KreoPensas
Well-known member
Don't use a relay bypass then.
SOLVED
SOLVED
Relay Bypass – do I really need one?
- Thread starter aquataur
- Start date
Hopefully not too tangential, but I’m curious about durability in high-use scenarios. For myself, I use 3PDT unless I want some intelligent switching functionality. No big deal.
But what about a touring musician that plays 100 nights a year and may stomp on that thing 10 or more times a night? Sure, that’s only 1000 clicks a year out of a rating of 30k. But I’m curious if anyone can speak to whether relays are more likely to outlive an equivalent build with a 3PDT.
But what about a touring musician that plays 100 nights a year and may stomp on that thing 10 or more times a night? Sure, that’s only 1000 clicks a year out of a rating of 30k. But I’m curious if anyone can speak to whether relays are more likely to outlive an equivalent build with a 3PDT.
Big Monk
Well-known member
@aquataur
Just a friendly heads up: Forums are great places to talk about DIY, gear, technical stuff, etc.
You seem mildly confrontational. You are not going to find anyone here gung ho either way for relay vs. mechanical switching.
They both have thier applications and I don’t believe anyone here is going to make a hard argument against either of them.
Yet you seem to be coming in guns blazing like someone came to you with a contrarian POV.
It’s YOUR thread. You set the tone for how the dialogue will proceed. Everyone is going to follow suit based on that.
I don’t believe anyone here feels intensely either way.
Just a friendly heads up: Forums are great places to talk about DIY, gear, technical stuff, etc.
You seem mildly confrontational. You are not going to find anyone here gung ho either way for relay vs. mechanical switching.
They both have thier applications and I don’t believe anyone here is going to make a hard argument against either of them.
Yet you seem to be coming in guns blazing like someone came to you with a contrarian POV.
It’s YOUR thread. You set the tone for how the dialogue will proceed. Everyone is going to follow suit based on that.
I don’t believe anyone here feels intensely either way.
vigilante398
Authorized Vendor
Are you by chance a user of The Gear Page? Your postings have a very TGP-ish vibe.
KreoPensas
Well-known member
Some people ask "is it The Best"
Meanwhile, I'm over here so tickled over the aesthetics that I'm playing with the switch for a half hour, listening to the tiny *tic*.
Edit: This is the *real* value here.
Meanwhile, I'm over here so tickled over the aesthetics that I'm playing with the switch for a half hour, listening to the tiny *tic*.
Edit: This is the *real* value here.
Last edited:
Random thoughts… I prefer soft-touch switches, either for use with a relay bypass system, or even a Boss style electrical switching scheme. But that’s my personal preference. To those who prefer mechanical 3PDT I say cool! (Unless they don’t post gut shots of their builds, that’s not cool! 
)
One thing on the 30k cycles for typical mechanical 3PDT switches though. I believe that number isn’t a guarantee so much as a MTBF, mean time between failure. Meaning, there’s probably actually a distribution of time-to-failure, probably bell-curve or similar. So just as a wild guess, I’m thinking most probably have a 20-40k typical cycle lifetime. But also the manufacturer probably assumes ideal soldering conditions, and anything short of that likely further reduces lifetime.
And for what it’s worth, go over to diystompboxes and read RG Keen’s numerous posts on the reliability - or lack thereof - of mechanical 3PDT switches. Besides his generous contributions to the DIY community, he’s actually worked directly in the commercial pedal business. If I remember correctly, he basically said something to the effect of virtually all failures were due to mechanical switches.
My other way of looking at it is similar to the soldering thing, in that when the manufacturer establishes reliability numbers, I presume they assume operation under ideal circumstances. I.e. you press directly down, with just the right amount of pressure, in a smooth, controlled manner. But in reality, we’re smashing these things with our feet, possibly during the heat of a gig. Inconsistent pressure, inconsistent angle of attack, etc. If you’re gigging regularly, that also means operation under diverse environmental conditions.
Maybe the switches are tested under more adverse conditions… but usually stuff tested like that is marketed as “ruggedized” or “military grade” or whatever.
Another way I think about it, simplicity versus complexity: I think there’s an argument that the 3PDT switch is more complex, because it’s combining two functions into one device: the “user interface” and the circuit switching. Whereas relay based systems are arguably less complex, because of separation of concerns. I’m a Unix command line guy, I like single tools that do exactly one job but do it well.
I think that “probability of failure increases with the square of number of components” rule of thumb has to be used in context. I mean, if you take it literally, consider a modern CPU with 10s of billions of transistors - how are they as reliable as they are in the face of that rule?
In software development, we also prefer simplicity. It’s generally less error prone, and easier to debug when there is an issue. But eventually, you bundle that complexity up into a library. Now, if you write a short, simple program that uses a complex (but long lived, time tested) library, is the program itself simple or complex?
I think the analog to the hardware world is the integrated circuit. You could make a simple line buffer with a single transistor or use an opamp. Is the transistor better strictly because it’s simpler? In some cases, depending on design goals and other constraints, it could be better… but in other scenarios the opamp would be better, despite the “complexity”.
As such with relay or electrical bypass - if you don’t buy my “separation of concerns” notion, and stand by the idea that the 3PDT is simpler, I still think it’s a stretch to call relay/electrical bypass “complex”. It’s a long-solved problem using commodity components exactly per their design. Nobody’s designing bypass schemes with rare/exotic components, or using parts in an “off-datasheet” manner.
All the above is a big part of why I personally prefer relay or electrical bypass schemes. And I simply prefer soft-touch momentary switches. But I’m certainly not looking down my nose at anyone who takes a different route. My preference is indeed more complex in terms of build time and component sourcing. And despite what I wrote above about 3PDT reliability, I’m quite sure that I’m never going to actually wear out such a switch! I’m not a pro, and even if I was switching my pedals 50x/day, every day, I’ve built so many pedals that I have backups for my backups!
Edit: I might be wrong about my 3PDT MTBF assumptions. Using this 3PDT Pro switch as an example, the verbiage is "Mechanical Life: 30,000 MAKE-AND-BREAK CYCLES". Not sure if that means MTBF as I assumed, or it implies rated for minimum 30k cycles? Also, the heat resistance is impressive: "We dipped these half way up the plastic casing in our wave solder bed for 15 seconds with no deformation and perfect continuity tests. Lugs stay firmly in place even under extreme heat." I suspect you could in all likelihood generally get quite a bit of mileage out of these switches.
Also, comparing to a momentary SPST (such as typically used by relay or electrical bypass schemes), such as this Pro-Grade SPST Momentary, it says "50,000 mechanical cycles; 6,000 electrical cycles". Not sure what that means exactly... why would you use it only mechanically, but not electrically? And if the actual reliability is dominated by the lower 6k number, that's disturbingly low!
However, I do think the two-wire momentary SPST is generally easier to replace. It's almost a wash compared to 3PDT with most PedalPCB boards, especially if you use the breakout board - then you only have to re-solder 6 wires. Three times the work of a 2-wire SPST, but you'll probably spend more time on setup and cleanup either way. And if you use modular connectors (like JST), and carry a spare, then it's theoretically field-serviceable at the gig.
On the other hand, some DIY effects, I won't mention any names cough cough Aion cough cough will put actual circuit components on the switch breakout board. Which means you either have to un-solder the actual switch (very painful), or get a whole new board, or try to DIY hack the equivalent circuit components.
It's interesting to me that the reliability for SPST momentary switches isn't much higher than 3PDT (or even significantly lower, if that 6k number is relevant to us). Ignoring the numbers I wrote, intuitively the momentary SPST should last longer because it's inherently simpler. I mean you could rig up a DIY momentary SPST with a couple paperclips or lengths of wire in a pinch. It's a spring and contacts. I wonder if that 6k number assumes high-voltage switching, where you're likely to have some arcing and therefore fouling of the contacts over time?
)One thing on the 30k cycles for typical mechanical 3PDT switches though. I believe that number isn’t a guarantee so much as a MTBF, mean time between failure. Meaning, there’s probably actually a distribution of time-to-failure, probably bell-curve or similar. So just as a wild guess, I’m thinking most probably have a 20-40k typical cycle lifetime. But also the manufacturer probably assumes ideal soldering conditions, and anything short of that likely further reduces lifetime.
And for what it’s worth, go over to diystompboxes and read RG Keen’s numerous posts on the reliability - or lack thereof - of mechanical 3PDT switches. Besides his generous contributions to the DIY community, he’s actually worked directly in the commercial pedal business. If I remember correctly, he basically said something to the effect of virtually all failures were due to mechanical switches.
My other way of looking at it is similar to the soldering thing, in that when the manufacturer establishes reliability numbers, I presume they assume operation under ideal circumstances. I.e. you press directly down, with just the right amount of pressure, in a smooth, controlled manner. But in reality, we’re smashing these things with our feet, possibly during the heat of a gig. Inconsistent pressure, inconsistent angle of attack, etc. If you’re gigging regularly, that also means operation under diverse environmental conditions.
Maybe the switches are tested under more adverse conditions… but usually stuff tested like that is marketed as “ruggedized” or “military grade” or whatever.
Another way I think about it, simplicity versus complexity: I think there’s an argument that the 3PDT switch is more complex, because it’s combining two functions into one device: the “user interface” and the circuit switching. Whereas relay based systems are arguably less complex, because of separation of concerns. I’m a Unix command line guy, I like single tools that do exactly one job but do it well.
I think that “probability of failure increases with the square of number of components” rule of thumb has to be used in context. I mean, if you take it literally, consider a modern CPU with 10s of billions of transistors - how are they as reliable as they are in the face of that rule?
In software development, we also prefer simplicity. It’s generally less error prone, and easier to debug when there is an issue. But eventually, you bundle that complexity up into a library. Now, if you write a short, simple program that uses a complex (but long lived, time tested) library, is the program itself simple or complex?
I think the analog to the hardware world is the integrated circuit. You could make a simple line buffer with a single transistor or use an opamp. Is the transistor better strictly because it’s simpler? In some cases, depending on design goals and other constraints, it could be better… but in other scenarios the opamp would be better, despite the “complexity”.
As such with relay or electrical bypass - if you don’t buy my “separation of concerns” notion, and stand by the idea that the 3PDT is simpler, I still think it’s a stretch to call relay/electrical bypass “complex”. It’s a long-solved problem using commodity components exactly per their design. Nobody’s designing bypass schemes with rare/exotic components, or using parts in an “off-datasheet” manner.
All the above is a big part of why I personally prefer relay or electrical bypass schemes. And I simply prefer soft-touch momentary switches. But I’m certainly not looking down my nose at anyone who takes a different route. My preference is indeed more complex in terms of build time and component sourcing. And despite what I wrote above about 3PDT reliability, I’m quite sure that I’m never going to actually wear out such a switch! I’m not a pro, and even if I was switching my pedals 50x/day, every day, I’ve built so many pedals that I have backups for my backups!
Edit: I might be wrong about my 3PDT MTBF assumptions. Using this 3PDT Pro switch as an example, the verbiage is "Mechanical Life: 30,000 MAKE-AND-BREAK CYCLES". Not sure if that means MTBF as I assumed, or it implies rated for minimum 30k cycles? Also, the heat resistance is impressive: "We dipped these half way up the plastic casing in our wave solder bed for 15 seconds with no deformation and perfect continuity tests. Lugs stay firmly in place even under extreme heat." I suspect you could in all likelihood generally get quite a bit of mileage out of these switches.
Also, comparing to a momentary SPST (such as typically used by relay or electrical bypass schemes), such as this Pro-Grade SPST Momentary, it says "50,000 mechanical cycles; 6,000 electrical cycles". Not sure what that means exactly... why would you use it only mechanically, but not electrically? And if the actual reliability is dominated by the lower 6k number, that's disturbingly low!
However, I do think the two-wire momentary SPST is generally easier to replace. It's almost a wash compared to 3PDT with most PedalPCB boards, especially if you use the breakout board - then you only have to re-solder 6 wires. Three times the work of a 2-wire SPST, but you'll probably spend more time on setup and cleanup either way. And if you use modular connectors (like JST), and carry a spare, then it's theoretically field-serviceable at the gig.
On the other hand, some DIY effects, I won't mention any names cough cough Aion cough cough will put actual circuit components on the switch breakout board. Which means you either have to un-solder the actual switch (very painful), or get a whole new board, or try to DIY hack the equivalent circuit components.
It's interesting to me that the reliability for SPST momentary switches isn't much higher than 3PDT (or even significantly lower, if that 6k number is relevant to us). Ignoring the numbers I wrote, intuitively the momentary SPST should last longer because it's inherently simpler. I mean you could rig up a DIY momentary SPST with a couple paperclips or lengths of wire in a pinch. It's a spring and contacts. I wonder if that 6k number assumes high-voltage switching, where you're likely to have some arcing and therefore fouling of the contacts over time?
Last edited:
Stickman393
Well-known member
This thread needs more stickman.
Stickman, ho!
Relays. I love relays. Why? Reasons.
The argument about complexity must be taken from both the electrical and the mechanical sides of the equation. Sure, a relay bypass involves more components, which leads to increased electrical complexity.
That said: modern electronic components are extremely reliable when not subjected to conditions outside of their normal operating parameters. Resistors do not drift as they used to in the days of carbon composition resistors, electrolytic caps tend to be the weak point but even those still tend to last decades.
Mechanical 3PDT switches typically do the job well enough, this is fair. But mechanically speaking, they are *far* more complex than a simple momentary switch. A momentary switch will short a set of contacts via a simple up and down motion, aided by a spring. The plunger bridges two points. A switch doesn't get much simpler.
The 3PDT on the other hand? Its an fairly complex machine. Three independent poles, the common on each needs to switch between two points in a synchronous motion. They work *very* well, but mechanically speaking there's a lot more that can go wrong.
Sealed relays are mechanically simpler than a 3PDT switch. The use of electromagnetism significantly reduces the number of moving parts, the motions/forces are comparatively small: they're extremely robust devices.
I'm a fan of using 555s for relay bypass too...this eliminates the need for a microcontroller.
The other advantage...*if* your momentary switch fails, which is the most likely component to fail in the assembly, you now only have to make two solder connections instead of nine.
I'll grant that in the grand scheme of things, it probably doesn't make a whole lot of difference, especially if one uses cheap switches. But there are momentary switches out there that far exceed the 30k lifespan of the cheapies, too. Build one with a lehle switch, and as long as your circuit is well designed you're about as close to fail-proof as is possible.
But I like using relay bypass for a much more squishy reason: it's fun. I like building them. And that's why I participate in this hobby.
Stickman, ho!
Relays. I love relays. Why? Reasons.
The argument about complexity must be taken from both the electrical and the mechanical sides of the equation. Sure, a relay bypass involves more components, which leads to increased electrical complexity.
That said: modern electronic components are extremely reliable when not subjected to conditions outside of their normal operating parameters. Resistors do not drift as they used to in the days of carbon composition resistors, electrolytic caps tend to be the weak point but even those still tend to last decades.
Mechanical 3PDT switches typically do the job well enough, this is fair. But mechanically speaking, they are *far* more complex than a simple momentary switch. A momentary switch will short a set of contacts via a simple up and down motion, aided by a spring. The plunger bridges two points. A switch doesn't get much simpler.
The 3PDT on the other hand? Its an fairly complex machine. Three independent poles, the common on each needs to switch between two points in a synchronous motion. They work *very* well, but mechanically speaking there's a lot more that can go wrong.
Sealed relays are mechanically simpler than a 3PDT switch. The use of electromagnetism significantly reduces the number of moving parts, the motions/forces are comparatively small: they're extremely robust devices.
I'm a fan of using 555s for relay bypass too...this eliminates the need for a microcontroller.
The other advantage...*if* your momentary switch fails, which is the most likely component to fail in the assembly, you now only have to make two solder connections instead of nine.
I'll grant that in the grand scheme of things, it probably doesn't make a whole lot of difference, especially if one uses cheap switches. But there are momentary switches out there that far exceed the 30k lifespan of the cheapies, too. Build one with a lehle switch, and as long as your circuit is well designed you're about as close to fail-proof as is possible.
But I like using relay bypass for a much more squishy reason: it's fun. I like building them. And that's why I participate in this hobby.
CR0SSBL4DE
Active member
PCB design is not just to avoid having hundreds of wires connected by hand.
In the real world, the wires and PCB traces are not perfect conductors: every trace/wire induces an electromagnetic field that affects all the other traces/wires in the design. That's why PCB designers use techniques as ground planes, shorter traces, ensuring return paths for signals, separating digital from analog, and even trace impedance matching for RF circuits.
You can see this issues on pedals as:
- Fuzzes and distortions self oscillating. In some cases, if the guitar is connected directly to the pedal, the frequency depends on the guitar volume pot position.
- Choruses with audible clicks, coming from the LFO.
- Different high frequency response on the same circuit on different PCBs. Same if boxing more than one circuit in the same enclosure.
- Noise from using a daisy chain to power multiple pedals, specially if there are digital pedals.
- Lossing tone with all True By Pass pedals off.
- Sections of the circuit that are not in the signal path, still altering the signal in some way. Detectors in compressors or envelope filters, for example.
There is plenty of open-source code for microcontrollers. Shamelessly linking my own code, and the credits and links section of my README has links to other open-source implementations. I'd argue the only really tricky part of writing simple on-off mcu code is the debouncing, and that's a well-understood, well-documented problem.
But if you only need simple on-off, then a microcontroller isn't necessary. I moved to using CMOS hex inverters with Schmitt trigger inputs (e.g. CD40106, 74HC14) to implement the logic of watching for switch presses and relay (re)setting. Boss/Roland does essentially the same thing in their bypass scheme, though they do it with discrete components rather than using an IC. Boss pedals are typically buffered and electrical bypass (rather than relay), but the discrete engage/bypass state management logic is effectively the same as using a relay.
This is what I was trying to say in my ramble above, but you put it much more succinctly.
However, doing a casual survey of common, readily available SPST momentary switches, many don't list any durability/reliability data, and those that do, aren't necessarily the huge increase compared to 3PDT one might expect. The one I linked above say 50k mechanical cycles, and only 6k electrical cycles.
Great, thanks, you just dramatically increased the cost of my builds!
Stickman393
Well-known member
Oooh! I can speak directly to this!
In any kind of switch...be it a mechanical switch, a relay, or whatever you have...several factors determine the longevity of that device.
One of those factors is the voltage with which the switch contacts are exposed to, another is the amount of current that passes through the contacts. Its important to realize here that switches operate by physically bringing two conductive materials into contact with each other. Those contacts are typically reasonably flat in order to maintain as much surface-to-surface area as possible within the design. It is also important to recognize that these contacts, while well designed, are not perfect conductors.
AC voltage, as a general rule, tends to be easier on switches than DC voltage. DC voltage has a nasty habit of "Arcing" across switch contacts, even at relatively low voltages. Keep in mind: AC voltage does this too, but because the "direction" of AC current is constantly flipping back and forth, it tends to be easier on switches. This is also highly dependent on the impedance of the connected circuit.
As an example, it's not uncommon to find industrial relays that are rated for up to 240vac at 5 amps OR 30vdc at 2 amps.
Every time an electrical arc passes through the air across the contacts, the precise location of the arc on each side of the contact tends to become super-heated. This will often result in a small recess, or pit, forming in the contact material.
These pits reduce the available surface area on each side of the contacts that can be used to transfer current, as well create a bit of oxidation of that area in the contacts. This leads to an increase in resistance across the contacts, which means that current passing through those contacts will generate more heat than a perfectly flat set of contacts. If this reaches a tipping point where that heat cannot be rejected quickly enough, those contacts will enter a death spiral where they will overheat and fully oxidize. This can even result in contacts getting so hot that they weld together in extreme cases.
So...all that is to say that the electrical properties or switches and relays tend to be presented *at full load*, or when subjected to conditions at their stated ratings.
The photos from that listing show the switch's rated electrical capacity: 3A at 250vac, or 5A at 125vac. Which is pretty robust. For reference, this is an SCI model number R13-85.
The current being switched by our momentary switches in relay bypass scenarios tends to be in the range of <9vdc at a few milliamps. In these circumstances, arcing is a negligible concern, and you should be able to get the full mechanical lifespan out of the switch contacts before the electrical contacts give out.
Last edited:
@Stickman393 - thanks, that's really useful info!
You didn't mention it, but I'm guessing that over time, wear and tear on the contacts (via arcing, or maybe even just friction) will cause the bounce behavior to change somewhat too?
Now I've gone down a SPST momentary rabbit hole. I think I'm going to grab a couple of those Lehle switches (not that I actually need them, but for bragging rights).
But more interesting, looks like there are two common kinds of contactless switches: Reed and Hall Effect. Contactless means the life expectancy goes up by an order of magnitude (over even the Lehle switch). I wasn't able to find any off-the-shelf Reed momentary switch. I seem to recall someone on the forum here DIY'ing Reed footswitches. I did find a some off-the-shelf Hall Effect momentary switches, pricing starting around $35 or more! That's a bit too much even for bragging rights!
You didn't mention it, but I'm guessing that over time, wear and tear on the contacts (via arcing, or maybe even just friction) will cause the bounce behavior to change somewhat too?
Now I've gone down a SPST momentary rabbit hole. I think I'm going to grab a couple of those Lehle switches (not that I actually need them, but for bragging rights).
But more interesting, looks like there are two common kinds of contactless switches: Reed and Hall Effect. Contactless means the life expectancy goes up by an order of magnitude (over even the Lehle switch). I wasn't able to find any off-the-shelf Reed momentary switch. I seem to recall someone on the forum here DIY'ing Reed footswitches. I did find a some off-the-shelf Hall Effect momentary switches, pricing starting around $35 or more! That's a bit too much even for bragging rights!
Stickman393
Well-known member
Iirc, reed switches are similar to relays in that they use magnetism to actuate, but instead of electromagnetism they use permanent magnets. Those do actually have moving parts.
Hall effect switches, however, are in fact solid state. They're set up kinda like Jfet switches, but when you pass a magnet over them they allow current to pass from one side to the other.
Basic hall switches are cheap, but making something out of them that will switch multiple poles from their commons to two different paths will require a bit of work. Something along the lines of the Jfet switching that companies like Boss do.
Hall effect switches, however, are in fact solid state. They're set up kinda like Jfet switches, but when you pass a magnet over them they allow current to pass from one side to the other.
Basic hall switches are cheap, but making something out of them that will switch multiple poles from their commons to two different paths will require a bit of work. Something along the lines of the Jfet switching that companies like Boss do.
Though with a relay in the right place the audio path can be made shorter.
One of the oddest things about pedal design is running the signal the whole length of the pedal twice from the jacks to the footswitch
And bingo! That is why I like this forum. It can get a little testy from time to time but overall this place is a beacon for all other online forums. Nobody gives a shit.
Nah, it's calm, reasoned and friendly, with only the occasional outbreak of memes.
Big Monk
Well-known member
And bingo! That is why I like this forum. It can get a little testy from time to time but overall this place is a beacon for all other online forums. Nobody gives a shit.
I float between a number of forums and you can spot someone pretty quickly who thinks this place is one of the others.
Not to say I am perfect either.
I was cussing people out over politics less than two weeks ago but I re-adjusted quickly. I mainly was mad that any of that stuff WAS creeping in here.
That was in large part my fault. It was one of the only times I ever posted anything like that, and it felt gross. This is basically the only place I interact with people on the internet (no social media)- I don’t want it tainted either.
I didn’t mind the cussing at all- it got the point across.
OK- relay bypass! I have a stash of Robert’s latching 555 boards, they’re great. I’d have to do a little creative thinking to get it near the jacks. Unless I do side jacks!
vigilante398
Authorized Vendor
TGP mostly feels to me like facebook for people that complain about facebook. It seems like >60% of the threads there have nothing to do with music. I occasionally read a thread here or there, but I mostly hang out there to peruse the classifieds.
There's a few folks around here who do "stacked PCB" builds, with a custom bypass board that mates to PCB-mounted input/output jacks. The actual effect circuit is directly below the bypass PCB. So in bypass mode, the effective wire length is roughly the width of the pedal.
But I agree, running the signal 2x the height of the enclosure is kind of wacky. In the PCB designs I've done, I've tried to put the bypass circuit at the top, near the input/output jacks. But the top is also where control pots usually live. So the tradeoff for short effective wire length is long (and often weirdly routed) traces to the pots from the actual effect circuit. The "stacked" two-PCB approach that some people are doing looks to be the best of both worlds.
KreoPensas
Well-known member
I am *still* learning to Not Engage.
