Wah Pedal Clipping

[Stratomaster]

Howdy,
     I have an extensively modified Vox V847.  The mods are listed below.
       
         F*llt*ne inductor
         1.5K resistor to a 2.4K
         33K resistor to 56K
         470 ohm resistor to 316 ohms
         trannies to BC109C
         true bypass
         sweep cap switch

   So long as I roll the volume down on my guitar to about 7 or 8 I don't get any clipping.  When the volume is full on, though, I get clipping.  Is there any way to get rid of that (i.e. increase wah headroom)?  I love the sound of the wah, so I would like to keep that intact, if possible.  Thanks in advance.

[petemoore]

  Other than the wah mods I know of no more wah mods, perhaps a 'damper' on the wah input like series resistor or voltage divider/
  have you tried reducing the gain [gain mod resistor?].
  and does it distort with MPSA18's or other HG/LN transistors,

[Stratomaster]

It seems to almost distort more with the MPSA18s.  I did reduce the gain resistor mod to 390 with no luck.  So I figured the clipping was inherent and reinstalled the 316 because it sounded better.

[jonathan perez]

reducing the gain resistor to a lower value (316) will only ADD gain.

try something like 470-510.

[petemoore]

  Whoops I must have forgotten I raised that resistors value and used it's structure to have something semi-substantial to add the trimpot to...twisting that gain control trimpot, it goes from less than unity, about unity, to maybe a bit above unity, IIRC it adds bass content as well as gain, that's where I'd look first for distortion taming, I would guess they are 1k8 and 1k pot parallel..that'd range from about 600 ohm to .0 ohm?, I would have to learn more math or get the DMM on a 2k2/1k paralleled circuit to tell you exactly that R range.

[Stratomaster]

reducing the gain resistor to a lower value (316) will only ADD gain.

try something like 470-510.

What I meant was I reduced the resistance decrease--rather confusing.  I raised the resistor to 390 from 316 with no change in distortion amount and a deeper sound.  I was just wondering if there was another way to get rid of the clipping as the 316 ohm resistor sounds amazing.  I've seen people on this forum put down to a 270 ohm resistor in there and not complain of clipping.  So I guess it's just a tradeoff for me.  Oh well.  Thanks for your help.

[jonathan perez]

from 316-390 shouldnt produce a deeper sound. 390-316 should.

what gets clipped, the wah or the amp?

a similar effect can be used with a 470-510 ohm resistor and a .012 sweep cap. or even .08 (if you have .01 caps in parallel.)

but i dont see how clipping is unusual, seeing how the gain is pretty high in Q1. i suggest you give 470 a listen, to see if it still clips.

i guess thats just my .02

[Stratomaster]

That's what I meant.  I went to 390 in an attempt to get rid of the clipping.  I didn't hear any less clipping and a reduction in depth of wah. So I decided to keep the 316 in favor of the depth of wah, since there was no improvement in the situation.  I can continue to roll back the volume on my guitar, but I was just wondering if there was a way to fix it electronically without much of a tone sacrifice.  Thanks.

[Paul Marossy]

Have you tried lowering the gain of Q2? That might help.

[Stratomaster]

Brought this one back to life.  I saw on the listing for the Crybaby 535Q that it runs on 18v to give "more headroom".  Do you think that if I added the charge pump to my wah that it would allow for the clipping to not occur?  Also, I'm thinking of raising the input resistor ( in an attempt to hit the pedal less hard) and adding the wah output buffer from tonepad to make up for loss in volume from raising the input resistor(just mess with the trimpot for  a while) .  Would either of these work? 

Also, it is the pedal that clips.  The amp has huge headroom (super reverb), and the 470 ohm sounds way to thin, but helps with the clipping (though not by much--the wah still clips).  I don't have a BC109 that has lower gain than the one I have in the pedal right now.   

[matt239]

100k input resistor, 470k emitter "gain" resistor, slightly larger sweep cap, to lower the range back down where you like it.

Those are the first, easiest things to try.