Harman Kardon PT2500 Preamplifier/tuner Review

Preamplifier/tuners are enjoying something of a resurgence these days, under a new guise: the A/V preamp/tuner, in essence an A/V receiver without the power amplifier. The genre saves weight, cost, and size while freeing the owner to pick and choose from the vast ranks of stand-alone power amps with one, two, or more channels.

Combining the preamp, surround-processor, and tuner functions in one box makes good sense. The consolidation reduces clutter and complexity, and chassis and power-supply resources are used more economically. The result can make for some excellent values, such as Harman Kardon’s $529 PT2500, which the company calls an A/V Surround Tuner Controller.

The PT2500 combines conventional preamp functions, Dolby Pro Logic surround decoding, two ambience-en-hancement music modes, and an AM/FM tuner. It features Harman Kardon’s trademark sculpted front panel and a simple layout with clusters of rocker-type pushbuttons for surround-mode and input selection as well as tuning. A large, motor-driven knob controls master volume, while three smaller ones handle bass, treble, and balance. A front-panel convenience set of A/V jacks is provided (these can override the rear-panel VCR2 connections when you push the front-panel VCR2 button), but there is no headphone jack.

Around back there are audio-only inputs for CD, aux, two tape loops, and a moving-magnet phono cartridge. Audio/video options consist of one VCR loop, a second, play-only VCR input, and an input for a laserdisc player. All of the PT2500’s video connections, including the dual monitor outputs, are composite-video RCA jacks; there are no S-video ports.

The PT2500 has the expected outputs for the front left and right channels and dual surround outputs. It also provides dual center-channel outputs, but Harman Kardon rightly warns that in most cases only one should be connected. (Then why include two?) There is a pair of subwoofer jacks, too, and the manual advises that these should either be connected to a dual-input powered sub (or a sub amplifier) or joined via » Y-cable for a single-in-put sub. This is unusual. It seems that the PT2500 sends separate left- and right-channel signals (plus the center-channel bass when the center-speaker mode is set to “small”) to its two sub jacks instead of summing the channels internally. Combining the outputs with a simple Y-cable works, but it seems to me that if you were to play a stereo recording with true stereo bass this configuration could cause some lower-octave cancellation.

The PT2500 does not provide a six-channel input (and switch position) to accept signals from an outboard Dolby Digital or other 5.1-channel decoder, which means that it is not capable of easily integrating the new medium. The manual does, however, briefly describe connection to an external Dolby Digital decoder with pass-through capability such as Harman Kardon’s own ADP-303 processor (see “Digital Surround a la Carte,” January 1997). The preamp/tuner’s six outputs are routed to the DD box, which then takes over as the signal source only when DD programs are played back. Otherwise, stereo and surround signals alike pass straight through to the power amps. This means, though, that the outboard processor’s master volume control must be used for DD playback, complicating system operation slightly.

Other rear-panel features include three convenience AC outlets (two are switched), AM and FM antenna connectors, intercomponent remote ports for intelligent control of other Harman Kardon gear, and a DC-trigger output for auto-on amplifier integration with HK (or compatible) power amps.

The supplied remote control provides a complete command set, including up/down buttons for master, center, and rear volume. It also includes keys to dim or turn off the preamp’s front-panel display, to select among Dolby Pro Logic, 3-Channel Logic, two music surround modes, and plain stereo operation, and to invoke a sleep-timer auto-shutoff routine. In addition, the remote supplies basic transport commands for CD players/changers and tape decks, presumably working only with Harman Kardon components as it is not a programmable or “learning” controller.

Setting up the PT2500 required nothing more demanding than connecting six RCA cables to my power amps and subwoofer, and a few more to my Digital Satellite System receiver, laserdisc player, TV tuner, and video monitor. The preamp’s only bass-management feature is the center-mode option, which you can set to “wide” (full-range), “small” (for an unspecified rolloff), or “phantom” (if no center speaker is used). I chose “wide” for my relatively full-range center speaker.

Channel-balance calibration using the on-board test-signal sequence and a sound-level meter was achieved quickly, and the result held the relative balance between channels quite well over a wide, 20-dB master-volume range. At the highest knob settings (above 12 o’clock), the left and right outputs lagged behind the center and surround channels by up to 2 dB, though in my system these very high volume settings corresponded to a peak sound-pressure level (SPL) of more than 100 dB. Within the range of what would be “normal” volumes in most systems (assuming the speaker or power-amp sensitivities aren’t unusually low), channel-balance accuracy should be very good.

The PT2500’s center- and surround-channel adjustments only deliver 2-dB precision between the minimum setting (a value of 22) and the maximum (100). That absolute range is huge — far more than I could imagine needing — but 2-dB steps are really too coarse for fussy home-theater types like me (I can easily hear level differences of 1 dB in full-surround playback). Depending on your luck with room size, placement, and speaker sensitivity, you may have to compromise a bit, or use your power amps’ input-level trims, if any, which is what I did. Another minor beef: Center/surround-level values are not stored in memory but are displayed on the preamp’s front panel. You’ll need to write down or remember these values if you wish to change them temporarily.

All of these criticisms are nit-picking, relatively speaking, and performance-wise the PT2500 was tough to fault. Dolby Pro Logic surround results were very fine, thanks at least in part to Harman Kardon’s use of the Analog Devices SM-2126A decoding chip found in many higher-end analog processors. Leakage of center-channel material to the sides (into the surround channel) was exceptionally low, and the small residue was relatively free of pumping or transient “spitting.” Pro Logic steering was smooth and accurate, resulting in a cohesive, believable front stage with well-produced soundtracks, and ambience delivery was of a similarly high caliber.

Overall, Pro Logic reproduction was bright, well-etched, and transparent, with a degree of low-level detail on subtle, subliminal sound effects that I judged a cut above what you will hear from merely average DPL designs. As is often the case, movie soundtracks occasionally sounded a shade bright (part of this may stem from the unusually large surround-channel noise-reduction miscalibration, which can have an effect on surround frequency responses). Since the PT2500’s tone controls do not affect the center channel, I occasionally missed having recourse to a “theater” curve or other front-channel-rolloff option.

The PT2500 proved quite quiet in its surround modes, especially in the front channels. Surround-channel noise in Pro Logic (and the music-surround modes) was obviously higher than in stereo, to the point that a faint, “idling-DC-3” roar was just audible from the listening position with a paused laserdisc, though only at master-volume settings a few clicks higher than reference level (75 dB SPL for -20 dB).

The PT2500 offers two additional four-speaker surround modes, called Theater and Stadium, which seemed quite similar. Both appeared to deliver unprocessed stereo to the front left/right channels, but while Theater sent a straight L - R difference signal to the surrounds, Stadium appeared to mix in a bit of crossed-channel stereo signal to widen the surround illusion. These modes’ best common feature is that you can adjust the surround-channel level independently for each one, and it is stored in memory until you reset it — the same is true for the Dolby Pro Logic and 3-Channel Logic modes as well. (The music modes also let you set surround-channel delay time independently, to quite an absurd duration.) Setting the Theater mode for a surround-speaker level 4 dB less than the Dolby-calibrated setting and a 26-millisecond delay, I produced a genuinely usable, all-purpose surround mode — subtle but quite musical.

In plain, two-channel stereo, the Harman Kardon PT2500 impressed me as very clean, dynamic, and “quick” sounding, with full treble extension and well-controlled, tight bottom octaves. The front-panel Direct switch, which bypasses the tone controls, did not, oddly, bypass any surround processing (though the manual claims that it will).

FM tuner performance was decent overall, but nothing to write home about. Sound quality from strong stations like my local NPR broadcaster was actually very good, permitting high-grade FM listening. But noise rejection and signal discrimination were no better than those of many midprice receivers while 1 was browsing among weak and distant broadcasts. Moreover, the PT2500’s rather slow autotune mechanism was frequently fooled by noise or multipath, stopping at empty and even “illegal” frequencies. AM reception was, by my highly scientific rating system, two and a half points above pitiful. In my semirural location, the PT2500 auto-tuned just two stations using the supplied loop antenna in its optimum orientation; I could squeeze out four more that yielded intelligible speech by searching the dial manually and playing with the antenna. The radio controls and thirty station presets with preset-scan operated as expected.

All in all, the Harman Kardon PT2500 worked well and sounded terrific with music, laserdiscs, and DSS broadcasts. Its remote controller proved relatively easy to learn and navigate, though its closely spaced keys are almost all identically shaped — and the surround- and center-channel level controls are too easy to change accidentally. If your home-theater system requires more power than a middle-of-the-road A/V receiver can provide, and if critical, long-distance FM listening will not be an issue, you should find the Harman Kardon PT2500 preamp/tuner a good value and a fine alternative to an all-in-one, high-power, “flagship” A/V receiver.

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