Marantz PM-78 inegrated amplifier: Ents would approve


Gallery Renovations Reviews

The Marantz brand has changed its owner several times during its nearly 70-year history, but has been consistently positioned as good hi-fi with audiophile aspirations – regardless of whether Marantz belonged to the Americans, the Dutch or the Japanese. In short, there are quite a few more than decent and respected models in Marantz portfolio.

Marantz’s other feature is the tendency to reuse proven designs. It started in the 1970s, for example the lowly Marantz Model 1050 was cloned into at least 4 other models sold in parallel and in later years under Marantz’s own and 2 other brands. A decade later, the PM-80 from 1990 served as the basis for many models to come over a dozen years, including Marantz PM-78 from the late 1990s.

Our first contact with Marantz PM-78 took place a few years ago, when an owner brought one to test speakers with it. Another opportunity came a few months ago; our reader brought a Marantz PM-78 for cleaning and adjustment.

Marantz PM-78 – cobweb

The amplifier certainly needed that. Inside we found a thick layer of dust and cobwebs. As far as adjustments go, DC offset was normal. The ideal value is 0 mV, the manufacturer recommended value is 0-10 mV; it is generally assumed that anything below 15 mV is good, 15-50 mV is OK but adjustment is recommended, above 50 mV – adjustment definitely recommended (although some manufacturers allow values up to 100 mV). In this amplifier, measured DC offset there was 4 mV in one channel, and 6 mV in the other, so in the range recommended by the manufacturer. But quiescent current required adjustment, it was too high in class A setting: twice the recommended value in one channel, 50% too high in the other channel. Adjustment procedure in this amplifier is not particularly difficult, but time-consuming: quiescent current has to be adjusted in class A/B within 30 seconds of turning the amplifier on, then you wait for half an hour and check whether the current has stabilized correctly, switch to class A, adjust again within 30 seconds, waiting half an hour again and recheck. Quiescent current adjustment in this amp takes at least an hour.

Built-wise, we were impressed by the amplifier’s power supply section with a large transformer and 12,000 μF main filter capacitors, as well as the power amp section, in which you can also see the characteristic HDAM modules responsible for voltage amplification. In the preamp section, the input and switching board looks good, but the tone amplifier board is quite messy.

Marantz PM-78 – HDAM modules

When it comes to functionality, the amplifier will satisfy most users. All standard functions are there: volume and balance, tone controls, main source switch, additional recording source switch and 2 separate tape monitor buttons, speaker output A and B switches, headphone jack.

Marantz PM-78 – front left

In addition to the basic functions, we have two switches, one crucial for the amp’s sound and one that could be dropped (we will explain why below): SOURCE DIRECT that allows to bypass tone controls, and CLASS A that, as the name suggests, switches the amplifier to operation in class A mode (in this mode, the amplifier’s power is limited to 25 W per channel). An additional advantage for many people will be remote control, which includes volume, source switching and turning the amplifier on/off. There is also one function only available from the remote control: MUTING. On the front panel there is a lamp indicating activation of this function but for some reason the designers did not add a corresponding switch, this function can only be accessed via remote control.

Marantz PM-78 – front right

On the back we have a set of inputs (all gold-plated), speaker outputs (banana plug-ready), remote control input/output (it allows to connect another device and control it using the amp’s remote control) and switched power outputs for additional devices (you can, for example, connect a tuner and while switching the amplifier on/off also switch the tuner on or off at the same time). The rear panel also contains speaker impedance recommendations. According to the manufacturer, the amplifier is designed to work with loudspeakers with 8 ohm impedance of higher, but we tested it with 4-ohm speakers and the amp performed without any problems.

Marantz PM-78 – rear, sockets

Before cleaning and adjustments we only did a preliminary listening test to identify possible problems with the amplifier. We had a more thorough listening session after adjustments. After cleaning and adjustments, the amplifier’s sound appeared to improve a bit; the owner later confirmed this. The listening session also reinforced my earlier opinion about this model. I would describe the sound of Marantz PM-78 as safe and pleasant, it is a fairly wide but non-engaging sound with a well-defined midrange. There is no shortage of details, but they are not particularly emphasised. The bass is… there. Mainly the mid and upper parts of it. Low bass is neglected, which was immediately evident when I compared the amp to my system based on a Harman/Kardon HK 725 preamplifier and Inkel MD2200 power amp. In addition, the Marantz PM-78 sound is too restrained, to the point of being lazy. It would be a perfect amp for Tolkien’s Ents, they certainly would not consider it “hasty”. Overall, it is a good amplifier for relaxing listening to jazz ballads in the evening. For livelier music it lacks… life. There is no shortage of power: at 95 W continuous power per channel (in A/B class mode) the amplifier can play really loud without sacrificing sound quality.

Marantz PM-78 – front, Class A on

In theory, switching from class A/B to class A mode should improve the sound by eliminating switching distortion, but in our system we could not hear any sound change at all, the only effect was limited power (to 25 WPC). The results were exactly the same in owner’s system and in the case of the other PM-78 that I had listened to earlier. On the other hand, switching to SOURCE DIRECT mode makes a significant difference. Most of our listening was done with this mode on (tone control circuits bypassed); we found that turning this mode off significantly degrades the sound. The sound loses its clarity and spaciousness, it becomes muffled. Clearly, no effort went to designing the tone amplifier. In our opinion, Marantz PM-78 with SOURCE DIRECT turned off is an insult to listener’s ears.

Overall, Marantz PM-78 is not a bad amplifier. It is quite pleasant to listen to and works well with relaxing music. But it lacks spirit for anything more lively; on top of that, there is no low bass. Tone controls must remain off or the amplifier will start to sound bad, while switching to class A does not bring the expected sound improvement. For this reason, the PM-68 would be a better choice – an amp identical to PM-78 except for this function, and cheaper. Considering the price, we can’t recommend Marantz PM-78 (unless you find a bargain).

Technical data:

Power output (RMS): 2×95 W into 8Ω (class A/B)
                                      2×25 W into 8Ω (class A)
Music power (class A/B): 8/4/2 Ω – 2x 120/185/220 W
Music power (class A): 8/4/2 Ω – 2x 35/45/50 W
Recommended speaker impedance: 8-16 Ω
Damping factor: 150
THD: 0,03%
Frequency response: 10 Hz – 65 kHz
Input sensitivity: line – 150 mV/40k, phono – 2,5 mV/47k
Inputs/outputs: Tape 1 (I/O), Tape 2 (I/O), Aux 1, Aux 2, CD, Tuner, Phono (MM), 2 pairs of speakers, headphone jack
Dimensions: 439 x 159 x 375 mm
Weight: 12,3 kg


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