Ramblings, thoughts, questions we hear, questions we receive, questions we ask ourselves… This page is a collection of all of them. We hope you’ll find some inspiration, get some questions answered or just spend some spare time usefully.
#2 Is an SMPS faster than a linear supply?
There are coarsely two topologies, one is a direct SMPS where the switch loop goes from the DC input, switching transistor, Hf transformer, rectifier, filter capacitors and then back via an optocoupler (mostly) to the switching comparator PWM circuit. This feedback circuit loop is much longer, and can never regulate as fast as the very short direct linear regulator circuit. The second, and better topology is an SMPS with a post linear regulator, this can be as fast as a linear supply at best obviously.
SMPS supply topology
Linear topology
Many brands talk about low noise SMPS supplies and regulators. When looking deeper into this, we always see the bandwidth for the noise is taken in the ranges like 0-100kHz. Due to the high switching frequency and small Hf power transformer the switched mode supply could potentially be better than a linear supply in that range. But when looking beyond this bandwidth, there is Hf noise which interferes directly especially with digital equipment clocks and signals, and indirectly with analogue signals, they have a much higher noise density. The linear supply will always be better in that range.
Beware, this Hf switching noise is not only within the electronic circuit, but also transmits through the air, and it is, once introduced, impossible to get rid of, you will find it through the whole system everywhere. Just plug an SMPS supply in your power block, without even connecting it, the sound stage clearly reduces.
Noise standard SMPS
Noise standard linear supply
These are noise spectra of two standard cheap comparable supplies, note the difference in absolute level and also the difference in Hf noise. Humming noise also typically is higher with a SMPS supply, since it rectifies directly from the mains, where a linear supply always has a transformer first, damping and filtering a lot of noise in the start. Please note, a better SMPS or linear supply off course will have less noise overall, but these relative differences can always be observed.
About the sound
The Hf noise typically make things sound harder and sharper and this can be interpreted as more dynamic and fast, but it definitely is not real and natural. In a good system with enough resolution itself and with the right attention, you can clearly observe this. We understand from a commercial point most commercial brand want to use SMPS, because it is cheaper, more efficient, smaller and has less weight, but for high quality audio, where we hope we all are aiming at, a linear supply is the only way to go.
#1 Why is the power supply important?
We often explain the importance of the supply and our view on designing with the analogy of a shower. If the water pressure and temperature of the hot water and cold water are fluctuating and not stable, you need a very complicated shower faucet to compensate for this, and even then the water will never be 100% the same pressure and temperature, I know you have felt this. Suppose the water pressure and temperature of the cold and hot water both were exactly the same all the time, perfectly stable, you can do with a very simple faucet, put it in one position and the water will be fully stable in temperature and with complete constant flow. Translating this to audio, with a very good supply, you can keep the amplifier very simple, save a lot of money on complexity and thus use better parts for the same money and get a better output and definitely a better sound, much more natural, musical and open, engaging. Once you have heard it…
The way we look at amplifiers (power, pre, but also analogue stages in DACs and streamers) is that they in principle do not exist. After all the power supply is always on at full power, the amplifier part modulates this supply, lets through more and less power towards the load. The power supply is the driving force, the amplifier is more like an attenuator. With a perfect power supply the amplifier circuit can be very simple, like the faucet in the analogy above. Designing from the power supply up will result in a completely different amplifier, with a different sound than what we hear these days generally. A bad supply asks for complex electronics, lots of feedback, and compensations like adding more power, to keep things stable. It is putting the cart before the horse.
200W and up amplifiers are totally ridiculous in home audio, you do not need it when an amplifier has a good supply to deliver that power. A 86dB speaker (which is already a very low sensitivity) needs only 64Watts to play 103dB continuously, this is the legal maximum at a live concert. Maybe a bit more for peaks. In a normal sized room sound accumulates, so you very probably need even less. Higher sensitivity speaker need less power obviously. Higher power is only made for specifications (marketing) and to be able to compensate the bad power supplies. And a big transformer and a big bunch of capacitors is not per definition a good supply, au contrair! More about this later..
Most brands today are designing down from the enclosure/looks, then functionality and specifications (again… marketing) and then see what money is left for the power supply. The supply is inside, people cannot see it, so less important.