Fullscreen HTML5Med Res (??MB)HTML4

HIFIREVIEW Marantz PM-35 Integrated Amplifier This high-quality 35 watt per channel amplifier from Marantz breaks new ground in design and manufacture. Reviewed by LEO SIMPSON Marantz is a hifi company that has been around for a long time although it has had a number of changes of circumstances over the years. To celebrate its 35 years of operation, Marantz has just released its 35-series digital monitoring series. This consists of the PM-35 amplifier, the ST-35 synthesized tuner and the SD-35 cassette deck. For the very first Silicon Chip hifi equipment review, we decided to make it timely indeed, and evaluate the PM-35 amplifier, a unit which we think will establish a performance benchmark for low priced hifi amplifiers. The PM-35 designation not only has some significance in the celebration of Marantz's 35 year history, it also indicates the nominal power rating of the amplifier - 35 watts per channel. Surprise, surprise. In appearance, the PM-35 is unmistakably Marantz and owes much to the award-winning PM-94 model. But whereas the $3300 PM-94 is intended for those with very big wallets, the PM-35 is very much the amplifier for everyman. It sports a good range of control facilities and manages to do so without looking too "technical" and, for that matter, without being too unobtrusive. I am one of those people who likes an amplifier to look the part; I am not keen on really spartan styling. The four main controls, volume, selector and bass and treble, are all good-sized knobs which are well labelled. The selector has an adjacent columnar display in which very tiny LEDs indicate the selected program source. The input source designations are CD (compact disc), phono (MC), phono (MM), tuner, and TV/aux. The seldom used Balance control is a small knob under the Selector. All the other controls are pushbutton switches: power, speaker selector, tone defeat, tape/DAT monitor, loudness and CD/phono direct. We'll talk more about the last switch later. On the rear panel, the PM-35 has two pairs of gold plated RCA sockets for the CD and phono inputs, plus another four pairs of sockets for the other inputs. There are four pairs of shrouded binding post terminals to enable the connection of two pairs of loudspeakers and there is also a voltage selector NOVEMBER 1987 11 The Marantz PM-35 has generous heatsinks and plenty of ventilation to keep the traI).sistors cool. switch (220/240V AC). The two core mains cord is removeable. Design philosophy Inside the chassis, the Marantz PM-35 may not look very different to another in its price range, at least on a casual glance. But close examination reveals that this Marantz represents quite a different design approach to that of most Japanese amplifiers up till now. Perhaps we should qualify that statement. Most Marantz equipment is made in Japan but is designed in Eindhoven. Paradoxically, the chief designer is the notable Ken Ishiwata who is undeniably Japanese. The Marantz PM-35 is different is at least two main aspects. First, it does not use hybrid modules for the power amplifiers. Hybrid modules have the virtue (for the manufacturer) of being small, self-contained and (probably) cheap. But they usually do not offer the same level 12 SILICON CHIP of performance or overall power output as a carefully designed amplifier of equivalent nominal power output, using discrete transistors. Second, the Marantz PM-35 does not use lots and lots of transistors. It uses relatively few. In the past, Japanese amplifiers did, and still do, seem to use transistors for the sake of having lots of them. The total semiconductor count was in fact a selling feature. By this approach a power amplifier containing over 100 transistors would have to be much better than one containing only thirty, wouldn't it? Not necessarily so. This is not a good engineering approach from the point of view of reliability or ultimate sound quality. Marantz has been clever in reducing the number of transistors and integrated circuits to the minimum needed to get good performance. In the phono preamplifier, there are only four transistors coupled with the dual operational amplifier stages. These provide all the gain required for moving coil and moving magnet cartridge operation plus RIAA/IEC equalisation. The power amplifiers account for the rest of the semiconductors. There are no active stages for the tone controls as these are incorporated in the negative feedback loop of the power amplifiers. The Marantz PM-35 is not the first amplifier to use such an approach but it is still relatively uncommon. Not only is the power amplifier circuitry simple and straightforward, so is the power supply. It consists of a fair-sized transformer and bridge rectifier feeding a pair of 6800µ,F 42VW electrolytic capacitors. The latter are Elna "hifi""capacitors which we assume have been included because of lower than normal internal impedance. Apart from the general simplicity of the circuitry another interesting aspect of the PM-35's circuitry is the CD/phono direct switch. The concept of the CD/phono direct switch is simple and is a good one. It has been used on other Marantz amplifiers, beginning with the PM-94. The idea is that you bypass a lot of circuitry and therefore do not have any distortion contribution from that circuitry. Usually, the omitted circuitry is mainly that for the tone controls. As we have already pointed out though, the Marantz has no tone control stages as such, so no active circuitry is actually bypassed by the CD/phono direct switch. This is shown on the block diagram in the owner's manual. The switch controls a couple of small relays to bypass the selector and tape monitor switches, and the balance control, to connect the signal directly to the volume control. Ostensibly then, there is no real point to having the CD/phono direct switch but a little further thought shows that there is. Consider that if a tape deck is connected to the tape monitor loop and other program sources are connected to the amplifier then both the tape monitor and selector switches could contribute to signal degradation in terms of loading, crosstalk and extraneous signal injection. Therefore, it is worth having. Another interesting aspect of the Marantz PM-35 is the beautifully finished front panel. At first sight this looks like another example of the normal high standard of finish which the Japanese consistently achieve with black anodised aluminium extrusions. It is no mean feat to anodise aluminium to a consistent colour (black is a colour, by the way, being a particular combination of aniline dyes used in the anodising process). But the PM-35 front panel is not an aluminium extrusion, it is plastic. It is by far the best finished plastic moulding we have seen and we would have been fooled completely had we not looked at the interior of the case. Well, what is the advantage to the user of having a plastic front panel, even if it is well finished. Sooner or later amplifier panels become scratched. On black anodised aluminium scratches The PM-35 is one of a series of Marantz hifi components. Here is teamed with the ST-35 digital tuner and SD-35 cassette deck. become very obvious with the result that the appearance is severely degraded - it looks tatty. If you have the misfortune to scratch the PM-35's front panel (and it doesn't scratch easily) it won't be nearly as obvious because the colour goes all the way through rather than being skin deep. Performance Having taken in all the interesting design features of the PM-35, we were keen to give it the once-over for performance tests. Marantz rate the PM-35 is terms of IHF, DIN and FTC specifications. IHF (music) power is quoted as 80 watts per channel into 4 ohm loads and 50 watts per channel into 8 ohm loads. For the FTC ratings, meaning continuous power for rated harmonic distortion of .025% between 20Hz and 20kHz, the PM-35 is rated at 30 watts per channel into 8 ohms and 35 watts per channel into 4 ohms. Signal to noise ratio for the moving magnet phono input is quoted at 86dB (IEC A-weighted) while the equivalent figure of the CD input is 96dB (IEC A-weighted). Without going into all the whys and the wherefores we can say that the Marantz PM-35 passed all the performance tests with flying colours - no problems at all. Well, you'd expect it, anyhow. Sound quality is very good, clean and unfussed. It must be rated highly, particularly among amplifiers in this price range. And the best part is the price. At $549, it is something of a bargain. To sum up, we are very attracted by the design of this amplifier. Its engineering is clever so that the overall product is electronically uncomplicated. It should give many years of faithful service and if it ever does need repairs, it will be an easy amplifier to service. We rate it highly. For further information and a demo, contact your hifi dealer. Marantz equipment is distributed by Marantz (Australia) Pty Ltd, Figtree Drive, Homebush, NSW 2140. Our thanks to Audiosound Laboratories, of 148 Pitt Road, North Curl Curl, NSW 2099, for the use of their facilities in the preparation of this review. 41:: NOVEMBER1987 13