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Valvecaster Tube Pedal

Discussion in 'Burnt Fingers DIY Effects' started by dtermined2play, Feb 17, 2014.

  1. dtermined2play

    dtermined2play Tele-Afflicted

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    Found a schematic and pictorial on building a vavlecaster tube pedal. I built it twice both times nothing but hum no guitar signal. Tube lights up but all I get is hum. Very frustrating to say the least.

    Not sure what I am doing wrong. Anyone here ever build one?
     
  2. FenderLover

    FenderLover Poster Extraordinaire

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    They are particular about having a solid, noiseless supply. Building from a kit may also have better build instructions than building from a schematic. You could probably post the instruction that you are going by and some good pics of your build for some help here. The better the pics, the better the help.
     
  3. dtermined2play

    dtermined2play Tele-Afflicted

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    Thank you. I am not sure how to tell is the supply is noiseless. It is just a 9v wall wart that came of a toy. I think I found one issue. I think one of my resistor values is wrong. Going to change it when I get home.
     
  4. bendeane

    bendeane Tele-Meister

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    If your power supply came from a consumer product, chances are high that its noisy as hell. Craig Anderton has a book with a project that can essentially filter a power supply very well, but a good audio grade power supply isn't that expensive. I tried to go cheap and used power supplies from cordless phones, calculators, and even the universal Radio Shack jobs that let you change the polarity and the voltage. All had noise issues.

    Used a Boss and a One Spot and one made by Planet Waves with no issues whatsoever. Each of these can be had new for between 19-29 USD. Worth the elimination of a headache.
     
  5. bendeane

    bendeane Tele-Meister

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    Oh and the Anderton project I mentioned is a pretty low parts count and may be able to just be built into the schematic pretty simply. I've got some parts coming for an unrelated project that is a really low parts count OD clone and I might test it in the enclosure with that circuit using a cheap cheap PS that produces noise with some of my factory pedals.
     
  6. dtermined2play

    dtermined2play Tele-Afflicted

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    Awesome thanks for the info. I finally got guitar signal. Although the hum is still atrocious at least I can hear what the pedal is supposed to do. I really need to get a 12au7 tube the ax7 just clips way too much. Has almost a synth sound to it.

    The biggest problem I found was an incorrect resistor value going from pin 2 to pin 4. It called for one meg due to lack of attention I put a 10 meg resistor on it. Duh. I also had a bad gain pot and a crappy tube socket. I got a better grade socket today and started over.
     
  7. dtermined2play

    dtermined2play Tele-Afflicted

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    I ordered a GT12AU7 silver series and a one spot from GC yesterday. Unfortunately the one spot is on back order.
     
  8. Fatknuckle

    Fatknuckle Tele-Holic

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    It is a neat little pedal. I am finishing up a Valvemaster variant currently, which is a modification having the gain off pin 1, and cathode resistors with bypass caps off pins 3 and 8. Different flavor. I find both like 12v better.

    image-1996822142.jpg
     
  9. dtermined2play

    dtermined2play Tele-Afflicted

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    Nice clean look on your pedal. Would you be willing to share a layout and parts list of your variant? I plan to make a couple more of these.
     
  10. Fatknuckle

    Fatknuckle Tele-Holic

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    Here is all I have so far. I changed the 47k resistor off pin 1 to a 150k to increase the overdrive, as it seemed too clean on the gain pot. Probably a 220k would be good. Bypass switch can be wired several ways.


    image-3344608752.jpg
     
  11. bblumentritt

    bblumentritt Tele-Afflicted

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    I've built several of these. They all sound great and don't hum. However, I did make a few mods to the basic Valvecaster schematic.

    I use a 12V power supply from E-H or someone like that from Musician's Friend. I filter the power supply in the pedal with a diode and filter cap.

    I use a 3PDT footswitch and LED.

    I changed a couple of component values.

    I use a 12AU7 type tube. A 12AT7 is brighter. A 12AX7 is no good.
     
  12. Keyser Soze

    Keyser Soze Tele-Holic

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    The primary reason these designs are so susceptible to noise is that they are running the tube heater as a series connection.

    12a_7 tubes can also run the heaters in parallel (V+ to pins 4 & 5, pin 9 to ground) at half the voltage (but twice the current) and then they become humbucking - thereby rejecting most of the power supply noise.

    The website where that schematic came from also lists a schematic for a 6111 sub-mini tube design. Part of that schematic is a voltage regulation system using a 12 volt input, putting out 6.3 volts. Something like that would be ideal for running a 12a_7's heaters in parallel configuration.
     
  13. limbe

    limbe Tele-Afflicted

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    I built the "Tube Distortion" that was designed by Ron Black and published in Guitar Player.It had a regulated power supply that delivered 12 volt 200 mA.The tube heater was connected in series like the Valvecaster.With regulated 12 volt,shielded cable where it was needed and careful lead dressing there is no noticeable hum!A simple power supply like this from the GGG site will do (with a 12 volt transformer and regulator of course).
    http://www.generalguitargadgets.com/pdf/ggg_ps_rps_sc.pdf
     
    Last edited: Feb 23, 2014
  14. Fatknuckle

    Fatknuckle Tele-Holic

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    I built my last variant with parallel heaters, and played it in church this morning along side of my first one, which has the Matsumin layout and series heaters. This new one used a separate exterior-regulated 12v supply, and was quiet as a mouse (as far as hum and noise). The other one likes the same 12v supply, but if I daisy-chain them both it hums horribly. I may switch it to parallel heaters too, but for now it joins the other pedals on the 9v chain.
     
  15. Fatknuckle

    Fatknuckle Tele-Holic

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    FWIW, I changed the heaters to parallel with a 7805 regulator and two diodes in series on the ground leg, so that one is in parallel now too. Sounds fine by itself, but I still can't put the two of the side by side on the same voltage supply.

    image-575159377.jpg
     
  16. dtermined2play

    dtermined2play Tele-Afflicted

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    Well I got the 12au7 tube and it was definitely better than the ax7. However the pedal really came to life when I re-wired it to the schematic that is posted above. I noticed the tube is glowing a little brighter than it did with the original wiring.
     
  17. dtermined2play

    dtermined2play Tele-Afflicted

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    Thanks fat knuckle for the schematic. I had to make a couple of changes just because it was what I had avail. The gain pot is A250k And the 10uf pots going to ground I had to use 22uf. It works great. Still has a lot of hum even using battery it is a little noisy. I may need to touch up some solder points. Also my house power is very noisy and pedals just magnify it.


    Thanks again for all the help. Just need to house it now.
     
  18. dtermined2play

    dtermined2play Tele-Afflicted

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    Well I got the one spot and had to reverse the connections on the DC jack. No hum, quiet as a mouse. Thanks for all the help guys.
     
  19. dtermined2play

    dtermined2play Tele-Afflicted

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    Brought it to church yesterday and ran it straight into the PA along with a delay pedal. Very nice tube warmth without lugging a 65lb amp around.

    I also tried swapping the tube for an ax7 and was suprised in the drop in output volume. The au7 went right back in :)
     
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