Modding a Vox V847-Help? Any pros out there?

Discussion in 'Effects, Pedals, Strings & Things' started by sweetpea, Feb 21, 2006.


  1. sweetpea

    sweetpea Supporting Member

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    :eek: I have purchased a Vox V847 that had a true bypass and a unity gain mod done to it. What else can help improve the tone? The wah sounds great but could use a bit more of a throaty tone with just a bit less harsh highs. I ordered a buffer from Area 51 to help out when using my Mcfuzz. Also, I installed a rocpot and was wondering if a couple of resistor changes would help out? I do not know where to purchase resistors and what ones to change? Also, should I replace the inductor with a Fulltone or Fasel? Any help would be greatly appreciated.
     
  2. eric-d

    eric-d Member

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    Did you try adjusting the throw of the pot? Give it a couple of clicks to the bass side, that'll change the sweep.
     
  3. Phil M

    Phil M Supporting Member

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    How do I do this? I got one about a year ago as a gift and it truly sounds terrible to me. I need to true bypass it at some point because it sucks the high end when it's in line, but how do I adjust the pot?

    Thanks.
     
  4. arexjay

    arexjay Member

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    Yep, I'd be interested in how to do this as well.
     
  5. eric-d

    eric-d Member

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    [​IMG]

    The switch is a Carling 316PP... Check smallbear, area 51, mouser.

    True-Bypassing diagram available at Fulltone's website.

    CORRECTION - In diagram, top position should be "TOE" position.
     
  6. amoebas

    amoebas Guest

    inductors make a world of difference, but they're expensive...


    you could get all mojo-like and install tropical fish caps and cc resistors :cool:
     
  7. sweetpea

    sweetpea Supporting Member

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    Any suggestions on where to get these resistors and tropical fish caps including the recommended values for each? Also, where can I pick up a nice inductor?

    Thanks.
     
  8. Jackie Treehorn

    Jackie Treehorn Member

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    You might try the vocal mod, which is changing the 33k resistor in parallel with the inductor to 100k. Don't overlook the transistors, either. It seems the consensus is that transistors with gains in the range of 300-400 work best, with Q1 being slightly higher. I've got 2N4401's in my V847 at the moment, slightly below 300. I measured one of the stock transistors and it was over 600. I also think trim pots on the emitters are a good idea to find the sweet spot. 2N4401's can be bought at Radio Shack and the ones I've bought there have been in the 265-280 range. I like to increase the electrolytic capacitor to a 10 uf for a more robust sound.

    I would also change the .01 uf input and sweep cap to polystyrene. They make a big improvement.

    But, the stock inductor has to go!
     
  9. Phil M

    Phil M Supporting Member

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    By the time you're all done you could just have a Teese. I never should've let that one go. Best wah I ever heard.

    Thanks.
     
  10. Jackie Treehorn

    Jackie Treehorn Member

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    Ah, but what's the fun in that? Antique Electric, http://www.tubesandmore.com, has the fasels for $17.99, and the rest of the parts would probably be around $7 more. Plus, you get to create your own wah sound...priceless!
     
  11. arexjay

    arexjay Member

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    Are there any sites, or can anyone tell me where to find all of the transistors, etc. inside the pedal that I can replace? This sounds like a really fun project!
     
  12. sweetpea

    sweetpea Supporting Member

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    How does the Fasel sound? And I may need to send you a pm when I get ready to give this a go as I am clueless as to what and where these resistors and caps are on the circuit board?:rolleyes: I am not to far from you as I reside in Folsom, CA. Thanks for all of the suggestions.
     
  13. astainback

    astainback Member

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    I personally tried out the 100k resistor and got some nasty feedback on the top end.. I put the 68k resistor in there and it sounded awesome..
    The 100k probably sounds better with other mods in addition to the 100k.
    I just did a true bypass and a vocal mod. I read somewhere to solder in a couple of wires with alligator clips to try different ones. I did it and it worked great. I suggest 68k.

    Even more, I suggest trying both and even more yourself.

    adrian
     
  14. arexjay

    arexjay Member

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  15. dmagalhaes

    dmagalhaes Member

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    The Vox inductors have 4 prongs vs the Fasels 2 prongs. How do you make that work?
     
  16. arexjay

    arexjay Member

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    I'm not quite sure how that works, that's why I'm asking everyone else!
     
  17. Jackie Treehorn

    Jackie Treehorn Member

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    [​IMG]

    Here is a picture from this site
    http://homepage.ntlworld.com/s.castledine/greenfuz/wah.html

    That shows some of the parts. The transistors are missing out of this picture, oddly. They are black pieces that reside between the two rows of components. I realize that some V847's have yellow, box capacitors instead of the blue and orange caps in the picture. However, this picture makes it easier to identify which ones to replace with which type of cap. The little blue capacitors in the picture are the ones I suggested replacing with polystyrene caps. One is designated the sweep cap, the other is the input cap which rolls off the bass response into the wah. The polystyrene leads to a clearer tone.

    The orange ones in the picture would be the ones you would replace with tropical fish or equivalent caps. The 33k next to the inductor is the one you would change for the vocal mod. Anything between 33k - 100k will work. I've consecutively increased this resistor, 56k, 74k, 100k, myself. I like the 100k best, but it's your choice. The 68k input resistor is the one changed for the unity gain mod, it cuts the volume into the wah - larger values give less volume. The 470R indicated on the picture is where I was suggesting substituting a trim pot in order to control the gain of Q1. Lower values give more gain. It affects the sweep somewhat as well as getting a good quack/resonance.

    Here is a really good article on wah mods: http://www.geofex.com/Article_Folders/wahpedl/wahped.htm

    Well, if you remove the Vox inductor, you'll see that two of the four prongs are connected together; you only need 2 connections on the inductor. There's lots of holes for those two connections so the board can accomodate a bunch of different inductors.

    Probably any of the aftermarket inductors are going to sound better than the stock inductor. The best selection I've seen is at http://www.banzaieffects.com. They also have different pots, and BC series transistors which are more "vintage correct" than the 2N4401's from Radio Shack.

    I've got the yellow fasel in my Vox V847 and it was a BIG improvement over the stock inductor. I've also got a square TDK inductor in another project wah which I like, too. Apparently these are the inductors everyone else hates, though. From what I've read, the halo's sound clearer. I go for vommitty tones. You can PM me if you need help.

    You want NPN transistors. Aside from the inductor, the parts are fairly common. You can order transistors, polystyrene caps, carbon comp resistors (Xicon, I think) at Mouser. Smallbear electronics is a safe bet, because you can tell him you're modding a V847 and he can give you appropriate transistors.
     
  18. sweetpea

    sweetpea Supporting Member

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    Jackie Treehorn.

    Thanks so much for going to that extra effort in helping us future wah mod junkies out! The pictures and descriptions are perfect for a electronic laymen like myself.

    Much appreciated.:dude
     
  19. dmagalhaes

    dmagalhaes Member

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    Which holes should I use to mount the Fasel? I just happen to have one hanging around.
     

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