Orca Pedal - Design and Building

[bettsaj]

I'm looking at designing and building an orca/reverse wah pedal.

Let me give a brief back story. back in the early 70 David Gilmour's roadie plugged his wah in back to front, effectively plugging the guitar into the output and the amp into the input and he got this sound.....

by altering the tone control on the guitar you get the different oscillations which give the effect of laughing etc... really cool effect. As a side note this effect only works with wah wahs that have no buffer (so I've been told), like the older Vox and Dunlop wahs, it doesn't work on modern wahs. In my own case I have a modified Area 51 Vox Clone wah that has a switch on the side to reverse the input and output so I can achieve the effect. However in my rig it's not working.....

Now in a normal guitar set up it's easy to reproduce, the guitar goes into the wah as the first pedal, then on to other effects (echo etc) before it hits the amp. It's not so easy in a rack based effects system where the switching system has buffers etc. My rig is not too complicated, but it does have a switching system, and currently the wah is placed after my drives in the system.

Someone has managed to build a "Orca" box with a built in line driver (which as we know is a buffer) this can be seen here... I'm assuming the buffer goes after the effect in the box.

Also the guy in the Aussie Floyd has a similar box that was built by Pete Cornish, check the video at 7.20

Now onto my quest..... Obviously to build this into a box it's a simple case of building a suitable wah circuit into a box, but wire the jacks in reverse. but is there a way of circumventing this buffer issue which prevents the effect from working unless it's the first in the effect chain? The 2 "Orca" boxes above both have line drivers so in theory they should work anywhere in the effects chain?? My own pedal does work, but only if it's first in line after the guitar, If I plug my guitar into the buffered input of the Loop switcher and then into the wah it doesn't work.

[bettsaj]

I've decided to build a Vox Clyde circuit so have started to order in the parts. I'll etch my own board as I have the layout for the Clyde. This could be fun 

[bettsaj]

I've been doing a bit more digging regarding this effect, and a while back Eye Rock Electronics sold a ready made wah/gull effect pedal. This is obviously just a wah circuit in a box. The knob on the top of the enclosure just alters the sweep when it's in Wah mode. but the interesting this is this. On effectsdatabase.com they state that:

The Gull function works off of the inductance of your guitars pickups, and tone circuit. It will NOT work after any other guitar pedal unless they are true bypass as well.

So, is that why the effect won't work on my rig? I have a switching system, and currently my audio signal path is as follows:

Guitar -> GCX Audio Switcher input

Loop 1   Tuner/Mute
Loop 2   Dyna comp
Loop 3   Mistress
Loop 4   Uni-Vibe
Loop 5   Phase 90
Loop 6   Big Muff
Loop 7   Colorsound Powerboost
Loop 8      Unused

The wah is in between loops 6 & 7. So loop 6 output to wah input, wah output to loop 7 input, then send and return to the colorsound powerboost. From there the signal goes to the pre-amp, and then the G-Force, then on to the stereo power amp.

When I try to use the reverse wah effect no other effects are on other than the delay on the G-Force. So there must be something around the input buffer on the GCX that's screwing the effect up. When I plug my wah directly into a small practice amp, and my guitar into the input of the wah it works faultlessly.

If I build a dedicated pedal I'd like to know if there's a way of circumventing the buffer somehow.

[Rob Strand]

The whole way that orca effect works is very much dependent on the interaction between the guitar and the wah.   I have an idea what it's doing but not down to how the signal bursts occur.

As far as buffered input wahs go.  Yes, it makes a lot of sense.  The oscillations occur at the input of the wah and any wah input buffer will prevent that signal getting out.   The input of the wha might even have to "float" so it only works when connected to a high impedance amp input.

Anyway I really suspect the GCX unit is buffering something.   I'm not familiar with the details of the GCX and I don't know what claims they make about true bypassing and all that.  If they don't make any such claims then it would make sense to have buffers.

One thing, do you have any pedals which load down the pickup and affect the tone?  One example is the interaction between a fuzz-face and the pickup?  What I'm getting at here is if the GCX is buffering the guitar output then that loading effect will be lost.

Perhaps an easier test is to wire one loop out then back in again with no pedal.   The point of the cable is to behave as a pass-through which gives you access to the signal wires.  Instead of a pedal get a 50nF cap and place it across the two cable wires.    Set the guitar controls to full then listen to the sound with and without the cap present.  If the GCX is *not* buffered the cap will act just like a tone control with which fully rolled off.   If the CGX is buffered then it should be fairly immune to the capacitance.   You can also do a test with a load resistor.

[Rob Strand]

I found this pic of the guts.  I hope it's the same version as yours,



I can see relays which would imply a true bypass switcher.    If that's true, the reason why it doesn't work could be obscure.    There's some jack going to the non-relay board.   Maybe that's a buffer on the other board?

[bettsaj]

The only difference with my GCX is that I had both long boards replaced with stereo loops, so now all 8 loops are stereo. Apart from that, the other 2 smaller boards are are the same

[Rob Strand]

I found this better pic (click to enlarge),


From what I can see the front jacks are the inputs - see below for details.

The circuit on the power supply board certainly looks like a preamp/buffer to me.   The 8 pin device is an OPA2134 which is a dual opamp.

So anyway, in my frustration trying to work out what that unit connects, I finally had to go to the manual,
http://www.voodoolab.com/gcx.htm
http://www.voodoolab.com/manuals/gcx_manual.pdf

So now things are clear.    The manual says,

- Guitar Input/Guitar Output:  The Guitar Input on the front feeds into a buffer and the output of the buffer feeds the Guitar Out on the back.

- Feed Thru/Feed Thru:   The Feed Thru on the front is connected directly through to the Feed Thru on the back.   There's no buffering.   The purpose seems only to function as a wire from the front to the back for convenience.

*** There's one caveat.  If you don't use the *front* panel Feed-Thru input, the back panel Feed Thru "output" is buffered ie. it's the same signal as the Guitar Out.

So basically you should use the Feed Thru on the front panel.

Now, by using the Feed through you might get other issue like signal loss driving long cables.

You could wire in the Guitar In/Guitar Out buffer on the output side, post effects, to operate as a buffer to drive the line side.  However that's only going to work for a mono system, since the buffer is only mono.

You will need a Y-cable from the Feed Thru on the back panel to feed the stereo switcher inputs.  So you can't use the two outputs on the back to split the signal.

[bettsaj]

I've re-thought the cabling and I've conceded that I need to have the wah straight after the guitar. To this effect i'm doing the following, baring in mind I have a snake I've got to take apart and rewire which I was trying to avoid:

guitar -> wah pedal on the pedalboard -> Pedalboard breakout box -> snake to rack 

All connections on the rack are at the back..... So.......

Snake audio input to rack interface -> A/B box, this also has a wireless input on it so I can switch from hard wire and wireless -> AB Box to GCX rear panel feedthrough -> front panel feedthrough -> front panel guitar input -> Rear panel guitar output -> loop 1 input

from there the signal goes as normal through the rest of the system. This enables me to switch between cable and wireless, but i do lose the wah when i switch the AB Box to wireless. I wanted to try and keep the wah available when I use the wireless system, but i've had to concede defeat on that and accept to make all this work i have to lose the radio system.

[Rob Strand]

I've re-thought the cabling and I've conceded that I need to have the wah straight after the guitar. To this effect i'm doing the following, baring in mind I have a snake I've got to take apart and rewire which I was trying to avoid:

guitar -> wah pedal on the pedalboard -> Pedalboard breakout box -> snake to rack

That *has* to work.

I wanted to try and keep the wah available when I use the wireless system, but i've had to concede defeat on that and accept to make all this work i have to lose the radio system.

If you *really* wanted you could build miniature wha circuit in a tiny box that you kept on you.  Not having done the orca trick I don't know how important the wah pedal part is.  If it's not important you could just have a preset trimpot in the box.

BTW you inspire me to listen to my Pink Floyd albums.  I've listen to them since the beginning - I wasn't even 10 yo at that time.  Time is an awesome track, great solo and the lyrics really make you think.

[bettsaj]

If you *really* wanted you could build miniature wha circuit in a tiny box that you kept on you.  Not having done the orca trick I don't know how important the wah pedal part is.  If it's not important you could just have a preset trimpot in the box.

That's exactly what I intend to do. I've just ordered a few of the parts to make a Clyde McCoy wah circuit. I'll make my own board... shouldn't cost too much, I think the most expensive part will likely be the Inductor, but even there I can likely get a cheap one. then it's just a case of wiring it internally in reverse.

Although I've conceded and changed the wiring of my pedalboard to rack to accommodate the wah, I thought it would be a good project to try and make a Orca pedal box, like the Pete Cornish box.
The Pete Cornish box isn't only an Orca effect box, it's also a AB box which enables you to switch inputs, 2 guitars into the one box. Obviously it has a line driver on the output stage to clean the signal up, but other than that it's just a wah circuit in a box. This will be fairly easy to build. so 2 3PDT switches. one to switch the effect on and off, and the other to select the input.

Pardon my ignorance, but what is the difference between a line driver and a buffer? I was intending on probably building a Klon buffer into the output stage of the effect.

[Rob Strand]

That's exactly what I intend to do.

Cool.

Although I've conceded and changed the wiring of my pedalboard to rack to accommodate the wah, I thought it would be a good project to try and make a Orca pedal box, like the Pete Cornish box.

It's like a box that does "all the stuff" that interfaces directly to guitars.   The Orca function is thrown in because it needs to interface to guitars.

Pardon my ignorance, but what is the difference between a line driver and a buffer? I was intending on probably building a Klon buffer into the output stage of the effect.

The difference lies in pedantic technicalities.    The short answer is they can be the same thing depending on the context of the meaning(s) and how pedantic you want to be.

Technically a buffer only has a gain of 1, has a high input impedance and a low output impedance.  If you had something which has a gain of 2.6 which did the same job it would still "buffer" the signal since it would have high input impedance and a low output impedance *but* you could argue it's functionally not a "buffer" as the gain isn't 1.

Line driver can have a few meanings.   The main two would be driving a long line (cable), and, simply being line level signals.   You might also see a 600 ohm line driver which isn't "low" impedance but it's not high either and "Line" could mean a "Line level" signal.   Also without other information line "driver" only refers to the output it doesn't really imply the input is high impedance.

A buffer could drive a long cable so it can be a line driver but some buffers might do that better than others.  If you buffer a guitar it can drive a long line but then the signals aren't Line Level they are Instrument Level.   You might still see such a thing call a line driver but technically signal level is only "Instrument level".

Not a clear answer really.  My point is you get a bit of mixing-up of common parts of the meanings and the specific parts of the meanings.

See here also,
https://www.diystompboxes.com/smfforum/index.php?topic=45475.0

[bettsaj]

I've just read that Pete Cornish, uses a line driver/pre-amp in all his effect boards and all effects have buffered feeds. My guess is his stand alone pedals like the Orca has just a buffered feed on the output... i intend to install a Klon buffer into the output of my Orca when I build it.

This makes for interesting reading,

http://www.petecornish.co.uk/case_against_true_bypass.html

[Rob Strand]

I've just read that Pete Cornish, uses a line driver/pre-amp in all his effect boards and all effects have buffered feeds. My guess is his stand alone pedals like the Orca has just a buffered feed on the output... i intend to install a Klon buffer into the output of my Orca when I build it.

On the whole it's a problem free method.  It's not unlike approach taken by Boss or any modern effects pedals.   

Quite a few old pedals load down the guitar when ideally they shouldn't. 

With buffering you lose the ability to use pickup loading as part of the sound.  An example is a fuzz face. It loads the guitar when the volume is full and you can back off the volume to clean it up.  If you buffer the front end you can try simulate a loading effect on the pedal for the volume-full case by building the pickup characteristics inside the pedal like this,

http://www.muzique.com/lab/pickups.htm

That kind of puts the overall sound of the pedal and pickup inside the box so you can then wrap buffers around it.

[bettsaj]

So... An update on my wah issue.

I have rewired my rig as follows:

Guitar -> Wah -> GCX Switcher

I have noticed now that my signal has reduced somewhat, I did expect this to be honest as I've effectively double the amount of cable I'm using by plugging into the wah directly from the guitar where before the wah was between 2 loops on the switcher. If I plug my guitar directly into the GCX bypassing the wah I get a nice clean dynamic guitar signal. I've placed a buffer (this one from Fuzzdog pedal parts https://shop.pedalparts.co.uk/Klon_Buffer/p847124_6346591.aspx) it's improved it a bit. I think I need to replace some of the jacks on my pedalboard, but I also think there might be another reason.

Question, if I have an audio cable in a snake along with a midi cable and a 240v power cable is it normal for the audio cable to suffer tone suck? i think this might be why i'm suffering signal degradation from the pedalboard back to the rack, even with a buffer.

Here's a fetching picture of my pedalboard before I rewired it. I now plug directly into the patch bay on the right of the board, from there the signal leaves the patch bay to the wah, then wah output to the buffer (not shown on the board in this picture) then buffer back to the patch bay. from there the snake takes the signal back to the rack.

I was thinking about installing the buffer into the patch bay but wasn't sure the best way to go around it. Secondly, if the power cable is interfering with the audio signal in the snake is a buffer the best way forward, or is there a better solution that you can think of? A dummy load circuit perhaps as you've detailed above? At the moment I only have a big muff in the rack, but I'm thinking of putting in a fuzz face as well so I need to be mindfull of how the fuzz face and likely the big muff too will react to a buffered feed

[Rob Strand]

Guitar -> Wah -> GCX Switcher

I have noticed now that my signal has reduced somewhat, I did expect this to be honest as I've effectively double the amount of cable I'm using by plugging into the wah directly from the guitar where before the wah was between 2 loops on the switcher. If I plug my guitar directly into the GCX bypassing the wah I get a nice clean dynamic guitar signal. I've placed a buffer (this one from Fuzzdog pedal parts https://shop.pedalparts.co.uk/Klon_Buffer/p847124_6346591.aspx) it's improved it a bit. I think I need to replace some of the jacks on my pedalboard, but I also think there might be another reason.

A long cable will lose highs but it takes quite a load on the pickup to have a level drop.  It doesn't seem normal and you would be right to suspect another reason.

I'd suspect the wah.   In fact it sound like the wah is not true bypass.   The best test would be to replace only the wah with a dummy box which wires a 6.5mm female to a 6.5mm female.  A true-bypass pedal set to the bypass state that would work perfectly.

Next substitute the long cable with a short cable say 1m long.

The result of those two test will tell you if it's the wah, the cable, or perhaps even both.

Question, if I have an audio cable in a snake along with a midi cable and a 240v power cable is it normal for the audio cable to suffer tone suck? i think this might be why i'm suffering signal degradation from the pedalboard back to the rack, even with a buffer.

I wouldn't expect rolling-up the cable or running cables side-by side to cause that.   You could get noise issues but that's a completely different problem.

Here's a fetching picture of my pedalboard before I rewired it. I now plug directly into the patch bay on the right of the board, from there the signal leaves the patch bay to the wah, then wah output to the buffer (not shown on the board in this picture) then buffer back to the patch bay. from there the snake takes the signal back to the rack.

One thing I'm missing is the lengths of each cable in the signal chain.  That will give me an ideal where problem is.   I'm not sure where the buffer is located, is it at the pedal board or remote end?

Secondly, if the power cable is interfering with the audio signal in the snake is a buffer the best way forward, or is there a better solution that you can think of?

You could try different cable but I have my doubts it would fix it.  The best remedy is distance between the mains cable and the signal cables.   A small step would be to put the mains on oneside of the bundle and the signal lines on the other.  You could even poke something between the cables to increase the general separation.  Small separations of 5mm or 10mm can help.

I was thinking about installing the buffer into the patch bay but wasn't sure the best way to go around it. ... A dummy load circuit perhaps as you've detailed above? At the moment I only have a big muff in the rack, but I'm thinking of putting in a fuzz face as well so I need to be mindfull of how the fuzz face and likely the big muff too will react to a buffered feed

I guess your problem now is exactly why Pete Cornish like buffers!   Even the mains signal issue is a problem that didn't need to be solved before.

I'm confused about a couple of things.  You were using the GCX switcher before without any issues.  My understanding is, in that setup, the guitar signal would have been unbuffered upto the GCX unit.  So that means the unbuffered guitar signal was going side-by side with the mains signal.  Also that means the Muff would have been fed by the buffer output of the GCX output in you old set up?

It would be good if you could draw-out the wiring of your set-up with the lengths before and after.
eg.
Guitar  ---5m--->   Patch  --5m-->  GCX in --->  GCX out.

[bettsaj]

Hi Rob, as requested here's 2 diagrams of before and after signal paths:

Before.

Guitar 20ft cable -> GCX -> Patch cable ->JMP1 Preamp -> Patch cable -> TC G-Force -> Patch cable -> Randall Power Amp

GCX loops are as follows:

• Tuner
• Dyna Comp
• Electric Mistress
• Uni Vibe
• Phase 90
• Big Muff
• Colorsound Power Boost

The wah is between loops 6 & 7, GCX loop 6 output -> 20ft cable -> patch bay -> patch cable -> Wah -> Patch cable -> patch bay -> 20ft cable -> GCX loop 7 input


After.

Guitar 20ft cable -> patch bay -> patch cable -> Wah -> Patch cable -> Buffer -> patch cable -> patch bay -> 20ft cable -> GCX -> Patch cable ->JMP1 Preamp -> Patch cable -> TC G-Force -> Patch cable -> Randall Power Amp

GCX loops are as follows:

• Tuner
• Dyna Comp
• Electric Mistress
• Uni Vibe
• Phase 90
• Big Muff
• Colorsound Power Boost

All cable is high quality Van Damme Pro series cable with Neutrik jacks. There are a few pancake jacks on the board purely for space reasons.... These are not a known brand, and could be lower quality than they should be.

[bettsaj]

I'd suspect the wah.   In fact it sound like the wah is not true bypass.   The best test would be to replace only the wah with a dummy box which wires a 6.5mm female to a 6.5mm female.  A true-bypass pedal set to the bypass state that would work perfectly.

I've got a Boss pedal I can use for that

Next substitute the long cable with a short cable say 1m long.

The result of those two test will tell you if it's the wah, the cable, or perhaps even both.

I'll let you know how it goes

[bettsaj]

Just swapped the wah for a Boss pedal and it improved, I didn't swap the lead to a shorter one... I've attached a photo of the wah pedal wiring... The switch on the left inside the enclosure is what reverses the input and outputs for the seagull effect. The footswitch looks like true bypass to me.... like this







What I will say is i think i'm getting distracted or confused around exactly what i'm hearing. When I say my signal has reduced somewhat, i think what I'm hearing is actually the high frequencies being lower, not an actual drop in volume. It's deceiving and gives the impression that you've lost volume when in fact I've just lost some of the highs. That is exactly what I would expect with 2 long 20ft cables which is what I have in effect got now between the guitar and the rack.

Previously, when the wah was between loops 6 & 7 I think maybe it wasn't as noticeable, even then there was still 2 x 20ft cables to and from the wah in the snake.......

[Rob Strand]

Hi Rob, as requested here's 2 diagrams of before and after signal paths:

Cool thanks, I can visualize things far better now.

The footswitch looks like true bypass to me.... like this

Yes, it's true bypass for sure.  I traced it out and I couldn't see any issues.  FYI, the footswitch shorts the input to the wah pcb when bypassed.

Just swapped the wah for a Boss pedal and it improved, I didn't swap the lead to a shorter one.

So what that's saying is it's not the wah and it is the cable loading the pickup.

i think what I'm hearing is actually the high frequencies being lower, not an actual drop in volume. It's deceiving and gives the impression that you've lost volume when in fact I've just lost some of the highs. That is exactly what I would expect with 2 long 20ft cables which is what I have in effect got now between the guitar and the rack.

That's what is going on for sure.   It makes sense.   Adding the boss pedal fixes is so that points to cable loading.

Previously, when the wah was between loops 6 & 7 I think maybe it wasn't as noticeable, even then there was still 2 x 20ft cables to and from the wah in the snake.......

For the old set-up you guitar went into the GCX guitar input so your guitar hits the buffer in the GCX fter 20ft of cable.  The other 20ft is on the output side of the buffer which doesn't affect the signal.   A buffer driving a 20f cable should not affect the signal.  The problem then was the wah wouldn't produce the Orca effect.

You need a set-up which exposes the wah to the direct guitar signal but after the wah you don't care so if you have a buffer after the wah (and the wah to buffer cable is short)  it should be fine to get the orca effect and you should not have any loading problems.

but ...

One thing that doesn't makes sense to in your new set-up is this,

Guitar 20ft cable -> patch bay -> patch cable -> Wah -> Patch cable -> Buffer -> patch cable -> patch bay -> 20ft cable -> GCX -> Patch cable ->JMP1 Preamp -> Patch cable -> TC G-Force -> Patch cable -> Randall Power Amp

Especially this part:

Wah -> Patch cable -> Buffer -> patch cable -> patch bay -> 20ft cable -> GCX

Here you already have a buffer between the wah and the second section of 20ft cable.    What buffer is that? To me it doesn't look like it's there or it isn't working.

From the boss pedal test we know a buffer can fix your problem.

[bettsaj]

I've been having an experiment, and when I tried the boss pedal I placed it outside the patch bay, so the signal was this:

Wah -> Patch cable -> Buffer -> patch cable -> patch bay -> BOSS PEDAL -> 20ft cable -> GCX

I've started to pay extra attention to the 2 patch cables that connect the wah to the patch bay. These were made up of good quality cable, and cheap pancake jacks. I believe that these jacks are causing an issue so have changed them to decent quality Neutrik jacks (see picture)



This has made a big difference. I may reinstall the buffer between the wah and the patch bay, or not. When the cable gets to the GXC it hits a buffer anyway before it goes through any of the effects pedals so i'm not really gaining anything by having a buffer at the start of a 20ft cable and one in the GCX at the end of the cable. Unless you know different??