The ancient Crown D-60 that I bought for $100 from my neighbor, Frank, has been driving my studio monitors for 17 years, and it is still my favorite among my power amps. Although it produces only 35W per channel, it delivers tighter and better-defined bass than some substantially larger amps. Crown's new Power-Tech 3.1 power amplifier sounds every bit as good as the D-60 and provides enough clean watts to handle every task I have given it.
WEIGHTY MATTERS
Only two rackspaces high, the Power-Tech 3.1's 16-inch depth requires an extradeep rack case, and its 37.5 pounds should be supported at the rear as well as at the front rack rail. Seemingly composed of neutron star matter, the 3.1 actually weighs less than many similarly powerful amplifiers with traditional power supplies, though it's somewhat heavy compared to the new breed of switching amplifiers.
Producing 540W per channel into 8• and 760W per channel into 4•, the output transistors are protected by a form of limiting that Crown calls Output Device Emulation Protection (ODEP). The amplifier is comprehensively protected against DC, shorted loads, transformer overheating, and other forms of antisocial behavior. The fan-cooled unit has a filter across its air intake that must be cleaned periodically.
EASY CONNECTIONS
Long on performance, the 3.1 is short on bells and whistles such as selectable limiters or filters. There is a red power light and LEDs for each channel between the frontmounted and recessed level controls. The LEDs glow green when signal is present and yellow if distortion reaches 0.05 percent. A lone pair of binding posts is provided for speaker connection. The 3.1 has two mono modes: bridge-mono for load impedances of 4• or greater and parallel-mono for loads of 4• or less.
Crown's Power-Tech 3 provided only a pair of TRS jacks for the amplifier's balanced inputs. The 3.1 adds a welcome pair of female XLRs wired in parallel with the TRS jacks so that one set of connectors may be used to pass the input signal to another device. The XLRs are mounted on a detachable panel, which hides a three-position switch that selects between input sensitivities of 0.775 or 1.4V, or 26 dB voltage gain, which is the PT 3.1's least-sensitive switch position. The 26 dB voltage gain setting constitutes an interesting feature common to a number of Crown amps: it allows for easy calibration between Crown amps of different power ratings so that they produce the same output for a given input voltage.
IN THE HOUSES
I had the good fortune to engineer a particularly diverse selection of events while reviewing the 3.1. First up were two concerts held in a 13,464-square foot ballroom in San Jose, California, as part of the Festival of Wales 2001. Performers included a Tribute to Welsh Rock (Dave Edmunds, Tom Jones, and Shirley Bassey), a prominent Welsh folk singer whose set was being videotaped for Welsh TV, a choir, and a Welsh triple-harp virtuoso. The first minister of Wales also addressed the audience. Powering stage monitors the first night and front-of-house the second, the Power-Tech 3.1 passed with flying colors. It had the juice to keep ahead of the bass and drums and the sweetness to convey the triple harp's delicate nuances.
Next, the Power-Tech 3.1 drove a pair of Bose 802 Series II speakers in an absurdly small hotel meeting room, where artists such as a cowboy yodeler, two harpers, two choirs, an a capella group, a country-bluegrass trio, a steel pan jazz ensemble, and a five-piece Australian rock band performed 20-minute showcase sets before an audience of talent buyers from 14 western states. Providing several times the power required by the speakers, the 3.1 held the little Bose drivers in an iron grip that imparted a hi-fi quality to the music and lent a studio sheen to the Aussies, by far the loudest act of the day. I noticed fan noise when powering the system up, but it was never an issue once the music commenced. (However, I might have reservations about trying the amp at a solo house concert or at a book reading.)
I then used the 3.1 to feed the monitors for a nine-piece Latin band performing at a boatyard customer appreciation party. Budget issues dictated the use of only four wedges for nine musicians, but all that clean, clear Crown power made the monitors equal to the task. Of course, the musicians' professionalism helped. Conventional wisdom says that distortion is more likely to cause speaker failure than clean amplification well in excess of a speaker's power rating, and that certainly was the case here. With the help of a little judicious limiting, my monitors came unscathed through every request for more level.
The power amp's final task was at front-of-house during an outdoor performance by an 11-piece band playing ‘20s and ‘30s jazz. It didn't even breathe hard. At every one of these performances, the only comments about the sound were compliments.
POWERING DOWN
Those contemplating moving up to an amp this powerful should do so mindfully. Proper engineering practices must be employed at all times to avoid ear and speaker damage. A big amp is also a hungry amp — the Power-Tech 3.1 can draw as much as 15 amperes of current, the maximum provided by many AC circuits. Care must be taken to ensure a sufficient supply of current to avoid tripping a breaker in midperformance.
The Power-Tech 3.1 is a solid, great-sounding, no-frills amplifier. It sits at the low end — although by no means the bottom — of the price range for similarly powerful amps. Some amps from respectable manufacturers can be purchased for less and offer larger feature sets. I suggest auditioning the Power-Tech 3.1 and competing amps to judge how they compare and, most important, how they sound.
POWER-TECH 3.1 SPECS
Inputs (2) balanced ¼" TRS; (2) XLR
Outputs (2) binding posts
Power 540W per channel @ 8• and 760W per channel @ 4• (stereo mode); 1,525W @ 8• and 1,090 watts @ 16• (bridge mono mode); 1,530 watts @ 2• and 1,080 watts @ 4• (parallel mono mode)
Frequency Response 20 Hz-20 kHz (±0.1 dB @ 1W)
S/N >100 dBA below full bandwidth power (20 Hz-20 kHz)
THD <0.05% full bandwidth power (20 Hz-1 kHz), increasing linearly to 0.1% @ 20 kHz
Slew Rate >13V per ms
Damping Factor >1,000 (10 Hz-400 Hz)
Load Impedance 4-8• stereo, 8-16• bridge-mono, 2-4• parallel mono
Dimensions 19.0" (W) × 3.5" (H) × 16.0" (D)
Weight 37.5 lb.
