Octave Switcher

[Uncle Krunkus]

Here's a simple octave switcher for stripboard which I made up. I'm going to put two of them in the ASM2. It's based on a circuit I saw at Laurie's ASM2 site, but it's fairly obvious.
R1-R5 are 10K 1% (Being close to 10K is not as important as being close to each other. eg 5*9.93K(exactly) is better than 4*9.99K and 1*9.92K)
The two trimpots are 10K 25 turn.
R6&R7 are the same value. You work it out like this:-

R6(7)=(V-7)/2*10K rounded down to any value less than 10K away.
Where V = the difference between your reference voltages.

So for my ASM2 the reference voltages are +/-10V. V=20
(20-7)/2*10K = 65K
So R6&R7 will be 62K

If your references were +/-9V like on the SoundLab, V=18
(18-7)/2*10K = 55K
R6&R7 should be 51K

The board solders directly to three of the lugs on the rotary switch (6pos).
Cut the board on the red line.
Note the four cuts in the tracks.
I'll add some photos to clarify soon.

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OctSwi.jpg
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[Uncle Krunkus]

Here are the pics of this thing actually put together.
Ignore the position of the resistors in the photos, that was before I finalised the stripboard layout. The main thing to note is how the switch solders to the board.

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OctSwi-b.jpg
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OctSwi-c.jpg
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