Question About Audio Research Preamp Specs

dsper
What does the "20K ohms minimum load" tell me?

As mzkmxcv stated 8 x output to input ratio is even fine.

But in this case the AR preamp would be capacitor coupled output, and the roll off in the low frequency could be too high if the partnering power amp is less than 20kohm input, with the size of the AR’s coupling cap. And so you may miss out on the low frequencies.

There are two way this can be fixed, don't get fooled into needing another preamp.  
dsper
1: If you own the AR pre, tell me the size (uF) of the output coupling cap, (it will be the big ones near each output) and what the poweramp input impedance is you want to use it with, and i’ll calculate at what low frequency it’s at -3db for you.
It’s a simple to correct if too small, with a $20 larger coupling cap, don’t go buying another preamp because of it.

2: Or you can go the other way and get the input impedance resistor (20cents) raised to 50kohm on the poweramp, if it’s fet input no problem, even a 100kohm

Cheers George

George
 Makes great sense here.
  easy to have a tech make the resistor changes on the power amp
 .sometimes I wonder if guys like Rowland and McCormick make amps input Imp so low that only their own preamps have an advantage even over great pre amps.

audioconnection
 George
Makes great sense here.
easy to have a tech make the resistor changes on the power amp
.sometimes I wonder if guys like Rowland and McCormick make amps input Imp so low that only their own preamps have an advantage even over great pre amps.

That’s more truth than fiction, we have a very good power amp maker here that has 1kohm input, and yes his preamp is 10ohms, so any other preamp sounds like **** into it but his doesn’t.
But the 1k input resistor on the amp is socketed and if removed the input becomes 68kohms, but he doesn’t advertise this, and any preamp/tube ss/or passive will drive it then.

Cheers George

1: If you own the AR pre, tell me the size (uF) of the output coupling cap, (it will be the big ones near each output) and what the poweramp input impedance is you want to use it with, and i’ll calculate at what low frequency it’s at -3db for you.
It’s a simple to correct if too small, with a $20 larger coupling cap, don’t go buying another preamp because of it.

2: Or you can go the other way and get the input impedance resistor (20cents) raised to 50kohm on the poweramp, if it’s fet input no problem, even a 100kohm

Cheers George audioconnectionGeorge
 Makes great sense here.
  easy to have a tech make the resistor changes on the power amp.

The reason ARC didn't do this initially was simply because the larger you make a coupling cap the more coloration no matter what type of construction. Larger caps start to get considerably higher inductance so even if you have the best Teflon its still going to be an audible degradation.
A secondary reason might also have to do with space. Adding long leads to make a part fit in a place that wasn't designed for it is a good recipe for noise pickup.

The reason ARC didn't do this initially was simply because the larger you make a coupling cap the more coloration no matter what type of construction.

Take that with a grain of salt. I do prefer direct coupling (no cap), best cap is no cap mentality. 

But dsper OP one of the best tube preamps hailed even by many tube and solid state preamp manufactures as being the best tube preamp ever made is the  Aesthetix Calypso preamp, and it has massive output coupling caps, as shown in this pic circled in red.
https://ibb.co/4Jb0bSV

Cheers George