on
that PCB. Did you build the Pitbull with the second voltage pot?  
   Both are inspired by a couple of older Tone Bender with Muff eq projects:
http://tagboardeffects.blogspot.com/2017/06/mictester-silicon-tonebender.html
http://tagboardeffects.blogspot.com/2012/12/hot-silicon.html

[HamishR]

Yes I built it with the "Volts" pot but if I make it again I will probably leave that off - the bias pot is far more useful.  I just posted a vero layout for it minus the Volts pot.  I have built the Hot Silicon before and mine didn't sound as good as the Pitbull!  I remember being impressed with it though.

[aelling]

Okay, found some room for the in & output to be wired to the board instead of to the pots. For the input this did mean moving some caps and a cut, adding a cut and a link, so I'll leave the original compact up for now. For the output there was an entire empty row you on the original compact, you can add the wires there easily.

[TrashCandy]

I've completed the compact layout and it works like a charm. However, I made three small changes.
* First I changed the 1k5 resistor to a 2k2 value to match a gutshot of the Scarab I found online.
* Second, I added a 4K7 resistor between the 10k resistor and Tone 3, this resistor was in the gutshot as well but wasn't in any of the vero layouts I found online.
* Last, I used some BC109C transistors which I had laying around.

[aelling]

TrashCandy wrote

I've completed the compact layout and it works like a charm. However, I made three small changes.
* First I changed the 1k5 resistor to a 2k2 value to match a gutshot of the Scarab I found online.
* Second, I added a 4K7 resistor between the 10k resistor and Tone 3, this resistor was in the gutshot as well but wasn't in any of the vero layouts I found online.
* Last, I used some BC109C transistors which I had laying around.

The layout is based on a tracing I did myself of an original Scarab Deluxe made in 2014/2015, there have been many versions of this over the years, but the values here are correct to my original pedal.