Origins of the SPDT and DPDT foot switch

[yeeshkul]

SPDT foot switch for a pedal was used for the first time in 1962 for Maestro Fuzz Tone, i am i right? Did they use a switch they had to have manufactured for that purpose or had it been a commonly used device by then? I would have the same question about later DPDT - was a DPDT foot switch developed for audio purposes or not? I am talking about foot switchies, not  slide or toggle switches. Thank you.

[Taylor]

When I buy Carling-style SPST stomp switches, they come in a Chevy (or some other car manufacturer) box, and are sold on ebay motors. These kinds of switches were used in cars in earlier times - my '75 Ford LTD had a stomp switch just like the ones we use, to turn on the highbeams. Never understood the point of this until I spent some time in rural VA, where there are no street lights, so you keep your highbeams on all the time, until somebody's coming the other way; you stomp so you don't blind the guy, then stomp again to see.

They are also used in old elevators - my last building in Baltimore had one like this as the emergency stop button - and in boats for various functions.

These switches were not designed for audio, and still aren't really. IMO better solutions than the 3PDT exist now.

[Processaurus]

Industrial vacuum cleaners where another intended use of those switches originally.  I used to drive a van with the stompswitch hi beams, love it.

I believe the 3pdt was actually intended for low voltage audio, not high voltage, like the relatively unreliable Carling switches.  I believe Fulltone initially had them developed, then EH invested more heavily in them, that's how hobbyists and little pedal companies came to be able to use them.

[yeeshkul]

Guys thanks for answering, that is exactly what i was looking for!

"IMO better solutions than the 3PDT exist now."
Can you gimme directions please? I am just trying to put together all kinds of switchng - all and pros, cons and so on.

[R.G.]

Taylor is correct. The footswitches which were and still are used for effects bypassing were never designed for low or line level audio use.

Instead, they were physically robust switches which were used for switching power on and off in automotive and industrial uses. If you look at the inscriptions on the switches, you'll usually find that they say something like  "125V 5A, 250V 3A", indicating that they are rated for power-line voltages and currents.

The reason this is important is that the signal level plays a big part in the reliability of switch contacts. Metals corrode to some extent in the viciously corrosive oxygen/water/salt/sulfur atmosphere we live in, with the rare exceptions of the precious metals like gold, platinum, and to lesser extents the other metals of the platinum group. Switch contact design is the province of the mechanical engineer working in concert with metallurgists. Electrical engineers are somewhat useless at the design of hard-contact switches, and are users much more than designers in this arena.

Metal oxides and other compounds such as sulfides and the like are either insulators, partial semiconductors, or resistive, none of which is what you want in an off-on electrical switch. So switch contacts are designed to either (1) never corrode, by the use of gold, platinum, etc. metal surface layers, (2) be self-wiping in action, so the mechanical movements actually scrub crud off the surfaces of the contacts as the switch is operated and/or (3) be redundunt, so that each switch contact has multiple points of contact in case one or more fails.

The signal level is important because high voltages and currents break through and burn away crud layers. With really high voltages, thousands of volts, it's quite difficult to get any switch to turn off because the electricity leaps through the surrounding air. KV-rated switches are often either oil or vacuum filled for the higher breakdown voltage or include things like arc-quenching magnets to "blow out" arcs. At very low levels, the voltage of the signal is too low to burn/break through even modest surface contaminations, so the contacts must stay pristinely clean or the switch won't make. This is why you find some relays rated as power relays, and others rated as "telephony" or "low-signal" relays. These have special contacts and construction to not crud up in air, be self wiping, and have both multiply redundant and/or high point-contact pressures to break through oxides.

In pedals, the early makers adopted the physically robust automotive and industrial switches which would not be crushed/broken (at least not immediately!) by stomping on them. This was a clear misuse of these switches, and the contraction of footswitches down to the Carling 316P in the early-modern effects era reflects that the Carling was the only commonly available power stomp switch that happened to be kinda/mostly reliable for effects. In recent years, Carling moved all its manufacturing out of the USA to survive, and recent Carlings are of noticeably lower quality and longevity in effects.

These things are absolutely not designed for audio. They were co-opted for use in pedals because they didn't get crushed by repeated stomping, and kinda/mostly worked when misused this way.

I believe the 3pdt was actually intended for low voltage audio, not high voltage, like the relatively unreliable Carling switches.  I believe Fulltone initially had them developed, then EH invested more heavily in them, that's how hobbyists and little pedal companies came to be able to use them.

I was there for this event, so I do happen to know this history. 3PDTs, and even 4PDTs exist as industrial switches with pushbutton alternate action, and did so before they became common for effects. But 3PDT stomp switches were rare. It wasn't all that easy to find even DPDTs. It will be difficult for people who don't remember a time before the internet to imagine, but at one time, finding a supplier in quantity of any industrial parts was a specialist's field. It was hard to find suppliers and harder still to find good ones, as the information simply was not available until you already knew who to call to find them.

3PDT switches were a rarity, but they did exist. I sold 3PDT stomp switches to effects hackers through my web site before Fulltone and the ones that followed. The ones I sold were labeled "Alco" and cost in the mid-teens of dollars if I bought them 50 at a time. I sold them at a $5 profit per switch. I stopped this when I realized that it would have been better to just sit and burn my currency than hold the inventory.   These did work, but they were less mechanically robust than the really needed to be, so they wore out mechanically faster than you need a stomp switch to do. They were rated for medium voltage use, not simply power-line use, so they were better and longer lasting electrically than Carlings, but shorter lived from the stomping.

They were actually made by Fujisoku as I remember. I tracked them back to the maker, asking for better prices and was disappointed when Fujisoku came back and told me that they would not warranty their standard line for stompbox use. I was reminded of the First Rule of Holes: when you find you're standing in a hole, stop digging. So I decided not to continue with 3PDT switches. At about this time, Fuller went at the problem another way. I have no direct knowledge of this, but have heard rumors of him asking a switch maker to combine the mechanical bushing/actuator of the Carling stomp switches with the contacts/action of the Fujisoku or similar. I don't know how that worked, whether the stories are true, or whether he was provided with a stock, but even rarer version of some other standard switch.

While that was happening, I came up with the Millenium Bypass.

Fuller sold 3PDTs, other people tracked them back to the makers or had other switch makers do similar or knock-offs, and the prices on 3PDTs started falling to their current level. It is possible that the 3PDTs you get today are specialized for guitar effect work, as that is the single biggest market for what is a very old technology and enough distributors have spent the time to find manufacturers that special ones may be available today. I don't know about EH's investment, or other possible work on them.

For a number of reasons, I use buffering and CMOS switching in everything I build for myself. It sidesteps the issues with hard-contact switches and is cheaper than even today's prices on 3PDTs.

"IMO better solutions than the 3PDT exist now."
Can you gimme directions please? I am just trying to put together all kinds of switchng - all and pros, cons and so on.

Let me add to that, I also think that better solutions to the 3PDT exist. I documented them on the geofex web site long ago. If you simply must use hard switches, every electrical contact is a possible failure point so you should MINIMIZE the number of switch contacts, not maximize them. Mechanical parts will always wear out, and the higher precision they are, the sooner this happens with you are stomping on them. So I think the DPDT plus Millenium Bypass is a better compromise in terms of reliability and cost. But people who can't get a two transistor circuit to work are stunned at the complexity of adding another half-dozen parts to get an LED to work. It's not a totally unreasonable fear when you think where they're coming from.

Actually, buffered bypass and CMOS switching is much cleaner and more reliable electrically. It also lets you use ONE mechanical contact, and spend your efforts on making that reliable. By actual experience, this is far more reliable.

[alparent]

Actually, buffered bypass and CMOS switching is much cleaner and more reliable electrically. It also lets you use ONE mechanical contact, and spend your efforts on making that reliable. By actual experience, this is far more reliable.

Do you talk about this on you site? I found info on the Millennium but not on this?

[alparent]

Got it! http://www.geofex.com/Article_Folders/cd4053/cd4053.htm

[smallbearelec]

I was there for this event...

I was also there, though from a different perspective from R. G.

Mike Fuller had spent the typical god-awful amount of money with a Taiwanese switch manufacturer to get this part made. It was an OEM item, made exclusively for Fulltone. The first lot was not reliable. At the time, Mike described to me having to take apart a few of them to figure out why they were failing. Fortunately, MF had both the intestinal fortitude and the perseverance to hammer the maker into working out the production problems. I suspect that the need of the manufacturer to avoid losing face may also have been a factor. Once the product was consistent, Mike had a nice monopoly for awhile. He was selling them through me, E-H and others, and began to get his money back.

I know that what became known as the "Blue 3PDT" was first made by the same factory that made the Fulltone switch. It would have required different tooling, not just because MF had an agreement, but because the body is a different plastic. I don't know whether E-H paid for this or the maker did. I bought the Blue switch initally from E-H, was later introduced to the maker by a couple of the boutique pedal-makers...the beginning of a beautiful friendship.

SD

[R.G.]

Ah. That fills in some holes. Thanks - I didn't know any of that.

And I don't know whether the contacts/mechanism of the Fuller 3PDT or the EH, or the ones now have been specialize for low signal level. There's certainly been time for that to happen. But they are probably better than the Carling and knockoffs of the Carling were.

[Mark Hammer]

3PDT switches were a rarity, but they did exist. I sold 3PDT stomp switches to effects hackers through my web site before Fulltone and the ones that followed. The ones I sold were labeled "Alco" and cost in the mid-teens of dollars if I bought them 50 at a time. I sold them at a $5 profit per switch. I stopped this when I realized that it would have been better to just sit and burn my currency than hold the inventory.  These did work, but they were less mechanically robust than the really needed to be, so they wore out mechanically faster than you need a stomp switch to do. They were rated for medium voltage use, not simply power-line use, so they were better and longer lasting electrically than Carlings, but shorter lived from the stomping.

You can see why Boss and so many other went to the momentary foot-treadle arrangement they did.  Though I imagine it was a good deal cheaper for a manufacturer buying in bulk, $22 Canadian 1993 dollars was not uncommon for a stompswitch, and obviously a deterrent to jumping into DIY wholesale.  When I bought my Shin-Ei Fy-2 fuzz in 1993, I bought it precisely because the price of the pedal ($20) was less than the price of buying a switch at that time!  I bought the pedal FOR the switch I could cannibalize.  The circuit was simply a perk, and it sat in my parts bin for a decade until someone provided some information to help hooking it up.

The stompswitches on older pedals from the late 60's and early 70's are frequently "wobbly" when you find them.  This is one of the reasons why I've blathered on, over the years, about where one situates the switch in the chassis, and about doing what you can to facilitate true up-down piston motion when stepping on them by keeping them as low as possible, and in a position that favoured less angular foot pressure.  My sense is that abuse encountered by angular pressure would stress the housing and plunger.

Maybe it's just me, but the weakest link in the switch would seem to be the little plastic arm that pushes the banana-shaped rocker contacts inside.  It takes a whole lot of heat to melt the plastic housing. The rocker contacts may get greasy, but they are essentially indestructible**  The plunger and the spring don't break, and the metal tabs don't get enough of a workout to be compromised.  But the plastic arm that makes the contacts move can break if you look at it sideways.

**Just as an aside, I bought some momentary X-wing DPDTs by accident last year.  While I could imagine some potential uses for them, I didn't have any desperate need for those applications at that time, so I took one apart just to see how it worked.  Lo and behold, the only difference between it and a standard latching DPDT was the shape of the rocker contacts.  So, just for the hell of it, I grabbed my needle-nose pliers and reshaped the contacts to be like the latching type.  Bingo!  Latching DPDTs!

[R.G.]

This is one of the reasons why I've blathered on, over the years, about where one situates the switch in the chassis, and about doing what you can to facilitate true up-down piston motion when stepping on them by keeping them as low as possible, and in a position that favoured less angular foot pressure.  My sense is that abuse encountered by angular pressure would stress the housing and plunger.

Absolutely true. One reason we went to plungers and momentary switches is that by far most of our warranty and repair work was footswitches. We sometimes got in one that had been "flat-topped" - it happened often enough that we had a special word for it. This was when the stomp switches and knobs were more or less all broken off by a sliding stomp that broke off most of the knobs and switches.

Our rate of return/warranty on the plunger/momentary setup is as near zero as you can get with anything that gets stomped on.

[zombiwoof]

edit...

"While that was happening, I came up with the Millenium Bypass."

edit

I thought the Millenium Bypass was your version of the bypass used in the RAT pedals?.  That's what I remember it saying on your GEO website.

Al

[R.G.]

I thought the Millenium Bypass was your version of the bypass used in the RAT pedals?.  That's what I remember it saying on your GEO website.

The basic idea of using the output resistance to turn on an LED was there in the Rat. What's unique is the use of the almost constant current reverse leakage of a diode in combination with a FET to make this work with output resistances up to as much as 1M. The Rat was limited in how much resistance, and that was fairly low, about 10K as I remember. The Millenium and its extensions, by using the very high input impedance of the FETs compared to even darlingtons to make this distinction, and to eliminate the problems in working with resistors over 10M as the Rat needed.

It's a little more than my version. It does things the Rat bypass can't.

[PRR]

> SPST stomp switches, ...in a Chevy ...box .... were used in cars in earlier times - ...to turn on the highbeams.

That was THE hi/lo headlight switch from the 1930s to about 1980. I still miss my 1979 BlunderBird, and still stomp the floor when headlights come over the hill unexpectedly.

BTW: it is SPDT, as you might expect from the function. Of course you can ignore the extra throw if you just wanna short/un-short a trem or reverb tank.

These things used to be very sturdy. As cars got VERY old you might have to replace it once.

There used to be several manufacturers (so GM and Ford could play one against the other for lowest price). Demand is now tiny, there's really only one distributor, and I expect they have out-sourced production to some faraway low bidder.

I thought someone remembered car starter buttons on the floor. These were not (originally) switches. They directly pushed the gears together, then put the big copper disk on the copper studs to juice the starter motor. I think I have seen such systems, minus motor, re-purposed for other high-current momentary switching. (A friend just saw a light airplane with this same scheme except you pulled a lever under the instrument panel.)

> They are also used in old elevators - ...emergency stop button

Mechanical emergency STOP buttons for heavy/dangerous machinery are a specialty, go far back in history, will break the WHOLE power of a large machine, and are VERY expensive. Industrial STOP buttons are large red mushroom-head and won't break in a REAL panic (you see your buddy being sucked-in). Elevator buttons may be more stylish and maybe not quite so rugged, but cost even more. Many of these things are being replaced with large heads over teeny buttons which switch milli-power control circuits.

The Carlings were used in lesser chores. Vacuum cleaners, blowers. They were handy when Fender et al added "effects" to guitar amps and wanted a hands-free remote control. AFAIK they were always the line-voltage contacts, even when switching 0.005V reverb signal. They usually lasted longer than the warranty, sometimes much longer. Contact tarnish is a problem, but the high CLUNK factor may shed oxide fast enough to work most of the time.

There was a line of push-pull switches based on telephone patchbay jack mechanisms, bushing frame and assorted fingers. (And Switchcraft has/had a pushbutton built on their standard 1/4" jack.) Strowger and ESS killed the telco patchbay business and I have not seen such products for 40+ years. Shame, because these WERE made to handle low-level signals.

Other than telco jack/switches, I do not remember any "complicated" heavy-duty switches. Many-pole/throw switches were delicate. If you need "rugged", or if you need frequent replacement, you use a simple rugged/cheap switch at the operator and use relays to do the many chores. I have a 1953 book with a few examples, but it is stinky so it is out in the garage and it is rainy tonight.

A rugged "momentary" switch is tough enough. "Alternate action" adds a whole nother level of monkey-motion to add cost and break a lot.

Has anybody dissected a steering-column hi/lo headlight switch? I imagine they are going toward logic control (most Japanese cars already use headlight relays) but I think my 2002 Honda uses an alternate-action mechanism. You'd have to get these awful cheap to justify the labor to mount the works, shorten the shaft, and add a pad to stomp on.

I was a little startled to see that a 3P3T switch was now readily available; and now we know who to thank.

[edvard]

I remember balking at the $15-20 prices of DPDT's back in the day.

and now we know who to thank.

Indeed.

These kinds of switches were used in cars in earlier times - my '75 Ford LTD had a stomp switch just like the ones we use, to turn on the highbeams.

I always wondered if automotive floor dimmer switches could be had at a reasonable price from the auto parts stores, but never researched it.
I guess it turns out at least they were available; dunno about the 'reasonable price' part...

As a side note, one time I found some reasonably-priced SPDT's at a surplus store and bought 4 or 5 of them.
The only time I ever boxed up a FuzzFace the need for true bypass was immediately apparent, so after much deliberation, I mounted two of those switches as close as I could side-by-side and wired them like a Double Pole, being VERY careful to stomp BOTH of them cleanly whenever I switched.  

Over the course of a few years I discovered that I hardly EVER played clean, so my habit became to box up dirt circuits sans switch and simply make judicious use of my guitar's volume control, which made my personal boxes even cheaper.

[joegagan]

this is a great thread. thanks, steve and rg for documenting some of the history.

rg, you've convinced me. your approach makes total sense.

[PRR]

> I always wondered if automotive floor dimmer switches could be had at a reasonable price from the auto parts stores

Part numbers and prices.

http://www.diystompboxes.com/smfforum/index.php?topic=59534.msg666233#msg666233

[drewl]

Other places I've seen the stomp switches is in footswitches for industrial machines, sewing machines, some in different test equipment through the years.