Ohm Walsh Micro Talls: who's actually heard 'em?

I disagree that a 10:1 ratio is a consensus minimum. IMO, people who state that ratio are either repeating what they've read in a thread somewhere, or they have limited experience hearing what different impedance ratios produce, or they simply don't know what they're supposed to hear. Consensus by repetition is an uninformed consensus.

The Bel Canto amps may work well with an SP16, but I'd still look for a lower output impedance to get the optimal performance from the amps. However, if you can find a good price on a used SP16, then it's certainly worth a try.

FWIW, a Burson buffer will correct impedance mismatches. Reviews state there is no sonic degradation when putting a Burson in the signal chain. I've not tried one.

YEs, the consensus also seems to be that the higher ratio the better for optimal interfacing between amp and pre (sounds kinky), so who knows where a 10:1 minimum comes from?

10:1 is based on reasonable power loss across the preamp output: the pream-amp circuit is a power divider. At 10:1 preamp to amp impedance only about 10% of the voltage signal is "wasted" in the preamp output stage. However, no preamp has a perfectly falt output impedance across the audible frequency range. The 10:1 should be applied to the peak output impedance of the preamp, not the manufacturer's stated nominal impedance. Impedance mismatch is a predictable source of coloration. The preamp is a voltage source that prefers to see an infinite impedance so that it is not loaded down which results in voltage sags and distortion.

The best SS amps use FETs for differential input stage for this reason.

BTW: My Walsh 5 Mk IIIs will be going back to Ohm for repairs on one driver. I spoke to John and decided to upgrade to the Walsh 5000. John says the improvement in sound will be "evolutionary," and they have double the peak power handling and go a little lower. I'll take any improvement I can get with these most fantastic loudspeakers.

Everybody,

Thanks for the advice. There's a Manley Shrimp up on A'gon right now. A little pricier than I'd like (and no remote) but output impedance is only 50K ohms, so I'm seriously considering it.

Fascinating discussion, by the way. I've learned a ton from you guys!

"output impedance is only 50K"

You meant 50 ohm, I assume, right Rebbi?