Amplifier power: Class A, AB vs D

[Chr1]

Wondering why all Class A/Bs aren't BASH these days?

Presumably cheaper to make and more efficient than a torroid. Do torroids have any advantages over a BASH type topology?

I guess possibly they could be more reliable?

 

[kyuu]

Do torroids have any advantages over a BASH type topology?

Audiophile mythology demands a toroidal transformer.

 

[Digital_Thor]

No doubt a properly made switch mode supply is the way to go today. But since amplifiers are often kept for years, it takes a bit of time for anyone to change their minds about it. Classic analogue amplifiers still work just fine for a lot of people.
Toridials are also expensive for both the manufacturers and the customer... And heavy. Switch modes supplies solves this yeasily.
But again, why should I spend a lot of money on class D and switch mode supply... When my class AB and H works flawlessly. We also established many times that most differences in sound between different amplifiers, mostly can't be heard at a certain 'good enough' point... Right?

 

[Head_Unit]

class D amplifiers use SMPSs and the latter has little headroom

If nobody yet noted, headroom is not necessarily a good thing. It implies the power supply is "loose" does it not? Which I out of vague intuition feel on some micro level might mean the sound is "loose." Or another way of looking at it is that headroom is fine, "high current" is fine, but there's really no substitute for just more than enough power.

 

[Head_Unit]

What has changed is that there's a lot of completely transparent equipment now available at what is considered budget priced that performs as well or in many cases better than the flagship stuff, but lacks the kudos and bragging rights of the expensive stuff.

What has NOT changed is the reluctance of folks to make blind tests of that

 

[Sokel]

Who says toroidals are expensive?
They certainly aren't, heavy,yes, that is.

Specially the ones for small amps up to 300W/channel/4 Ohm or something are cheaper that a decent SMPS including a small forest of decent caps.

Where SMPS makes sense is at way higher power amps where weight and size start going way up.
An amp doubling down to 1 Ohm at 2.5kW for example can easily exceed 30 Kg, including some decent heatshinks for thermals.

Edit: yes, I know that a 2.5kW/ 1 Ohm amp would be comparable in weight if passive cooled, heatshinked, no matter the class.

 

[Digital_Thor]

Who says toroidals are expensive?
They certainly aren't, heavy,yes, that is.

Specially the ones for small amps up to 300W/channel/4 Ohm or something are cheaper that a decent SMPS including a small forest of decent caps.

Where SMPS makes sense is at way higher power amps where weight and size start going way up.
An amp doubling down to 1 Ohm at 2.5kW for example can easily exceed 30 Kg, including some decent heatshinks for thermals.

Edit: yes, I know that a 2.5kW/ 1 Ohm amp would be comparable in weight if passive cooled, heatshinked, no matter the class.

Those well wound low noise 600VA ones here, cost quite a bit.... I think around 300 US$ each. Then you have capacitors. I have 16 in each of my big class H amplifiers.... around 10-15$ each - 8 for +/-60V and 8 for +/-120V.

 

[Sokel]

Those well wound low noise 600VA ones here, cost quite a bit.... I think around 300 US$ each. Then you have capacitors. I have 16 in each of my big class H amplifiers.... around 10-15$ each - 8 for +/-60V and 8 for +/-120V.

Way under 150 euro for "Audio Grade", for 200 euro you get some fancy too if you have a look:

TTSA0600 - Transformer AUDIO TSA600VA - voltage from 55 to 100 V

Audio grade transformer is dedicated for use in power amplifiers and other high-end

sklep.toroidy.pl

You can also find cheaper in Asia, we talk Europe here.

Plus 8 caps and the rest, about 200 euro for a Europe made, DIY one.
Put that on scale for a company, and it's half or less for Europe made and fancy.

So...

 

[Digital_Thor]

Used Nichicon, didn't want to skimp on quality - and so far it just works, which makes me a happier owner

 

[Sokel]

Used Nichicon, didn't want to skimp on quality - and so far it just works, which makes me a happier owner

And it will keep on working for decades no problem I suspect.
Simple trafos are immortal.

 

[Chr1]

Sorry for being a dufus. Most of my amps have torroids.
Am I right in thinking that they can be less efficient but are generally more reliable?

 

[Sokel]

Sorry for being a dufus. Most of my amps have torroids.
Am I right in thinking that they can be less efficient but are generally more reliable?

Toroidal trafos themselves are super efficient, typically more than 90%.
And as I wrote above, pretty much immortal.

It's the rest of the circuit that defines efficiency, etc.

 

[Chr1]

So why do modern, particularly class Ds use switching power supplies?

 

[Sokel]

So why do modern, particularly class Ds use switching power supplies?

Weight primarily I suspect (which has a long chain of implications), ease of integration with ready-made PSUs, size, etc.

Again, for higher power amps it makes more sense for SMPS if one wants to keep the cost down.
And I mean all cost, right to the client.

 

[EJ3]

Weight primarily I suspect (which has a long chain of implications), ease of integration with ready-made PSUs, size, etc.

Again, for higher power amps it makes more sense for SMPS if one wants to keep the cost down.
And I mean all cost, right to the client.

but...does that keep it out of the landfill. longterm?

So why do modern, particularly class Ds use switching power supplies?

Something else that they do not tell you about SMPS:

Failure modes​

For failure in switching components, circuit board, etc, see Failure of electronic components.
SMPSs tend to be temperature sensitive. For every 10-15 °C beyond 25 °C, failure rate doubles.<a href="https://en.wikipedia.org/wiki/Switched-mode_power_supply#cite_note-51"><span>[</span>49<span>]</span></a> Most failures can be attributed to improper design and poor component selections.<a href="https://en.wikipedia.org/wiki/Switched-mode_power_supply#cite_note-52"><span>[</span>50<span>]</span></a>

(EJ3: so if it is inside the box with your amp, it will most likely get more than 10C above 25C. And maybe inside it's own wall wart case, also.
Basically, with one, you are accepting the fact that it will fail sooner than us older folks are used to for a PS.
And who knows what it will take out when it does).

Power supplies with capacitors that have reached the end of their life or suffer from manufacturing defects such as the capacitor plague will fail eventually. When either the capacitance decreases or the ESR increases, the regulator compensates by increasing the switching frequency, thereby subjecting the switching semiconductors to ever greater thermal stress. Eventually the switching semiconductors fail, usually in a conductive manner. For power supplies without fail-safe protection, this may subject connected loads to the full input voltage and current, and wild oscillations can occur in the output.<a href="https://en.wikipedia.org/wiki/Switched-mode_power_supply#cite_note-lowyat_341368-53"><span>[</span>51<span>]</span></a>

Failure of the switching transistor is common. Due to the large switching voltages this transistor must handle (around 325 V for a 230 VAC non-power-factor-corrected mains supply, otherwise usually around 390 V), these transistors often short out, in turn immediately blowing the main internal power fuse.

Power supplies in consumer products are frequently damaged by lightning strikes on power lines as well as internal short circuits caused by insects attracted to the heat and electrostatic fields. Those events may damage any part of the power supply.

Precautions​

The main filter capacitor will often store up to 325 volts long after the input power has been disconnected. Not all power supplies contain a small "bleeder" resistor which slowly discharges the capacitor. Contact with this capacitor can result in a severe electrical shock.

The primary and secondary sides may be connected with a capacitor to reduce EMI and compensate for various capacitive couplings in the converter circuit, where the transformer is one. This may result in electric shock in some cases. The current flowing from line or neutral through a 2 kΩ resistor to any accessible part must, according to IEC 60950, be less than 250 μA for IT equipment.<a href="https://en.wikipedia.org/wiki/Switched-mode_power_supply#cite_note-cap-est-54"><span>[</span>52<span>]</span></a>

 

[Sokel]

but...does that keep it out of the landfill. longterm?

We will have to wait and see, key is implementation, quality and a bit of luck.

Have a look at PC's PSUs for example. Lots of quality ones run for decades no problem, specially at cases where they put them on the bottom so heat is less.
Others are literally disposable.

Linear ones on the other side barely dissipate any heat (unlike nice SMPS's who need heatshinking) , put them a little far from the output devices at a full size case and that's it.

To my opinion, cheaping on the caps (at whatever PSU) should be a crime punishable by listening to a bright speaker 8 hours a day

 

[EJ3]

We will have to wait and see, key is implementation, quality and a bit of luck.

Based on what I have seen, MORE than a BIT of luck.
Due to people having been taught to go after the cheapest deal possible ("Look what I got and you'll never believe how CHEAP I got it for") attitude leads manufacturers to build CHEAP which creates the planned(or not, but it happens anyway) obsolescence.
Because they build as cheap as they can, as that is what the general public gets off on.

 

[Head_Unit]

So why do modern, particularly class Ds use switching power supplies?

Somewhere here there is a thread showing among other things that the audio can actually be cleaner, in particular no 50/60 Hz and harmonics bleeding into the audio. Like everything else, I'm sure the devil is in the details. You can make a cheap linear or SMPS or a top quality.

I'm quite certain one factor keeping linear going is it is long well known and easy to make beefier: just get a huger toroid, more and bigger caps. And it feels heavy/beefy and if well laid out looks more cool than a computer power brick.

 

[tineared]

I’ve been buying LEDs for 15 years, and in my totally unscientific experience, longevity has greatly improved. Also, flicker.

This is my experience as well.
Living in S Florida, I appreciate that the bulbs don't combat my AC by acting as a bunch of little heaters and I especially like being able to choose the color temperature for different locations.
3200K for cozy spaces, 4K for general lighting and 5-6K for task lighting.
I research the reliability of brands by reading the reviews on Amazon.
Better than sliced bread, though not particularly related to amplifiers

 

[Taiga]

Q: How many audiophiles does it take to change a light bulb?

A: One. But they keep replacing them with new ones when they still work fine.

[feel free to add your own response]

BTW - My class D amplifier has a bright red “slam” button to add that special feeling in hard to drive speakers.