Vox v847 - Help me replace caps, etc with "better" stuff

[wannabweiland]

Hey guys, I'm kind of new to this, but I've done my fair share of repairing and soldering lately. I acquired a USA Vox v847 wah and I'm about to make it true bypass and do the vocal mod. I saw on youtube there was a kit awhile back that changed some components to higher quality stuff (big orange cap, maybe some tropical fish) but I'm not sure what I need or how to get started exactly. Can anybody walk me through it or at least point me in the right direction? I will say that I'm not super tech savvy, but I promise to TRY to keep up. Thanks!

[FiveseveN]

Might want to take a look at this: http://www.diystompboxes.com/smfforum/index.php?topic=100767.0

[Liquitone]

I modded my 1994 USA V847 2 years ago. I tried the reissue Dunlop red Fasel and thought it sounded better than the inductor in my older Vox (cilynder with a bolt on top) , but I thought the stock inductor (black cilynder with flat top and green dot) in the last wah I modded to actually be perfect and even better than the fase reissue. The red Fasel got microphic and way too growly at some point during all the swapping and modding , not sure how that happened.

Replacing the transistors with lower gain ones can sound pretty great if you want a less gainy cleaner sound (R.G.Keen mentions Q2 has little effect on the tone, so start with Q1). I prefer BC109's with a hfe around 400. The stock MPS in the Voxes are much higher gain.
Tropical fish-caps are very often recommended yes. As FireseveN pointed out, the 'Sound'  of capacitors is a touchy, debated subject. I tried the tropical fish-caps though and I do like them. Trying out different pots can be good too, though not cheap but is a good way to adjust the vocal behavior of the wah.
The Sweep cap mod is the most useful in my opinion. My first wah had a 6-position rotary which helped deciding with values I liked. My last Wah has only 3 positions and I prefer 0.1 cap position the most because it get's me closest to the Hendrix sound. 0.22 or even 0.33 can be great fun with a clean guitar, but I think it gets too muddy/growly when distorted.

I messed up quite a lot of Wah's with modding when doing too many mods at once. I got all sort of problems I couldn't trace back so my advice would be to take it one mod at a time, test it out for a while and document exactly what you've done each step. Then try another Mod, and if that screws things up undo it right away. I still haven't fully mastered wah circuits. It sort of baffles me how such a simple little circuit tries to devy my attempts to get it right.

[zombiwoof]

If you want your wah to sound more like the original Clyde McCoy Vox wahs, I would go to the Fuzz Central site, and find the page about the Clyde McCoy Wah.  It shows the differences in values between the Vox RI and the original.  I would change the inductor to one of the better ones around, either one of the Fasels (Yellow is more vintage, Red is cleaner), or my choice would be something like the Whipple Halo or other good Halo repro inductor, change the pot to an ICAR taper type (Joe Gagan sells a great new sealed pot), and definitely change out the transistors to ones in the 300-400 hfe range.  There is maybe one or two other resistor values that are different in the RI wah, I'd change those to the vintage value, and add true bypass switching.  The only caps you might want to change are the two .01 uf ones, in the original they were polystryrene, in the RI they are poly film caps.  I don't know if this makes any difference or not, but I wanted to make mine as close to vintage as possible.  As for the .22uf caps, I don't think you need to change them, it would only be a cosmetic issue, as Trop Fish caps were just metallized poly caps and probably won't make any difference in sound.  Basically just make the changes that get the parts back to the original values and types, and upgrade the bypass, transistors to lower value, and put in a more vintage type inductor.  This got me the results I wanted.  I too first tried a bunch of those different component changes that are detailed in several articles online, but it just didn't work out right.  Putting it back to vintage values and component types did the best for me.

Al

[wannabweiland]

Quick question: If I have a 4PDT switch just laying around, can I use that instead of the 3PDT for making the wah true bypass? Probably a dummy question, but figured I'd ask.

[mth5044]

Yep. 3PDT, 4PDT, DPDT, SPDT, xPDT all operate under the same idea that there is a common lug then two lugs that are switched too. The single, double, 3, 4 just determine how many times this schem is copy and pasted.

[zombiwoof]

You can use the 4PDT switch if it fits OK, just use the rows of lugs that are needed (two rows for regular TB, and an extra row if you want to add an LED).  The other row or rows you just leave unused.  It's kind of overkill, though and takes up a little more space.

Al

Quick question: If I have a 4PDT switch just laying around, can I use that instead of the 3PDT for making the wah true bypass? Probably a dummy question, but figured I'd ask.