Amplifier power: Class A, AB vs D

[DVinylfan]

We are living in a golden, classless era of amplifiers

 

[xlinknz]

When double blind listening tests are brought into the mix there's very little to debate.
To quote a old post by Peter Aczel
"Vastly exaggerated in importance by the audiophile press and high-end audio dealers. In controlled double-blind listening tests, no one has ever (yes, ever!) heard a difference between two amplifiers with high input impedance, low output impedance, flat response, low distortion, and low noise, when operated at precisely matched levels (±0.1 dB) and not clipped. Of course, the larger your room and the less efficient your speakers, the more watts you need to avoid clipping."

Paste This In Your Hat.

Paste This in Your Hat!

The irony is whether there are audible differences due to better measurements occurs across all components, DACs, speakers, input devices etc

Imagine if this site had all measurement charts marked up to show human audibility thresholds

NB: I had to laugh when I saw the following on the Benchmark AHB2 product sheet "Don't settle for the limited performance of class-D amplification."

 

[Ted G]

From the Gemini: Richard Clark, a legendary figure in the car audio industry and co-founder of Autosound 2000. For over 20 years, he famously offered a $10,000 prize to anyone who could distinguish between two power amplifiers in a blind "ABX" listening test.


Despite thousands of participants—including self-proclaimed "golden ears," audiophiles, and industry professionals—no one ever won the money.

The Core Philosophy


Clark’s challenge was based on the controversial premise that all well-designed amplifiers sound identical as long as they are operated within their linear power limits (not clipping) and are level-matched. He argued that the "warmth" or "detail" people often attribute to expensive amplifiers is actually the result of small differences in volume, frequency response, or psychoacoustic bias.

 

[kyuu]

NB: I had to laugh when I saw the following on the Benchmark AHB2 product sheet "Don't settle for the limited performance of class-D amplification."

You have to admit it's a better line (for marketing purposes) than: "Our amplifier's technical performance is largely, if not entirely, inaudible compared to cheaper and smaller class D alternatives."

 

[bigguyca]

@Mnyb thank you again for the reply. Yes it has nostalgic value (I've own it 35 years) and is definitely collectable at least in NZ, it works so I won't get serviced. It was in the mid 80s considered very high end (but I got 2nd hand at low cost). The matching pre amp I did have work done on it as it stopped working so was recapped and the switching relays etc replaced

I was curious to see how it compared to newer amplifiers not just the likes of modern premium amps like the Benchmark AHB2 but also newer smaller Chinese amps. It also has on the spec a bunch of design characteristics e.g "accurate rendition of subtle musical detail" etc that are not specifications. Obviously measurement would show the benefit (or not) of the specifications and design after 40 years. The qualified audio engineer who repaired the pre amp has loads of measurement gear but it would cost to have measured

It will be interesting to see if I notice any sound difference using the Fiio DAC via the matching pre amp and direct to the before mentioned power amp

My longer term plan is to get an a modern integrated with pre in and pre outs so if either of the vintage pre and power amps fail I can still use one or the other in conjunction with the integrated

NB: Interestingly here Bench mark talk about class A and A/B for that product but seem careful not to explicitly classify the amp as class A or A/B etc. My vintage amp has a number of similar design characteristics/goals as the Benchmark reflecting I assume all high spec amps strive for the same goals

Bench mark?

Per memory, The Benchmark AHB2 power amplifier is neither class A or A/B.

 

[oleg87]

yes mine states "the output stage is operated at a higher than usual bias current , remaining in class A operation up to several watts output. This keeps the transition between devices out of the low level signal region and helps to prevent loss of subtle detail in the recorded signal.

Some UK companies e.g. Musical Fidelity used fans in addition to heat sinks to reduce weight...

Whether there is benefit in class A seems to be debatable topic

The benefit of class A is that it excludes the possibility of crossover distortion. If there is no crossover distortion to be heard in a given amp, then class A operation would only yield an advantage to people who also need a space heater.

 

[bigguyca]

Class D amp better sound and efficient power (reduce electricity bill). Just add the class D amp to your pre-out or rec-out of your class A/B. It will disable power amplifier on your class A/B.

We’re living in the modern era where electricity consumption must be reduced, save the planet, climate change, etc, etc. Please please don’t use Sub-Woofer. Those subs were in ancient times. Don’t go back.

Obviously you are joking. In checking the calendar it's not April 1st, you are a bit early or perhaps late.

 

[kyuu]

Bench mark?

Per memory, The Benchmark AHB2 power amplifier is neither class A or A/B.

The AHB2 is class AB with an SMPS.

 

[OldTimer]

Obviously you are joking. In checking the calendar it's not April 1st, you are a bit early or perhaps late.

I stop using Subs since 20 years ago. It’s not broken but I enjoy music better than without it.
And after my neighbor bring an axe to the front door of my home. Also it save my electricity bill.

 

[popej]

the output stage is operated at a higher than usual bias current , remaining in class A operation up to several watts output. This keeps the transition between devices out of the low level signal region and helps to prevent loss of subtle detail in the recorded signal.

"Subtle detail" sounds like a marketing term. Technical term could be for example THD. If you check in manuals for amps design, you will find, that optimal bias for lowest THD is somewhere around 50mA. Quite common value for AB amplifiers.

 

[xlinknz]

"Subtle detail" sounds like a marketing term. Technical term could be for example THD. If you check in manuals for amps design, you will find, that optimal bias for lowest THD is somewhere around 50mA. Quite common value for AB amplifiers.

"subtle detail" was an example but the marketing in my product sheet is less overt than the Benchmark product sheet , my spec has THD <0.03% (note its a 40 year old amp) and doesn't have more on that and does not say what the bias was. Unfortunately the (local) designer passed away a few years ago otherwise I would ask him. I tend to listen at low volumes (so may benefit from the "several watts of class A"?) unless my wife is out then I can play at 50% of the volume dial otherwise the 185w at 8 Ohms will risk blowing my bookshelfs!

 

[Digital_Thor]

The AHB2 is class AB with an SMPS.

Actually, class H to be precise. It's kinda more efficient than normal AB, because it only switches to the higher rail voltage during peaks.

 

[kyuu]

Actually, class H to be precise. It's kinda more efficient than normal AB, because it only switches to the higher rail voltage during peaks.

Class H is just a variant of class AB.

 

[RexrothPigeon]

We are living in a golden, classless era of amplifiers

"The history of all hitherto existing society is the history of class struggles (until now)."

 

[Digital_Thor]

Class H is just a variant of class AB.

Well, potentially much more powerful.
Then take it all, class TD, class A input, class B amplifier with class D switching rails.

Lab Gruppen | Technologies | Class TD Output Stage

www.labgruppen.com

 

[melomane13]

Well, potentially much more powerful.
Then take it all, class TD, class A input, class B amplifier with class D switching rails.

Lab Gruppen | Technologies | Class TD Output Stage

www.labgruppen.com

it is BASH amplifier...

 

[Digital_Thor]

it is BASH amplifier...

Not entirely - though the difference is small. BASH uses an analog buck converter, whereas Labgruppen uses a class D buck converter.
I dont know about BASH, but Labgruppen has well known great reliability, which of course counts the most in pro audio.
Class D are getting really good, all on its own, with no need for any other class/type.

 

[EJ3]

It's mostly about efficiency. Class-D sends most of the power to the speakers without wasting energy as heat inside the amplifier.

Class-A is the least efficient, basically generating the same heat when the amplifier is silent as when it's putting-out full power.

Switching power supplies are similar to class-D amplifiers, especially the voltage regulator which switches on & off at a high frequency rather than regulating voltage by turning partially-on. (The energy is stored in capacitors and inductors so the DC power can come-out constantly.) The high frequency much higher than the 50 or 60Hz power line frequency allows the use of a smaller-lighter transformer.


"Audiophiles" like stuff that's expensive and outdated. Some people like class-A tube amps.

And Class G or H?

 

[melomane13]

Not entirely - though the difference is small. BASH uses an analog buck converter, whereas Labgruppen uses a class D buck converter.
I dont know about BASH, but Labgruppen has well known great reliability, which of course counts the most in pro audio.
Class D are getting really good, all on its own, with no need for any other class/type.

BASH (Bridged Amplifier Switching Hybrid) is not a brand but a patented amplifier topology.
The original patents were filed in the mid-1990s (around 1994–1996).
As with most audio amplifier patents (20 years), the protection has now expired, making the topology free to use today.

A BASH amplifier is a class-AB audio amplifier powered by a switching (class-D-style) tracking power supply.

 

[EJ3]

BASH (Bridged Amplifier Switching Hybrid) is not a brand but a patented amplifier topology.
The original patents were filed in the mid-1990s (around 1994–1996).
As with most audio amplifier patents (20 years), the protection has now expired, making the topology free to use today.

A BASH amplifier is a class-AB audio amplifier powered by a switching (class-D-style) tracking power supply.

Thank you for clarifying that.
I knew what BASH is but could not think of a good way to express it.