Linear Power Supply Unit L-50

 170.40 186.00 Incl. VAT
 142.00 155.00 Excl. VAT

Low-Noise Linear Power Supply Unit (LPSU) for powering various analog/digital devices



In a world loaded with tons of Switched Mode Power Supplies (SMPS) it became clearer than never that even though its bulky size and weight, the Linear Power Supplies have more advantages than faults.

That’s why here is offered a small-size Linear Power Supply Unit (LPSU) suitable for replacing the noisy SMPSes used for powering a network streamers, DACs, audio players, Raspberry Pi-based boards, USB-powered digital equipment etc.

Actually, this is the smaller brother of our previously introduced product – a  Linear Power Supply Unit L-100. L-50 is built using the same well-proven discrete topology but with half its power (and hence weight and size).


– Input voltage: AC 115V or AC230V (according to the destination country or user request)
– Output voltage: DC 5V/12V/15V (user-defined values are also available upon request)
– User selectable option for 8mm. aluminum front panel (black anodized)
– Dimensions: 115x170x60 mm.
– Transformer Power: 50VA
– Weight: about 2.2kg
– Output DC cable with barrel jack 5.5/2/5 mm. (OD/ID) or micro-USB connector
– Possibility for different output connectors upon customer’s request
– Built-in trigger-type over-current protection (in case of protection’s engagement the unit must be turned off for a while in order to recover its normal work)
– Built-in trigger-type overheating protection preventing the unit from burning in case of serious malfunction
– Front panel LED
– Possibility for upgrade of DC cable with custom-made one

Schematic description

The regulator has all-discrete topology. No Operational Amplifiers are used. This allows complete design control over all operating points and parameters for superior performance. Low noise, high PSRR.
There is a bridge rectifier block on the input which is filtered with a massive electrolytic capacitor on the output. This greatly reduce the ripple charge voltage and hence helps for better output filtering.
The error tracking stage is based on a differential amplifier built with dual transistors chip which ensures the excellent thermal stability and equality of its parameters.
The differential amplifier is cascoded which greatly reduce the input noise influence over the error (differential) amplifier and Erly effect.
A Zener diode is used as a voltage reference. It is fed by a Constant Current Source attached to the output of the regulator which dramatically minimize the noise and ripple through the Zener (and hence at the input of error amplifier). The High-frequency Zener noise is additionally filtered by a Low-pass filter between Zener diode and error amplifier.
The output stage consists of power-Darlington bipolar transistor working in Common-Emitter mode. This allows the regulator to work as a LDO (Low-DropOut) with smaller difference between Input and output voltages which diminishes the thermal dissipation over the regulation transistors.
At the input of the regulation transistor is placed a trigger-type over-current protection network which engages at a given output current and turns-off them. Once the protection is engaged, it can stay in this mode for an unlimited period of time which prevents the system from doing any harm even in a human absence. In order to return to normal operational mode the regulator must be turned OFF for a while (to discharge the electrolytic capacitors) and then turned ON again.
And since SAFETY is a thing we care about a lot, a thermal switch is added in parallel with the over-current protection. This way even if the current protection is not engaged (which is almost impossible) the output regulation transistor will be turned OFF when the heatsink’s temperature reaches 85°C.


Measurements of DC and AC voltages were taken with Keithley 2015 Multimeter while the spectrum plots were drawn using RTX 6001 Audio Analyzer. The obtained results are as follows:

– Line regulation (AC input voltage between 216 – 235 V): 0.05%
– Load regulation (DC output current between 0 – 2 A): 0.05%
– Measured Power Supply Rejection Ratio (PSRR): -120 dBV for fundamental harmonic (100 Hz)

Measured PSRR at 1.8A output current

A DC cable ended with barrel jack 5.5/2.5 mm (OD/ID) is provided along with the unit. In case some different connector is required contact us prior to place the order.

Instead of the standard DC cable a custom made one can be used:

This is a “star-quad” cable which consists of 4-wire AWG22 silver plated wires with PTFE insulation.

The unit is available with 8mm. aluminium front panel (milled and anodized) or without panel while retaining all functionality.

User can also choose between 3 fixed output voltages – 5, 12, 15V or Custom defined voltage.

In case you want a LPSU with Custom output voltage (different from the 4 listed above), please contact me via the contact form in order to discuss the possibility for LPSU production. Then in the process of ordering you should leave a note for desired output voltage.

What the buyer will receive:
The package will contain 1 pcs. FULLY ASSEMBLED and tested Linear Power Supply in a steel case and 1 pcs. DC cable.

Note: The AC Power cable is not provided.

The unit will be shipped with Priority AirMail Registered (or equivalent courier service where applicable). The tracking number will be sent to the customer after shipment.

Additional information

Weight 2.3 kg
Front Panel

Present, Not Present

Output Voltage

5V, 12V, 15V, Custom voltage