Next step: tube pre or tube power amp?

The load to the speakers you have is better if it comes
from a SS amp.
Buconero117 (Threads | Answers)

I disagree. 8 ohm nominal impedance with a 6 ohm minimum is a reasonably
flat impedance curve which can be handled without any problem by a push
pull tube amplifier.

91dB sensitivity is a non-issue. It can be driven by either a SS or tube amp.

Frankly, IMO, the OP has his choice of SS or tube amp (provided the tube amp
is a push pull design). He may even have the opportunity to use an OTL tube
amp.

You can figure out your minimum power needs by remembering that you double the power for each 3db gain in loudness. So the 91db sensitivity at one watt needs 2 watts for 94, 4 for 97db and so fourth. This gives the MINIMUM required, which is not necessarily the ideal power but is a rough guide. I doubt if you would need 75 with your current speakers but if you intend to change it can't hurt to get a larger amp as long as it is of the same quality.

Keep in mind the power required for dynamic peaks in music. An "average" listening volume of 91dB can reach 100+dB peaks pretty easily. At a 107dB peak on 91dB speakers, the amp is putting out 64 wpc, and the requirement jumps to 128 wpc for a 110dB peak.

Also keep in mind the sensitivity number is measured 1 meter from the speaker drivers. So, 91dB measured from a listening position in a medium to large room will translate to a higher measurement at 1 meter from the drivers.

In my medium size room, it's pretty easy to approach a decibel level that requires 60wpc from the amps.

09-09-09: Stevecuss
I'd prefer a tube power amp for WAF and convenience - I can hide it behind some fake greenery in our AV cabinet...

Tube amps that I've owned throw out more heat than any Class A SS amp I've owned. So you may not be able to hide a tube amp in your A/V cabinet. Just something else to think about.....

Hi Jmcgrogan2,

thanks for that input and I'd considered heat. Our AV cabinet is open - a cutout in the wall of the house, essentially, so it has plenty of ventilation above and around it. I use a fake green planty thingy in front to cover the front of it. Who knows, maybe my wife will love the glow of tubes...