Amplifiers using "switching power supplie"

Hey guys:
I just learned the term "switching power supply". Its theory was explained to me by an engineer. I understand that they use an oscillator after retifying the AC and smaller transformers. A link to a site is
Link to amp with switching power supply

I have no idea how this amp sounds, but I am curious about the virtue of using this technology and its application to our passion.

.....inquiring minds want to know

nfa: the purpose of a power supply is to give your amplifier stage "clean" power. By this, I mean DC voltage with very little AC ripple, and very little voltage drop under peak power demand.

It doesn't matter how the amplifier gets this "clean" power, whether it is from a switching supply or a conventional supply.

One thing to note, the cheaper switching supplies tend to be "noisy."

I haven't seen many cost comparisons between switching supplies and conventional supplies, but the good switching supplies tend to cost as much as the conventional supplies. The big savings is in size and weight. Maybe someone else can comment on the cost trades.

Hope this helps a little.

Thanks, ratpack.
I have no intention of making changes (I love my 7700 and 755). I learned a term, new to me, and thought I ought to know more about it.

I'm building a final 7*240W @ 8 Ohms (or 7 * 400W @ 4 Ohms) this fall.
Using 7 Coldamp class D modules and 2 Coldamp SMPS power units.
All arrived, look lovely.
Best thing: no excessive weight, almost no cooling (91% efficiency while class D,AB,B are only 30...45%).
See my other postings on the subject.
Will test this amp against my 7700.

Most general purpose products these days, especially computer, use switching power supplies. All ATX power supplies for computers are switching power supplies, as are many of the bricks for external equipment.

The main benefit of this is they can be smaller and lighter. For audio applications, they need to be shielded because the switching generates noise heard as audio intereference. They also generate switching distortion on the electrical line, which may also need filtering.

Does this "noise" affect audio playback if the input devices are close? Which amplifiers shield properly and which do not? How is the outlaw's switched amplifier with respect to generated noise?

Joel

I'm not aware of Outlaw using switched power supplies in their amps, Joel.

How does the 2200 work?

Joel

The 2200's amp is a hybrid: class AB up to around 80W, then class G beyond that. A class G amp uses a power supply with a series of voltage rails and switches between them so that the power supply output more closely matches the actual demand at the time. From what I've read, this is not the same as the type of "switched power supply" that's being discussed here (those switch the current on and off very rapidly to control the output voltage, so it's a different sort of switching). At least that's what I understand of the matter - hopefully someone better versed on power supplies can sort us out if I'm wrong.

I am sorry about the confusion. I thought a switching amp was a switching amp. Now learn there are different types-thanks for the clariifcation.

So does Class G lead to RF noise?

This is a factor for me. I have an older Hafler DH-200 I built 25 years ago in my system (handles two side speakers). It is beginning to show its age. Design Concepts will upgrade it for about $600 and 2 M2200s are about the same cost. So I am trying to figure which way to go.

Joel

I've never heard of class G amps producing RF noise, and my Model 200's haven't given me any problems (even when I used them to drive my main speakers).

Never heard of class G myself, but class D is certainly prone to generating RF noise, because of the high amplitude spikes present in the circuitry, most of a few hundred kHz, and the harmonics of course.
So SOME care should be taken in designing class D amps, to avoid this.
Well screened cabinets and internal cabling, and compartimented units, should be sufficient to accomplish this.

Switching and tracking power supplies are sort of completely different things.

What happens to the S/N and THD in the M2200 when it delivers more than 80 watts?

Joel

You'd have to ask the Outlaws themselves for the details, but I wouldn't expect the signal to noise ratio and THD to exceed the rated values under either class AB or class G operation.

gonk & barend are correct. Class G is not technically switching, although it does "switch" power rails.
A true switching power supply actually breaks up the input power fromthe wall and switches it at a high frequency to adjust to the power demands at the output. This switching causes lots of noise, electrical, RF and in some cases mechanical. The filtering is critical to not having this noise get through to the actual audio signal.

Class D is a bit different in that it is switching the input audio signal, and adjusting the output based on the input demands. I have heard class D, but have not done any critical listening or measuring to see whether it has a significant noise contribution.
By far as others have said, with the exception of class D, a clean DC power is what all amplifiers need for the output circuits.