F5 input impedance

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
The input impedance doesn't have a significant effect on the gain of the amplifier,
and it would be an odd preamp that had issues with the input impedance range we
are talking about. The Rogue would appear to want something at 22 Kohm or
greater based on Stereophile's measurements.
The input resistor is bound by 3 things:

1 The input capacitance of the power amp. You want the input resistor to be 10x lower than the capacitive resistance at the highest frequency you are interested in.

2. The output impedance of your preamp / source. You would like the resister to be 10x higher than the output Z.

3. Tradition. Tube amps are typically 100K ohm. Solid state range from 10k to 50k ohm.

There may be an opportunity to optimize noise, distortion, frequency response or something else.