Cat in a Can

 I had a rough start to the working week last week, so a bit of retail therapy was in order. Going to my favourite hock shop I saw this with a $299 price tag. A piece of 1973 ancient history/juvenilia from one of the most iconic synth makers of all time; a bizarre unique design (and nomenclature); a very good price; and a cool FX pedal to boot? Hell yes!

It did not disappoint. The Funny Cat AG-5 is a unique design that has an "SDS" distortion, (over) drive section switched in and out on the right, and a rather unique envelope filter ("Harmonic Mover") switched on the left that, on at least one of its three settings, has an attack that is just like a cat's meow (hence the name). It was a contemporary of the similarly oddly named, but now highly sought after, Bee Baa two stage fuzz pedal, that sells for even more that this little guy (which itself has an indicative sold price hovering around $500 AUD on Reverb).

The physical design is pure 1973, a solid sheet steel enclosure that takes up a fair chunk of space, mechanical foot switches, battery operation only, and controls out of harms way and out of sight/out of mind of the guitarist - all on the back (audience) side of the unit.

Controls are straightforward - an output level adjust for the SDS, a mix control between the Harmonic Mover output and whatever goes into it from the SDS footswitch, and three envelope responses for the Harmonic mover. In keeping with the time it was made, the circuit is buffered at all times and has a rather low input impedance - true bypass loving tone questers look elsewhere!

I tested it with my Yamaha active pickup bass, and it could range from hard to tame, with the Harmonic Mover ranging from nasty-in-a-good-way (on the fastest envelope setting) to remarkably musical on the more docile setting. The crazy filter circuit (a transistor warping an RC circuit) has a unique character.

The unit opens up easily-there are four thumbscrews on the side, two of which serve as a hinge for the bottom plate when loose, and two that can swing out of the body.

The insides look just how they would have in 1973-note the green stuff around the screws, jacks and pots - this would be Loctite adhesive or similar, that has done a stellar job of holding everything together for half a century, despite the beating the outside case has taken. The cleanliness of the inside is also a tribute to the  well-sealed enclosure, and the little steel box for the battery is a nice touch. Note also the "blind hole" between two of the pots-there is another between the footswitches under the circuit board. The case was common to the Bee Baa, which had an extra pot and footswitch. 

Check out the copper patches on the circuit board-the rest is silver because it would have been soldered in a "solder bath", but these areas would have been masked off with Kapton tape or the like to keep solder out so parts could be attached later. Hmmm, let's have a look to see what they are...

So why does it have three little circuit boards sticking out, when they could have been put onto a single bigger card? To answer this, we have to consider how things were in audio electronics in 1973. 

A few years before, largely due to the genius of Bob Widlar, the monolithic (ie "chip") operational amplifier (opamp) had revolutionised electronics. A compact, accurate, versatile amplifier was now something that could make electronic design easy, rather than using traditional cascaded transistor based circuits with complex assembly due to lots of parts. 

Problem was, these new little wonders were expensive. Even the uA741, which is remembered now as middling at best, cost about $5 US each in 1971, and for a cost conscious Japanese guitar pedal builder this was probably a deal-breaker. 

At the time there was an alternative used in high-end mixing consoles due to the limited gain-bandwidth performance of early IC opamps, which limited their ability to amplify weak signals such as microphones while keeping the full audio spectrum intact. Companies like Neve and API made opamps from "discrete" parts (ie old-fashioned transistors and resistors) on a little submodule, and these are still made today by and for recording equipment purists, despite ICs having long-since caught up.

So what did Roland do? Unlike the Bee Baa, which has the old-fashioned cascading transistor technology, the Funny Cat was based around the new opamp tech but used cheap-and-cheerful roll-your-own opamp modules. As transistor matching is important for opamps, it is my guess that individual modules needed to be quality tested for performance before they could be soldered in. 

There are good transcriptions of the main Funny Cat circuit around, and people have managed to sell clone PCBs of it, but the clones all use IC opamps which will not have the organic imperfections of the original. I believe this is so because the opamp modules do not appear to have ever been documented. Well, a fun Saturday evening later, that is no longer the case...

The circuit is very simple (though not as simple as, say, the Moog Modular CP3 opamp circuit). It is designed for low power usage and single supply operation, with a Class A output (no crossover distortion, unlike classic 1970s low voltage opamps such as the LM324 or LM358). Also, Roland made life more complex for themselves by putting the negative feedback resistor, usually an external component, on the opamp card. This means that the Funny Cat requires two different card types with different feedback resistors. It seems that Roland didn't trust the circuit to be stable with the feedback resistor on the "motherboard" and wanted to keep it very close to the transistors it bridged.

Anyhow, there goes a first look at a true original from Roland. While I love it, I have a feeling that some of the out-of-control behaviour with the Harmonic Mover is due to a dried-out low-range envelope capacitor - watch this space!

BBD and me

In my previous post about the Roland stringers, I mentioned that they all used the Reticon SAD512D chip, but the second iterations of all these designs (circa 1980) switched over to Panasonic chipsets. I thought I would mention a bit about why this happened, and why a dead SAD chip make you, well, sad.

Reticon was actually an early pioneer in the use of CCDs, both in BBD (Bucket Brigade)delays and video sensors. Although co-founder Gene Weckler wasn't part of the Traitorous Eight who left Shockley and co-founded Fairchild, he followed a similar path, working for Shockley straight out of university, then Fairchild, then onto his own startup in 1969.

Their products included the SAD (Sampled Analog Delay) chips, of which there was the SAD1024 with two independent 512 stage delay units, and the SAD512 which was basically a SAD1024 where one half of the chip had failed testing (a 1000-transistor chip in the early 70s would have been a biggish deal to produce in quantity. To understand how these worked, one cannot think of them like a digital memory chip, or even a digital delay line like the Princeton PT2399 (their distant descendant), where every location can be in use simultaneously. 

The reason these were called Bucket Brigade was that they consisted of a line of capacitors and electronic switches connected to each other. As a voltage came into the chip at one end it was progressively passed through the entire chip, but instead of being done so in a ripple arrangement, where one voltage is passed out and each other voltage shuffles forward one by one, half the storage locations would be empty at any given time, and each next cycle would either sample an incoming signal and shuffle existing locations forward by one, or output a delayed voltage and shuffle existing locations forward. This may seem inefficient, but it removed the need for complex circuitry to address each delay location individually, as well as ensuring that all locations moved forward simultaneously within a single clock cycle. Indeed, all one had to do was connect the gates of half the bucket transistors to a clock input, and the gates of half the bucket switches to another, and send alternating signals to each clock input. 

What the SAD512D did was no longer make the 512-stage delay line an afterthought, but shrink it down into a compact 8-pin package. It also included some circuitry to generate the alternating clocks from a single square-wave input, thus making the chip very guitar pedal-friendly. 

So sunshine and roses, right? Well, in 1977 EG&G bought Reticon, and it appears they really wanted them for their optoelectronic tech as all further refinement of the SAD BBDs seems to have ceased before Reticon was shuttered for good by its parent company decades ago. Enter Panasonic, who soon developed rival products and continued refining their performance and voltage requirements, and by 1980 had convinced Roland to switch over to their products, even though the Panasonic MN series BBDs always required two external clocks. Eventually both the SAD and Panasonic MN chips were discontinued in the face of digital tech, and became very expensive on the aftermarket. Eventually Uli Behringer's CoolAudio reissued the MN series chips, leaving the SADs high and dry and consigned to history's dustbin. What did not help either is that the SAD chips have a reputation for dying (ie my RS09) and this has further constrained supply and made second-hand parts suspect.

However.....

It appears that SAD512Ds are available again-not officially of course. The Chinese semiconductor market can be a wildwest of recycled scrap parts, sometimes labelled to be that what they are not, or even non-working chips which have been labelled to con desperate and gullible Westerners. Worse still are US Ebay sellers who import this junk and resell it offering it an air of legitimacy at a higher price. Still...when used SAD512D chips that are probably on their way out fetch triple-figure prices, it's tempting...

 

And indeed I was tempted. So after spending $A15 on AliExpress, this arrived...

The total lack of antistatic packaging was not promising.

And no mistaking the engraved printing for a new-old-stock 1980s manufacture (ink printed) chip. Still, testing time!!!! First up the testing rig:

Followed by removing the precious original from the pedal board for safe storage (after disconnecting the battery)

Then the unknown chip in circuit.

Results: both chips were non-functional. As static damage to both chips in transit is unlikely, one can only assume they were duds to begin with. Lesson learned. On to the repair!