Anderton Freq. Boost - simple question...or so I think?

[Brossman]

http://www.muzique.com/schem/ca-eq.gif

Here's the schematic.  If I change the value of the 10k resistor that's in parallel with the series freq. center caps(say, with a pot), does that change the center frequency's value?

[[edit]]  I just realized that this may throw off the bias for the ICs... is this important for the proper functionality?

[Mark Hammer]

Is your intent to:
- make it variable, for tuning purposes?
- use another value because you ran out of 10k?
- tinker with the gain?

[Brossman]

Is your intent to:
- make it variable, for tuning purposes?
...
- tinker with the gain?

Yes.  These are two things I'm looking at.  How would changing these values affect the overall tone spectrum produced, or rather, changed?

[stringsthings]

http://www.muzique.com/schem/ca-eq.gif

Here's the schematic.  If I change the value of the 10k resistor that's in parallel with the series freq. center caps(say, with a pot), does that change the center frequency's value?

if the values of C1 and C2 are changed, then the center frequency of the filter is changed.

if you are interested in changing the values of other parts in the circuit, one suggestion is to simply make the part substitution on a breadboard, veroboard, PCB, etc .... and then measure the results ...

since this circuit has a low-parts count, this would make a great "lab" experiment ...

for example, breadboard the circuit using C1=C2=0.01uF and measure the result .... then change C1 and C2 to 0.005uF and measure the result ... ( in this case, you can measure the results with just your ears ... a boost at 4kHz sounds quite different than a boost at 2kHz ... if you access to a nice signal generator and a scope, then you can tinker to your heart's delight ) ... ... then you could try different values that Anderton didn't specify .. say 500 pF for C1 and C2 ...

[Paul Marossy]

When I built mine, I used a rotary switch to give me four different options for C1 & C2.

Full schematic from Anderton's book is here: http://www.diyguitarist.com/PDF_Files/FreqBooster.pdf

[Mark Hammer]

Note that stages can be cascaded.  That is, one could stick another identical stage in series, and simply use a 3-position (on-off-on) DPDT toggle to select between 3 similar cap values within a "range", such that you can have 2 or more resonant boosts.