rangemaster question.

[makaze808]

Hello. In the Austin Treble Blaster article the rangemaster is described as having the ability to and gain increasingly as the notes get higher. It states that at 440hz there is no gain.

What components are setting the 440hz 0db gain parameter?? 

Sorry if I should have got this from the atricle.

Woz.

[darron]

posting a schematic is nice too.

the rangemaster sort of doesn't really boost treble. it makes a curve to cut out the bass frequencies a little and then just boosts everything else. by the time that you boost it the bass is almost where you started but the treble is much higher.

the simple trick it uses is a high pass filter. the first input coupling cap is 4n7 (0.0047uF) or 5n. This lets a certain amount of treble to pass and then slowly rounds off bass frequencies until 1Hz passes nothing. Make the capacitor bigger and you boost more frequencies, smaller and you get a more trebly sound. It's a very low-part EQ huh? sure keeps the circuit part-count down.

stock it produces a very tweed and bright sound. if you want a mid boost the best value i've found is about 22n (0.022uF). putting something like 220n (0.2uF) will make it a full range boost.


hope that helps.

[makaze808]

Thanks. So the 5n (4n7) input cap somehow mathematically relates to 440hz?

Thanks, Woz.

[darron]

ahh. sorry. maybe i missed the point of the question

check this out:
http://www.muzique.com/schem/filter.htm

the bias resistors also form a part of the high pass filter.

or the formula:
http://www.generalguitargadgets.com/richardo/distortion/index.html

[R.G.]

Thanks. So the 5n (4n7) input cap somehow mathematically relates to 440hz?

It does, but only through its combination with all the other impedances connected to that input point, as Darron said.

Resistor-capacitor (RC) filters have a characteristic rolloff frequency determined by the product of the two. Neither one by itself has any special frequency, at least down in the audio range.

[Electric Warrior]

ahh. sorry. maybe i missed the point of the question

check this out:
http://www.muzique.com/schem/filter.htm

the bias resistors also form a part of the high pass filter.

or the formula:
http://www.generalguitargadgets.com/richardo/distortion/index.html

That's why they used the emitter resistor for biasing

[makaze808]

Thanks all for that.

[petemoore]

http://www.generalguitargadgets.com/richardo/distortion/index.html
  C1 = 1/(2 * PI * 0.001M * 40Hz) = 0,039µF = 39nF
  2 x 'PI' x .001 x 40 =
  0.2512  When I punch 3.14 in where it says 'PI'.
  And the 1/ means divide by 1, which = 1
  Someday perhaps even I'll master decimal point placements, I was just foolin' around with the calculator again, to see if, maybe this time I could actually read and replicate a touch of math.
  Every once in a while I take a stab at it just to make sure it's way over my head.
  How is your math ?
  Thank you for posting the link, Darron !
  Excuses for posting my test results on the main forum.
  2x 3.14 = 6.28
  6.28 x .001 = .00628
  .00628 x 40 = .2512

[makaze808]

Thanks all.

Darron, I put a switch in for 3 caps,  5n 100n 220n,  the 100n is too close to the 220n sound so I'm gonna put the 22n in you suggest. Thanlks.