Pearl PH44 schematic?

[Mark Hammer]

I have lucked into one of these babies, and would like to know more about what's inside, particularly with respect to maybe inserting a ramp-up/down feature to the dual speed selection.  If I look for the schem, all that seems to crop up is the one for the 4-knob Pearl phaser ( http://www.effectsdatabase.com/model/pearl/soundspice/ph03 ).  The one I'm getting is the 6-knob with slow/fast speed selection ( http://www.effectsdatabase.com/model/pearl/soundchoice/ph44 ).  Any links?

[Earthscum]

I may have the schem at home. Ill check after work and if I do I'll dropbox it. The one I have is some kind of PWM phaser, I believe. I think 6 op amps, so 3 stages

[Mark Hammer]

This one purportedly has 1440 degrees of phase shift.  If my math is correct, that would suggest 16 stages, which I am highly doubtful of.  But, I'll see when I take possession and pop the hood.

[nocentelli]

I have lucked into one of these babies

<edit>schematics are at the other place: Here's a link -

http://s853.photobucket.com/albums/ab93/bernardduur/Schematics/

I believe it's traced from my unit - I sent it to bernardduur to fix the regulator, before I had ever considered trying to build pedals myself</edit>

Does it work? I had one for a while. The phaser sound is pretty good, not particularly exciting (I prefer my smallstone actually) but the ramp is cool, and the enclosure is just about the coolest-looking thing I have ever seen:







What really bugged me was the input control and associated circuitry: I found it impossible to set to a useable level, since it seems to control the bypass buffer level as well as the effected level. If the level was good for "on" it was too quiet for bypass; Set it right for bypass, and you end up overdriving the phase sound..... Aaaaaarghhhhhh!

[Mark Hammer]

Well those would be traits I am hoping to ameliorate, armed with a schematic.

can't see what you posted from work, but I look forward to seeing it tonight at home.  Thanks.

[Mark Hammer]

Snagged the schems.  Many thanks.  That IS one complicated sumbitch, ain't it?

[Earthscum]

Yeah, definitely not the schem I had. I have chorus, flanger, ph03 and the same PH44 "core" schem all right together, and had just skimmed this folder the other night digging for some switched resistance stuff.

[Mark Hammer]

Thiose diagrams are going to come in handy.  The vendor of the pedal informed me that, after trying it out for the first time in 25 years, it doesn't work.  Fun times ahead! 

It seems that the pedal already DOES a ramp-up/ramp-down thing.  Very interesting.

[Mark Hammer]

Picked it up, and took it apart.  Here are some gutshots.  Like I say, that's some kinda phaser!  Hard to see, but it includes an NE571 compander chip, in addition to a whack of TL062s.  Nice sturdy chassis.  The main board connects to the daughter board via easily detachable connector cables.  This is gonna be fun!

[daverdave]

1440 degrees of phase shift would suggest 8 stages, not 16. The 90 degree shift is at the resonant frequency set by the timing components (the resistor and capacitor forming the first order filter at the non-inverting input in the case of the standard allpass used in most designs). From the schematics it looks like it has 8 stages.

[Mark Hammer]

I was always under the impression that each stage could add up to 90 degrees of shift, such that two stages at maximum shift would provide a signal of opposite phase (180 degrees) to the input, providing the cancellation.  At least that's the impression gleaned from the popular literature.

I won't argue the point since I'm just an observer not an EE.  I'll also be among the first to admit that the "information" provided in manuals, product reviews, and ad copy can often be inaccurate or misleading.

Can anyone provide an orthodox perspective on what the traditional phase-shift stage does in theory?

But you're correct, there are "only" 8 stages.  From the little nuggets that Osamu Hoshuyama has posted, it would appear that individual stages can easily be reconfigured as other than allpass (e.g., lowpass), making it possible to "phase-filter" this thing.

[analogguru]

Can anyone provide an orthodox perspective on what the traditional phase-shift stage does in theory?

For sure...... but why ?  When all has been covered already in this article from 1976:
rubidium.dyndns.org/cag/pdf/eti447.pdf

and from 1977:
http://electronicmusik.wordpress.com/tag/everyday-electronics/

enjoy reading,

analogguru

[Mark Hammer]

Thanks.  I was well-familiar with the ETI 6-stager (bought the Canadian issue with it back in 76 or 77!) but had never seen the other one.

I popped a few batteries in the PH44 (it uses a pair of 9v and regulates the 18v down to 12v) and fired it up.  Nothing.  Tried measuring a few diagnostic voltages, particularly the 12v regulator.  A-HA!!  Nothing even remotely close to what I ought to see.  Removed the regulator, and installed another.  BIngo bango, worked perfectly. 

A very nice phaser, and worthy of its reputation.  The "manual" control allows for dialing many flavours.  At some point, I may explore installing a 4-stage/8-stage switch.  Although I'd like a slightly longer ramping speed, the ramp-up/ramp-down is really nice.  THe remote footswitch jock is also nice.  I imagine I'll replace the various LEDs in it with somethng more efficient, so I can cut down the current drain (it draws 24ma).  There are 3 LEDs, one for peak (clipping indicator), one for speed (on at all times), and another for bypass/effect.  Cutting the current requirements of all by 2/3 will extend the batteries a bit further.

Now I don't mind letting go of my other phasers.

[lars]

Picked it up, and took it apart.  Here are some gutshots.  Like I say, that's some kinda phaser!  Hard to see, but it includes an NE571 compander chip, in addition to a whack of TL062s.  Nice sturdy chassis.  The main board connects to the daughter board via easily detachable connector cables.  This is gonna be fun!

It would be nice if these pictures weren't on blursabucket!!!

[radio]

You might find it in the build docs of deadendfx. Dino was working on it

However I don't recall if he s already done with the PCB and worse I don't

recall the name.

Sorry for not being more specific!

[Mark Hammer]

He borrowed mine for it, and in his usual industrious fashion, reverse engineered it.  Looking at the DEFX site, the board is currently available.

[tubegeek]

Right click on image. Copy image address. Paste into your browser, and delete anything before "photobucket" in the URL. You'll go to the unblurred image. Then you can download it and use the image upload feature here to put it on the local photo hosting. A pain in the ass but doable. I did one, above.

[Mark Hammer]

Thanks for that, Jeremy.  I owe you one! 

[tubegeek]

Thanks for that, Jeremy.  I owe you one! 

You may not be quite so happy once you discover just how many popup ads you're about to have to "X" out of!

[PMowdes]

Dino and I have built it but the PCBs aren't available, we haven't finished verifying the build.  It needs a boat load of matched transistors which is a pain