MI audio tube zone?

[mhartington]

So I was some research and come across this

http://schematic.exteen.com/mi-audio-tube-zone

seems like a layout for one of MI audio tube zone.  Very tempted to attempt but i have a few things bother me.  In this version it seems like that they have a 3 way selector for mid voicing. How would i hook up a pot instead of the switch.  Also, whats the deal with the double pot lug for gain. Just curious what it is called because ive never come across one before. Im probably gonna run it off 18volts from a charge pump, this youtube video shows it at 18volts and it sounds pretty awesome, check it out

http://www.youtube.com/watch?v=18SjPtJWJJo&feature=related

[JohnnyC]

ive got the tubezone (6 big knob one) and its a great pedal...clean boost to high gain mesa like tone.
i run it at 18V

[Quackzed]

looking at the layout, the switch in the middle (scoop) is through a 3n3 cap. when switched one way, its parallel to a 4n7 cap , and the other way its parallel with a 27n cap. so middle is 3n3, one side is 3n3 plus 4n7 = 8n , and the other side is 3n3 + 27n =30n3 .so if you wanted to use a pot instead, a 100k pot wired as a variable resistor  in series with a 27n cap -and a 3n3 cap wired in parallal to both of them, like a 'cap blend pot' ,should cover the range of all the switch positions.

._____/-----0  0--0-----27n------\________.
          \------------3n3------------/
just remove all three caps mentioned, and replace it with above wiring the dots to the pads where the old 3n3 was.

[mhartington]

so if i am understanding you right, i could wire it up like this



where the X's are, i would remove the caps and wire the 100k pot as if it was the 3 way switch?

[Lurco]

you could try to ask michael ibrahim himself? http://www.diystompboxes.com/smfforum/index.php?topic=47501.0

[slacker]

You want to keep the 3n3 and 27n caps then wire lugs 1 and 2 of the pot to where the blue wire was (the trace going to the 3n3) and lug 3 to where the brown wire was (the trace going to the 27n cap).

[mhartington]

You want to keep the 3n3 and 27n caps then wire lugs 1 and 2 of the pot to where the blue wire was (the trace going to the 3n3) and lug 3 to where the brown wire was (the trace going to the 27n cap).

alright but what about the 4n7 cap, does that stay in or get taken out

[slacker]

The 4n7 goes. The idea is with the pot at maximum resistance the 27n is basically out of the circuit so you get the same response as just having the 3n3 which is "Scoop". With the pot at minimum resistance the 27n is in parallel with the 3n3 so you get "Hump" and in between you get a range from "Scoop" to "Hump" with "Flat" in there somewhere.

[mhartington]

so like this.



also, what is with the word "tant" next to the elecrtos?

[DrBoogey]

also, what is with the word "tant" next to the elecrtos?

Those are tantalum capacitors, but could be normal electrolytic capacitors as well!
http://en.wikipedia.org/wiki/Tantalum_capacitor