SHOEHORNING A (SUPER) STRAT
PROCO RAT 2, REVISITED
01/23/11- In some movies, there's a scene where the protagonist encounters clues which seem to tell him to turn back... but of course he doesn't, because he wants to believe in a more hopeful interpretation of the clues. I'm revisiting the Proco Rat 2 after having installed a "cursed" Boss SD-1 overdrive circuit in my Ibanez RG2550Z. The SD-1 circuit I'd installed was found in a baggie, half-way "processed" (cut in half and jumpered) and abandoned, but I didn't remember why I'd abandoned it. I wanted to believe, because I didn't want to buy another SD-1 and go through all the work of cutting it in half, jumpering it and folding it. I found a couple wiring errors, thought "aha!", and managed to get it working... except for an oscillation problem when turned up full tilt with the guitar's pickups in standard humbucker mode. I tried bunches of construction/shielding fixes to solve the problem (short of replacing components), but when maxed out with the humbuckers, it always seemed on the verge of squealing: Sometimes it would, and sometimes it wouldn't. I also noticed that it was an awfully noisy circuit, with a lot of background hiss. After a couple weeks of this (and becoming very proficient at removing the neck, opening its guts, sealing it up, installing the neck and tuning) I finally cried "uncle" and decided to do something about it. This time, I started looking at other alternatives.
Enter the Rat The first alternative I investigated was the Fulltone OCD pedal. It has a lot of positive reviews and a loyal online following, touting its transparency, sensitivity to picking dynamics and overdriven amp-like distortion. Yadda, yadda, yadda. For me, its big attraction was its basic 3-knob/2 switch configuration, which held promise for onboard installation. It's a spendy pedal but not outrageously so, considering the range of over-the-top prices that most boo-teek pedals command... so armed with my faith in the reviews, I took the plunge. I wasn't disappointed-- it's a very well-behaved pedal with practically zero background hiss and a very full bass response, compared to the SD-1. This transparency makes it very suitable for a clean boost. It also has a greater range of fuzzy/flubby distortion at its far end than the SD-1. However, perhaps because of this, it seemed to lack the distinctive "bite" of the SD-1. I'm not a tone connoisseur and I don't particularly value transparency; I'm okay with pedals that radically change the guitar's natural voice (Hell, I even like Digitech's DF-7 Distortion Factory). While I was trying to make up my mind, I started playing around with the Rat 2 pedal I'd installed in my ugly-ass Roger Mayer modded Crybaby wah pedal: That turned out to be the aggressive voice that I'd been looking for, and the background hiss wasn't bad at all, considering some of the snarly tones that I was coaxing out of it.
In my original encounter with the Rat 2, I concluded that the SD-1 was a better choice than the Rat 2 for an onboard install because I envisioned problems with the Rat 2's 100K pots, and because the Rat 2 was an "unruly beast", with a lot of interaction between the controls. In retrospect, I may have been justifying a decision I'd already made since interaction between controls is a given in all OD/distortion pedals-- in fact, that's one of the rationales for putting the controls on the guitar, so you can quickly and easily change them to fine tune the sound. It's all very subjective stuff: I think at the time, I was interested in a more conservative, bluesy overdrive tone, so the Rat 2's radical range of tones didn't appeal to me. Tastes change, and nowadays I'm more appreciative of the extended range of distortion that the Rat 2 provides. At the other end of the distortion knob, the Rat 2 can sound pretty clean (between 1 and 1.25 on the dial, LOL). The Rat circuit seems to fit the personality of the Ibanez "Super Strat", with its pointy horns: High-gain and Floyd-Rose style whammy bars just seem to go together, IMO.
The Controls This time, I didn't consider the 100K pots to be a problem because I was willing to do without a tone control in bypass mode-- It's a good thing to have, but admittedly, I don't use the tone control that often. Therefore, I didn't need to come up with a ganged pot a make a Drive/Tone control, which greased the wheels during the planning stage. (Although I did come up with a solution once the project got underway.)
Another issue had been the Rat 2's final output (Level) pot. It's a 100K audio taper pot hanging out at the tail end of the circuit, which clearly isn't the same as the bypass mode's stock 500K audio taper volume pot. I tested a 500K pot in its place and it sounded fine, so it probably wouldn't have been an issue. However, since the circuit's background hiss is so minimal, I decided to use the stock 500K volume pot at the front of the circuit, before the on/bypass switch, and use a 100K trimmer to set a fixed maximum output at the circuit's tail end. The circuit is very sensitive to input level, so (IMO), the ability to change that is more useful than the ability to change/ground the circuit's final output level. The trade-off is that if the volume is turned down at the front of the circuit, the circuit will still output its operational noise/hiss. If the circuit were fairly noisy that would be a problem, and putting the pot after the circuit would make more sense; like I said, this is a fairly quiet circuit.
The Dreaded Knobs In my first encounter with the Rat 2, I immediately ran into a problem trying to remove the control knobs, destroying all 3 pots in the process; in this rematch, I didn't even try to pull them off. I used my Dremel's cutting wheel and a screwdriver to split the fuckers down the middle and peeled them off the knurled shaft to reveal why the knobs don't slide off: They're frickin' glued on!
The benefit of removing the pots intact is that they're the correct value and configuration: 100K audio/log taper, with knurled shafts. You don't have to buy them if you've harvested them intact. Although 100K audio taper 16mm pots aren't impossible to find, they're less common than 250K and 500K, and it can be difficult to find them with the knurled shaft, which is what you want if you plan to use Strat knobs.
Modding a Switch Pot Another benefit is that the small 16mm pots are the same size as the push-pull switch pots that are readily available to guitar modders from places like Stewmac. This means that if you need a 100K switch pot but one isn't available, you can use any value of switch pot, disassemble both pots and swap the carbon trace. [Note: to remove the carbon trace from the plain pot (unlike the switch pot), you have to remove the nylon/contacts fitting, which is secured to the aluminum shaft by a flared end. You have to destroy the shaft's flared end to get the fitting off, so you can't easily reassemble the plain pot after you've removed the carbon trace.] Amazingly, the carbon traces of my two pots were structurally identical, right down to the alignment notches on the sides that interlock with tabs on the metal sleeve. I'm glad it worked out: I like to have a redundant battery cutoff switch so I can leave the guitar plugged in without draining the battery.
Modding a Ganged Pot While I was at Radio Shack looking for trimmers, I found a 100K ganged stereo pot in the 16mm size, with the identical alignment notches on the carbon traces. Although some folks look down on the 16mm pots as junk, I haven't had any problems with them and their near-modularity is pretty useful. It was easy to pry off the bottom carbon trace and replace it with the 500K trace I'd swapped from the switch pot. I therefore had a ganged 100K/500K pot, which let me add a bypass mode tone control. Almost. The only problem is that the pots are not completely modular, so the solid shaft couldn't be switched out with a split knurled shaft. I'm a little neurotic about wanting Strat knobs on this guitar, so I drilled through a Strat Tone knob, fitted a grub screw, and grinded a flattened area on the shaft. This was much easier than modding a full-sized TBX pot to get rid of the center detent and loosen the feel (as I'd done for my SD-1 mods).
The Circuitboard The surprising thing is how simple and barebones the Rat 2 circuit is (1 op amp, 1 transistor, 3 diodes, 13 capacitors and 12 resistors), compared to the SD-1 circuit (1 op amp, 6 transistors, 7 diodes, 18 capacitors and 30 resistors). They're all full-sized components (not tiny surface mount), and fit on a single-sided circuitboard that can be trimmed down to 1-1/2" x 3" (without switches and pots)-- or 1-1/8" wide if you shorten traces that connect to the pots. The assembly quality (China, most likely) is pretty haphazard, with components not seated flush and aligned crooked on the circuitboard, and with uninsulated wire used for circuit input and output from the switch. However, despite what I'd read, it's a tough little sucker that's easy to work on, and handled the trauma of having the pots desoldered and pried off without traces peeling up.
Clearly, the prices these things command are not directly related to their actual production cost or cost of components (although the enclosure is pretty sturdy). It's kind of irrelevant though since the price is driven by consumer's demand, not manufacturer's effort. The SD-1, for all its superior manufacturing, design technology, and parts count (and it isn't even a modern pedal design) sells for about half the price. Boutique pedals with manufacturing technology similar to the Rat 2 (but assembled with more loving care), often sell for many megabucks more than the SD-1. The bottom line is that demand determines price, and demand is driven by the results and the consensus of popular buzz that the results create. If there's a generalized lesson here, it's that guitar stuff does not demand cutting-edge technology, and most of the stuff that many people like was invented many decades ago. The popular Fuzz Face has even fewer parts than the Rat, and the construction quality of the pricey sought-after versions looks like prototype-quality... like many of the holy grail stompboxes of yesteryear. A transistor with better operation specs doesn't necessarily sound better. A circuitboard doesn't need to have neatly placed components and pretty solder joints to do its job. Mysterious stuff, this.
Conventional wisdom has determined that the Chinese-manufactured Rat 2 is inferior to the old version (naturally, since it's not available anymore), and that the op-amp must be replaced with an LM308N IC. Although (as I said) I'm not a tone connoisseur and couldn't hear any appreciable difference between my modded Rat 2 and the off-the-shelf one, who am I to argue? It's fun to mod. There are other mods out there that you can find through Google that can help you find whatever holy grail tone you're after (or that someone else determined was a holy grail tone that you should seek).
The Switch Most stompbox circuitboards are pretty easy to figure out for transplanting since they're basically input/output, controls, power and the black box circuit. True bypass switches can make it a little more complicated since the inputs and outputs don't go directly from the jacks to the circuitboard. To identify the less-obvious circuitboard functions (input, output, ground, & power), it's necessary to study the switch, since that's where all the hardware (jacks and circuitboard) connects. This is a 3-pole, double throw switch, but its 3 x 3 matrix makes figuring it out a little more difficult since a quick visual inspection is ambiguous: It isn't clear which terminals are connected when the switch is clicked. There's an unused terminal that you can use to determine continuity (with an ohmmeter) between adjacent terminals in either of the two switch positions (it's 3 ganged switches, and they're all switched the same direction at the same time). Once you've figured out which are the 3 separate switches, the rest is pretty easy to figure out.
Although it doesn't have to be wired this way, in mine the center terminal connects the ground (uninsulated) to a thin white wire when the effect is on-- this connects the ground to the LED through a resistor on the circuit board, which completes the circuit, and the LED glows. When doing the onboard conversion, you don't need this LED (since it just eats power), so you can omit this connection and the LED won't light up. Every milliamp saved equals longer battery life.
The remainder of the switch can be copied (more or less) verbatim and wired to the double-pole, double-throw toggle switch in the guitar. Naturally, the specific connections in the guitar (output from pickup selector and the volume knob) will have to be substituted for the jack input, depending on how you want it to work (volume before or after the circuit). If you wire a passive tone control, you can connect it globally at the volume pot, or at the switch so that it only affects the bypass mode.
The Jacks These are pretty easy to figure out; As usual, a stereo jack is used to disconnect the battery's ground wire when the guitar is unplugged (or maybe it's the amp in this case? I've forgotten.). The 9-volt battery is tied to the external power jack (a mini 1/8" phone plug, which is not a popular standard these days)-- the most important thing is to figure out which is the "hot" lead and which is the ground. Oddly enough, the "hot" lead connects to the circuit board with a black wire (which usually indicates ground), and the yellow lead from the circuit board is ground. The ground's circuitboard trace circles most of the edge of the circuitboard, so you can tap from several places, including the "Level" pot pad.
Installation Before opening up the RG2550Z (again), I tack soldered the jacks and battery to the circuitboard for a final test, just to make sure that it still worked. You never know, and it's best to find out while the circuit is outside the body. Fortunately, it still worked, so it was time to tackle the long-awaited installation. Gutting the old circuitboard and cleaning the guitar's innards was very gratifying since the wiring tends to get uglier and uglier the more you work on it to fix problems. With it cleaned out, I did a test fit of all the parts just to make sure that everything fit and that the guitar's pickguard would fit back on. Even though the board is very narrow, it's a little bit longer than the folded SD-1 board was. I didn't want to route any more wood, but if necessary, I would have. Again, it's best to find out about this before the circuit is soldered in the body. Fortunately, everything fit, so soldering could commence. The last phase went so quickly and smoothly that it was somewhat anti-climactic.
The Test Drive Even though I'd played through my wah-spliced Rat many times before, it's always been as a set-and-forget stomp box effect. Having the knobs at your fingertips as you play is a very different experience, especially for this circuit since it's so much more "schizophrenic" than most OD pedals (although "muliple personalites" might be more appropriate; a kinder description would be "versatile"). Easy access to the knobs encourages you to explore the extremes of its behavior.
Exploration reinforces several observations, one of which is that minute changes in the pot settings can make a huge difference, and that the interaction between the input volume, distortion, and filter controls can radically alter the way the controls work. This makes for an interesting time learning its behavior. A few of the extremes seem pretty unusable (IMO), like the deep, deep underwater stuff and the super screechy fuzz that mushes everything together and clips the input of anything that comes after it.
The Distortion control spans clean, overdrive, distortion, and near-fuzz, although the lion's share goes to distortion. Dialing it all the way back gives a clean sound that can be a fair match for the bypassed tone, but with extra treble if you dial up the filter. Once you dial out of the clean zone (it doesn't take much), the output level rises and the notes grow a fuzzy edge. As you raise the distortion, the bass level rises, but the output level doesn't change much; it just gets fuzzier, more clipped sounding and with a less distinct attack.
The circuit boosts the treble into the razor-sharp territory and the Filter control acts like a treble-cut tone control (I wired mine so that it sweeps in the same direction as a standard tone control). It seems to me that the circuit doesn't cut treble as fully as some stock guitar tone controls do, noticibly when the dirt is dialed out. Like most tone controls, it has an effect on the output level, except waaaay moreso: It's probably good for taking leads with a huge treble boost, which really helps you cut through if you're playing in a loud band.
I put the volume control (without a treble bleed capacitor) before the input to the circuit, so it too has some tonal impact in addition to its effect on the circuit's level of distortion. With the pot dialed back, some treble disappears which can lead to some "cocked wah" tones, and with a high level of distortion, I've heard some vowel-ish harmonics. It's easy to set up so that riding the volume will take you from clean to a preset level of overdrive or distortion... and if you decide that you want just a little bit (or a lot) more, it's just a knob-tweak away.
I imagine that the main drawback of an onboard Rat would be that the circuit offers so much seemingly random tonal variety between the interactive controls that it encourages futzing and knob-wanking. Unless you know the circuit's behavior fairly well, you may not be able to dial in a desired sound as quickly as you could with a more predictable and narrow-range OD pedal: It's easy to overshoot and land in some nasty screechy stuff.
This circuit seems to have more razor-like screech than most overdrive pedals, and the curious way that bass increases as you raise the distortion level can make the circuit sound thin at some good "bite" settings when you play at a low volume, or mushy if you dial back the screech and increase the distortion when playing loud. It may be necessary for you to adjust the amp's EQ controls to tame that raucous treble and set a preferred level of bass and midrange. However, would those EQ settings work well for the bypassed sound, and at different volume levels? One of the reasons that I like Digitech's Distortion Factory is that it has an extensive set of EQ controls (although they're squeezed into the a tiny space, with stacked pots). Unfortunately, it's not suitable for an onboard circuit since it's got bunches of knobs and consumes lots of power. Nevertheless, it's tricky stuff since loudness greatly affects the perception of bass: What may sound thin at low "bedroom" volumes sounds a lot fuller when you crank up. (That's why home stereo amps sometimes have a "Loudness" switch.)
Ponderings Naturally, it would be great if you could do all the fine tuning on the guitar itself, but that's one of the tradeoffs of onboard circuitry: You get immediate fingertip control of certain parameters, but there isn't much real estate for very many parameters unless you go knob-happy. The Rat circuit is pretty flexible, but ultimately depends on the amp to deliver the goodies.
An often-mentioned use for overdrive and boost pedals is setting up the amp for near breakup with the pedal giving a mild, fairly uncolored boost to kick it over the edge into natural tube overdrive; however, if you can get channel-switching overdrive and distortion from your amp at the tap of a footswitch or by riding the guitar's volume knob, why bother with a stompbox pedal? All overdrive stompboxes are just electronic circuits, limited by their enclosure size and their location on the floor. There's nothing that prevents them from being integrated into an amp, where controls can be separated from footswitches, and where there's more real estate on the panel face for adding controls for all sorts of things; controls that are accessible while you're standing instead of squatting to tweak tiny controls squeezed onto the face of the enclosure. Rack-mount systems address this issue and retain modularity, but are perhaps overkill and are less accessible to the non-touring hobbyist and the semi-pro who buys pedals one at a time.
Modern amps have many more bells and whistles than the old school Fenders and Marshalls. With those amps, any distortion was a byproduct of the circuit design and how the amp was used or abused, so self-contained effect pedals were the only way to go if you wanted something extra that the amp by itself couldn't deliver. However, with modern amps like the Mesa Boogies and Fender's Super Sonic (for example), you may have to make a choice between whether to use the amp's built-in distortion options, run external effects into a clean channel or an effects loop, or accommodate the stompboxes somehow, just because you own them. It's waaaay more complicated now because of all these options and choices.
The point is, they're all just different interface options with some overlap, but with distinct features... and they coexist nicely. The stompbox interface offers something that amplfier distortion don't- the ability to easily customize the mix of circuits and reconfigure the signal path. They're kind of like a breadboard prototyping platform. Modern amplifiers offer a self-contained solution with many control options, but they're hard-wired in (although some are programmable through a computer). Multi Effects boards are sort of a hybrid-- they're self-contained floor units, but programmable with a wide but fixed set of options (that can be modified within limits through firmware updates).
Onboard distortion effects are a one-trick pony but allow you to quickly and easily adjust essential stompbox circuit parameters on the guitar while you're playing, a unique and useful feature not available in stompboxes or amplifier distortion. Line 6's Variax greatly expands this concept, but is still constrained by the fact that there's only so much space on a guitar to put controls. This fact-of-reality also applies to guitars that interface with synthesizers and guitar processors through 13-pin outputs: There's so much adjustment potential, but you can access only a small fraction of it from the guitar interface while you're playing. Roland's VG-99 system (and Line 6's POD bean design) deals with this by being mountable on a stand so that you can reach over and tweak while you play, while having jacks for an external footpedal interface. Messing with all the cables and complexity can be a bit much, but it's the price of being able to tweak everything to your heart's content in a relatively immediate way. There are times when I just want to plug straight into my Twin Reverb and play; in that case, having onboard distortion available on demand is just gravy.