Pass X600 (1999)

The X600 is a monoblock power amplifier from Nelson Pass's Pass Laboratories, rated at 600 watts and reviewed by Anthony H. Cordesman in the July 1999 issue of Audio. That review is essentially the whole documented record for this model — the fact sheet behind this page is otherwise empty, and no manufacturer documentation has surfaced in our research. What follows is drawn from that single review.

Cordesman was unreserved in his praise, calling the X600 the best thing Pass had built to that point and ranking it above the company's own Aleph 1.2 monoblocks, which he used as references. He reported that it drove his speakers to absurd levels on bass drums without running out of steam, and that above the deep bass he could find no fault with it in transparency, timbre, or what he described as musical life. Audio (July 1999, p.61–62) is also the source for the front-panel meter, which reads current draw rather than output power — the needle sits near mid-scale until the output stage transitions from Class A into Class AB. The review notes the amplifier is biased so that the two halves of the circuit stay symmetrical, with the output stage running in Class A at lower levels before sliding into AB.

A separate chunk in the same review (p.69) mentions that the frequency extremes slightly betray a midrange that "made m—" (the OCR cuts off mid-sentence), so we can't fairly characterize that criticism. Surviving detail on the X600 beyond this review is thin: no confirmed production years, original price, weight, or service information are recorded here, and the model should be treated as documented primarily through its period press reception rather than through factory data.

• Type: monoblock (mono) solid-state power amplifier
• Rated output: 600 W (per Audio, July 1999)
• Front-panel meter: current draw, not output power
• Bias: Class A at lower levels, transitioning to Class AB
• Reviewer: Anthony H. Cordesman, Audio, July 1999

eBay Listings

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.

Related Models

• Eico 3150 (1967)
• Fisher CUSTOM-ELECTRA-I (K-14/K-15) (1957)
• Fisher CUSTOM-ELECTRA IV (E33/E44) (1960)
• Akai AM-2400 (1978)
• Akai AM-2600 (1977)
• Akai AM-2650 (1975)
• Akai AM-2850 (1975)
• Akai AM-32 (1978)
• Akai AM-73 (1973)
• Heathkit AA-32 (1960s)