tc electronics xii programmable phaser guts

Fender3D · Post by **Fender3D** » 04 Dec 2014, 13:03

Thanks guys,

arph, yes very nice and versatile...
LFO modulation is hyper triangular, very musical.

I just changed the switching system, added LFO rate LED, and tweaked some values for deeper notches...

The 2 trimmers might as well be 2 controls, one is noise gate sensitivity, the other changes the "color" of the effect (shifts the notches higher or lower).

Gonna build another, I wanna see what I can do when 2 pedals are linked by the "program" jack...

Fender3D · Post by **Fender3D** » 04 Dec 2014, 13:03

Thanks guys,

arph, yes very nice and versatile...
LFO modulation is hyper triangular, very musical.

I just changed the switching system, added LFO rate LED, and tweaked some values for deeper notches...

The 2 trimmers might as well be 2 controls, one is noise gate sensitivity, the other changes the "color" of the effect (shifts the notches higher or lower).

Gonna build another, I wanna see what I can do when 2 pedals are linked by the "program" jack...

Ice-9 · Post by **Ice-9** » 05 Dec 2014, 01:05

Much nicer layout that the hideous mess of the original

armdnrdy1 · Post by **armdnrdy1** » 09 Dec 2014, 23:01

Hey Federico,

What did you use in place of the unobtainium XR4212 and RC4149 op amps?

And how is this phaser programmable?

Build looks great!

armdnrdy1 · Post by **armdnrdy1** » 10 Dec 2014, 00:37

Aahh...here's the user manual that explains the connections.

http://support.tcelectronic.com/entries ... r-s-manual

I guess I'll look at the schematic to see exactly what it's doing.

Fender3D · Post by **Fender3D** » 10 Dec 2014, 14:43

Hey Larry,

I'm fond of TL0xx, 074 in this build.
(R.G. said "when in dubt, use a 2N5088" referring to NPNs, I could mimic him saying "when i dubt, start with 741, then scale to a better device until it works..." referring to op-amps)

I guess they're even less noisier than stock ICs...

"Programmable" is a bit tricky, since I can't imagine a guitar player down on knees swapping plugs, on stage...

Anyway there's a stereo jack, whose ring affects depth and tip affects "range" or the "starting point", (notice that one trimmer simply sets this starting point).
By appling a stereo jack with 2 resistors, one GND-tip and one GND-ring, you can "program" different phaser settings.

Since these are connections after the LFO, and working as variable resistors to GND, you can connect a volume pedal acting as a flanger's manual control, another XII's program...

I started populate another board already ,just waiting for photocouplers...

PS
look at how simply they made a noise gate out of a comparator...

armdnrdy1 · Post by **armdnrdy1** » 11 Dec 2014, 03:03

Thanks for the explanation Federico,

I took a look at the drawing but..was thrown off a bit by the labeling numbers...1R, 2R, 2L, 3L etc.

This drawing is kind of hard to follow in places. Yes..the 339...I didn't notice that. That's a departure from the norm!

Fender3D · Post by **Fender3D** » 11 Dec 2014, 14:25

I know...
It's easier if you imagine looking at the (Cliff) jack sockets from connection side, 1R GND lug, 1L GND switched lug and so on...

U3a is a nice way for inverting signals (ie, instead of ADA flanger's phase switch)....

armdnrdy1 · Post by **armdnrdy1** » 11 Dec 2014, 17:45

Got it...the jack drawing is viewed from the pin side. The "L" and "R" is Left and Right.

That is confusing! I think that a standard symbol for the jacks would have been much more self explanatory!

So a pot is controlling the signal inversion instead of a switch?

Fender3D · Post by **Fender3D** » 11 Dec 2014, 19:02

Yep,
it's the "real world" version of the variable gain op-amp you can find on books...

: op-amp_variablegain.gif (4.82 KiB) Viewed 1756 times

it has inverting gain (-1) on one side, no gain in center and non inverting gain (1) on the other side.
BTW it's a perfect fit for Tayda's W20K Tone Control Potentiometer with Center Detent

P_V_P · Post by **P_V_P** » 10 Apr 2023, 16:51

I understand that eight and a half years in the life of a DIYER is not just a lot, but a lot. And the pedal is so interesting that interest in it is still great, and sooner or later, those who are looking for information on it will stumble upon this publication. I'm one of them.
Fender3D, please share your impressions of "your vision" of TCXII. Did you like the result /are you satisfied? What replaced the XR4212 and programmable RC4149? Is it possible to see the pcb in any format?Patience and delicious sound for all of us.