Optimized design

To achieve such quality, while still delivering class-leading power, means optimizing each section of the amplifier for its task, just as would be done in a design using a separate preamplifier and monobloc power amps. Commonly, amplifiers use a single transformer, with separate power supply regulation for the preamplifier and power amplifier sections; the PM-10 takes things much further.

A dual-mono design, it has separate power supplies for the preamplifier and each of the power amplifier channels, with one transformer dedicated to the preamp to ensure the delicate signals passing through that section of the amplifier aren’t affected by the demands of the high power output stages. There’s also a dedicated supply for the microprocessor controlling volume adjustment, input selection, and so on, ensuring no noise from the control section finds its way into the audio path.

Pure analog

Another important part of the noise-reduction here is the fact that the PM-10 is a purely analog amplifier: many rival designs are today including digital-to-analog conversion or adopting digital amplification and volume control, but Marantz keeps things as clean and simple as possible with its highly-developed all-analog design.

Why? Well, though it may seem convenient to have a DAC in the amplifier, digital circuitry is, by its very nature, noisy (in the electrical sense) and can interfere with the delicate analog signals passing through the amp. That’s why Marantz chooses to design its Premium Series range with any digital-to-analog conversion in its SA-CD/CD or network music players, keeping its amplifiers as pure and clean as possible.

What’s more, to make the most of that purity of design, the PM-10 has also been designed with the option of working in ‘Purest Mode’: when engaged, this deactivates any superfluous circuits, giving the signal the cleanest possible path through the amplifier. There’s also a Power Amp input, taking the signal straight from the input section to the power stage to let the unit work as a pure power amplifier.

Fully balanced, from input to final power section

The benefits of balanced audio layout have long been understood: unlike a conventional layout, one half of the signal path is in the ground plane of either an amplifier or a cable, balanced working uses two conductors or paths – one for positive, the other for negative – and an entirely separate ground to protect them.

The benefit in cables is that any external interference will affect both positive and negative conductors, but since the signals they are carrying are the mirror image of each other, they will mutually cancel out any effect – which is why such cables are widely used in pro audio and studio applications, where sources of hum are common, and the longer cable runs involved makes them particularly prone to picking up interference.

The same is true when balanced working is applied to audio circuitry: not only does this mirror-imaging of the layout, in which identical components are handling the positive and negative ‘legs’ of the signal, cancel out any potential interference, it also means any noise or errors introduced in the circuitry will also be canceled out.

An additional benefit is that balanced working also uses stronger signals than unbalanced designs, simple because both halves of the circuit are active – rather than just having one-half pushing and the other just providing the ground, here we have a ‘push pull’ operation. And a stronger signal means one less susceptible to any outside interference: the more signal there is, the less obvious any noise will be.

The PM-10 uses a fully balanced layout, from the input section all the way through to the final power amplifier section: it has two sets of balanced inputs, and also conventional unbalanced line-level inputs (plus a high-quality phono stage), the signal from these inputs being converted to balanced working before being passed through the amplifier. By keeping the signal balanced all the way through the amplifier, and combining that with an optimized power supply design, the Marantz engineers are able to achieve maximum noise rejection throughout the audio path, and the highest possible signal purity.