Joyo Phaser mod

[Mark Hammer]

4M3 may well be the limit of what a reasonable modest sweep can be, unless the value was chosen to somehow complement how they wanted to set the gate-bias.  I know when I tinker with it, or when I have an unlabelled 3-way toggle that I haven't used in a while and forget which position is widest sweep, the width of the sweep is not very apparent unless I: 1) turn the resonance up a bit to make the highest point of the sweep more apparent, and 2) make the speed at least medium fast.  Under those circumstances, the contrast between narrower and wider sweep becomes more apparent.  T'were I, I'd use a 3-way on-off-on toggle to use 4M3 as the default and then switch in one of two parallel values to drop the effective resistance.  22M will bring things down to around 3M6, and 10M brings it down to around 3M.

I like to replace the 1M fixed resistor, coming off the wiper of the bias trimmer, with a 510k fixed resistor and a 500k/470k variable resistance.  This moves the frequency range of the sweep around from low and gurgly, to high and swirly.  Set the bias trimmer with the added variable resistor to max resistance, tyo produce the most gurgly sweep.  As you reduce the extra pot's resistance, the overall range will shift upwards.

[@Gustavo G.C.]

[youtube]Helo! Im new on DIY eletronic sircuits and Im interested on modifing my Joyo Vintage Pheser adding an switch to vibrato mod (just like the mod on the MXR 90 Phaser)... Could some one help me?

Here is the link of a demo of this modification: https://www.youtube.com/watch?v=6yhRXrRk1sg

[@Gustavo G.C.]

Helo, Rick. How are you?

I am textig you to ask about this mod's that you have done into an Joyo vintage phase: "I've added a three position resonance switch, a dry lift switch for vibrato and I strapped a 330R resistor across the resistor in line with the speed pot to get the maximum possible speed out of it."...

As I am new on guitar pedals mod's world I don't know how to do it... Could you help me?

Thanks for the attention!

[RickL]

Wow, that was a while ago. I don't remember specifically how I did the mods (Mark Hammer is great at explaining this stuff) but if I remember correctly, the Joyo phaser is pretty much a copy of the MXR phase 90. Find a schematic of that pedal and you'll have one pretty close to the Joyo version. I probably used the  Tone pad version http://www.tonepad.com/getFile.asp?id=42.

If you use that schematic and find the equivalent components on the Joyo board:

The resonance mod uses a dpdt centre-off switch to switch the red 22k resistor either in or out or some smaller value (can't remember what I used -experiment or use a trim pot).

The dry lift for vibrato uses a spst switch to connect or disconnect the bottom red 150k resistor. This is the dry signal. Removing it makes the phaser sound like a vibrato.

The speed mod just adds a resistor in parallel with the red 4k7 resistor connected to the wiper of the 500k pot to lower its value. It looks like I used a 330 ohm resistor. I probably temporarily soldered a 10k or so trim pot across the 4k7 and trimmed until I got the fastest speed I could get before it stopped working, then replaced it with a resistor equal to the value that the trimmer was set to. This will also slightly speed up the slowest speed, but you probably won't notice much difference.

[Mark Hammer]

Folks may want to take a look at this recent thread: https://www.diystompboxes.com/smfforum/index.php?topic=128189.0

[RickL]

I've just read back in the thread and it looks like the Joyo doesn't actually have the 22k feedback resistor for resonance that the Tonepad schematic has. You'll need to add the resistor between the two points indicated by dotted circles in the picture further up in the thread. The dpdt centre-off switch will let you add the resistor, a different value resistor (either smaller or larger) and no resistor. Don't go much below 18k or it will likely squeal, but experiment. Mark's suggestion is to use the switch slightly differently than I did by putting an 18k and 25k in series between the two points. The switch shorts either the 18k, the 25k or neither resistor for three different feedback values (the higher the resistance, the less the resonance). The 43k value is high enough that it will sound very close to having no resistor.

Sorry, I don't know which of the 150k resistors you'll need to lift to get vibrato. You'll want the one that connects to either pins 1 and 2 or pins 6 and 7 of one of the op amps.

Try the ramp mod too. It gives a couple of variations to the LFO shape and is very easy to do.

[Mark Hammer]

Doing the mods may be easier than finding room in the enclosure for any related switches!  Gustavo may want to consider a rehouse in a larger box, like a 125-C, to make room for the necessary controls.  Although, looking inside one - assuming it looks like the pic below - there may be room for one toggle, oriented horizontally (i.e., sticking out the side, rather than out the top) pointing out the right side of the pedal, above that diode, and another, also horizontal, pointing out the rear edge of the pedal, above where the pads for the power jack is.  I suppose it depends on the size of the toggles you find.    Whatever their size, I suspect there is not enough clearance to have them sticking out the top (vertically).  There might be, above the legending over the jacks, but that comes very close, too close, to the stompswitch.

However, given how much space the jacks take up, it seems like there is plenty of room underneath the board to install horizontal toggles.