Some Funny Cat queries

[Mark Hammer]

I've built several Funny Cat clones for myself, using RG Keen's Silly Feline schematic and layout, with a few mods.

1) Instead of Modes A, B, and C. I have essentially the "normal" mode (A) and the "chaos" mode (C), and variable sensitivity and decay-time controls (the basic difference between A and B but with more variation).
2) A filter range control (hi/lo), similar to what one sees on a Mu-Tron III, for a little more sonic variation.

I'm impressed with the SDS (soft distortion) sound, and am going to put together a pedal with ONLY that sub-circuit.  I find it to be an incredibly thoughtful and innovative use of bad envelope ripple, and a somewhat unique sound.  HOWEVER, two things that puzzle me:

a) Is the inclusion of op-amps in the Silly Feline a mod in itself, and not part of the original?  I ask because I see no visual evidence of them in the "ungooped" AG-5 modules available at the Moosapotamus site.  Indeed, there are way more transistors in those modules than exist in RG's posted schematic.

b) Assuming an op-amp based version of the circuit behaves like a discrete version, what would be your choice of op-amp?  I'm thinking of a plain vanilla LM741, but there may be a reason to make a different choice.

Opinions?

Would an all-discrete version of that front end behave "better" than an op-amp version?

[PRR]

Funny Cat looks like this?
https://www.rd.com/wp-content/uploads/2023/04/Hilarious-Cat-Memes-10.jpg

Other possible lynx:
http://geofex.com/PCB_layouts/Layouts/funnycat.pdf
Same but asks for donation: https://www.synthxl.com/roland-ag-5-funny-cat/
https://www.swapmeetdave.com/Humor/Cats/Cats1.htm


Some guy in Ottawa once made plans to start finishing things one by one.
https://www.diystompboxes.com/smfforum/index.php?topic=46058.0

[Mark Hammer]

Well, it DID get finished, but now I'm curious about the SDS, specifically.  But it IS important to preface "Funny Cat" with "Roland", when searching. 

[Mark Hammer]

Probably also useful for me to title the thread Funny-Cat queries, rather than Funny Cat-queries.

[Rob Strand]

There's been some updates and I'm sure way back in the day (2003/2007) I drew-up a schematic as a best guess for the discrete opamp boards.  Then some time later some non-gooped pics were posted which allowed some of the values to be refined.   I couldn't find a schematic, perhaps it's in some old CAD files.

I think this post was from 2007 on this forum:

    Re: Funny Cat - Mode C
   Reply with quote Modify message

Here's my last set of notes:

* 1) RG's "last schematic":  The Mode switch is incorrect but the PCB is correct.  There is a link across B&C switch contacts in the op-amp feedback path. There is a link between A&B on the DC control side.  Some of the "other" schematics in RG's set show the correct switch wiring.

* 2) 3-way Switch:

The three-way switch controls the gain and time-constant of the
of the rectifier circuit that controls the sweepable filter.

Mode   Gain   Time Constant   Comment
A   low   in      Subtle sweep
B   high   in      Exagerated sweep
C   high   out      Self modulated (under water sound)

* 3) Confirmations from Charlie (May '03):
- R10 is 15K ohm
- pots are linear not log.
- Confirmed Switching: There is a link across B&C switch contacts in the op-amp feedback path. There is a link between A&B on the DC control side.
- The volume for the three switch positions is about the same.

Apart from these touches I have a high level of confidence we got this one right.

The 15k vs 47k resistor was mentioned here,
https://www.diystompboxes.com/smfforum/index.php?topic=121951.msg1148767#msg1148767

The there was some more stuff posted here in the same thread,
https://www.diystompboxes.com/smfforum/index.php?topic=121951.msg1148774#msg1148774

[Rob Strand]

Here's a new trace of the discrete opamp module.
Refer to RG's schematic for the R5 value.

Schematic with test circuit connections:


Module to opamp pin equivalence:
(1) = op amp + input, (2) = op amp - input
(3) = op amp output,
(4) = op amp ground, (5) = opamp +vcc
R5 is a feedback resistor built into the module.

PCB pics:

[Mark Hammer]

WOW!  Thanks for that, Rob.  I appreciate your diligence.  I've already started populating a perf build to fit into a 1590A, but am using a socket for a single op-amp, that may be able to accommodate a discrete daughterboard that could allow direct comparison of the chip-vs-discrete versions.

It's stinking hot and humid here, these days, so I may be a little slow in reporting back.  But I will, eventually.

[duck_arse]

 

I have these pics, from somewhere. shows 470k instead of 100k? are the three sub-board circuits identical values, or one/some different?

[Mark Hammer]

1/8W resistors can make that even smaller.

[Mark Hammer]

Okay, a little confused here.  Rob's drawing (which I have no reason to doubt) connects the inverting pin of that first module to ground through 10k/10uf.  RG's schematic has that inverting pin going to ground through a FET and 1uf cap.    Insomuch as it is the ripple in the halfwave rectifier that "wiggles" the gate of that FET to produce the "soft distortion", I'm unclear as to how what Rob drew will produce that "sonic burr".

Ideally, brother RG would chip in here, and clarify the differences (or explain why the sonic similarities).

In any event, I think for now I'll stick with the Silly Feline op-amp version, since its sound is what motivated me in the first place.  Once the sonic correspondence between the two circuits is made clearer for me, I may attempt the discrete version.

[Rob Strand]

WOW!  Thanks for that, Rob.  I appreciate your diligence.  I've already started populating a perf build to fit into a 1590A, but am using a socket for a single op-amp, that may be able to accommodate a discrete daughterboard that could allow direct comparison of the chip-vs-discrete versions.

It's stinking hot and humid here, these days, so I may be a little slow in reporting back.  But I will, eventually.

No problem at all Mark.  I suspect it will sound OK with the opamp.   Just the same it's interesting to try the real thing once to see if there is any subtle differences.

We're the opposite, it's getting cold here, but compared to your area of the world it's quite mild.

I have these pics, from somewhere. shows 470k instead of 100k? are the three sub-board circuits identical values, or one/some different?

Thanks for the pic.  I'm sure I've got that set of pics in my archives and I'm sure I've already traced it at some point. 

The resistor difference is in the notes on my schematic and on RG's schematic: one feedback is 470k and the the other two feedback resistors are 100k.   There's two types of modules with different resistor values.  (Your PCB pic has a 470k and my PCB pic has a 100k.)

Okay, a little confused here.  Rob's drawing (which I have no reason to doubt) connects the inverting pin of that first module to ground through 10k/10uf.  RG's schematic has that inverting pin going to ground through a FET and 1uf cap.    Insomuch as it is the ripple in the halfwave rectifier that "wiggles" the gate of that FET to produce the "soft distortion", I'm unclear as to how what Rob drew will produce that "sonic burr".

The part outside of the box on my schematic was only a test circuit to check the discrete opamp.  It's not the full soft distortion circuit.

To get the soft distortion:
- Start with RG's schematic
- Replace the opamp on RG's schematic with the boxed area
  on my schematic.
  (Essentially replacing the op amp chip with the discrete opamp circuit.)
- Change R5 in my boxed area of my schematic to 470k.
  (The modules have a built-in feedback resistor but the
   off the shelf opamps obviously don't.)

[PRR]

Note the drawing error on the input jack, R.G.s PDF. Tip and Ring got swopped.