Amplifier power: Class A, AB vs D

[MasterApex]

The audible observation is obvious when used with speakers that at bass region has low impedance with highly capacitive or inductive phase angle (forcing the amplifier to work drastically out of phase).

May be the related measurement is amplifier power supply headroom , does anyone know how to measure this unit under complex load?
Perhaps my Purifi Class D, with its potentially current-limited SMPS and complex correction loops, might show a very slight strain compare to my Levinson 536 that has massive output stage and linear power supply can simply muscle through the reactive load without needing to correct as aggressively.

I read that for any Switching Power supply, if the demand exceeds its design limits, it can cause a very slight "compression" or softening of the dynamic transient, robbing the sound of its ultimate slam and authority.

Perhaps I need to explore new Purifi Class D amp with better power supply design , does linear power supply version exist?

 

[Sal1950]

PS (from earlier today) Not to be redundant, but I still wanna know the SI units for bass slam.

 

[Sal1950]

16:25 "I got all of that one bro" LOL

You just can't fix stupid.

I eeeee he says.

 

[xlinknz]

Good to see a thread on amplification

I have vintage high end pre and power amps I've owned for 35 years. My amps are class A/B and the 185W (at 8 ohms) power amp weights in at 12.4kgs. I have no idea how the specs compare to modern class D amps (I should compare) but my limited understanding is class A is inefficient, gets hot (hence size) and is therefore expensive to mass produce but has the or had benefit of low distortion

That said I plan to connect a DAC that has a preamp so will be interesting to compare sound via the vintage pre amp and direct to the power amp.

I may also acquire a small class A headphone amp

 

[Waxx]

A lot depends on what amp, old high end is all over the place, from very clean (Bryston) to very distorted. But if it works for you, you don't have to change. And if you want to stay in class AB, the Benchmark ABH2 is class AB and one of the best measuring amplifiers arround, as clean as the best class D and way above our treshold for noise to be hearable. Bryston (also class AB) is also neutral enough to be invisible.

But at this level the class of the amp does not matter anymore, they all sound the same. The difference is in the efficiency of using power and size/price. Class D is way more efficient with power and in general smaller and cheaper, with much less heat dispensation.

 

[OldTimer]

Good to see a thread on amplification

I have vintage high end pre and power amps I've owned for 35 years. My amps are class A/B and the 185W (at 8 ohms) power amp weights in at 12.4kgs. I have no idea how the specs compare to modern class D amps (I should compare) but my limited understanding is class A is inefficient, gets hot (hence size) and is therefore expensive to mass produce but has the or had benefit of low distortion

That said I plan to connect a DAC that has a preamp so will be interesting to compare sound via the vintage pre amp and direct to the power amp.

I may also acquire a small class A headphone amp

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.

 

[Chr1]

Ahem. Class D certainly doesn't necessarily give better sound. Also, disconnecting the pre/power sections of most integrated amps won't reduce their power consumption by much. You will most likely actually be using more power by adding an additional amplifier. Class D, or otherwise.

From what I can make out, the extra efficiency of Class D is usually only at higher power outputs too. Most amplifier power losses at normal levels, are usually down to the power supply used. Regardless of the class of amplifier.

They are certainly usually smaller and lighter tho.

Just bought a Topping Mini 300 for £105 and loving it. It's my first Topping amplifier since the early TP60 many years ago. Hoping it's a cheaper, more robust version of the PA5. Sounds great and no sign of clipping driving my Tannoy V12s, EQd to play down to 37Hz. And even when playing way louder than I need.

 

[Purité Audio]

A lot depends on what amp, old high end is all over the place, from very clean (Bryston) to very distorted. But if it works for you, you don't have to change. And if you want to stay in class AB, the Benchmark ABH2 is class AB and one of the best measuring amplifiers arround, as clean as the best class D and way above our treshold for noise to be hearable. Bryston (also class AB) is also neutral enough to be invisible.

But at this level the class of the amp does not matter anymore, they all sound the same. The difference is in the efficiency of using power and size/price. Class D is way more efficient with power and in general smaller and cheaper, with much less heat dispensation.

Hybrid rather than traditional AB.
Keith

 

[OldTimer]

Ahem. Class D certainly doesn't necessarily give better sound. Also, disconnecting the pre/power sections of most integrated amps won't reduce their power consumption by much. You will most likely actually be using more power by adding an additional amplifier. Class D, or otherwise.

From what I can make out, the extra efficiency of Class D is usually only at higher power outputs too. Most amplifier power losses at normal levels, are usually down to the power supply used.

They are certainly usually smaller and lighter.

Just bought a Topping Mini 300 for £105 and loving it. It's my first Topping amplifier since the early TP60 many years ago. Hoping it's a cheaper, more robust version of the PA5. Sounds great and no sign of clipping driving my Tannoy V12s, EQd to play down to 37Hz. Even when playing way louder than I need.

what class A/B amp cost $100? how does it sound?

As long as no speakers connected to speakers terminal of the class A/B amp, there won’t be any power produced by the amp. That’s why speakers can destroy amp, not the other way around.

 

[DonH56]

As long as no speakers connected to speakers terminal of the class A/B amp, there won’t be any power produced by the amp. That’s why speakers can destroy amp, not the other way around.

Obviously there is no power delivered to the (non-existent) speakers, but the amplifier itself still dissipates power, due to bias current in output and driving stages. A class A amplifier still dissipates full power at idle with no speaker connected, whilst a class AB or B amplifier dissipates less (perhaps much less) due to smaller bias (idle) current in the output stage. Class D usually dissipates less idle power but the output stage is still switching, and control and driving stages still present, so there is still some dissipation with no speaker connected.

A bad amp can destroy speakers just as bad speakers can destroy amplifiers.

 

[OldTimer]

Obviously there is no power delivered to the (non-existent) speakers, but the amplifier itself still dissipates power, due to bias current in output and driving stages. A class A amplifier still dissipates full power at idle with no speaker connected, whilst a class AB or B amplifier dissipates less (perhaps much less) due to smaller bias (idle) current in the output stage. Class D usually dissipates less idle power but the output stage is still switching, and control and driving stages still present, so there is still some dissipation with no speaker connected.

A bad amp can destroy speakers just as bad speakers can destroy amplifiers.

For the last 3 decades, I already damaged 2 amps using same speakers. That’s what I mean speakers can destroy amp. Until now still using the same speakers with new amp.
Yamaha 20 years, Onkyo 10 years, now the amp is Fosi Audio V3. I usually play music very loud.

 

[Waxx]

Hybrid rather than traditional AB.
Keith

No it's not. It has a SMPS and rail voltage regulation, that is true but the amplifier circuit is class AB, and the psu system does not change that. It's not a traditional class AB with linear psu altough. And even those today have mostly a switchnig voltage regulation behind them.

 

[xlinknz]

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.

As mentioned I plan to connect a (Fiio K13 R2R) DAC to my pre amp which I read somewhere is class A (but the specs don't say that) which in turn connects to a matching 185w class A/B Power amp (the spec says the first several watts are class A)

I do know if the DAC is class A/B or D. I may also try the DAC connected directly to the Power Amp too just to see if I can hear any different

A lot depends on what amp, old high end is all over the place, from very clean (Bryston) to very distorted. But if it works for you, you don't have to change. And if you want to stay in class AB, the Benchmark ABH2 is class AB and one of the best measuring amplifiers arround, as clean as the best class D and way above our treshold for noise to be hearable. Bryston (also class AB) is also neutral enough to be invisible.

But at this level the class of the amp does not matter anymore, they all sound the same. The difference is in the efficiency of using power and size/price. Class D is way more efficient with power and in general smaller and cheaper, with much less heat dispensation.

Thank you for the link to the review of the Benchmark ABH2. I found it hard to compare to what I have but my (12kg) 40 year old class AB power amp has the following specifications 185w at 8 ohms, frequency response: -3db at 3Hz and 70Khz, hum and noise: at least 100db below full output, 20Hz to 20KHz unweighted, Distortion: inaudible, THD 0.03% or less, dynamic range: 110 db+ (and a bunch of other specs like slew rate, input impedance, input sensitivity, load impedance etc)

 

[Sal1950]

We’re living in the modern era where electricity consumption must be reduced, save the planet, climate change, etc, etc.

Yea right, all the while they're pushing us to ditch our modern high horsepower, fuel efficient gas burners.
Ill pass.

 

[melomane13]

PS (from earlier today) Not to be redundant, but I still wanna know the SI units for bass slam.

Watt !

 

[mhardy6647]

What ho!

I mean, Watt, Ho!

 

[Mnyb]

As mentioned I plan to connect a (Fiio K13 R2R) DAC to my pre amp which I read somewhere is class A (but the specs don't say that) which in turn connects to a matching 185w class A/B Power amp (the spec says the first several watts are class A)

I do know if the DAC is class A/B or D. I may also try the DAC connected directly to the Power Amp too just to see if I can hear any different



Thank you for the link to the review of the Benchmark ABH2. I found it hard to compare to what I have but my (12kg) 40 year old class AB power amp has the following specifications 185w at 8 ohms, frequency response: -3db at 3Hz and 70Khz, hum and noise: at least 100db below full output, 20Hz to 20KHz unweighted, Distortion: inaudible, THD 0.03% or less, dynamic range: 110 db+ (and a bunch of other specs like slew rate, input impedance, input sensitivity, load impedance etc)

If the power amp holds up to its original spec and has no problem, why replace it ? Maybe some service and it’s like new again if it’s starting to show issues after all those years ? It’s probably good enough ( meaning can drive speakers and has inaudible distortion and low noise )

So an option is a full service of your old amp , it might cost some $
If service cost starts to approach half the price of a new amp I would start to look for a new amp ?
But, if it has nostalgic value or is a collectible classic maybe it’s worthwhile to keep it going.

 

[Mnyb]

As mentioned I plan to connect a (Fiio K13 R2R) DAC to my pre amp which I read somewhere is class A (but the specs don't say that) which in turn connects to a matching 185w class A/B Power amp (the spec says the first several watts are class A)

I do know if the DAC is class A/B or D. I may also try the DAC connected directly to the Power Amp too just to see if I can hear any different



Thank you for the link to the review of the Benchmark ABH2. I found it hard to compare to what I have but my (12kg) 40 year old class AB power amp has the following specifications 185w at 8 ohms, frequency response: -3db at 3Hz and 70Khz, hum and noise: at least 100db below full output, 20Hz to 20KHz unweighted, Distortion: inaudible, THD 0.03% or less, dynamic range: 110 db+ (and a bunch of other specs like slew rate, input impedance, input sensitivity, load impedance etc)

The AHB2 is 100 watt , but you need more complete figures and measurements to compare in different impedance etc .

 

[xlinknz]

@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

 

[MaxwellsEq]

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

It's worth noting that most designs of Class A/B amplifiers are Class A up to a certain point. It all depends on the bias point. It's often possible to increase the level at which a Class A/B amplifier remains Class A through increasing the bias point, but that increases standing current which can cause overheating of the PSU and output stage. Large heatsinks are heavy and costly to ship and amplifiers are often engineered to a price-point.