Ref 3 Impedence Mismatch HELP please

The problem here is that the output impedance of the ARC goes higher as the frequency goes lower. If driving a high impedance this is no problem, but a middle impedance like 10K (less than 2000 ohms being 'low impedance'...) is problematic as the coupling caps at the output of the preamp are rolling off the bass with the reduced load at the output.

There is no good way to fix this- either you somehow find a way for the preamp to drive a higher impedance or change out the preamp.

We got around this problem by direct-coupling the output, so there is no bass roll off. Herman is right, there is far too much variance in high end audio so there is not likely to be much in the way of standards, about all you can expect is that tube amps will likely have an input impedance of 100K or higher, whereas its likely that with most solid state components 10K is more likely.

Herman, Bifwynne's suggestion is a good one- Tom is a good guy and knows his stuff.

If you install larger coupling caps, the caps themselves will color the sound to a greater degree.

The bottom line here though will be that if you use this preamp with this crossover, you are likely to wind up with some sort of coloration or artifact- this is a tricky problem to get around.

Sgr, FWIW, you don't have to go to transistors to run 25 feet of balanced cable to a crossover. You just need a preamp that can do that. Our preamps can drive over 100 feet of cable, and they are all-tube; plus they can drive input impedances as low as 600 ohms with no problem- 10K is a piece of cake :)

I have held the opinion for over 25 years that if a preamp or other device like a DAC has an XLR output, then it should also support the associated balanced standard. The standard is simple: in addition to proper pin connections on the XLR, it requires that the device be able to drive a low impedance, 600 ohms being typical (meaning that 10K should be no worries). It also requires the the ground (shield) not carry any signal current (IOW, the signal occurs entirely between the inverted and non-inverted phases, ignoring ground).

Most modern preamps in high end audio with balanced outputs don't support the standard, being unable to drive low impedances and also using the ground connection as part of the signal (which increases susceptibility to cable problems). ARC is one of them. This causes confusion, because with balanced operation you are supposed to be able to use long interconnects without loss. This will not be true if the preamp does not support the standard!

To my knowledge, we are the only tube manufacturer that supports the balanced standard (BTW I would love to learn that I am wrong). OTOH there are a good number of transistor preamp manufacturers that do support the standard. If there is ever any question, just ask 'What is the longest cable this preamp will drive?' If 50 feet is out of the question, the preamp does not support the standard.