Vox Wah Mods

[Voxin]

Hello all, I plan on doing a few mods to my V847 tonight and before I head down to electronics store wanted to get your opinions on the mods I'm interested in. 

Vocal mod: I noticed that most people go with a 68K resistor for this mod...has anyone ever put a 100K value resistor in (like the old McCoys)?

Gain and Bass: What value should I replace the 470ohm resistor with?

Mids: Should I replace 1.5K for a 2K or 2.2K resistor here?

Volume: Because my wah is true bypassed, I have noticed that there is a slight drop in volume when it's on, nothing major, but I was going to change out the input resistor as well.  It seems like 47K is pretty common, any suggestions?

Thanks all for your input!   

[tcobretti]

I replaced all of those with trimpots so I could tune.  I pretty much ended up settling on the Clyde McCoy values.  I prefer the 100k vocal resistor.  The values you want for your feedback resistor and the resistor on the emitter of Q1 arereally dependant on the inductor you are using, which is why I like the trimpots.  I like my wah to boost just a bit, and I think I've got about 50k dialed in on my trimpot, but I also have an output buffer that boosts the signal a bit.

[Voxin]

This is amazing...THANKS!  Exactly the type of info I was looking for. 

Short of trying it myself (I'm still at work), how would you describe what the 100K resistor sounds like?

Thanks again.

[Voxin]

Oh yes, and I only have the stock inductor right now, looking into geting something else.  Any advice?

[tcobretti]

If I move my trimpot to the opposite extreme (i.e. very little resistance), the wah sounds kinda like turning up a tone knob on your guitar; it just gets brighter, but there is very little quack.  So, as you increase that resistor you get a more abrupt shift from low to high, or more quack.  If memory serves the original patent had no reisistor there, or basically infinite resistance.  So, any value is fair game if it sounds good to you.

I just bought the Fasel inductors from Aron who runs this site, and they are both great.  The yellow is a little dirtier and sound more Hendrix-like to me, while the Red is brighter and cleaner.  If you play P-90s or humbuckers, I would probly get the red fasel, and if you play single coils I'd get the yellow.  Like I said, I found I had to tune the resistors I mentioned before to each inductor to get the best sound I could.  That said, the stock inductor in the V847 pretty similar to the yellow and not a bad inductor, so it wouldn't be at the top of my list for changes.  Once you get the wah sounding really good, then swap the inductor and it'll sound a little better.

BTW, my wah has the original V847 circuit board, I just pulled the particular resistors and soldered in trimpots.  The only one that is pretty tricky is the input resistor, because there is not enough space for the pot.  So, I moved to components around it to the underside of the board so I had space for it.

[Voxin]

Thanks for the advice.  I was planning on getting all of the mods done and then choose a new inductor.  I was originally going to just put plain resistors in the wah, but after talking to you, the trimpots sounds like a better idea!  I better go dust off my ohm meter!   

[petemoore]

  Inductor changes everything, well not everything but the wah may need re-tweeked a bit after an indy change.

[Voxin]

I'm definitely going with the trimpots then, at least I won't have to spend the time soldering in new resistors.

[Voxin]

Ended up dialing everything in like the Clyde McCoy but with a little more mids.  As for the vocal resistor, I ended up going to about 76 with it.  Thanks!

[tcobretti]

I'm glad it worked for you!

[jonathan perez]

Ended up dialing everything in like the Clyde McCoy but with a little more mids.  As for the vocal resistor, I ended up going to about 76 with it.  Thanks!

so its not REALLY like a clyde...hahah...

arielfx sells halo inductors for the true to vintage sound...

area51 sells a custom inductor, for a fat, rich tone....one of my favorites...

and....uh.....i think thats it....

 

[Voxin]

Yes everything worked out great.  I really appreciate all the help.

I guess, it's an "Almost Clyde McCoy Wah"!   

I was reading up on the halo, I've also noticed some inductor kits that you can wind yourself, so we'll see.

[Samy]

Sorry, i don't want to hijack the topic but i think there's no need to create a new one...
I want to mod a Vox847 and place a Switch to change from guitar to bass wah, is it possible ?
I need to find the schem, can anyone point me to the right location?

Thanks.

[jonathan perez]

sure. grab a decent DPDT, or SPDT, and drill a hole...

secure it, then you the following options with the sweep cap:

(up) guitar-.01
common
(down) bass- .022+

check out my wah myspace for soundclips on how deep you think you want it to go...

myspace.com/sunshinewahs

in text format, if youre using a DPDT, both legs of each cap go onto the two lugs, two on top, two on bottom like this

cap   _ _
        _ _ back to the holes on the board
cap   _ _

can you dig it? with a SPDT, one leg of each cap will go to the switch, and the other legs soldered together, and a return from the board sent from where the legs of both caps connect, as well as one wire from the common (middle) lug.

cap _
      _ common
cap _

[Samy]

Thanks thebattleofmidway, that was quite clear.

[jonathan perez]

oh good, im glad you got it. 

what sweep caps will you be using?

[Samy]

I think i´ll use a rotary switch and place some caps between 0,01µF and 0,068µF .

[jonathan perez]

thats what i did. ive made some simpler ones with basic DPDT switches, but i think rotary is the best way to go.

try .0082-.068

[Opencan]

I can't help it but trying to upgrade the DPDT version a bit.

wouldn't it be better off doing it like that:


it will save space on the board if my way of thinking is right.

[alextheian-alex]

HEY tcobretti!  Thanx for posting that chart... that saves a lot of leg work.