Vox wah wah mods

[Spencerleehorton]

Yeah good stuff CJ, I will do the fumble around until I get something I like!! Or maybe I’ll never get it?
I’ve certainly got some idea of how not to get what I want so far, so some progress has been made and I’m fairly happy with one of the wahs with the red Fasel with stock values, just need to tweak from there I reckon!!

 

[Spencerleehorton]

Some good reading here about the wah fuzz problem.

Scroll down to where it says


http://me.aquataur.guru/musicstuff/clyde.html

 

[Spencerleehorton]

Here is a comparison of the alibaba wah wah enclosure bits I got compared to the cry baby/vox bits.
The tension clip as you can see is much smaller than the crybaby/vox.
Also the rack gear is shorter and not angled so doesn’t run smooth and falls off the thread!!
I’m sending this one back!!

 

[dai h.]

These are some of the missing schematics from Gus (I did get his permission) on a couple of the wah threads at aron's forum. The first one (if I understand correctly) is based on the Maestro Boomerang circuit, and the second to better allow the use of tapering resistors.

https://www.diystompboxes.com/smfforum/index.php?topic=77870


https://www.diystompboxes.com/smfforum/index.php?topic=90118.20

 

[Spencerleehorton]

ive designed a new rack teeth bit which is longer and has correct size teeth and will get it 3d printed as a mate has a machine, also will make a better version of the tension clip, this new wah body should then be fine.

 

[Spencerleehorton]

If you do a search for nylon P clips that is the tension clip, I’ll check the size but I think it’s about 12-15mm, will measure tomorrow.
15mm is the big one in my picture and works well.

 

[dai h.]

FWIW, Dunlop sells a lot of parts for their wahs (that plastic thing I'm guessing is an off the shelf part) :

https://www.jimdunlop.com/internal-cable-clamp/

plus the metal strap underneath, the retaining pin(?) thing that fixes the treadle to the base, the rubber tread on top, etc.

re: the gear, I thought that was straight (no angle)--but perhaps I'm misremembering (or didn't see that)?

 

[Spencerleehorton]

Yeah Dunlop sells them but for ridiculous prices when the nylon p clip you can just get for £1 or under at a hardware store.
The rack piece I havent seen for cheap either, to 3d print it takes under 10 minutes and costs pence.

 

[Spencerleehorton]

Have put the new wah together today and wound a new inductor and I have 28ohms at 501mH so pretty much bang on!!
Stock values sounds pretty good and have installed 3pdt switch with red led.
Have tried the 2n5457 buffer with wah first into fuzz face and it does sort of work only if you have the fuzz control fairly low, as soon as it’s over half it looses the wah sound again.
I still prefer fuzz face first into wah so far but will build the fox Rox buffer and try that and see if it’s better or as good as the way I prefer.
Tomorrow I will try the trimmer wah board I have and start to dial around and see if I can find a better than stock setup.

 

[Spencerleehorton]

here is how the fuzz and wah wahs sound so far!!

 

[Spencerleehorton]

I haven’t built the fox Rox buffer yet but then realised I’ve got a poly tune 3 and it has a buffer in it, so wah first in line then the poly tune, then fuzz and as long as the fuzz is about half way the wah sounds pretty good, less harsh than when the wah is second in line, first time I’ve got it working and sounding pretty good, will continue this investigation and try and tweak all the trimmers in the wah to see which works best.

 

[Spencerleehorton]

Would like some advice on working out Q factor of inductor.
I have found the calculation but wanted to check I’m doing it right, might invest in a lcr de5000 at some point but would like learn the old school way of number crunching first.

2 pie (6.28 x frequency x inductance / resistance)
My inductance meter tests at 202 hz
And inductance is 500mH and it’s 30 ohms

So is it:
6.28 x 202 x 0.5 / 30 = 21

?

 

[Spencerleehorton]

I think I’ll connect my scope and see if I can see what’s going on!!

 

[Spencerleehorton]

well i plugged in my wah with the fox rox buffer as per this version

https://www.freestompboxes.org/viewtopic.php?t=25452

ive made 3 and none of them work today!!!?

i can hear a faint wah in the background but very strange that they all dont work?
ive checked it several times and ive changed all the caps and the chip and double checked the resistors and everything fine?
lots of people have said they have had problems getting it working, so ive taken it out and just put in a 50k trim on the output and it works fine, the buffer to my ears did sound better but the 50k trim pot will do.
i suspect this fox rox buffer copy probably isnt an exact copy?
ill do a LTspice simulation and see if i can figure it out.

 

[Spencerleehorton]

The LF351 I got of eBay I think maybe fakes and that’s why none of them work?
Strange that one seemed to sort of work although was low level and could have been a wiring mistake.
I put in a TL071 and the circuit works fine but the TL071 is not fast enough to be switched in and out?

 

[Spencerleehorton]

I’ll try a LM318 as it should be faster and wide bandwidth.
Got refund for the LF351 and I’ll try and find a better source for a few more.
Maybe try out some other versions OPA do something I have loads of ICs so will check if I’ve got anything suitable.

 

[CJ]

Does anybody have a schemo for a GCB-95 E version (two 2n3904's) Thanks!

edit: got it>

 

[CJ]

traced out a GCB-95 E Version,

has a few changes from schemo above:

0.22 caps feeding pot instead of 0.001
2.2uf instead of 4.7uf on inductor
100/16 on pwr supply instead of 0.0011
390 ohm instead of 470 ohm emitter resistor,

 

[MidnightArrakis]

traced out a GCB-95 E Version,

has a few changes from schemo above:

0.22 caps feeding pot instead of 0.001
2.2uf instead of 4.7uf on inductor
100/16 on pwr supply instead of 0.0011
390 ohm instead of 470 ohm emitter resistor,

>> Is the inductor still 660mH?

/

 

[CJ]

Inductor measurements

V vs L

100 Hz

0.230 vac 625 mH
0.316. 712
0.411. 740
0.504. 757
0.576. 756
0.670. 756

400 Hz

0.273. 617
0.572. 630
0.874. 656
1.230. 693
1.584. 713
1.963. 737
2.313. 743


1000 Hz

0.591. 534
1.342. 604
2.240. 673

Looks like a ferrite pot core is pretty linear when it cones to inductance vs level and frequency.

Next consideration would be wire size and winding technique vs hi end frequency response as capacitance is more of a problem when it comes to toroidal winding.