Different Kay tremolo speed approche - would it work?

[alparent]

As I understand it, the Kay Tremolo speed pot ajusts the speed the two 4.7 caps get discharged.
And the two 10k resistors set the speed they get charged.

What if instead of the 5k pot to ground I put in a fixed resistor (any sugestion on the value would be appreciated) to ground, but used a dual (lets say 25k linear) pot instead of the two 10k resistors to adjust the speed the caps get charge.
Would that work? Would it give us more range? I there a reason not to do it like that?

Thanks to all the knowlegable people who will answer this post. 

[R.G.]

As I understand it, the Kay Tremolo speed pot ajusts the speed the two 4.7 caps get discharged.
And the two 10k resistors set the speed they get charged.

That's not exactly correct. What is really happening is that the 10Ks and the 10uf  make a lowpass filter with a certain phase shift and the 4.7uFs and the speed pot make a high pass filter with a different phase shift, and the two add at the base to make a single frequency that is less attenuated than all the others, so the circuit is resonant at that frequency, so if it oscillates, it oscillates at that frequency. The speed pot changes the highpass filter's frequency and phase.

However, you are correct with this suspicion:

What if instead of the 5k pot to ground I put in a fixed resistor (any sugestion on the value would be appreciated) to ground, but used a dual (lets say 25k linear) pot instead of the two 10k resistors to adjust the speed the caps get charge.
Would that work? Would it give us more range? I there a reason not to do it like that?

Changing the two resistors would give more range if you could do it some way to avoid this also changing the bias on the transistor's base at the same time. There are ways to do this, and changing those two resistances, and even better yet.

The three resistances and three caps in this circuit are called a "Twin T" filter. The twin T filter works best with the series caps (4.7s) being half the capacitance of the one to ground (10uF) and the series resistors (10ks) being - uh, either half or twice, have to look that up - of the shunt resistor between the two 4.7uF caps. There is some frequency change with the single speed resistor as shown, but it gets much wider if you can change all three at once and keep the best ratio between them.

Of course, the simplest way to do that is with a three- or four-section pot, which makes it less desirable.

So yes, changing more than one of the resistors at a time would give more range, but you have to worry about how the transistor gets biased and make that stable somehow to keep the output big enough.