Tau pipe phaser in a wah pedal

[Ronan]

Inspired by Dino's (Digi2t) Tau phaser build and clip, I decided to have a go at making something similar but small enough to fit in a wah pedal. Here's a rough sound clip:

https://dl.dropbox.com/u/61170900/Tau%20phaser%20pcb%20sound1.mp3

I don't have the circuit in the wah pedal yet, its still in progress, but the circuit is working fine on the bench with the inbuilt LFO. Some pics:









I was relieved when it worked and nothing smoked. I ran it up on a variac, since all the IC's are soldered in. I used matched pairs of BC550C to save space, it took a long time to match them, then I retested hopeful pairs and when happy with the match, I superglued them together, so they couldn't get mixed up, even if the cat lay all over them. The power supply is a voltage doubling type, with 317/337 regulators for approx +/-15VDC, run from a wall wart rated 12V AC at 500mA, which delivers 14.7V AC at 130mA. The circuit is minus a few parts, no pseudo stereo out, no CV ins/outs, due to space constraints. There is a basic guitar preamp with x 4.7 gain at the input though. The circuit is copied from and very close to J. Haible's 20 pole phaser here:
http://www.jhaible.de/tau/jh_tau.html

[Mich P]

Wow, amazing job on this Ian !!
Mich P.

[Processaurus]

It sounds really cool!  Are the chorus-ey sounds towards the end of the sound clip still just the phaser?  It sounds in between chorus and phaser.

[Ronan]

Are the chorus-ey sounds towards the end of the sound clip still just the phaser?  It sounds in between chorus and phaser.

Yes that's just the "phaser". It is a bit of a chameleon in that it can do more than just "phaser" sounds. It was originally sold as a kit "flanger" around 1980. I recorded that clip with a dirt box (used at the very end of the clip) and an ROG Tonemender (clean preamp with bass/mid/treb) straight into a generic soundcard on the PC, no other effects at all. Sorry about the playing, a bit rough, but gives an idea. It is quite a versatile unit.

[digi2t]

The phaser REALLY excels with dirt. I've been running it behind my Gemini Dual Fuzz, and it just kicks my ass every time. I've only built two phasers so far, the Korg Mr. Multi, and this one, and the Tau really takes the cake.

I'm really curious as to what the Infinitphase will sound like. I also have a Son of Storm Tide flanger board in the wings, but I really love the Tau. Nice job on the strip down to a wah. Simply extraordinary work man! Three thumbs up. 

[pinkjimiphoton]

ian, that's outstanding bro!!

of course, we need vero!!

just kidding, of course. not really!!

[Ronan]

Hey thanks for the kind comments guys. Waiting on a 100K pot and some 220 wet and dry to finish the pedal.

The phaser REALLY excels with dirt. I've been running it behind my Gemini Dual Fuzz, and it just kicks my ass every time.

Yep, Dino, you did a really good job showing all the possibilities with dirt on your demo clip here, dirt + phaser starts around 6 minutes:
http://www.diystompboxes.com/smfforum/index.php?topic=99289.0

(but I forgot to include the link in the first post!) 

I'd like to build another one and put it in a standard box, it *might* fit in a 1590BBS but it would be a very tight fit with the stomp switch and in/out sockets. Might be pushing the limits too far, the pcb is 4" x 2.7" and has components underneath which adds to the enclosure depth requirement.

I did the usual minimum batch of 10 pcb's, so there's a few spare pcb's if anyone has a masochistic urge, the BOM and transistor matching are a bit daunting, and there are some minor issues with a few pcb hole sizes but no deal-breaker. It's very much a prototype, warts and all.

[armdnrdy]

Nice job Ian!

So the wall wart is a 24 volt center tapped? 12/0/12

[Ronan]

No, it's just a 12V AC wall wart with a single secondary (only 2 wires going to the pedal), which uses a voltage doubler to make around +/-20V DC, then each rail is regulated. Same principle as page one on this pdf here:
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=48536&g2_GALLERYSID=8490da22d0130715c2638b0537dd51cf

[armdnrdy]

Gotcha,

I forgot about that method. I've always been a bit leary about creating a bipolar power supply in that fashion after reading that the power is kind of "dirty." But...I also see a bunch of 1000uf caps!

Since you have built this PS, what's your take on it?

[Ronan]

This is the second pedal I've built using this power supply, and I can't fault it, can't hear any noise/weirdness, and the circuits sound good. I picked the caps for good or best ripple current rating in the required physical size. I'm using LM317/337 rather than fixed regs, no particular reason other than J Haible used them and I figure he knows a lot more about quiet power supplies than I do

[armdnrdy]

Good to know!

I had to source a 12/0/12 AC wall wart that was outlined for the Infinite Flanger build. That transformer wasn't easy to find and wasn't cheap when I found one! Almost $50 with shipping!

I've toyed with the idea of bringing in AC voltage to create a bipolar supply kind of like what Dave Fox did with the Paradox. I think I'll give it a try! Thanks for the info.

[pinkjimiphoton]

ian,
i'll bite man...how much? hit me via pm!