Originally posted in the wrong section. This is what happens when you try to multitask too much on a workday :).
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I went to a forum/workshop in Kansas City that featured local builders in the music scene here. Shaun and Marq from Seuf Guitars were there as well as Paul from Scarlett Amps. I know both companies (Paul works on my tube amps, and Shaun repainted my Jaguar), but perhaps the largest name there was Josh from JHS (which is from Grandview, a suburb of KC). It was an incredibly well attended forum where the smaller guys were surprised with the number of questions (Shaun told me "I thought it was going to be the Josh show"), but I had a specific question for Josh about switching, one that I'd like to share here along with his response.
I'll give you some background with the question first. When I started pedal building 4 years ago, I became obsessed with boost pedals. So much that the 3rd and 4th builds I ever did (a clean boost and a treble boost) are still on my board. I've longed for putting these two builds together in the same enclosure with the ability to switch the order for the two effects. Knowing that doesn't work so well for a treble boost, I began exploring the topology of John Patton's Fallstaff Overdrive, a buffered treble booster. After coming up with a few tweaks that got the sound to where I wanted, I had one last thing I wanted to add - an internal switchable buffer on the treble boost side as this sits first in my chain and I don't use a buffered tuner pedal. This all appeared to work fine until it didn't. I got a lot of hum in that part of the circuit. I soon realized the notion of the switchable buffer seen in a pedal like the KTR uses a 3pdt switch, which was a much bigger design undertaking than the way I had done it.
Ok, onto my question. I asked Josh how he decides whether a pedal will be true bypass or buffered bypass. His answer changed the way I'm starting to look at switching. He mentioned that switching is hands down the most complicated part of a pedal often as people was the bypass or circuit engage to happen with no noise. Seeing how the thing is a mechanical part, this is incredibly hard. He also mentioned that the myth that true bypass is "better" is just that and is based more on the early boutique builders's ability to get their hands on 3pdt switches to wire them up than some better sound. JHS pedal switching is designed per pedal; if true bypass fits that circuit with minimal noise, they'll go with that. Or they'll go with a buffer. Or opto. Or relay. I've been thinking about switching on the end result of the effect (true bypass or buffer). I'm now starting to think about it based on whether or not the transition between the effect and the bypass signal has no big click, and figure out how to make it happen. Perhaps you all think this way already, but I didn't.
One final thing. Josh mentioned through all of his studying and research into switching, he feels that the Japanese may have gotten it right with the Boss/Ibanez design of the flip/flop transistor design. I see very few of these in DIY pedals. I also think it would be incredibly difficult to build a stand alone board for this type of switch and market it as such, which is why I don't see any of these. So to the people who do layout, why don't you use the flip flop switch design? Has the relay switch, which I think at a mechanical level achieves a similar workflow, replaced them in modern building?
Thanks for reading. The more I get into building, the more I realize how far I have to go in understanding.
I think the boss/ibanez design is ignored because of the "myth" of true bypass being better.
It's interesting to hear it explained that way. Decent perspective.
Well.... when was the last time you heard a pop upon switching a boss pedal?
I think a lot of the buffer hate comes from badly designed circuits that would cause frequency loss even when "off".
Also that the elaborate flip-flop switch circuits of boss and ibanez take up a lot of board space and parts cost. Now that 3pdt's are cheap one doesn't really Need to bother with work-arounds.
Quote from: somnif on April 03, 2019, 08:41:57 PM
I think a lot of the buffer hate comes from badly designed circuits that would cause frequency loss even when "off".
100% agree with this. A buffer doesn't make good circuits sound bad, or bad circuits sound good.
One of the outstanding things in the DIY community that I think may be true is that people don't design flip/flop switches because relay switches have the same end effect. I don't think they're cheaper (the parts look more expensive), but there are less of them and they are a smaller board footprint.
Much of what I've been reading around switch sound was found on the AMZ website: http://www.muzique.com/lab/pop.htm (http://www.muzique.com/lab/pop.htm). I am most interested in reason #2, and the effect that something like a flip flop switch has on it (or how it prevents it). I also have looked at #3, and assume the mechanical contact bounce in a 3pdt is worse than a momentary spst (again, observations, no actual evidence of it).
Given how expensive JFET's are getting it wouldn't surprise me if the gap between them and relays gets smaller and smaller.
Quote from: Timko on April 03, 2019, 06:09:44 PMI've longed for putting these two builds together in the same enclosure with the ability to switch the order for the two effects. Knowing that doesn't work so well for a treble boost, I began exploring the topology of John Patton's Fallstaff Overdrive, a buffered treble booster.
Really, it doesn't? Please elaborate.
QuoteThis all appeared to work fine until it didn't. I got a lot of hum in that part of the circuit.
Hum doesn't have anything to do with the switching. There is something else you're doing wrong.
QuoteOk, onto my question. I asked Josh how he decides whether a pedal will be true bypass or buffered bypass. His answer changed the way I'm starting to look at switching. He mentioned that switching is hands down the most complicated part of a pedal often as people was the bypass or circuit engage to happen with no noise.
If that's the case for him, he should try reading a book.
QuoteHe also mentioned that the myth that true bypass is "better" is just that and is based more on the early boutique builders's ability to get their hands on 3pdt switches to wire them up than some better sound.
That's not a myth. In some ways they are superior to buffered switching: they are a real copper path without any resistance, they won't introduce any electronic noise. In other ways electronic switches are better: no bounce, they can be ramped... It's not black and white, and nobody ever who understands a switch (duh) argued that it is.
QuoteJHS pedal switching is designed per pedal; if true bypass fits that circuit with minimal noise, they'll go with that. Or they'll go with a buffer. Or opto. Or relay.
Or maybe he just copies the switching that was used in the original pedal he is cloning (http://freestompboxes.org/viewtopic.php?f=6&t=18293&start=20#p265961)? You either want a buffered bypass, or you don't. You either want a hardware switch, or you don't. What does that have to do with switching a flanger or a booster? And the fact that he didn't support that statement with any sort of arguments or examples, probably means again he is clueless.
QuoteI've been thinking about switching on the end result of the effect (true bypass or buffer). I'm now starting to think about it based on whether or not the transition between the effect and the bypass signal has no big click, and figure out how to make it happen. Perhaps you all think this way already, but I didn't.
Sorry to be so blunt, that's just non-technical jabbering, same as from Josh the expert.
QuoteOne final thing. Josh mentioned through all of his studying and research into switching, he feels that the Japanese may have gotten it right with the Boss/Ibanez design of the flip/flop transistor design. I see very few of these in DIY pedals. I also think it would be incredibly difficult to build a stand alone board for this type of switch and market it as such, which is why I don't see any of these. So to the people who do layout, why don't you use the flip flop switch design? Has the relay switch, which I think at a mechanical level achieves a similar workflow, replaced them in modern building?
If you build a Fuzz Face, the flip-flip circuit takes more parts than the effect, not very satisfying. 3PDT switch is the easiest solution from a building standpoint, so that's what DIY guys use. A relay is more akin to a 3PDT switch, it is a mechanical switch with a metal path for the signal, it bounces. You need to learn to differentiate between the actuator and the actual switching element for the signal. With the 3PDT, it's the same. With everything else, it isn't.
Ouch.
Quote from: Timko on April 03, 2019, 06:09:44 PM
Has the relay switch, which I think at a mechanical level achieves a similar workflow, replaced them in modern building?
Well, sort of. Your input signal is always running through part of the flip-flop setup, whereas with a relay and microcontroller, you can set it up for true bypass (if you want). It's also less parts and no EOL hen's teeth (through-hole JFETs). And, you can do other interesting things, like have it move the input to ground for XX ms during the switching process to eliminate switch pop from discharging coupling cap (or wherever it might be coming from). The flip-flop is/was an effective and elegant solution, but as I said above, it's got a big footprint and now critical parts are scarce/costly.
Quote from: Timko on April 03, 2019, 06:09:44 PM
The more I get into building, the more I realize how far I have to go in understanding.
Me, too!
Quote from: TFZ on April 03, 2019, 10:40:39 PM
QuoteHe also mentioned that the myth that true bypass is "better" is just that and is based more on the early boutique builders's ability to get their hands on 3pdt switches to wire them up than some better sound.
That's not a myth. In some ways they are superior to buffered switching: they are a real copper path without any resistance, they won't introduce any electronic noise. In other ways electronic switches are better: no bounce, they can be ramped... It's not black and white, and nobody ever who understands a switch (duh) argued that it is.
Its not quite that simple however. Cables, wires, traces, leads, they all have resistance AND capacitance to them. Its small, but real. And those factors can degrade your signal (usually in the form treble loss, but can get into the upper mids sometimes). The more stuff between your guitar and your amp, the bigger a problem this can be. So if you're on stage with a 50ft cable, or with 30 pedals warming the floor in front of you, your sound may end up a bit more wooly than you'd expect.
Enter the buffer. Even a simple buffer (assuming its well designed) will keep your signal strong and healthy. Unfortunately, some pedals don't play well with the high input/low output impedance of buffers, so you need to take that into account when building your effects order (early Fuzzes and Wah pedals are notorious for this).
And, oddly enough, some artists actually LIKE that cable induced signal degradation (example, Jimi Hendrix had a fondness for extra long coiled cables because they "warmed up" his tone).
So in reality, both true-bypass and buffered-bypass have their uses. What will be best depends on the needs of the circuit, the wants of the player, and the individual situation of the rig.
For those who are mathematically/engineerically inclined, here is a good article digging into the effects (ha, pun) cable capacitance/impedance will have on your signal in various situations:
http://screaminfx.com/tech/why-and-when-to-use-a-guitar-buffer-pedal.htm
Quote from: somnif on April 04, 2019, 07:31:00 AM
Quote from: TFZ on April 03, 2019, 10:40:39 PM
QuoteHe also mentioned that the myth that true bypass is "better" is just that and is based more on the early boutique builders's ability to get their hands on 3pdt switches to wire them up than some better sound.
That's not a myth. In some ways they are superior to buffered switching: they are a real copper path without any resistance, they won't introduce any electronic noise. In other ways electronic switches are better: no bounce, they can be ramped... It's not black and white, and nobody ever who understands a switch (duh) argued that it is.
Its not quite that simple however. Cables, wires, traces, leads, they all have resistance AND capacitance to them. Its small, but real. And those factors can degrade your signal (usually in the form treble loss, but can get into the upper mids sometimes). The more stuff between your guitar and your amp, the bigger a problem this can be. So if you're on stage with a 50ft cable, or with 30 pedals warming the floor in front of you, your sound may end up a bit more wooly than you'd expect.
Enter the buffer. Even a simple buffer (assuming its well designed) will keep your signal strong and healthy. Unfortunately, some pedals don't play well with the high input/low output impedance of buffers, so you need to take that into account when building your effects order (early Fuzzes and Wah pedals are notorious for this).
And, oddly enough, some artists actually LIKE that cable induced signal degradation (example, Jimi Hendrix had a fondness for extra long coiled cables because they "warmed up" his tone).
So in reality, both true-bypass and buffered-bypass have their uses. What will be best depends on the needs of the circuit, the wants of the player, and the individual situation of the rig.
Yes, all true. But I was specifically only talking about the switching. It does have other implications, as you stated. To me the most sensible, general approach would be: have at least one pedal with buffered bypass in your setup, in the beginning, or after the fuzz, whatever makes sense. And make the rest true bypass with either 3PDT or relay switching. This way you will mitigate the disadvantages of having only cable between the guitar and the amp and can have as many hardware switches as you want afterwards.
I honestly can't understand how this topic can be made up to be such a complicated issue. I have used thousands of 3PDT switches, I've only ever had three switches that were bad from the start. One didn't switch at all, two were loud. But neither I nor anyone else I've sold to ever had a problem with noise from switching. Maybe there are fundamental quality differences between them, I don't know. But if that really is a problem, buffered bypass (use an opamp instead of transistors if you intend to cascade more of these) with JFETs or optocouplers can be made silent. Instead of "cutting" the signal like a harware switch does, their resistance can be ramped up or down over the course of a couple milliseconds.
Quote from: somnif on April 04, 2019, 07:31:00 AMUnfortunately, some pedals don't play well with the high input/low output impedance of buffers, so you need to take that into account when building your effects order (early Fuzzes and Wah pedals are notorious for this).
I'm firmly of the opinion that its ridiculous to still build and design pedals that way. It's 2019 for god sakes, we've put men on the moon and sent probes to Pluto and beyond. And we still can't build a Fuzz Face that plays nice with buffers? Either the laziest design since Porsche keeps on releasing the same 911 every year, or yet another sign of guitarists being so arch conservative they would even have frowned upon the invention of fire. And pedal designers knowing this so they won't even bother.
Quote from: culturejam on April 04, 2019, 03:10:50 AM
Quote from: Timko on April 03, 2019, 06:09:44 PM
Has the relay switch, which I think at a mechanical level achieves a similar workflow, replaced them in modern building?
Well, sort of. Your input signal is always running through part of the flip-flop setup, whereas with a relay and microcontroller, you can set it up for true bypass (if you want). It's also less parts and no EOL hen's teeth (through-hole JFETs). And, you can do other interesting things, like have it move the input to ground for XX ms during the switching process to eliminate switch pop from discharging coupling cap (or wherever it might be coming from). The flip-flop is/was an effective and elegant solution, but as I said above, it's got a big footprint and now critical parts are scarce/costly.
Thank you for this. After I spent a good deal of time reading through various published documents on switching schemes, I was noticing some similarities and differences between thew two approaches. This sums it up well!
Quote from: culturejam on April 04, 2019, 03:10:50 AM
Quote from: Timko on April 03, 2019, 06:09:44 PM
The more I get into building, the more I realize how far I have to go in understanding.
Me, too!
It's reliving to hear someone with the building resume as you is still constantly learning. I know I'm heading in the right direction :).
Quote from: culturejam on April 04, 2019, 03:10:50 AM
The flip-flop is/was an effective and elegant solution, but as I said above, it's got a big footprint and now critical parts are scarce/costly.
The Flip Flop circuit wasn't something that Roland came up with(and Ibanez copied). It's used in all kinds of other electronics applications. There are bajillions of flip-flops in a single CPU. I've never really looked around but you could probably find a simple flip flop circuit in IC chip form rather than having to built it discrete.
https://en.wikipedia.org/wiki/Flip-flop_(electronics)
The specific issue that made me start to look around and find out about true bypass was my tube screamer. If the gain is above noon and it's bypassed, you can still hear the distortion coming thru and it did not sit well with my clean sound. I think it has something to do with the trasistor cutoff
Edit: I guess I didn't realize that Boss and other makers like DOD have been using a BA634 "T type" flip flop chip in some of their pedals (like the DD-2) for a long time
Interesting! I did some reading through the TH Customs blog (it's GREAT if you haven't read it) and found numerous articles published on the topic of switching. I found them quite interesting as he explores a number of ways to accomplish switching. The one I'm currently investigating is using a relay with an NE555. It appears to be a current hog but it doesn't involve microprocessor coding.
The FET-based switching is reliable, zero noise and very cheap, and I agree that it is an engineering marvel that can't really be improved on for what it does. But here's my take on the reasons it doesn't see much use in DIY.
1) While none of the parts are expensive, the parts count is still very high, with 20-30 components needed to make it all work, depending on the number of switching points needed throughout the circuit (usually 2, but sometimes 4 or more). In automated PCB assembly (wave soldering or SMD) this is no big deal and cost is the only factor. But in DIY, the time to place & solder 20-30 components is significant and it far offsets any cost savings.
2) It requires the use of a tactile switch. Boss & Ibanez have designed their entire enclosure around tactile actuation, but we don't have that luxury using Hammond-style boxes. There aren't any good options for rugged panel-mounted tactile switches that are easy to hit with your foot, and so we are pretty much out of luck for tactile options.
The panel-mount soft-touch momentary switches we see everywhere don't work for FET switching because they're "bouncy" and the FET switching doesn't have any debouncing built in. It will trigger a flip-flop for each electrical contact that is registered, even if they are less than a millisecond apart. Microcontroller relay code always has a debouncing function to mitigate this, but that's a luxury that only comes when you get to write code.
For all this, I would take it a step farther and say that the '80s Japanese convention of a PCB that fills the full area of the enclosure, with a mess of wires running to all the pots & other hardware, is still the most reliable method of assembling pedals. The likelihood of a broken solder joint is very, very low and typically the electronics (esp. electrolytics) will fail long before any of the hardware does. Ease of disassembly and repairability is high.
But again: not practical for DIY. If you handed me all the parts to a Boss pedal, it'd take me a full 8-hour day to assemble everything. It only works because they make them in the thousands, and at some point they hit an efficiency threshold where they can cut a profit on selling a DS-1 for $29. (They're up to $49 now, but that was the sticker price when I bought my first one in 2002.)
I do agree that buffers are a good idea and they get undue criticism from people who don't know much about electronics. True bypass isn't bad by any means, but it is overrated, in the sense that it's thought of as the hallowed end-all. IMO something like the Klon switching system is the way to go for DIY. A very high quality quality buffer, but using hard switches with minimal supporting components.
aion, I've just begun rehousing a BOSS pedal and instead of converting to true bypass, like I've done in the past, I hoped to keep the buffers and just replace the switch. So far it's worked fine, even when i tried to "trick" it by pushing softly. It hasn't been properly road tested yet so am I just lucky right now? Has anyone else rehoused a silmiar Boss, Ibanez etc, but not converted to true bypass?
(https://i.imgur.com/7aZtgRH.jpg)
Lucky, I would say. Different flip-flop methods have different levels of tolerance. I haven't tested it out personally with Boss's flip-flop (though I have heard of people having issues with it) but I do have direct experience with others where each time it was basically a 50/50 chance that you were going to switch it or not. But all it takes is one misfire in a live show though and you'll never trust it again.
All switches are bouncy. Hardware debouncing has been around before software debouncing. There is also enough hardware debouncing with just the resistor and cap off the switch for the boss flip flop type circuit. Schmitt triggers are dirt cheap and also work well for switch debouncing. One of my last projects for someone didn't use any software debounce even though it used a PIC. It was much easier tbh. The issue is that there are more parts and the circuit is not really understood by casual DIYers. A 3PDT is much more convenient.