Help extracting an Ibanez electronic switch from a TS 808 schematic...

[Morocotopo]

 Hi, I´ve been trying to make an electronic switch for my builds, It´s hard to get DPDT´s in my country (Argentina), but i can get sturdy, solid momentary footswitches, also, I want to avoid any kind of pops. since I don´t plan to chain 99999 effects together, I´m not that concerned about added noise. I already built a Tone God switch (works but pops), a DOD style switch (couldn´t get it to work)... So, now I´m looking at the Ibanez one, I have the schematic downloaded for a TS 808 w/ the switch, but i´m having difficulties with how to implement it. So, some questions (I´ve numbered and/or outlined the sections I have doubts about in light green):


- I should have 4 connection points with the FX circuit, right? In, Out, FX in, FX out? But in the schem, I only see 3 (numbers 1, 2, 3, marked "SW")!!! Do you know wich one is wich, and where should the missing connection go?

- I need to include the part of the circuit marked 4 because it provides the Vr, right? (yes, I know, the battery of  course I do need..) And what about the unmarked diode, any clue about wich one it is? Is it a reverse battery protection one?

- What about the transistors marked 5 and 6? are they buffers? so, by leaving them out, I will have a non buffered electronic bypass?

- The resistor marked 7, is a 22 Ohm one? or 22K (missing K)?

I hope posting the modified image is OK with the author...

Once I understand the circuit fully, I intend to make a PCB design for it, test it, and if it works, share with anybody who needs it.

Thanks in advance to anybody that can help me!

[Morocotopo]

Sorry the image is kind of big, I´m not sure how to make it smaller...

[zachary vex]

assuming that this schematic is correct, you need the first 2SC1815 and all of its support components up to the 1uF cap (which drives the effect).  you'll need to supply Vr (which is probably cut off on the right).  you'll need all of the components below and including the fets connected to that first 2SC1815.    you'll need the B100k (or any kind, really) Volume pot and the circuitry to the right of it.  all in all, the switching system is as complex as the audio circuit is, and is interdependent on part of the audio circuit to work.

this type of switching system is NOT recommended for fuzzes because it isolates the guitar's volume control from the fuzz circuit... which is generally a no-no.

[R.G.]

this type of switching system is NOT recommended for fuzzes because it isolates the guitar's volume control from the fuzz circuit... which is generally a no-no.

It seems like Ibanez and Boss do OK with it. Why is this a no-no?

[Morocotopo]

 So Zachary, basically what you´re saying is that it´s not usable for an independent electronic switch? well, there goes my attempt...
I also have a boss bypass schematic, I wanted to make this one because the Boss one has more components, and looks more complicated.
Have to go, thanks for your responses, I´ll check later.

[zachary vex]

this type of switching system is NOT recommended for fuzzes because it isolates the guitar's volume control from the fuzz circuit... which is generally a no-no.

It seems like Ibanez and Boss do OK with it. Why is this a no-no?

because the isolation causes the impedance relationship to change.  for example, with a fuzz face, the input impedance is pretty poor.  consequently, it reacts differently to your guitar's pickup/volume control depending on the position of the volume control... when the volume is way down (but still audible) the impedances match much more closely and the fuzz face brightens up dramatically as it cleans up completely.  with a buffer between, the impedance feeding the fuzz is fixed and the user can no longer introduce impedance changes to alter the performance of the fuzz circuit.

fuzz face-type circuits generally sound "dead" after a buffer.

[Melanhead]

You could try a relay circuit ... You'd just need a driver and flip/flop chip like this:

http://www.saburchill.com/tech/electronics/elect027.html    the driver circuit is on this page.

http://www.uoguelph.ca/~antoon/gadgets/relays/relays.html   Driver circuit with flip/flop on this page

I built a circuit a few years back to mute the speakers in our 5.1 mix room using relays, a driver circuit and a 4013 flip flop chip  ... I may be able to find my schematic somewhere as I can't remember exactly what I did

I'm not sure what the current draw would be though and it may be hard on batteries, but would give you true bypass.

There's probably more info here about relay switching as well ... The biggest thing about using relays is making sure they don't pop when discharging ... The above circuit should prevent this and would be way easier than the boss/ibanez switch to build.

I've never tried it for a pedal as I order the 3PDTs from Aron.

[Melanhead]

this may be useful but it uses 3 chips ...

http://www.ee.washington.edu/circuit_archive/circuits/bypass.gif

or this post:

http://www.diystompboxes.com/smfforum/index.php?topic=43400.0

[R.G.]

because the isolation causes the impedance relationship to change.  for example, with a fuzz face, the input impedance is pretty poor.  consequently, it reacts differently to your guitar's pickup/volume control depending on the position of the volume control... when the volume is way down (but still audible) the impedances match much more closely and the fuzz face brightens up dramatically as it cleans up completely.  with a buffer between, the impedance feeding the fuzz is fixed and the user can no longer introduce impedance changes to alter the performance of the fuzz circuit.

Oh... I see. Gosh I'd forgotten that... 



Did you maybe mean that there are some few older distortion pedals that depend on a direct connection to guitar pickups, so that you have to be aware of that and allow for the fact that it may not be the right bypass for some few circuits? That it's pretty good for most pedals but that there are a few exceptions where it won't work well?

Not being a native speaker of US English (I'm from the South, suh.) I miss subtlties like this. 

[zachary vex]

because the isolation causes the impedance relationship to change.  for example, with a fuzz face, the input impedance is pretty poor.  consequently, it reacts differently to your guitar's pickup/volume control depending on the position of the volume control... when the volume is way down (but still audible) the impedances match much more closely and the fuzz face brightens up dramatically as it cleans up completely.  with a buffer between, the impedance feeding the fuzz is fixed and the user can no longer introduce impedance changes to alter the performance of the fuzz circuit.

Oh... I see. Gosh I'd forgotten that... 



Did you maybe mean that there are some few older distortion pedals that depend on a direct connection to guitar pickups, so that you have to be aware of that and allow for the fact that it may not be the right bypass for some few circuits? That it's pretty good for most pedals but that there are a few exceptions where it won't work well?

Not being a native speaker of US English (I'm from the South, suh.) I miss subtlties like this. 

no,  i mean exactly what i said.  sorry to hear about your difficulties.

[Mark Hammer]

Now boys!   

If we substitute Zach's use of "NOT" and "no-no" with "works better in many ways when directly coupled to the guitar's volume control" I think we'll have a compromise.  I suspect Zach, that you're thinking more in terms of discrete non-diode-based distortion, where such things are likely to matter more.  Morocotopo's question also seems to be more broadly based, encompassing stuff that may well have a buffer and 2-3 opamps before one ever gets to the distortion-producing aspects.

Of course, if there is anything in between guitar and fuzz, like a compressor or wah, then all bets are off, right?

[zachary vex]

substitute fuzz-face-type circuits for fuzz in my original statement and you get what i really meant.

[R.G.]

substitute fuzz-face-type circuits for fuzz in my original statement and you get what i really meant.

Oh, good.

That's what I thought you certainly must have meant.

And thanks for helping me out. I was afraid that Mother Nature had changed the Rules when I wasn't looking.

[zachary vex]

substitute fuzz-face-type circuits for fuzz in my original statement and you get what i really meant.

Oh, good.

That's what I thought you certainly must have meant.

And thanks for helping me out. I was afraid that Mother Nature had changed the Rules when I wasn't looking.

i don't recommend that bypass circuit for anything, really.  it doesn't have any headroom and it doesn't have very good tone/texture, mother nature or not.

[Morocotopo]

Thanks everybody, so the Ibanez switch is a no-no...
OK, then I think, my next options, in order of (I think) suitability:
- R.G. switch (4045). Supposedly, because of biasing, doesnt pop?
- The one by Chris Robbins. Anyone tried it? Also, is a single pole double throw momentary switch this?: A and B connected, when activated A connects to C, when released, A connects back to B (does that make sense?)
- The Boss one. Have to design PCB!!!! Complicated!!!!

I don´t think I want to try relays, I´m still trying to understand electronic switches! But, if all else fails...

On the other hand, somebody showed me the electronic switch by Craig Anderton, but I saw that it has a 2 battery power supply, and +9 /-9 V, could it be adapted to be used with a standard battery/ DC power jack, as most pedals, and a momentary switch (it needs a SPST push-on push-off one)?

I´m kind of lost here...

Will I end ordering DPDT´s from Small Bear? Oh, my poor wallet...

Thanks

[R.G.]

i don't recommend that bypass circuit for anything, really.  it doesn't have any headroom and it doesn't have very good tone/texture, mother nature or not.

OK, I see. Actually I don't recommend it for anything, really either.

But I also don't tell beginners that it's generally a no-no. I personally resist the urge to do that because some highly thought-of pedals use it and they sell many, many pedals to repeat buyers. It seems that it's at least a commercial yes-yes, and with some fairly finicky customers. I guess that I figured that if it was that well thought of by that many people, I would couch any criticisms I personally held in terms of what it does and doesn't do measurably instead of hand-wavingly. But that's just me. I always hate it when I go off on some opinion that I've stated as fact and I get my feet nailed to the floor, in a metaphorical sense. I've had that happen to me enough that I hardly have any toes left. 

As to not having any headroom - is that *zero* headroom? It won't conduct *any* signal? Or it won't safely carry a guitar signal? Or it will carry a guitar signal, but just barely, having zero more headroom than the guitar signal? And what guitar signal is is just barely as big as? Single coil? Humbucker? Distortion humbucker? Old low-output Rickys?

I'm also interested in the tone/texture it doesn't have very good of. Do I translate that as it having a tone or texture that you personally don't like, or that you've taken a poll of and most people don't like? Or it sounds like corduroy instead of satin? Come to think of it, what is a good working definition of "good tone" or "good texture"? I've always had a hard time getting a good, solid definition for "tone" and "texture" in guitar sounds. They seem like really waffly words that people throw around but don't really have much meaning when you look hard.

I'm stuck in my old, outdated measurement-oriented ways, I guess. I have the kind of archaic viewpoint that If I say that something can only accept a signal of, say, +/-200mV before the input buffer clips, that it carries some meaning. And I say things like having an input impedance of only X means the treble rolloff starts at Y. Silly, really, when one can just say "bad tone" and have it be so much more descriptive.

Sorry to have caused so much confusion.

[zachary vex]

i don't recommend that bypass circuit for anything, really.  it doesn't have any headroom and it doesn't have very good tone/texture, mother nature or not.

OK, I see. Actually I don't recommend it for anything, really either.
...As to not having any headroom - is that *zero* headroom? It won't conduct *any* signal? Or it won't safely carry a guitar signal? ...

for someone who demands such precision in comments from someone else, you might think through the consequences of your circuit designs before you send your website's visitors on electronic mis-adventures.  case in point... it only takes a single look at a single project to find a major case of bad-planning... your Improved Hum-free A/B/Y has no separate filtered/unfiltered power supplies (adding a single resistor to each side of the bipolar supply would have done this) to guarantee that the LED switching won't click.  in addition, your choice of LED control circuits guarantees that the positive battery will drain at a rate of 4mA more, likely twice as fast as the negative supply, resulting in the positive battery being replaced twice as often as the negative... of course, few people will do a current check to see which battery is bad and will simply replace both, resulting in the waste of a perfectly good neative supply battery.

a better approach would be to suggest ultra-bright leds such as the 351-3232 from Mouser and to tie the current-limiting resistors to the opposite supply instead of ground, forcing both batteries to share the load and balancing noise, and then to increase the current-limiting resistors to something like 47k, resulting in a current savings of >3 mA, which theoretically could double battery life.

next time you feel compelled to correct my comments here, i'll oblige you and those builiding your projects with another circuit correction... thanks, R.G. "Should work, but I haven't built one" Keen.  now THAT sounds like hand-waving to me.  8^)

[Morocotopo]

Boys, I sure appreciate and learn from all of your responses, I´m just starting in this whole "make your own pedals and actually try to understand how they work" business.
plan of action (hopefully, success will be achieved somewhere before the last step):
- Build R.G. switch
- PCB and build Robbins switch
- PCB and build Boss switch
- Curse, scream, buy DPDT´s
- Forget about stompboxes and turn to yoga

Hopefully, I will get back with some good news at some point...

Please, don´t fight, everyone is entitled to his/her own opinions...

[Mark Hammer]

In some 8 years of graduate school, I ended up taking about 7 statistics and research design courses at several universities, all from different people.  One of the things I learned was that methodologists all think that everyone else is wrong and that their method is the only one really worth pursuing!

So, the price of hanging around brilliant diligent people who truly understand the methods involved is that you have to put up with their bickering about who did it "right".

Of course, the irony lost on both these guys is that I'm the one who's right, dammit!!

[calpolyengineer]

Of course, the irony lost on both these guys is that I'm the one who's right, dammit!!

Touche!

-Joe