Zvex - Probe series

cortezthekiller · Post by **cortezthekiller** » 07 Sep 2009, 13:43

Hey, Welcome to the forum.

Is the photoresistor part of the wah circuit tied to ground? Go over the layout and schematic comparing to your's and look for any differences. Also, are the led's oriented correctly?

I've made the inductorless wah circuit a few times to control with a light source and have had no issues in that regard.

Perhaps post some images of the build to allow others here to see if there are mistakes.

odnoder90 · Post by **odnoder90** » 07 Sep 2009, 15:30

Thanks Cortez,

I used the VTL5C9 and I have connected a LED in parallel to regulate it visually. When the hand approached the antenna increases the LED brightness, so I think they are connected properly.

These are the layouts I made.

cortezthekiller · Post by **cortezthekiller** » 07 Sep 2009, 16:28

From the probe layout I see that Q2 was labelled as 3906, but the design calls for an NPN (3904, 2222 etc.) Unless this is a typo that may be the problem (with the revolutiondeux design anyway)

Also, the 2 trim pots affect the range of the antenna, some settings making the led go from on to off, some from off to on, and in between.

Also do have the schematic drawn for the wah, though it looks to be a crybaby-esqe design. Mainly the photocell section replacing the pot on the wah and how it was implemented. This is critical to getting the right sweep of the wah.

odnoder90 · Post by **odnoder90** » 07 Sep 2009, 17:22

For Q2 it's only a mistake on layout, on circuit, I have used a 2n3904.

The wah is based on Vox v847, I connected the output of the VTL to LDR on wah layout. The probe and wah are 2 separate circuit.

cortezthekiller · Post by **cortezthekiller** » 07 Sep 2009, 17:35

Perhaps check out the "Anderton Wah Retrofit" section on the Technology of wah pedals for how to implement the LDR:

http://www.geofex.com/article_folders/w ... wahped.htm

duman · Post by **duman** » 02 Nov 2009, 10:50

Hi, I attempted building the tremolo version of the probe not too long ago and I hoped that someone could help me out. First of all, I'm using a cd4093be, 5.1 zener, I increased the cap in series with the antenna tenfold, and increased the sensitivity resistance on the trimpot to about 2M. I tried using various sizes of antennae. As of now, the probe still will not light up smoothly, with only about a half inch of usable space from the antenna.

The other problem is noise. The high frequencies coming off of the 4093 bleed into the guitar signal, and it doesn't help that the volume is simultaneously increasing. Like what others were saying, grouding myself makes the noise more bearable, but it is still there. Before looking more into the zvex trem, I jumped the gun and put the ldr in between a dual op amp a la tremulus lune. I tried distancing the two parts of the circuit about 2 inches, and even put an aluminum shield in between the two with little or no success. Are Op amps more prone to picking up noise compared to the components in the SHO?

Sorry if this thread is near gone, but I'd really appreciate it if someone can help me.

devastator · Post by **devastator** » 02 Nov 2009, 15:53

What kind of atenna I could use for that probe circuit ? (I'm making the project posted by Soulsonic few pages above)

~arph · Post by **~arph** » 02 Nov 2009, 16:18

duman wrote:Hi, I attempted building the tremolo version of the probe not too long ago and I hoped that someone could help me out. First of all, I'm using a cd4093be, 5.1 zener, I increased the cap in series with the antenna tenfold, and increased the sensitivity resistance on the trimpot to about 2M. I tried using various sizes of antennae. As of now, the probe still will not light up smoothly, with only about a half inch of usable space from the antenna.

I should stick to the orignal values (use an unbuffered IC too) . Especially with a 2M sens trim it could turn out impossible to dial it in correctly. When built to spec. the key is in the adjustment of the two trimpots.

As for the noise, did you increase any cap values in the oscillator section too? if so you might have decreassed the oscillator frequency into the audible range. Again here. stick to the posted values.

I agree the circtuit is a bit picky. Earthtonesaudio did lots of research on probe circuits and came up with a simpler opamp version. Search for earth and space wah on the forums.

~arph · Post by **~arph** » 02 Nov 2009, 16:22

devastator wrote:What kind of atenna I could use for that probe circuit ? (I'm making the project posted by Soulsonic few pages above)

Copper clad PCB material is a fine choise, but any flat piece of conducting metal should work fine.. The larger the antenna, the better the range.

devastator · Post by **devastator** » 02 Nov 2009, 17:23

Ok I'll try to find that, the store close to my home must have a kind of "Copper scotch".

Post by **Space Jm** » 02 Nov 2009, 19:57

The zvex solution is really tricky to tune...not really stable to my ear.

You can try the earth and Space Interface with a single AOP.

It is more stable but works opposite to the ZVEX solution.

It dim the led once the hand is approach..instead of light in..or the opposite I do not remember.

duman · Post by **duman** » 02 Nov 2009, 21:23

~arph wrote: I should stick to the orignal values (use an unbuffered IC too) . Especially with a 2M sens trim it could turn out impossible to dial it in correctly. When built to spec. the key is in the adjustment of the two trimpots.

As for the noise, did you increase any cap values in the oscillator section too? if so you might have decreassed the oscillator frequency into the audible range. Again here. stick to the posted values.

I agree the circtuit is a bit picky. Earthtonesaudio did lots of research on probe circuits and came up with a simpler opamp version. Search for earth and space wah on the forums.

Thanks for the reply. I had initially followed briggs' schem pretty much exactly except for the 4093. Without anything tweaked, I couldn't get it working untill I exceeded 250k on the trimpot value. Could a buffered 4093 be that much of a problem?

sickness · Post by **sickness** » 03 Nov 2009, 16:56

The IC you are probably looking for is a CD4093 which is a quad dual input NAND with Schmitt triggers... The entire antenna is pretty simple and for the rest of the circuit you can use anything that can be driven using an LED. For example the wah probe is probably the classic inductorless wah made by Colorsound many years ago driven by a Vactrol (If you want a schematic for the antenna part just let me know and I'll post it here).

I also want to comment about the general concept of operating a pedal with your foot in the air. I think it is a cool gizmo but you can't really use something like this for a long time since your muscles will contract as the foot looks for terra firma. This is an instinct and the mechincal footpedal does a great job in "cheating" the foot because it can feel the support under it.

earthtonesaudio · Post by **earthtonesaudio** » 03 Nov 2009, 17:44

sickness wrote:I also want to comment about the general concept of operating a pedal with your foot in the air. I think it is a cool gizmo but you can't really use something like this for a long time since your muscles will contract as the foot looks for terra firma. This is an instinct and the mechincal footpedal does a great job in "cheating" the foot because it can feel the support under it.

Very true. I played a genuine Wah Probe and it was comfortable to use while seated, but standing not so much. Of course you could also use the proximity technique with a standard rack-and-pinion setup, but the only benefit is not having any pots to wear out.
In the next prototype I make I want to incorporate some form of footrest or pivot point to make it a little more ergonomic. The hard part is coming up with something that doesn't require the use of lots of fancy power tools.

Jarno · Post by **Jarno** » 03 Nov 2009, 19:28

Maybe a wooden block for your heel, and then have the antenna just under your toes and not under the rest of your foot (because then it wouldn't work, wouldn't it)? The antenna would be a lot smaller, maybe that's not an option.

sickness · Post by **sickness** » 04 Nov 2009, 05:08

earthtonesaudio wrote:
sickness wrote:I also want to comment about the general concept of operating a pedal with your foot in the air. I think it is a cool gizmo but you can't really use something like this for a long time since your muscles will contract as the foot looks for terra firma. This is an instinct and the mechincal footpedal does a great job in "cheating" the foot because it can feel the support under it.
Very true. I played a genuine Wah Probe and it was comfortable to use while seated, but standing not so much. Of course you could also use the proximity technique with a standard rack-and-pinion setup, but the only benefit is not having any pots to wear out.
In the next prototype I make I want to incorporate some form of footrest or pivot point to make it a little more ergonomic. The hard part is coming up with something that doesn't require the use of lots of fancy power tools.

I also thought about using somekind of pivot that should be located pretty much in the same position where the pivot on a wah pedal is. I took a wood block and a big copper tube I had around and tried it out... I'm afraid it was almost as bad as lifting the foot in the air and if the pivot is not wide enough it will easily sink into the shoe (unless you have boots with some heavy sole). After that I kind of gave up on the idea... I have another one that I don't have enough to check (work work work). I thought about taking a block that has a curve to on one side it and place it on the floor. This way the foot will always have support at the point that is pressed against the device. The problem is that this does not look very elegant and it sure won't feel as nice as a wah pedal does but it has no moving parts so building it could be pretty easy. I guess one could use a similar antena that will be located around the upper 1/3 part of the block so the foot will actually get close to it in a some-what linear fashion. Another idea could be chaging the sensor all together and use a simple capacitive sensor based around an MCU. I guess that could make it so complex to build that one could easy get a used wah on ebay, gut it and install a pot controlling an LED and have the same end product (but in a nice box)

guiddruid · Post by **guiddruid** » 04 Nov 2009, 14:03

or use an LED, an LDR and a simple shutter, like in a Morley wah... more reliable, fewer electronic components... and probably off topic - sorry

duman · Post by **duman** » 05 Nov 2009, 09:28

sickness wrote:The IC you are probably looking for is a CD4093 which is a quad dual input NAND with Schmitt triggers... The entire antenna is pretty simple and for the rest of the circuit you can use anything that can be driven using an LED. For example the wah probe is probably the classic inductorless wah made by Colorsound many years ago driven by a Vactrol (If you want a schematic for the antenna part just let me know and I'll post it here).

Isn't the Schmitt trigger the buffer that we don't want?

btw, I replaced my components with the original values, but one thing that I did differently was replace a radioshack 2n3096 substitution with an actual one, and it helped out (no need to up the trimpot to unreasonable values, and 90% of the noise is gone). Putting in a 7.5 zener decreased sensitivity for me. I'm still not getting optimal sensitivity, and hopefully getting a cd4093 will do the trick. Does anyone know where to find any?

ech0es · Post by **ech0es** » 25 Nov 2009, 22:23

probe clone

http://www.pedalparts.co.kr/shop/goods/ ... tegory=036

T1bbles · Post by **T1bbles** » 10 Jan 2010, 14:08

soulsonic wrote:Okay, here is the PCB layout:
members/soulsonic/Gallery/WahProbe/Ghos ... %20PCB.pdf
members/soulsonic/Gallery/WahProbe/Ghos ... Layout.pdf

It works good; no noises!

Hey guys, I was looking into building this little bad boy, just one question though; what value and taper does 'sensitivity' have to be?

Thanks a bunch,

M