Cyrus 40 PSU

Power supply design sits at the foundation of audio performance. Every amplifier, DAC, and streamer is only as good as the power feeding it — a noisy or unstable supply corrupts the signal before the audio circuit has any chance to work with it. The 40 PSU is Cyrus's external power supply for the 40 Series, and it takes a more sophisticated approach to this problem than a conventional outboard supply.

The 40 PSU does not simply provide a cleaner version of what the host product's internal supply already does. It communicates directly with the host product via its own on-board microprocessor, adjusting its output configuration in response to what the host product actually requires. The result is a supply that is consistently optimised for its partner rather than operating at a fixed output regardless of demand.

Five Independent Power Supplies

The 40 PSU contains five independent power supplies. All five outputs route to the connected 40 Series component through a single multi-way umbilical cable. The five supplies are:

A high-capacity logic supply to power digital circuitry in the connected component. Two fixed-voltage supplies intended for sensitive, low-voltage analogue circuitry. Two variable-voltage, high-capacity supplies for low or high consumption analogue circuitry — these also carry two unregulated voltage settings that can be applied to boost power supply capacity in high-consumption circuitry such as power amplifier stages.

The voltage outputs are: low voltage supply in standby +5V DC, low voltage supply operational +5V DC; fixed voltage supply in standby 0V, fixed voltage supply operational +24V DC; variable supply in standby 0V, variable supply regulated +10V to +45V DC, variable supply unregulated +45V or +56V DC.

A Mini USB port is provided for firmware updates.

This architecture is not a single upgraded power supply dropped into an external box. It is a system — one that separates digital logic power, low-level analogue power, and high-current analogue power into independent domains and delivers each of them at the correct voltage and current capacity for the job.

What It Does to the 40 Amp

Connected to the Cyrus 40 Amp, the 40 PSU provides the power amplifier section with a substantial boost of clean power, further stiffening the main power supply rails. The amplified signal tracks the input signal more accurately — you hear this as greater transparency and more resolved detail. The preamplifier section is driven entirely by the 40 PSU, providing a stiffer supply and greater accuracy. The internal supply, now relieved of these demands, focuses on powering the DAC section — and because it is doing less work, it does that job more robustly. In Cyrus's own listening tests, the improvements included more weight, more authority, better detail, better attack, and more accurate control of the rise and fall of notes.

What It Does to the 40 CD

Connected to the Cyrus 40 CD, the 40 PSU powers the master clock — which directly affects jitter — and takes over supplying the CD motors. Motor drive circuits are electrically noisy; they change velocity constantly, and that noise belongs outside the box. The 40 PSU takes it there. It also powers the analogue side of the DAC, leaving the internal supply to handle the digital side — a separation that limits the transfer of noise between domains. The sonic results Cyrus describe include improved timing, better control of bass notes, more accurate note edges, and enhanced imagery.

What It Does to the 40 ST

Connected to the Cyrus 40 ST streaming transport, the 40 PSU takes over powering the analogue side of the DAC and the BluOS network module, providing a cleaner, more stable supply to both. The result is greater detail, better control, and more space around instruments and vocals — a wider, more precisely defined presentation from the streamer.

Microprocessor Control

The on-board microprocessor is what distinguishes the 40 PSU from a conventional external power supply. It communicates directly with the host product to determine the optimal configuration for each output voltage. All voltage outputs are digitally controlled internally — not fixed at manufacture, but actively managed. This means the 40 PSU adapts to what the host product needs rather than providing a static output that may or may not match the demand at any given moment.

Chassis and Build

The 40 PSU is housed in the same 40 Series aluminium chassis as the components it partners. At 9.4kg, it is a substantial unit — the weight reflects the power supply components inside it rather than cosmetic mass. A five-year warranty is provided.

Technical Specifications

Who Is It For?

The 40 PSU is for the owner of a Cyrus 40 Series component — the 40 Amp, 40 CD, or 40 ST — who wants to extract more from it without changing it. It is a planned upgrade rather than an impulse purchase: the improvement it brings is real and specific, but it requires a compatible 40 Series host product to connect to.

It is also worth considering at the time of purchase rather than as a later addition. The 40 PSU port is built into every compatible 40 Series component, and buying the two together allows the system to perform at its best from the outset.

Buying from Martins Hi-Fi

Martins Hi-Fi has been in Norwich since 1968. Elizabeth Gould runs the business today, and we stock only brands we have heard properly and stand behind.

The 40 PSU is available to hear in our Norwich showroom, connected to compatible 40 Series components so you can assess the difference for yourself.

When you get in touch, you'll be speaking with Dave, Chris and Tim — experienced specialists who can advise on this product and your whole system.

Contact us at info@martinshifi.co.uk, call 01603 627010, or WhatsApp on 07554 687137. You can read more about how we work on our Why Martins Hi-Fi page. We are at 85–91 Ber Street, Norwich, NR1 3EY.