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Had a minor fault in 1995 which was professionally repaired see receipt attached to page 62, no problems since.
HIFI REVIEW Circa 1987
THE American based company Harman Kardon currently makes several integrated amplifiers of which the PM655 is the second from top in price and power output. It is manufactured at a plant in Japan. A nominal 60 Watts per channel into 8 Ohms unit, it has several features which indicate that it has been specifically angled towards quality hi-fi applications. Indeed quality is a word to describe ever y aspect of the unit’s construction and presentation: another could be robust, for all the controls and connectors have a sort of ‘heavy duty’ feel to them reminiscent of equipment much more common a generation ago-as exemplified then in the UK by Ferrograph, for example.The PM655 is a heavy (10.3kg) unit of pleasingly chunky dimensions. It is available in two colours, “champagne gold” or black, although the difference only refers to the front since the case itself is black in either instance. The front panel carries continuously variable rotary controls for volume (a high quality ALPS potentiometer), balance, treble and bass (centre indents for the last three), with rotary switches for input selection, tape out (allowing two-way dubbing or recording from one source whilst listening to another), tape monitor, speaker selection (two sets catered for) and cartridge trimming capacitance (see below). There are push buttons for power on, mono/stereo, high and low frequency filters, bass and treble turnover frequencies (again see below), tone defeat, “bass contour”, moving-magnet/moving-coil cartridge selection and a pre/main amplifier loop.From all this it will be seen that the PM655 is very well appointed as far as switching options and facilities are concerned and it also includes one or two sensible ‘frills’ which most manufacturers nowadays do without. Of these perhaps the most obvious are switchable capacitance trimming for the moving-magnet cartridge input and the ability to access the point in the circuit between the pre- and power amplifier sections, this being brought out to sockets on the rear panel (output impedance 620 Ohms, which is low enough to drive any normal line-level load) and selected from the front panel switch mentioned above. Such an option can be used when ‘active’ loudspeaker systems are to be driven, for example, a line-level crossover being patched in at this point with a second, separate power amplifier being employed to drive, say, the tweeter sections while the PM655’s own power section drives the woofers. Similarly, an active processor such as the KEF KUBE or, if you’ve a need for such a thing, a graphic equalizer, can be equally well patched in here.The cartridge loading feature is al so controlled from the front panel, via a four-position switch which adds 100, 200 or 300pF to the existing capacitance of the arm lead itself. Some moving-magnet cartridges are sensitive about the capacitive load they ‘see’ and some provision for adjusting this can produce a more even overall frequency response. The moving-coil ‘head amplifier’, or prepreamplifier, is housed in a small plastic box which is mounted on the main input board near the relevant sockets. The bass contour boosts the low frequencies for use with small loudspeakers or can double as a ‘loudness’ compensation network for use at low listening levels. Unusually it also includes a phase correction network which is claimed to help preserve clarity.The rear panel sports an array of 20 nickel-plated phono sockets for the line-level and cartridge connections and eight binding post terminals of the type which accept bare wires for the loudspeaker cables. The mains lead on the review model was a two-core captive type but the booklet suggests that three-core is sometimes supplied as an alternative. This is of no practical import, however, since the relevant part of the internal circuitry is properly insulated and it is an easy matter to run a separate earth wire to the rear panel ground screw if required for hum screening purposes.Several aspects of the circuitry indicate that this amplifier means business. Harman Kardon have gone for a wide bandwidth, low feedback design to help preserve transient and dynamic accuracy and maintain phase linearity, and they have catered for loudspeakers which have awkward impedance characteristics, providing the PM655 with a short term current capability of some 45 Amps. All discrete circuitry is used i.e. no integrated circuits-which HK also make special claims for in terms of overall performance. Two stage RIAA equalization is employed, again with a view to achieving the best performance, using low levels of feedback.The internal layout of the PM655 is sensibly arranged around a massive, centrally located heat sink which carries the output transistors (the cabinet is ventilated top and bottom and must stand so as to allow the free passage of air-in practice it runs just slightly warm). Separate left and right channel power supplies are employed, with only the transformer common to both. Two sets of loudspeakers can be connected, as mentioned above, and the actual switch mechanism for these (a heavy-duty rotary type with self wiping contacts) is located adjacent to the terminals on the rear panel and activated from the fascia knob by a linking rod, thus obviating the necessity to run the high current wiring up to and back from the front panel. The outputs are muted for a few seconds at switch-on and are automatically disconnected in the event of a short-circuit. Power on, tape monitor and input settings are indicated by small LEDs.How it performedI have seldom been as impressed with a n integrated amplifier as I was from the start with the PM655. Sonically it does all the right things, accepting compromizes in very few areas, which is a remarkable achievement at the price. Particularly impressive is its ability to separate out complex musical strands and to establish a tangible, well-nigh three-dimensional image. Tonally it sounds ‘wide open’ with a crystal clear, sweet top end which is entirely free of sibilant edge. My initial listening was via Compact Disc with two notably ‘difficult’ discs (by which I mean taxing and highly revealing of problems in the signal chain): the Pergolesi Slabal maler (DG CD 415103-2GH) and the Hilliard Ensemble’s disc of seventeenth-century Glees and Catches, “The Singing Club” (Harmonia Mundi CD HMC901153). Both of these have difficult-to-unravel vocal lines which seldom come across to best effect. Here they were the delight they should be. Turning to LP, a similar kind of performance obtained, with background noise and hum quite inaudible via moving-magnet at the listening position, and virtually so via Me.Tone controlsI must confess that I have little use for tone controls and filters during most of my normal listening, but occasionally some tailoring of the signal can help. I particularly liked the PM655’s approach of (a) being able to bypass them altogether for ‘purist’ listening and (b) having a choice of turnover frequencies: 200Hz and 400Hz for the bass and 2kHz and 6kHz for the treble. This gives greater flexibility and a more subtle adjustment than many more straightforward and conventional tone control arrangements.
THE FOLLOWING ITEMS WILL BE LISTED eBay SOON
Harman Kardon TD392 Ultra Wideband Linear Phase Cassette Deck
Harman Kardon HD200 Compact Disc Player
Harman Kardon TU909 Digital Synthesized Quartz-Locked Tuner
dbx 3bx Dynamic Range Controller
All the above are in excellent working condition, no scratches on front panels or minor damage anywhere, includes User Manuals, Original Boxes and Packaging
JBl 4410 Professional Series Studio Monitors x 1 Pair, Technical Manual & Data Sheet
Thorens TD 166MK11 Turntable, User Manual, Alignment Template and Original Box & Packaging
May consider posting within the UK via carrier 22.50
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Category: Sound and Vision:Home Audio and HiFi Separates:Amplifiers and Pre-Amps
Location: Northampton