Tube powered Wah Pedal help

[tbryanh]

Sounds cool. You might consider taking an off-the-shelf expression pedal and bolting a sealed chassis to the side or end of it. Then drill a hole for the wires to travel between them. Expression pedals can be purchased with only a pot inside, no other circuitry.

[Casey4s]

Like Paul said, I wasn't criticizing your draftsmanship - it's quite good - but there's a reason it's a dying art. The convenience of automated BOM generation that keeps up with your drawing changes (KiCAD is actually pretty miserable in this regard), netlist/wirelist generation, and tightly integrated layout (even for tag boards, a full-sized plot is a very handy thing) are all pretty compelling.

But hey, if pencils work for you, they work.

No sweat, I wasn't offended... you are not the first person to suggest I go CAD, but most of the time I am the only one looking at my drawings. At this point in my life I think I am just going to stay PAD (Pencil Aided Drafting).

[Casey4s]

R.G. Keen emiled me and suggested some changes to by initial design which are incorporated in this version of the schematic. (Rev 2) I discovered the power transfomer I intend to use has no CT, so I changed to a full wave bridge rectifier too.

I am ordering the parts from AES and Weber this evening or tomorrow and will make the turret board over the next couple of days.




And my layout sheet.





Any last minute comments before I get the soldering iron out?

[Paul P]

I'm looking forward to your report on how it works and sounds once you're
done.

One little thing, I believe the 'recommended' way to wire the AC line-in
is to have the fuse come before the switch.

Paul P

[Casey4s]

I'm looking forward to your report on how it works and sounds once you're
done.

One little thing, I believe the 'recommended' way to wire the AC line-in
is to have the fuse come before the switch.

Paul P

Thanks for the input Paul,

You're right, but I never would have actually built it that way, I just messed up the drawing when I redrew the power supply.

I am also going to parallel the two sections of V2, but decided not to redraw the schematic to reflect that.

[sportster4eva]

The only thing that I had noticed is where V2 grid gets it's reference from, through R15 tied to V1b cathode. That looks like it will bias the grid positively compared to it's (v2's) cathode? In your schematic it shows V2 having only a 1.8k cathode resistor, and no plate resistor. Is that intentional? I may be way off here, but that just struck me odd. Can you or another of our bottleheads clarify this?

[Casey4s]

The only thing that I had noticed is where V2 grid gets it's reference from, through R15 tied to V1b cathode. That looks like it will bias the grid positively compared to it's (v2's) cathode? In your schematic it shows V2 having only a 1.8k cathode resistor, and no plate resistor. Is that intentional? I may be way off here, but that just struck me odd. Can you or another of our bottleheads clarify this?

Thanks for the well thought out input and question. This one I had to think over a little bit I talked (eMail) to R.G. Keen and this is his suggestion to refrence the signal from the cathode of the cathode follower (V1B) as shown. so at this point I am going to run with it as is and see what happens.

And no, I don't intend to use a plate load resistor for V2. I had originally put one on the plate (was R7) but it was not needed so I deleted it.

Thanks again...

[Casey4s]

I got mos of my parts together and started assembling the "Guts" of this thing a day or so ago.

First I had to build a chassis box

[Casey4s]

I started putting my turret board together waiting on the rest of my parts, and the full wave bridge rectifier.



Then I started the Mechanical assembly, cutting all the holes and mounting tha big components.




There was no way to make this small, so I went the other direction and just went BIG with everyting, it may not be pretty when it's all done but it should at least be a conversation piece...

[Paul P]

I like that brake of yours. Must come in real handy.

I have a question or two. Is that a rotary switch you've got there
beside the big capacitor ? What does it do ? Your schematic shows
a wah pot, which I presume will be a pedal of some sort. Have you
decided how you're going to do that ?

I'm looking forward to hearing about what it sounds like. I've been
wanting a wah pedal and it would be neat to build one.

Paul P

[Casey4s]

I like that brake of yours. Must come in real handy.

I have a question or two. Is that a rotary switch you've got there
beside the big capacitor ? What does it do ? Your schematic shows
a wah pot, which I presume will be a pedal of some sort. Have you
decided how you're going to do that ?

I'm looking forward to hearing about what it sounds like. I've been
wanting a wah pedal and it would be neat to build one.

Paul P

I have two different kinds of inductors for this project. One is a Fasel (red) 500 mH inductor as used in most Dunlop and Vox wah pedals, and the other one is a really small iron core OT that can also be used as an 5oo mH inductor. The rotary switch is so I can go from one to the other and then both in parallel to try to voice the wah a little differently. This was a last minute decision to add this so my schematic does not reflect the modification.

The actual pedal will be seperate and will plug into the guts box via a stereo jack. I have some 2 conductor sheilded cable I am going to use for that. I will use the sheilding as the ground connection between the pot on the pedal and the guts box.

My intent is to make a wood box of sorts to cover the sides of the guts box so it doesn't have that unfinished look to it. I will have to wait until the weather is better to do that though. I can only work for a couple hours at a time because it is so freaknig cold in my garage.

I hope to have this working by this time next week less the actual pedal which I need to wait on weaher for also. I will wire up the pot and plug it in and operate it by hand to trouble shoot the project.

[Casey4s]

I did a little soldering in the past couple of days, this is probably the messiest looking thing I have ever built, I am sorta embarrassed to even show these pics. I am just not good at working in such tight places with tubes stuff, this in itself has proven to be a bit of a challenge.

All I really need is to install 3 jacks, the circuit board, and wire all of that up as well as the step on by-pass switch. I am almost finished with the initial phase of this thing. I have my fingers crossed.




This view shows the two inductors mounted on a small board and attached to one side of the chassis.





This view shows the Rectifier baord and all the big AC wiring every where, what a freaking mess. I will be amazed if this does not make noise.

[Paul P]

This view shows the Rectifier baord and all the big AC wiring every where, what a freaking mess. I will be amazed if this does not make noise.

I've noticed the same thing. Everything's nice and clean on paper then you
add all the wires and it turns into a big mess .

Sometimes I could make a wire real short but the possibility of re-using
the part in some future project makes me want to leave as much lead length
as I can. Power transformer is bad in this respect.

I don't think your wiring's that bad.

This is like brain surgery. I understand the Japanese were so good at
assembling small stuff because of the women's small hands. I envy
them their small fingers. I have sausages and sometimes there's just
too many of them in the way and I can't see what I'm doing.

Paul P

[CarlZ]

Is it just me or did you take the schematic off of your photobucket? Nothing is displaying for me.

-Carl

Disregard. Everything showed up when the page refreshed after I submitted the reply.

[Casey4s]

Is it just me or did you take the schematic off of your photobucket? Nothing is displaying for me.

-Carl

Disregard. Everything showed up when the page refreshed after I submitted the reply.

Hi Carl,

Thanks for stopping by.

My schematic is not a CAD product but I am usually the only one who has to look at it anyway.