Tuesday, 29 January 2013

Lava Rim 2

Another request. Aron Nelson's Lava Rim 2. I have no clue why the input level control pot is called "Bias". That's the reason why i used quote marks around it...


15 comments:

  1. 'Bias' following Fulltone labels?

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    1. Or Briggs'. I would personally rather call that "Pre-Gain".
      +m

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  2. Thanks Miro! I'll build it now, noticed that you're missing the drive pot value.

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    1. So i do :) Thanks for noting. I'll update it right away...
      +m

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  3. This comment has been removed by the author.

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  4. It works great but, all the trimmers should have a connection between 2 of their lugs, it can be between lugs 1&2 or 2&3, because the way they're right now makes them work just like a 2 position switch.

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    1. 2 position switch? It doesn't quite matter if the pot's pins 1 & 2 are connected together.. For example:
      - Pin 1 is not connected
      - Pin 2 connects to power supply
      - pin 3 connects to transistor's collector
      The resistance between supply and collector rises when pin 2, the middle pin, moves towards pin 1. It would be exactly the same amount of resistance between pins 2 and 3, regardless of whether pin 1 is connected or not.

      Schematic has them connected, but the two extra links to achieve that do practically nothing...
      +m

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    2. yes, you´re right, but then, i don´t know what is causing them to act like that, maybe it's because of this: in the schematic, 9v goes to lug 1 or 3 of the trimmers, the same with the one connected to the clipping diodes, not lug 2, maybe i'm practically saying the same as before, does this make sense? maybe the trimmers are just damaged or something. I´ll check them.

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    3. You could try to adjust 100K and 50K to the point where it sounds the best as those are used to bias the transsistors. The 5K is used to dial the clipping to suitable level. In the clockwise position the clipping is maxed, and it should tame down when the trimmer is turned CCW.
      +m

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  5. I know but, what i meant is that they're acting like a switch, because when i turn them, i just get somethig like an on/off effect in a really short rotation, and in the rest of that rotation, there is no change.

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    1. That's to be expected, as there's only tiny part of the sweep that biases the transistors correctly.
      +m

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    2. oohh! that's what happens! Thank you very much! then its verified sorry for that! :)

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    3. Great! Thanks Luis!

      Biasing is one of the worst things (in my opinion) in all builds. Specific transistors get biased correctly only with exactly correct resistance. But when it works, it's pretty much worth all the trouble.

      I'll tag it right away!
      +m

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  6. Now i'll put my hands on the wampler modded dist +, btw, this one sounds really great. Thanks!

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