Impedance Question?

The Dared apparently has a low input impedance.

Yes as you stated 100ohms in your previous post, which will drive any poweramp.

But being a tube it will be capacitor coupled, and if that cap is not big enough in uF, that 100ohms output impedance can start to rise in the bass and increase that 100ohms, and if it rises enough, into a 10kohm amp you could get bass rolloff.

The cap needs to be at least 5uF into 10kohm, to be rolling off the bass -3db at 3hz which just starting to rolloff at 20hz

This is why direct coupling is so good, no cap to **** things up and to colour the sound.
Best cap is no cap.

Cheers George

And that is why I'm leaning towards a direct coupled SLP-98 with some 50's JAN tubes.

@georgehifi oh man, sorry. I didn't mean to repeat myself. I've the schematics for my pre somewhere, I'll see if I can figure out what value the coupling cap is. 
What formulae are you using to calculate low frequency roll off?

(2 pie x 10kohm x 5uf)

6.28 x 10000 x 5 to the minus 6, = then 1/x (reciprocal) the answer
which equals -3db @ 3.18hz

Cheers George

Before anyone corrects me on pie, I’m an Aussie we love our beer, meat pie’s/ with blood.

Cheers George