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Classic gear from yesteryear; vintage audio standing the test of time.

RE: Ever auditioned

As in: why do two preamps that measure the same for frequency response and output impedance have noticeably different low bass with the same power amp and speakers?...If I knew why, maybe I could fix the weak one.

Very good question. From my experience with both tinkering with existing designs and comparing related ones, I'd venture to say the difference lies with the power supply. FWIW, the Pass Labs Xs preamp uses 100,000 uf of capacitance. :)

I find that "conventional wisdom" as to how stiff one should be seems to be underestimated using sine wave testing. The very best sounding gear I've heard employs heroic sized ones. :)

edit: I think I might have previously relayed this story, but I think it bears repeating. A Frank Van Alstine modified FET-5 preamp replaced my Citation 11 in 1976. Along with upgrading the quality of the passive parts and using LF356 op amps in place of LM301s, he greatly beefed up the power supply. That was also the era of "double Dyna 400" where he not only increased the number of output devices, but significantly boosted the size of the power supply via an external cabinet. As an inquisitive teenager passionate about sound quality, I followed his lead with an Audire One power amp acquired about the same time. It ran 20,000 uf of capacitance using ~ 50V rails for 100 watt/channel output. Julius Siknius' designs were clean, but I wanted more. So, I replaced the bridge with a 30A unit and added another 60,000 uF in an external cabinet. That increased the energy from 25 joules to 100 - which coincidentally was the value of my later 1981 Threshold Stasis 3 acquisition with comparable wattage.

Sonic difference? Much improved bass punch and dynamics with my Magnepan MG-II speakers. And, the music played on for about thirty seconds following power down. :)





Edits: 09/11/16 09/11/16

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