Discrete Voltage Regulators for Audio Power Supplies

• 125dB Input Rejection.
• 3uV RMS Noise @5Vo, 5.8uVRMS Noise @ 15Vo (20Hz – 20KHz).
• Excellent Transient Response.
• < 2V Dropout Voltage.
• Stable With Ceramic And Low ESR Output Capacitors.
• 1 Amp Output Current (Internally Limited And Protected).
• Fully Discrete Design – Right Down To The Error Amplifier.
• On – Board 10uF Tantalum Polymer Output Capacitor.
• Precision Thin Film 0.1% Tolerance Resistors.
• +/- 1.5% Output voltage accuracy.
• Available With Positive Or Negative Fixed Output Voltage Of 3.3V – 24V.
• Available In 3 Industry Standard Pin Outs.
• Perfect for audio power supply and Eurorack power supply designs.

These discrete voltage regulators will outperform all monolithic voltage regulators in a TO-220 package in input rejection, output noise, transient response, and load regulation. The table below details the vastly superior performance of the Sparkos Labs devices to a wide array of monolithic voltage regulators.  They are optimized for Audio power supply designs and for use in your Eurorack power supply.

The discrete design of these devices allows for numerous internal capacitors which are impossible to fabricate in a Monolithic IC. There is an onboard output decoupling capacitor which eliminates the need to add one externally. The error amplifier of the device is also fully discrete and is based on the SS3601 discrete op amp slightly modified for this application. The internal reference voltage is a precision shunt reference with post RC filtering for extremely low noise performance.

These discrete devices are a series pass design with a fully discrete error amplifier that compares a feedback voltage to a reference voltage, and in turn controls the pass device.

In order to replace a monolithic regulator with these discrete devices in your audio power supply, one must know the polarity, pin-out, and output voltage of the device that they wish to replace. A Digikey search of the part being replaced will usually provide the relative information. If one is replacing an adjustable type regulator, the output voltage that it is set to must be known so an appropriate discrete regulator can be chosen and installed. This assumes that any adjustable type regulator is set to a fixed output voltage within the circuit. It should be noted, that in order to replace an adjustable regulator, the resistors that set the output voltage must be shorted out (the resistor to ground) and removed (resistor from Vout to ADJ)

Attempting to make these discrete devices dynamically adjust their output voltage by using POTs or voltage dividers on the ground pin is not recommended in order to achieve the specified performance. If a device being replaced is mounted to a heat sink, that same heat sink should be used with the discrete replacement device. One does not need a larger heat sink when replacing an existing voltage regulator with one of these discrete devices. The existing heat sink will suffice.

Since the tab of these discrete devices is tied to Vin, an electrical insulator should be used between the tab and the heat sink to prevent the heat sink from becoming live with Vin.

The input and output bypass capacitors within the existing circuit should also be adequate and do not require any modifications for normal operation. If the output capacitor closest to the regulator is of ceramic or film type, better transient response might be obtained by removing it.  This is because ceramic and film capacitors will degrade the phase margin of the device because of their low ESR. In these instances where the output capacitor is removed from the circuit, the internal 10uF tantalum polymer capacitor will be sufficient as an output capacitor, and the device will operate with a higher phase margin and less transient response ringing.

The best transient response can be obtained by using a Panasonic EEU – FR1H101B electrolytic capacitor (100μF 50V 65mΩ ESR) as the output capacitor. This capacitor can be used to replace the existing output capacitor or it can be added in parallel with it. It should be noted that the correct polarity must be observed during the installation of these electrolytic capacitors.