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All measurements were made after the YBA 2 had been preconditioned by running it at one-third full power into 8 ohms for an hour, which thermally stresses the amplifier to the maximum. Its heatsinks were very hot at the end of this period. Interestingly, however, those who say that solid-state components need no warmup should note that the amplifier's THD+noise, initially 0.09% for 1W into 8 ohms, dropped by a factor of more than five—to 0.016%—by the end of this preconditioning period.

The YBA 2 HC's voltage gain measured 27.6dB into an 8 ohm load; its…

I was on the phone with John Atkinson. He'd almost scratched a hole in his head trying to figure out how to do the Follow-Up of the YBA 2 before moving from Santa Fe to New York. I heard a flashbulb pop.

"Unless..." he said sweetly, "....you wanna do them, J-10!"

It's hard to describe the sound of the other shoe dropping, but I heard it.

"Uh...okay, JA!"

I had reviewed the YBA Signature 6 Chassis preamplifier and Passion 1000 monoblocks, so I was familiar with YBA's "house…

MACH 1 started off by selling their DM-10 loudspeaker direct to the public with a 30-day return policy, but has now set up a small network of specialist retailers. The company has kept up its profile in the…

Description: Three-way dynamic loudspeaker with sealed-box bass alignment. Drive-units: 1" concave ceramic-dome tweeter, 5.5" polypropylene-cone midrange driver, 10" woofer. Crossover frequencies & slopes: 250Hz, 3kHz, fourth-order Linkwitz-Riley filters. Frequency response: 30Hz-20kHz, ±3dB. Nominal impedance: 6 ohms. Sensitivity: 89dB/W/m. Recommended input power: 35-500W.
Dimensions: 13" W by 46" H by 16.5" D. Weight: 150 lbs each.
Serial numbers of samples tested: 107A/B.
Price: $10,995/pair (1994). Optional spiked, nonresonant platforms: $250/…

The DM-10 Signature generally doesn't make too many demands on the amplifier. Its calculated B-weighted sensitivity was a little below specification but still average at 87dB/2.83V/m, while its impedance plot (fig.1), measured with the Audio Precision System One, didn't drop below 4 ohms, and with only minor-magnitude changes above the upper bass. This means that its sound won't change significantly with amplifiers featuring high output impedances. Phase-angle values, too, are generally small. Note, however, that in the midbass, a lowish magnitude is combined with…

In his review of the Mach 1 Acoustics DM-10 Signature loudspeaker (p.131), Dick Olsher correctly perceived somewhat limited low bass from the DM-10, despite a respectably low measured system resonance at 24Hz. With a modest bass Q factor, fair in-room bass should have been available down to 25Hz if the woofer excursion was up to it.

The reason for the discrepancy can in fact be seen in the individual response of the woofer and in the electrical signal actually driving the woofer motor coil, available thanks to the…

There were other off-…

I've been meaning to write about the B&K ST-140, but keep getting sidetracked. Well, the Steve Kaiser/Frank Van Alstine flap (footnote 1) gives me an excuse.

Seriously, I wouldn't want to see this controversy—essentially a feud between B&K's John Beyer and his ex-partner, Steve Kaiser—obscure the point that B&K products are among the finest values on the market today.

JGH reported the B&K ST-140 one of the best amps under $1000 two years ago; I think it's one of the best amps, period. That's…

You can build a decent tube preamplifier for under a grand, and quite a few manufacturers have done so: the MFA Magus), the Conrad-Johnson PV7, the Lazarus Cascade Basic, the Audible Illusions Modulus. But a tube power amplifier for much under a kilobuck? That's just not possible, although the Quicksilver monoblocks retailed for just under $1000 when they first came out. It's the transformers in particular that make tube amps so costly to build.

So if you're on a budget, you might combine…