I personally just think that the power supply, and more accurately the non-linearity and ripple caused by crappy power supplies is what causes a piece of gear to sound digital.Īnalog is just digital that's been pressed to LP. People may say a better mac mini power supply makes the sound more analog-sounding. I'm yet to find a power conditioner that can hold it's own against a Topaz Isolation Transformer with 146dB common mode noise rejection.
Ultimately it's a cheap trick, but has poor tradeoffs. Ferrite tends to work fairly well on digital gear for rolling off what people consider to be digititis. While I can't say for certain, almost ALL power conditioners that boast a "more analog" sound are using suppression capacitors and ferrite cores. In theory that cancels out common mode noise in the same way balanced analog circuitry works. That means rather than having 120v on the hot conductor and 0 volts to ground on the negative, you have +60 and -60, which are out of phase. I was offering to build my supply to a few people for $400.Īs I understand it, the ECM uses Balanced power transformers. My supply had a much larger impact on the sound, but both are very nice pieces of gear. I borrowed the boulder supply from a friend of mine, one of the reasons I wanted to build one myself. If you need to deliver 110W with 50W lost in regulator I would pick at least 250W transformer. Current spikes from bridge/capacitors have much higher RMS value than average value heating copper (windings) while high frequency content is heating the core. Transformer is also a problem because 110 W supply requires almost twice rating because of the nature of load. You can do much better with modern regulators.
In addition LM338 has very poor ripple rejection equal 0dB (none) at 100kHz. This means 8.5V x 6A = 51W (big heatsink). I requires almost 3V input output differential making it total of 8.5V drop across regulator if you provide for +10/-20% line variation (3V +18.5Vx0.3). Fast switching brings more noise pollution.Īs for designing with LM338 - I did it over 20 years ago and would not do it again. "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." - Only for efficiency sake. Older regulators like LM338 are sensitive to output capacitors' ESR - might start oscillating when ESR is too high but also oscillate when it is too low. 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.
0 kommentar(er)
