Multi-FX switching idea

[DavidS]

Here's a thought I had a while ago, thought I'd share it.

If one built their pedals with some solid-state element in the switching, such as a PIC with relay control (a la Transmogrifox), you could add a little 1/8" jack to each pedal to control it's bypass state from a central module. Imagine a little floor unit that had small cables snaking out to each effect unit. The cost would be less than all of the jacks and plugs necessary for standard loop controllers, of course, the effects would have to modified or designed with this in mind.

Just a thought, maybe someone will run with it.

DavidS

[R.G.]

That's not a bad idea.

You can already do this with all Boss and Ibanez effects by adding the jack for the switching signal, as they already have the internal electronic switching stuff.

[troubledtom]

hell yes!!!!!
     peace,
            - tom

[Transmogrifox]

I had the thought to try that.  Should be pretty easy, especially considering what RG had to say about it (with Boss and Ibanez pedals).

Another project that I want to bring into being over the years is a master looper station where the order of pedals can be programmed.   It would be like a big relay matrix.  Then I could add some mixer modules so you could also do certain combinations of pedals in parallel also.

Once that's working, and the preset controller is solid--here's where it goes really tech (and expensive):  Touch screen display with downloadable pedal icons (as in a picture of each one of your stompboxes) that are touch-screen draggable so you can drag them and drop into the position you want them.  Furthermore, you have a name assigned to the icon, so the name will display on a little LCD or 7-segment display right under each switch. 

Due to the nature of floor stomp controllers, the touch screen display would probably have to be rack mountable and communicate with the floor controller via radio or MIDI.

[R.G.]

a master looper station where the order of pedals can be programmed.   It would be like a big relay matrix.

You mean like these...?

http://www.geofex.com/Article_Folders/juggler/juggler.htm, 4 November 1999
http://www.geofex.com/Article_Folders/fxswitchr/fxswitchr.htm, 18 January 2000
http://www.geofex.com/Article_Folders/ASMOP/ASMOP.htm, 28 October 2001
http://www.geofex.com/Article_Folders/ASMOP/asmop1d.pdf
http://www.geofex.com/Article_Folders/ASMOP/asmop1e.gif

Nobody seemed terribly interested, so I quit adding on to it.

[Dave_B]

Nobody seemed terribly interested, so I quit adding on to it.

I predict that will change now.  We seem to be approaching a critical mass on control circuits with introduction of the digital section of the forum.  Pure speculation on my part, but I think the addition will attract people who excel at that sort of thing.  People who may have wandered off thinking no one was interested. 

[troubledtom]

Nobody seemed terribly interested, so I quit adding on to it.

I predict that will change now.  We seem to be approaching a critical mass on control circuits with introduction of the digital section of the forum.  Pure speculation on my part, but I think the addition will attract people who excel at that sort of thing.  People who may have wandered off thinking no one was interested. 

or some stubborn dumb shit like me that'll somehow make it happen
    peace,
          - tom

[Transmogrifox]

a master looper station where the order of pedals can be programmed.   It would be like a big relay matrix.

You mean like these...?

http://www.geofex.com/Article_Folders/juggler/juggler.htm, 4 November 1999
http://www.geofex.com/Article_Folders/fxswitchr/fxswitchr.htm, 18 January 2000
http://www.geofex.com/Article_Folders/ASMOP/ASMOP.htm, 28 October 2001
http://www.geofex.com/Article_Folders/ASMOP/asmop1d.pdf
http://www.geofex.com/Article_Folders/ASMOP/asmop1e.gif

Nobody seemed terribly interested, so I quit adding on to it.

Incredible!  I wonder how I missed all that as you were developing it. 

I have some questions regarding the PWM phaser:  why did you use a single-ended transistor driving a CD4049 to drive the CMOS switch control gates?  Was this related to the sum of the input capacitance of the gates exceeding the uC's recommended max capacitance driving?  If so, did you try it without the buffer just to see if it really made any audible difference (be it noise, distortion or limited sweep depth)?

[varialbender]

If the project were to become as big as Transmogrifox described, would you even need to modify the pedals? Wouldn't it be a good idea to make a 'bypass' pedal, like a loooper, where you put your current pedals in the loops and can mess with them from there?

[R.G.]

If the project were to become as big as Transmogrifox described, would you even need to modify the pedals? Wouldn't it be a good idea to make a 'bypass' pedal, like a loooper, where you put your current pedals in the loops and can mess with them from there?

That is what the switching project articles from GEO suggest.

The external switching input and the massive, any-order switching are two different ends of the spectrum.

[varialbender]

From what I understood, there was mention of using external input any-order switching, and I didn't understand why, since it's possible to do it as a loooper. For some reason, I didn't make the connection that you had already mentioned it. Thanks and sorry

[Mark Hammer]

The remote switching controller also addresses some of the concerns that some folks have for the little plastic boxes like the various Danelectro and now the Behringer pedals.  A remote controller eliminates the need to rehouse the pedal guts into something that folks are willing to stamp their feet on, or simply a bigger target.

Just keep in mind, however, that not all pedals that use FET-switching or CMOS switching necessarily use the same momentary connection.  From what I've seen, both Boss and DOD use a momentary ground connection, where some of the Dano pedals I've seen schems for use a monentary connection to V+.  Wiring up a 1/8" jack for the first type is a breeze.  Wiring up a similar jack for the latter involves a slightly pickier wiring arrangement (using tip and ring only) and a 1/8" stereo jack.  Not a huge pain, but you do have to pay attention to some things.

[David]

a master looper station where the order of pedals can be programmed.   It would be like a big relay matrix.

You mean like these...?

http://www.geofex.com/Article_Folders/juggler/juggler.htm, 4 November 1999
http://www.geofex.com/Article_Folders/fxswitchr/fxswitchr.htm, 18 January 2000
http://www.geofex.com/Article_Folders/ASMOP/ASMOP.htm, 28 October 2001
http://www.geofex.com/Article_Folders/ASMOP/asmop1d.pdf
http://www.geofex.com/Article_Folders/ASMOP/asmop1e.gif

Nobody seemed terribly interested, so I quit adding on to it.

Wrong-o, mon ami!  I was terribly interested, but I couldn't wrap my head around the cross-point switching concept.  I still can't.  Last summer I ran out of time to deal with it.  I intended to revisit this in the future.

The future is here.  Hi-hi, ho-ho, the GT-3 has got to go!

[Peter Snowberg]

Remote switching brings another potential problem with it in the form of ground loops. I would suggest using optocouplers for the actual triggering. The normally closed switch contacts in a jack could be used to pass the flip-flop control to the bypass switching when no plug is inserted, but the plug would have to supply a signal that turned the effect on or off in the absence or presence of a ground connection. The opto could than supply that ground when needed.

I think remote switching built into all pedals with the capability is a great idea.

[DavidS]

Wait, why not just have relays on the control module side which have no common connection, and isolated jacks? No ground loops, no issue as to how the switching is being done in the pedals.

[R.G.]

Wait, why not just have relays on the control module side which have no common connection, and isolated jacks? No ground loops, no issue as to how the switching is being done in the pedals.

That is how I did the relays versions of my switcher, and for that reason.

I think maybe Peter was concerned about a ground loop with a multi-FX switcher that used the internal electronic bypassing of Boss and Ibanez pedals.

Peter???

[Peter Snowberg]

I think maybe Peter was concerned about a ground loop with a multi-FX switcher that used the internal electronic bypassing of Boss and Ibanez pedals.

Peter???

Correct. 

[Transmogrifox]

RG:  Now the hardware question about the PWM phaser:  why did you use a single-ended transistor driving a CD4049 to drive the CMOS switch control gates?

[R.G.]

why did you use a single-ended transistor driving a CD4049 to drive the CMOS switch control gates?

It took me a minute, but I figured it out. It's a level translator between the 5V supply of the PIC and the 9V supply on the rest of the pedal.

That phaser circuit works well, by the way, but you do have to make sure that the PWM is running at well over audio. 38kHz to 44kHz is a good start.

If you use a chip without the internal A-D of the 87x series, you'll also have to use caps on the pots to sense pot setting. I find that using the internal A/D for pots is a great way to do it.

[Transmogrifox]

Thanks...
The CD4049 is supposed to be a level converter, so the single-ended transistor shouldn't be necessary.  We used the CD4050 (CD4049 noninverting brother) for this purpose with a senior design project.  We were actually able to drive it high and low using a 0-3V DSP output.

It may be that the CD4066 control gate is the same ( I would have to double check with the data sheet, though).  I think I'll have to build this PWM phaser with my tap LFO now.  Does anyone know if it is adequate with 8-bit resolution?  Nice thing about uC's is that they can be reprogrammed so the circuit doesn't have to change.  I better calculate the maximum resolution I can get using the internal clock to see if I can add a bit or two PWM resolution without getting too close to the audio range on PWM frequency