Pass Labs xa160 ( testet 2003 )
To my surprise, given its bulk, the XA160 didn't meet its specified output power of 160W into 8 ohms. I checked both samples, which measured the same, then re-measured them using a Neutrik generator and an analog oscilloscope, in case there was some incompatibility between the Pass Labs and my Audio Precision System One. The result was no different.
Fig.3 shows how the XA160's measured THD+noise percentage changes with measured output power. (The wall AC voltage was 124V for these measurements.) The actual output power at clipping (defined as 1% THD+N) was 165W into 16 ohms, 118W into 8 ohms, 59W into 4 ohms, and 29W into 2 ohms. As I've said, the two amps measured virtually identically in this respect, meaning that this is unlikely to be due to a sample fault. [A subsequent e-mail from Nelson Pass concerned the fact that early samples of the amplifier suffered from a production error, resulting in the low maximum power. This has been corrected, Iw as told.JA.]
The Pass Labs' measured performance left me scratching my head. Its massive construction, high heat output, and high price suggest a limitless delivery of wattsyet, assuming neither review sample was malfunctioning, the XA160 offers only moderate power. Its current-limiting of the clipping points is also something that historically has been regarded as a bad thing in a solid-state power amplifier. But like its highish output impedance, this is something that is more typical of tube designs, which might well go some way to explaining why MF felt the XA160 to sound like a tube amplifier.John Atkinson
Jeg legger inn denne kun som illustrasjon.... Grundighet både avdekker og oppklarer ...
mvh
Kjell P..