Preamp Output Impedance and Amplifier Input Impedance

We received some questions about DAC4800A (and Cherry) input impedance, which is 10K. Here was our response:

It's simple... You get more noise with higher input impedance. Going from 10K to 100K might cost as much as 3dB, but since stock SNR is over 114dB, there's room. We don't do this stock because most preamps have a 600 ohm or lower output impedance, more than 10:1 (the typical "rule of thumb") to drive the amp. We opted for better SNR. The current of the preamp's output driving 10K is VERY low (microamps), so that's not really a significant factor. We can modify amps for 100K input impedance when requested, but there is some rework required.

We don't recommend preamps with AC coupled outputs, although these are few and far between. AC coupling between the preamp and amp creates a high pass filter that can rob you of low bass response.