David Foister's review of the CD17 KI Signature CD player in our October issue made mention of a forthcoming amplifier to join the Marantz KI Signature range, and here it is already. The "KI Signature" appendage means that the product in question has been reworked personally by Marantz's audiophile wizard Ken Ishiwata. The PM-66 KI Signature integrated amplifier comes with a new "KI Signature" brass plate on the front, a signed certificate and, possibly less welcome, a price tag of 400 which is quite a step up from the original PM-66SE at 230.

As will emerge later, I have been left in no doubt that this sort of price is fully merited if one compares the sound quality with that of competing, say up to 500, rival designs. The unit also looks the part. A wholesale change to copper plating for the chassis and rear panel, aimed at improving the earthing at all stages and "controlling the effects of interference from the eddy currents present, that can spoil the sonic enjoyment", does a lot to enhance the visual impression of up-market value. I was tempted to use the amplifier upside down and back-to-front just to savour all that shiny copper, but this isn't very practical.

Used the right way up, the PM-66 KI still looks pretty good. It is taller than the average hi-fl separate and as black as ink. However, ventilation slots in the top let us peep into the interior, where there is more gleaming copper (even the external fixing screws are copper plated). Near one end is a new design of toroidal transformer, extra deep and using high purity copper wire on a high-grade core, with a copper top plate to finish things off.

Next, between parallel manyvaned heatsinks for the output stages, comes a single high-quality printed circuit board carrying all the components apart from those mounted immediately behind the front panel. Special care has been taken over the design of the (moving-magnet) phono stage as a reminder of Ishiwata's audiophile compulsions. He has made many component changes, following lengthy subjective testing, and apparently involved nine UK companies in the redesign process. Manufacture is under the watchful eye of UK Product Manager, James Lane.

Operation could hardly be easier. The front panel, reading from left to right, carries the Power on/off switch and LED indicator, remote control sensor window, headphones socket (inserting the jack plug silences the loudspeakers), Mute indicator, Source Direct button (which sends the source signal through a minimal path, bypassing the balance control and tape monitor switches), rotary Input selector knob for Phono, CD, Tuner and Auxiliary plus a pair of Tape I and Tape 2 buttons (selecting Tape 2 automatically sets up the tape dubbing mode, allowing the playback signal from deck 2 to be copied to deck 1), large motorized volume control and Balance.

To satisfy the armchair-bound user, the amplifier is supplied with a remote control handset which provides only volume up/down and mute/demute. In what looks like a slight waste of resources, the handset is the Marantz RC-66PM with no fewer than 43 buttons and is really designed to control all the functions of any group of other Marantz units including CD, cassette, tuner and VCR.

On the back panel are 16 phono sockets for the various inputs and Tape 1 and 2 record outputs, with the disc input sockets gold-plated (as are the CD sockets) and distanced from the others alongside an earth terminal. The loudspeaker binding posts (only one pair of loudspeakers is catered for) are substantial enough to accept quite thick wire, or 4mm plugs if the blanking-off studs are removed. There is a captive two-wire mains lead and input/ output sockets for a remote control bus connection to other Marantz units. Power output is rated at 2 x 70W into 4 ohms or 2 x .50W into 8 ohms, with distortion at 0-008%. Line-level input sensitivity is 150mV which may lead to rather low settings of the volume control for some source units, and MM phono sensitivity is 2-5mV. Frequency response limits (-3dB points) are 5Hz and 70kHz, with IEC/RIAA response accurate to within 0.5dB, and A-weighted signal-to-noise ratio 97dB.

Performance
While my eyes had supplied plenty of evidence of the cost-no-object approach of the designer, I lost no time in putting my ears to work on the much more important question of sound quality. I was not disappointed. Judged by the ultimate criteria of one's recollection of the sound of live music heard in exemplary acoustics or, dare I say it, one's very best LPs scrupulously stored and optimally reproduced, this amplifier delivers ear-satisfying results.

Ken Ishiwata's fussiness over components and his considerable knowledge of how to fine-tune circuitry to his own taste have certainly paid off. There is no high frequency glare or indeed any of the attention-grabbing hardness of tone heard from many so-called 'hi-fl' amplifiers. Instead, the unveiled forward presence of the entire midband appears to continue seamlessly to the upper limits and then gently recede. If this marginally sweetens the extreme highs, I would argue that so does sitting in the best seat in a concert hall (quite a few rows from the front) where distance has softened some of the excessive on-axis treble all too often captured by the microphone.

As for the bass end, the response seems have been extended to the limits of hearing, where only a few CDs (and no LPs or broadcasts) containing organ pedal or deep bass notes venture. Yet, again, this musically impressive effect has been achieved without undue emphasis, leaving the impression of a warm, natural balance which is being effortlessly repro duced. Indeed the amplifier showed no signs of temperament at any time, even when I turned up the volume to louder settings than I normally consider necessary.

For most of my listening I relied on familiar CDs which I have identified as providing quick and reliable tests of individual audio response features. But I also listened to some private tapes and, to check out the phono input, some well-loved LP records. The latter have seldom, if ever, sounded better; I therefore regard the decision to build an above average phono stage into this amplifier (unlike some recent designs where the pickup input is treated as an uncritical afterthought or left off altogether) a real bonus which should give users a renewed interest in exploring their vinyl disc collections.

Test measurements simply served to confirm these favourable subjective conclusions, with a clean sheet of results all equalling or surpassing the specification claims. Critical listeners should seek out this amplifier at a dealer who is able to put on a good demonstration;