Switching Thoughts from a Local KC Workshop

[Aentons]

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

[Timko]

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.

[aion]

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.

[Netnnk]

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?

[aion]

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.

[gtr2]

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.