Adcom 555,B&k St 140, Mccormack .5 dna

The McCormack .5 with an Audible Illusions preamp. This will easily compete with the newer offerings from most companies. The other two amps are not in the same league.

I have two GFA-555II's, and they are very powerful, and will handle a 4 ohm load with no difficulty. They are pretty strong on bass reproduction, too, but my guess is that sonically, the very excellent McCormack DNA-.5 will be noticeably superior. Interestingly, I will (hopefully fairly soon) be comparing my 555II's to at least amps from Krell, McCormack and Theta (and possibly others) as I contemplate an upgrade for my 4 ohm Thiels. The Adcoms drive them just fine, but I am looking for a better sonic synergy match.

Tom.

I'd rule out the B&K ST140 for 4 Ohm load. The McCormack's higher in-put impedance would probably make it the most compatible of the candidates for the usually high out-put impedances of most tube pre-amps, just be mindfull of the tube pre's volume control/voltage out-put and the sensitivity of the McCormack. While the Adcom and the McCormack sound different they both fullfill your sonic criteria.