Friday, 20 November 2015

Quadcaster

Four Valvecasters in series!
You can find the original schematic here.




21 comments:

  1. We Need More Tubes))) Cool pedal! Thanks!

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  2. Thank you very much Alex.I been working on a version of this with three 12AX7,mine sounds great but has a horrible low end hum i cant get rid of.I built a charge pump to boost power on pins 1 and 6 to 30vdc,so i think the charge pump is cause the hum but not sure just guessing?

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  3. Did you use shielded wire for the ins and outs? Not sure if the charge pump would cause the low end hum but I know if I made one I would for sure use an isolated 12VDC power supply for starters

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  4. Some info here and schematic for a real tube-one that shows his 33V DC from an internal DC/DC converter for pins 1 and 6. http://tomsguitarprojects.blogspot.ch/2014/10/RealTube-One.html

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    1. http://tomsguitarprojects.blogspot.ch/2014/10/dc-dc-converter.html
      That is the converter.
      Hopefully this info helps out...

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    2. I'm wondering if any pump is enough to give out enough current for four tubes. Is it all silent when the converter is out and circuit is fed with 12V instead?
      +m

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    4. Anyone have a source for the LT1613 chip? I can only find it on DigiKey and that's SMT only.

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  5. I wound up useing my MXR gate after the 2 tubes and now the circuit is perfect.thanks for all the info guys.i still have alot more testing to go with this,once i get all the bugs worked out ill post a schematic since im no good at making vero

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  7. Good to see the spammers have found us.

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  8. Where could clipping diodes be put in. Just found this site I'm going to setup an account in a sec but I got really excited when I found this.

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    Replies
    1. Put the clipping diodes before the volume, but after the tone control. What I do is I put two diodes side by side, so that the opposite ends of each diode is touching, then twist the leads, solder them together, and snip off the leads you don't need.

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  9. Cool. I think I'll do it with switchable input caps and a switchable diode section.

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  10. Thanks for this one.. Super excited to get it working!
    When I first tried it out with a 12V 500mA wall wart I had a terrible hum and hardly passed any signal. I've now upgraded to a 12V 10A power supply (I think originally from a laptop) and it passes signal fine, however there is still a lot of low frequency hum as well as some high frequency oscillation, even when all the trimpots are set fully CCW. The hum goes away (or is at least less noticeable) while I'm playing, however the sound is a bit farty/saggy. Any ideas?
    Cheers!

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    Replies
    1. PS. Tube voltages are:

      V1
      11.25V
      -322.7mV
      217mV
      3.8mV
      11.88V
      5.75V
      -0.4mV
      3.8mV

      V2
      9.7V
      0.1mV
      0.925V
      3.5mV
      11.8V
      5.47V
      1mV
      3.3mV

      V3
      9.98V
      0.5mV
      0.75mV
      2.7mV
      11.89V
      5.85V
      3.9mV
      2.7mV

      V4
      9.86V
      0.1mV
      0.853mV
      1.1mV
      11.89V
      6.55V
      -97.8mV
      1.8mV

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    2. Got it! Changed to a 15v 1A power supply and ran into a pair of L7812 regulators; 1 for the heaters and 1 for everything else.
      I'd call it verified!
      On a side note, it sounds better to me with 12AU7s in V1-3 and the 12AT7 in V4.

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    3. Good call. I like this idea better than the 33v charge pump. Think I'll give this a try. Thanks to Alex for the layout!

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