They are also not as easy to design as it seems. Linear regulators are noisy, require huge transformers are most often unregulated. Modern switching power supplies are switching at zero voltage/zero current while linear power supply switches at max voltage.Īs I understand it you need about 6A for this supply while LM338 is rated only 5A (continuous). The lowest I know to operate is about 50kHz - non audible. Mintzar - I don't know of a single switching mode power supply that operates in audible band. Send me an email and I can potentially get you started. That means the regulator, resistors, capacitors, and diodes all have to be able to handle 6A of current (preferably something like 10-12A MINIMUM for safety). What I do is build a 22V PSU and regulate it down to 18v5. What I can tell you is that you need to build an 18v5 PSU capable of outputting 6A. The only tidbit of "plans" are the pinout for the iSense DC connector for the Mini.
This is a design that I did the research for and constructed myself. The off periods are why switchmode supplies sound noisy and often mechanical.Īs for the Mac Mini PSU. Ideally you would want the switching frequency to be so fast that it would be impossible to tell when it turned off and back on. Switchmode supplies with a switching frequency in the audible spectrum have a moment where zero current flows, the lower the switching frequency the more noticeable those periods of off time become. If you start with an amplifier, but have a crappy source the signal can only be as good as the source. And if you build a better supply for your source you start with better. The power coming from the wall is the power used to create every signal in your audio system. Granted, most companies don't put expensive power supplies in their gear, it's just too expensive to manufacture for a large company. Companies like Bel Canto, W4S, Nuforce, etc all use switching supplies and are incredibly noisy and dry sounding. EVERY switchmode supply I have heard was noisy compared to a linear supply. The switching aspect is well above the audible spectrum. My amplifier is a Class D amplifier with a Linear PSU. Switchmode supplies in many products on the market DO NOT have their switching frequency above the audible spectrum, however.
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