What Does the Foxx Phase?

[anotherjim]

I don't believe the sweep pedal necessarily has to have a switch. It selects between LFO or Manual pot (the manual works like a "filter matrix" such as on the EM flanger).

Not quite correct.

The "toe" switch chooses between manual pedal sweep and LFO speed. Look at the upper part of the toe switch. It connects the treadle pot to the LFO.

This is where the problem is. One would have to redesign the circuit to switch from auto LFO, to manual speed and manual sweep.
There would have to be another switch.

That's why it makes more sense to build this into a pedal enclosure. Nick is a Brian May fan....what would Brain do? 

I see your point -  but my point is that with the "toe" switch mounted on the phaser enclosure NOT in the expression pedal, then all is well. The toe switch functions as original whether or not an expression pedal is plugged in. I didn't think we were aiming for independent controls so you can go back to a preset LFO speed after waggling the sweep manually.

[armdnrdy]

I think that you're missing my point.

The pot in the schematic is shared via the toe switch between the speed control and the sweep control.

If this circuit was built "as is" with the controls mounted on the enclosure...there would be a useless sweep control on the enclosure.

The circuit would have to be redesigned to delete the sweep control.

With that being said...since Nick is a fan of how Brian May uses this Foot Phaser, and he would have to build/modify an expression pedal to work with this circuit....why not just built it as original inside of a wah shell?

Edit:
One could build this circuit into a regular enclosure and delete the speed/sweep pot. It can be "diverted" to the expression jack but...the effect would be useless without the pedal.
The board that Nick worked up is small enough to fit inside of a wah shell so....my thought to build it as the original remains.

[bluebunny]

...since Nick is a fan of how Brian May uses this Foot Phaser . . . why not just built it as original inside of a wah shell?

Why not build it inside a large clog? 

[armdnrdy]

...since Nick is a fan of how Brian May uses this Foot Phaser . . . why not just built it as original inside of a wah shell?

Why not build it inside a large clog?  

Or a clog for the treadle! Insert your foot into the shoe and go to town!
I like your way of thinking outside the box! or should I say...inside the clog!  

[anotherjim]

Oh now I'm baffled Armdnrdy...

"The pot in the schematic is shared via the toe switch between the speed control and the sweep control."
Yes, I never thought otherwise. Just one pot.  Why would it care if that pot is an integral panel mount or external pedal mounted one?

I'm looking at the scheme and imagining an external expression pedal connection via a switched jack next to the existing control  which has become a panel mounted  pot. When a pedal is plugged in, the panel pot is disconnected by the jack switch.

When the expression pedal isn't plugged in, why would this manual sweep control pot on the enclosure be useless?  - it would have exactly the same function according to the toe switch - do exactly what the pedal control pot would do - surely? It's only there to provide a control when an expression pedal isn't used. Yes, while an expression pedal is plugged in, the panel control will not function  - but so what?

I'm pretty sure the aim was to provide the pedal control functions without using a pedal.  I'm at a total loss as to why what I'm suggesting to achieve this shouldn't work.

[nickbungus]

As Jim says above, that's the way I thought it would work.  By having an expression pedal plugged in, R26 would be taken out of the circuit and this functionality would be handled by the expression pedal which would house a pot that would give me 0-100k resistance.

[armdnrdy]

Well...if you go back and read reply #42, Jim inquired how you were planning to box it. You provided a link (reply #44) to a wah enclosure that you purchased. It was Jim that mentioned the expression pedal jack.

It is my impression that your original goal was to build a work alike of the original Foxx Foot Phaser.

Jim,
The enclosure mounted sweep control could be used to get "%^&*ed" pedal filter sounds as you mentioned but...you can do the same with the pedal with the addition of varying the filter while playing. So...to me...having an enclosure mounted control isn't as useful, and to be honest...sort of redundant.

The word c-o-c-k-e-d was blocked above. 

[nickbungus]

I'm just grateful for all the help and I'm glad to explore all options.  The expression pedal bit just made it more flexible in terms of enclosures and as a total novice, it was also interesting as to how this could be achieved.

The build I've got is definitely a MkI.  I've made a few mistakes here and there that I've had to 'repair' (bodge), so design/build improvements and recommendations are so helpful.

[anotherjim]

All cool - carry on 

[nickbungus]

Ok... Its not pretty but its now in an enclosure!  My overall skill level is around the p*ss poor mark, but I can take the boxing of effects to a whole level below that.



But it works, and as far as Mark I goes, its done.  I'm going to make another one and hopefully learn from my mistakes.

[armdnrdy]

There you go!

Take a resistance measurement of the treadle pot: Toe up, and toe down.

See how far away from 100K you are. There are ways to remedy that.

Have you ever come across any measurements of an actual Foxx Phaser?

[nickbungus]

Hmmm.  Very interesting.  I could definitely tell I wasn't getting the full range but I did think I was closer.  The discarded cheap wah also used a 100k pot, so there was no need to change it.

Anyway, here are the readings:

Toe up 61.5k

Toe Down 1.6k

Its a great sounding Phaser but I'm starting to think the manual mode and fast mode are pretty useless.  I doubt Mk2 will live in an expression shell.  I can get a great tone from it without.

Have you ever come across any measurements of an actual Foxx Phaser?

No, I've never even seen one, let alone played one, let alone measured one!!  There was a re-issue a few years ago but that looked like it was a slightly different design with three speeds (or rather speed ranges) available.  I just missed out on buying one of these on eBay the other week.  The schematic I used I believe is for the original 70s version.

[nickbungus]

See how far away from 100K you are. There are ways to remedy that.

I'm still interested as to how this can be achieved though.

[anotherjim]

Is the pot gear movable or pinned in some way? It should be possible to get it closer to zero at toe down.
Is it a log or linear pot? At half rotation, it would read about 50k if it was linear.
The pot can be a larger value (220k), and the range tweaked to 0-100k by putting a fixed resistance (find the value with another pot first) in parallel with it.

[nickbungus]

Great stuff Jim as always.

Thanks

[nickbungus]

I've just bought the materials for V2 and I intend to try a few mods such as the range control suggested by AnotherJim.

A mod that I think would be really beneficial would be a level pot.  One of the main criticisms of the fOXX is the volume drop when the pedal is engaged.

Is there an easy way this can be achieved or would it be better to add a boost circuit to the end of the signal chain such as a EHX LPB-1 as previously discussed?

[anotherjim]

There is an easy way to boost the output. R49 could be increased. 220k would be a bit more than 6dB boost. There is a tone change with that though. R49 & C20 form a low pass filter and increasing R49 may well make it sound darker. As designed, the filter is cutting over 7khz, which doesn't really affect guitar tone, to keep it similar, C20 would need to be halved for every doubling of R49.

A booster will give you what you want without necessarily affecting the tone - unless it's designed to.
LPB-1

You may well need to increase the value of C1 to avoid bass cut.

[armdnrdy]

You can also increase the gain in the last phase stage. (R46)

You might try putting a 20K in there to start.

Also...have you looked at gut shots of the original Foxx Phaser? Much can be learned. 

The rotary switch has a couple of caps tacked to it. A 22µf and a .47µf. (I've seen tants or electros)

The reissue has these two caps placed on the board instead of the switch.

Even though the rotary switch is labeled "slow" and "fast"...from what I can tell, the rotary switch is a 2P4T (10 lugs) and there are four speeds. That's where the other two caps come into play.

I don't believe that the drawing you are working with is of the final production product.

There are no good sound sample available that go though the speed settings but, here is a review that mentions the differences between the reissue and the original.
http://freeforumzone.leonardo.it/lofi/Foxx-Phaser-Review-by-mark-Reynolds/D6055180.html

The review states that the original has two phase speeds, and two "ring modulator settings".
There is a chance that the two fastest speeds where perceived to be "ring modulator" sounding to the reviewer, or....the original that this individual owned had issues. (bad caps)

[nickbungus]

I was speaking to a guy called Mike Ryde online over the weekend actually.  He really is an aficionado when it comes to the Brian May sound.

He believes there were 2 70s versions as well as the re-issue with the 4 speed settings.

It would be interesting if I could source another schematic from a different version.

Going off this from the Effects Database, the controls describe what I have built.

[nickbungus]

If you look at the schematic it references number #1482 which is probably this version.

The gut shots on that closely resemble my build, which is unsurprising as I heavily used it as a reference for placing my components.