Like Peanut Butter and Chocolate — Nelson Pass / 2002

Pass Labs XA Series Power Amplifiers For over ten years, the Aleph series of single-ended Class A amplifi ers have received praise for their outstanding sonic defi nition, warmth, and smoothness; and have often been compared favorably with the very best tube amplifi ers. The Aleph topology achieves state-of-the-art performance with a very simple linear design, and is additionally one of the most stable and reliable audio amplifi ers in existence. A considerable number of audiophiles have found themselves bi-amping their loudspeakers, putting Pass X amplifi ers on the bottom for power and control, conjoined with Alephs on the top… More...

Matching Devices — Nelson Pass / 1993

After you acquire the devices, you will need to test them. You might consider running lots of tests on these transistors, but only one is essential: measuring gate-source voltage versus current. The greatest variations occur here, and it is necessary to do some matching to get proper performance. This test will also tell you whether or not the device is broken. The test is simple and requires a power supply, a resistor, and a DC voltmeter. Figure 12 shows the test hookup for N- and P-channel types. The supply source resistance (R1) is nominal, and is found from I =… More...