tube wah by rg at geofex

[numpty]

I understand that a number of practical versions of this project have been built and would like to know whether they are and improvement on the best solid state wahs out there?.
Also, is there an all tube schematic available which does not incorporate the mosfet, ie the cathode follower version?.

[cd]

FYI, if you're got $2000 burning a hole in your pocket:

http://cgi.ebay.com/Toob-Wah-All-Tube-Wah-Wah-fmr-Roger-Mayer-apprentice_W0QQitemZ7394569485QQcategoryZ41422QQrdZ1QQcmdZViewItem

[Headbuttking2]

http://www.blueguitar.org/new/schem/_fx/tubewah.jpg

I dont know if this helps.

[sta63bmx]

Sarcasm ahead.

"It goes far beyond the traditional transistor wah. "

Yeah, right to the bottom of your wallet, sucking out every crumb of cashola. 

"An exclusive, proprietary compression-expression circuit increases the wah-ness of the Toob-Wah™..."

I measured it with my digital volt-ohm-wahness-meter and I really couldn't tell a difference.  It might have been the tone-sucking solid-state devices in my DVOWM, though.

What's with the corn snake in the one picture?  I would have to say that this effect takes the GOT TO BE ALL TUBES MAAAAAAAAAAAN hype farther than I have previously seen.  We must also ensure that the electric power coming from the wall to our amplifiers is produced by ALL TUBE point-to-point wired power plants using only SPrague Black Beauty and Bumble Bee capacitors.

Bask in the hype, like the glow of the noonday sun...

"Because of the all-tube circuitry, there is no tone sucking. "  Gonna have to go to the thread bomb.



Omitted Qualifier: "...uness I put this 50 ohm resistor between my input and ground."

[TELEFUNKON]

been through the Mojo Thread yet, youngSta?

[The Tone God]

Atleast it is not just a wha with tubes in it instead of transistors. There are two different factors with that circuit that make it different. One is the tubes and the other is the design circuit itself. The question is what part really brings something new to the game.

The tube section seems to be running at a sufficient voltage to have an affect but how much is it really doing at that point ? I don't hear wha people complaining that their wha response is to stiff or that it sounds too cold its tough to say without trying one.

The other part is the circuit itself. There are some interesting features. Could those feature be done with solid state ? Probably. I doubt anything going on in there is tube specific so you could build the circuit replacing the tubes with solid state and get those features.

If you use a good amp and tunned a solid state conversion of the circuit right I doubt you could tell the difference. Maybe if you used it with a SS amp it might bring something to the table but not much I think.

So the tubes might be just a gimmick but the circuit seems interesting.

Andrew

[R.G.]

With reference to the tube wah at geofex:

I understand that a number of practical versions of this project have been built and would like to know whether they are and improvement on the best solid state wahs out there?.

I liked the sound of the prototype. Several reports I've had back on that particular circuit have been glowing.

The only thing that matters is whether you like it, and you can't tell that without building one. Unfortunately, as you find in the ebay "toob-wah" mentioned in this thread, anyone who's actually built a similar device, particularly if they're trying to fish your money out of your pocket with it will tell you it's an experience second only to the first time you cuddled up to a member of the opposite gender. Your ears are the only good measure. Having fifty people swear that it's great won't help you hear it.

Also, is there an all tube schematic available which does not incorporate the mosfet, ie the cathode follower version?.

There is, but why? Frankly, a tube cathode follower will "improve" this circuit only by making it something you can call "all tube" in your adverts if you sell it. The source follower is just as good here, if not better.

But I'll tell you how to do it. Remove the MOSFET. Connect the plate of a triode where the MOSFET drain was. Connect the grid of the tube where the gate was. Connect the cathode of the tube where the source was. Change the source resistor from 10K up to between 51K and 82K. Done. The tube will not provide as clean a feedback drive. It's really very much like the source follower after the plate of the first tube, but with only one source resistor.

The other tube wahs I've seen use either a multiple feedback active filter setup or an AM radio variable capacitor, not the Vox wah circuit. In my experience, I prefer the Vox wah circuit's sound. You may prefer other sounds.

No way to tell without building one, unfortunately.

The fellow with the ebay unit seems to be into selling... hard!

There have been a number of attempts in the past to build a tube-based wah-wah, but the builders always made the same mistake: they tried to fit the entire circuit inside the case of a traditional wah-wah. No ALL-tube circuit could fit in that space, let alone a real tube power supply, etc.

I made no particular attempt to do that. In fact a case wasn't even particularly part of the project.

So they used only one tube and a lot of transistors and MOSFETs.

Perhaps the commercial units did. I used a MOSFET in the place where it would work transparently and save putting in a second tube.

They ended up with a low voltage, "starved" tube, tube-flavored design that was still filled with tone-killing transistors

Any time you see a reference to transistors sucking tone, killing tone, etc. there is about a 98% chance that what you're reading is advertising, trying to get a grip by displaying "tone icons". More the point, the geofex tube based wah is not a low voltage device.

and generally hummed badly from the magnetic field of the power supply sitting there in the case right next to the inductor.

Could be. Stuffing too much in too small a box is a recipe for bad results. But this sounds like a reason for using a great big old box.

There's another cautionary item in there.

All-tube, high voltage circuit
Tube rectified
3 x 12AX7
1 x 5Y3
Sprague Atoms, Orange Drops
Carbon Comp resistors

When I see things gleaned out of tube guitar amps being applied to effects, I get this itchy feeling that my wallet is under attack.

It is good to run tubes at normal tube voltages, and starved circuits do sound starved. However, a tube rectifier is of no particular value in a two-tube unit. Sag is obtainable by resistors. And this begs the point - do you even want your wah to sag? Maybe, but how would you know? Ever heard one before? No? "Sag" is a tone-icon, displayed to make you feel in the know about clever, insider tube equipment.

Enumerating mojo caps is another tone icon, as is "carbon comp resistors". There are places where carbon comp has its uses, and there is a tone change associated with them, but only in those specific uses - see the article at GEOFEX.

[Paul Marossy]

I should give this one a try sometime! I am really curious as to how it sounds.

[Headbuttking2]

Major props on the tube wah design R.G.

I am probably going to build me one when I get home from school.

2 questions is though.
I see how you explained how your circuit has the possibility of 2 12AX7s..
but the Toob-Wah has 3....
Where do you think the third is/used for? just curious....

For the power supply..
Is it possible to use just 2 transformers instead of the wall wart?
I see how 2 transformers would take up alot of space, but electronic goldmine has them as 10 for 5 bux which is a steal.

Thanks again man.

[twabelljr]

I should give this one a try sometime! I am really curious as to how it sounds.

Let us know what you think tomorrow morning when your done.

[Paul Marossy]

Let us know what you think tomorrow morning when your done.

Smart a$$.  Actually, I'm working on a layout right now that would allow most of the stuff to go inside of a CryBaby shell. I just have to figure out the power part of it now. In my experience, inductors are very sensitive to hum, so the power supply needs to be a good distance from the circuit board or it'll pick up hum. 

[R.G.]

Is it possible to use just 2 transformers instead of the wall wart?
I see how 2 transformers would take up alot of space, but electronic goldmine has them as 10 for 5 bux which is a steal.

Sure, two transformers back to back would work fine. It makes the hum issue harder. Ideally, you'd make your B+ and filament power in a separate steel box, then carry it over on wires to the circuit for lowest hum. But BE CAREFUL with whatever you do here. This is not a 9V battery.

but the Toob-Wah has 3.... Where do you think the third is/used for? just curious....

I don't know. I haven't seen one yet.

In my experience, inductors are very sensitive to hum, so the power supply needs to be a good distance from the circuit board or it'll pick up hum.

The inductors are VERY prone to hum pickup. However, you can :
- change the orientation; transformer leakage is highly directional, so rotating the transformer and inductor often produces a minimum arrangement. It's quite dependent on the exact transformer and inductor, though.
- use a toroidal power trans, they don't leak nearly as much
- shield the inductor, the transformer, or both. Cover them in copper foil from the crafts store, soldered into place so only the leads can exit. Careful and don't melt the insulation or short things out, though. Use a soft steel shield, and cover as much of the transformer and inductor as possible. Copper shorting shields force the flux back into the transformer by eddy current action, iron "shorts out" the magnetic field by being highly permeable.

[numpty]

Hi
   I found all of you comments very interesting. That Ebay tube wah looked like bulky amateur build and obviously not worth the money. If some people have achieved good results with the geofex RG tube project then its worth experimenting with. I'm its sure its possible to incorporate one if not two 12ax7's into a crybay size housing and then use a separate compact stand alone  PSU with a dc heater supply.

[Paul Marossy]

Yeah, I was thinking toriodial transformer inside the shell. Got any leads for one that would work in this application (and would also be physically as small as possible)?

[jonathan perez]

a weebit OT, but i dont care what anyone says, the TOOBWAH is garbage. listen to the sound clips on their website. what wah should sound like that? i would NEVER use it! i get the same sound if i put my wah in the effects loop of my amp! AND THATS NOT GOOD!

though when i get a chance to build one, im going to do it right. but i see no point in having an "all tube wah"...ill build one just to say i did, and sell it for 50 bucks. in your face, mr. apprentice! "YOURE FIRED!"

the ooooold maestro boomerang wahs on the other hand DID have american amplifier parts...but to be using the types of parts found in my Plexi is just a no no...i mean...how do you make something that already sounds fantastic sound better? ADD TUBES?! nah...ill stick to my trusty Area51...i only paid 150 for it and the battery lasts forever...no wall wart/melting wallets/bent-in-half bank cards here!

[Headbuttking2]

Thanks R.G.

[puretube]

to each his throne...

[R.G.]

Ton, would you care to elaborate?

[puretube]

to each his throne...

`t was a reply to reply#14, R.G.,
missed no.#15 inbetween, since I`m not online anymore...

[EDIT]: and probably influenced by reply#3...

[Headbuttking2]

On that Tubewah schematic..

It says the power comes from a power supply.....?

9 volts???