What is it? The SilentSwitcher is a solution for powering your small-signal audio circuits with quiet, low noise and efficient power, totally separated from the mains. Audio projects are steadily getting smaller and the power supply with its transformer and rectifier and reservoir caps remain as large and looming as ever. I had been looking at switched-mode power supplies before and was never quite satisfied, but that has recently changed a lot for the good. The very high requirements for tablets and smart phones have driven switcher technology to incredible quiet and low noise performance. Also, linear (post) regulator performance has leapfrogged those old audio standby's like the LM137/337 series.
What does it for me? Almost any small signal audio project will benefit from a SilentSwitcher. A RIAA phono preamp; a line preamp with or without tone controls, an active filter, buffers, cross-overs. Electronic volume controls, headphone amps; anything that has opamps in it. Opamp and discrete audio circuits almost always run at +/-15V, and even if the are designed for say +/-12V or +/-16V, they will almost always run fine at +/-15V. At 150mA (or more, see below at powering options) it's enough for all but the most power hungry circuits. The 6/5/3.3V output would be ideal for a DAC or streamer with a dedicated controller. The 0.5A current (up to 1A with extra power option, see below) goes a long way to power a dedicated unit with a display, some relays, LEDs, etc.
SilentSwitcher is a very high performance turnkey power supply for such mixed systems. The linear post-regulators have a PSRR of over 60dB at more than 1MHz - exactly what is needed to clench what little ripple remains from the switcher. I also put a lot of effort in designing the PCB to avoid excess radiation; very low impedance ground- and current paths, sort traces, decoupling caps right at the source, etcetera.
The SilentSwitcher is not a kit: you will receive a fully assembled and tested board.
Outputs Analog circuitry mostly wants to be fed with +/-15VDC, so that was the target for my design. But increasingly the analog is combined with something digital, a DAC, a microcontroller, LEDs, relays, etcetera. So, the SilentSwitcher outputs +/-15VDC at up to 150mA each, as well as a jumper-selected 6V, 5V or 3.3 output at up to 0.5 amp (see below for higher-power options). The 6V option is handy in case you want to regulate locally to 5V or 3.3V.
Connectivity There are 2- and 3-pin headers on the PCB to connect the load, and a 2-pin header for an On/Off switch. The connection to the 5V source is through a B-type USB connector or a standard 2-pin screw-type connector block. You can mount the PCB on the back of your enclosure with a hole cut out for the USB-B - no further input wring required. (The pic shows the prototype with a screw-terminal). The assembled and tested board will be delivered with a separate USB-B connector and 2-pin screw terminal, so you can mount the connector that fits your need.
Supplying the supply The SilentSwitcher runs from a standard 5V/2.1A USB charger. For total separation from the mains, run it from a PowerBank. And you can also use a wallwart or (LiPo) batteries, anything between 3V and 10V will do (higher voltage allows higher outout currents - see below). The start-up of the various parts of the SilentSwitcher is timed such that the inrush current doesn't get above 2.5A, even at max load
- Outputs (analog): +15 and -15 VDC at 150mA* each;
- Output (6/5/3.3V): selectable 6, 5 or 3.3 VDC at 0.5A*;
- Output noise (analog): see graph below;
- Output noise (6/5/3.3V): less than 1mV broadband
- Output impedance (analog): less than 10mΩ (+15V) and 80mΩ (-15V) at 20kHz (see graphs below);
- Output impedance (6/5/3.3V): less than 3mV drop with 100mA current step.
*The current specs (150mA at the +/-15V and 0.5A at the 6/5/3.3V simultaneously) are such that they can be used with a standard 5V/2.1A USB charger. They are not actual limits; if you use a higher input voltage source like batteries (max 10VDC) or a wallwart delivering 9V at 2A, the available output currents are doubled.
A testimony from a well-known audio designer, quote: "I am very impressed. No hum, no hiss, great sound, very simple to use, compact. I think what you did here is a stroke of genius."
Risks and challenges
I have already produced a small prototype run that works flawlessly. It is powering some of my projects. A few beta-tester have put it through its paces and one of them provided the independent measurements shown here. The final version will have some minor changes to allow the choice of screw-terminal or USB-B on-board connector for input power. I have also obtained quotes from a professional manufacturer including functional tests. There are no known risks for this project.Learn about accountability on Kickstarter
- (30 days)