Newbie Question: Ibanez/Maxon Phase Tone

[cps]

Hi,

I'd like to try building my own Ibanez/Maxon Phase Tone:

http://www.maxonfx.com/pt999.html

Is there a schematic available for this pedal anywhere?

Cheers,

Chris Share

[smoguzbenjamin]

Hi Chris, welcome

If it's still in production, chances are you'll either have to pay for the schemmo, or that you can't find it. Besides, if you've never built anything before this might be a big thing to start with. Try building something a little less complicated like a distortion or overdrive before you attempt a phaser If you have enough experience, go right ahead. Look at the phase 45 or phase 90 at www.tonepad.com for phaser designs that are known to work. IMHO a phaser with more than 4 stages sounds too thick anyway

[Marcos - Munky]

I have the schematic for the 909. Isn't the same unit, but if you want it send me a e-mail.

[Mark Hammer]

Marcos has already made the offer, so I'll let him send you the schematic.

The PT90 and PT909 are not especially exotic in terms of design or parts requirements.  They use 2SK30AY FETs as the control-elements/variable-resistors, and these are still readily available.  

The only noteworthy aspect of the design is that it uses a resistor/cap combination between the gate and drain of each FET.  This tends to improve distortion characteristics of FETs, such that they can tolerate somewhat hotter signals before distorting.  It is not a rare exotic difference, but is not commonly found on all FET-based phasers.

Other than that, it is essentially no different that a MXR Phase 90, a cheap Danelectro phaser, or any other 4-stage phaser made by Rogue, Rocktek, Arion or any other budget line (and given how cheap the cap/resistor add-on is, maybe even some of them have it too).

The electronic switching is entirely unnecessary.  In fact, if the FET switching is ignored (we can explain how once you get the schem in your hands for viewing), that makes it easier to implement a vibrato mod.  If you cancel the dry signal, and keep just the phase-shifted portion, you get a nice wobbly-pitch vibrato effect.  Unfortunately, like most commercial phasers, the stock PT909 simply cancels the wet signal to achieve a "bypass".  So if you step on the momentary to cancel the effect AND have a dry-cancel for vibrato, you won't have either wet OR dry signals at the output.  Kinda quiet....but not in the desired way.  If you use a stompswitch to bypass the whole thing, then you can set the dry signal however you want.

My own personal preference is to build the Ross Phaser clone at Tonepad.  This is also a 4-stager, but has the following to recommend it:

a) there is a PCB layout available, whereas you're pretty much on your own for the PT909
b) FETs will need to be matched for the PT909 but the chips used in the Ross are already essentially "matched"
c) the Ross can be adapted to a "phasefilter" configuration which opens up some really interesting possibilities soundwise that are simply unobtainable with FET-based phasers like the PT909 (see Charlie Barth's "Frankenstone" - a modded Small Stone which is very close to the Ross - for soundclips and comments http://www.moosapotamus.com/frankenstone/frankenstone.htm)

[Marcos - Munky]

To tell the truth, I didn't heard the Ibanez phasers, but if you want a cool sounding phaser, build the Phase45 from Tonepad. I didn't built it (yet), but there's a soundclip in the old ROG site. I don't remember the name of the new site with the old articles and soundclips, but there's a link in ROG site.

[cps]

Hi Everyone,

Thanks for the replies!

I do have some experience with electronics so I'm not a complete newbie!

The reason why I'm interested in the Ibanez/Maxon Phase Tone is because a friend of mine had one many years ago, and I distinctly remember that it sounded amazing.

I've also owned and used some of the later Ibanez Phasers and they definitely don't sound as good.

I'll check out the Tonepad website. Maybe I'll have a go at their phaser if I can't get hold of a schematic for the Ibanez/Maxon one.

Cheers,

Chris Share