Input Impedances

A project log for Muffsy Phono Preamp PP-2

An Improved AudioKarma CNC Phono Stage

skrodahlskrodahl 03/16/2015 at 14:390 Comments

Although the default input impedance for most cartridges is 47k ohm, many are reporting that other input impedances are giving better results.

The standard CNC circuit has the following impedances, selectable with a four-way DIP-switch:

These values are quite sound, but having the possibility of paralleling up to four resistors should give a few more useful options. The four values above don't give many other options though.

How about using these values instead?

Let's see what we end up with:

(Values in bold are equivalent to the original CNC circuit)

There are a few options that are too close together to be useful (which I haven't listed in the table above), but we get quite a range to choose from nonetheless.

Well, that's settled then. New input resistors all around for the evolved CNC circuit.