Quote:
...they all said that even the big brands are using switching P/S, it must be OK.
The thing is, those companies' engineers have
done the engineering. (One hopes, anyway.) They didn't just ask a broad question, then someone said "yes," so they whacked a switcher in there. They knew the switching frequency, they knew their budget for filtering, they knew the amplifier's FR and PSRR...
Most importantly, I think these other engineers knew their quality goal: they knew what success would look like when they achieved it.
So, you can blindly follow these other engineers
if:
- you're using the same SMPS
- the same filtering
- the same amplifier stage
- and have the same quality goal/definition of success
The fact is, it's simply a lot easier to succeed in DIY with a linear power supply.
On the other hand, it's a lot easier to succeed in the high-volume commercial world with a switcher, because size, cost and weight matter more in volume.
Let's say going with a switcher saves you $15 in parts per unit. Plus, it might save you another $1/unit in packaging, warehousing, and shipping due to the lower volume and weight. If you did it right, it might have cost you $5,000 of engineering time to solve all the problems you bought by choosing a switcher. If you sell 100,000 of these things, that NRE only amounts to a nickel per unit, so it's a clear win.
Now consider the same problem in DIY terms.
If you choose not to solve the problems you bought along with that switcher, you might ruin a perfectly good audio circuit. The easy fix is to buy/build a new linear supply, so you've wasted ~$10-25 on the switcher. Clear loss.
If you do choose to solve these problems, the $5000 in NRE time will look different. Let us say it amounts to three months of weekends instead, in DIY terms. And in the end, you've only solved the problem for one unit, unless you're making a project for others to build, in which case you'll still be lucky if the volume goes into the single-digit thousands. Is solving SMPS problems your idea of fun? If so, great, you have a new fun DIY project that'll keep you busy for months! If not, are you willing to trade three months of weekends for ~$15, a few ounces, and a few watts?
To answer your title question, yes, I have indeed heard the noise of a switching power supply. It was a $1 DIP-8 based switching controller that I DIY'd up on a solderless breadboard. It had a 10 kHz switching frequency, and I didn't filter it beyond what was recommended in the switching controller's data sheet. In other words, I'd done about everything I could to fail, and I succeeded in failing.
I heard a high frequency buzz in the headphones when I turned the amp on. I chose not to spend the three months of weekends on the SMPS, to make it achieve the audible performance of a linear.
Is that another way of saying, "Don't use switchers?" No, it means, "Do the engineering."
I have direct knowledge of at least three highly-regarded headphone amplifier designs that used switching power supplies. And in all cases, they all got negative feedback (the other kind) when people realized it, because there is a knee-jerk reaction to SMPSes in the audio world. So my second piece of advice is, if you use a switcher, and you've done it right and know it, don't brag about it.