Duncan´s Tone Stack Calculator question

[juan_felt]

Hi again!

I've been messing around with the Tone Stack Calculator and I have a couple of questions about it.

What does Zsrc means exactly, and how can I calculate it?
What is the "load" resistor that is connected between the output and the GND? (Also, how can I calculate it).

Anyway, thanks!

[pappasmurfsharem]

Hi again!

I've been messing around with the Tone Stack Calculator and I have a couple of questions about it.

What does Zsrc means exactly, and how can I calculate it?
What is the "load" resistor that is connected between the output and the GND? (Also, how can I calculate it).

Anyway, thanks!

Zsrc is the estimated impedance of the stage prior to the tone stack I THINK. Someone smarter will correct me soon I'm sure.

The "Load Resistor" would generally be the Volume pot for most of those tone stacks

However I believe some of them are 1meg, so you'd what to use something stompbox friendly like 100K, however that will alter the response and/or the loss of the tone stack. So THEN you would want to scale the other values in your tone stack. for instance multiple the cap values by 10 and divide the resistors/pots by 10

[anotherjim]

Nick's right to me.
It is the source impedance.
If you're designing something yourself, you can cheat this out if you have the tone stack after an opamp then you can call Zsrc 0 or something practical like 100ohm. Follow the tone stack with another opamp and you can set the load impedance to equal the input resistor of that.

Generally, a passive tone control needs zero source impedance and infinite load impedance to function at it's component values. In practice, most would assume perfect impedance and tweak the calculated (which will be in the right ballpark) tone stack values on the breadboard.

[GibsonGM]

Zsrc is the source, and the load is the input impedance to *whatever comes after*.

You're both right.

Ex:  You have a gain stage, output impedance is 600 ohms...you send the output to a tone stack...Zsrc is 600 ohms.  Then, you go from the tone stack to a gain recovery stage, input impedance 250K, let's say.   That would be your load.     AnotherJim hits on this for the design stage.

Mess around with the values to get an idea of what happens if you change a nice low Zsrc to something high, or make the following stage input Z ("load") really really low!     Sometimes it's not too important; other times, yeah, it's a big deal!