Burmester 218 - Reviewed amp buzzes

[Doodski]

They are minimising the losses and providing for much greater continuous current, better linearity etc.

But all those devices need bias current, which means a more capable driver stage, more idle losses, more expense, etc.

I think the manufacturers, on the whole, do a good job. It's pretty hard to destroy a set of outputs even with a full power short in a modern amplifier with decent protection.

There was a period in the early 80s where a lot of commercial (and DIY) high power designs sailed a bit too close to the wind in SOAR. But speakers were less reactive, more efficient and of a generally higher nominal impedance than they are in 2024.

The Class Ds render most of this moot as they have such incredibly low RDS(on) and consequent device losses are minimal.

The bias requirement as you say are another expensive add-on for the circuitry to work well. Thanks for the refresher. The newest class D from Hypex does seem to have leaped ahead in design and specs so that it is near a Purify in power output linearity and mechanical design too. With each iteration the class D is improving. I wonder how far class D will go in the effort to switch people over to class D and take over market share from class A/AB and as we see now class B too. The power output wars have begun.

 

[restorer-john]

The bias requirement as you say are another expensive add-on for the circuitry to work well. Thanks for the refresher. The newest class D from Hypex does seem to have leaped ahead in design and specs so that it is near a Purify in power output linearity and mechanical design too. With each iteration the class D is improving. I wonder how far class D will go in the effort to switch people over to class D and take over market share from class A/AB and as we see now class B too. The power output wars have begun.

Class D has already won the consumer electronics amplification war.

It's in every flatscreen television, every bluetooth loudspeaker, every mobile phone, pretty much every modern OEM car audio system, they even run the audio amplification in self serve checkouts at the supermarket.

Most new professional sound reinforcement gear is now Class D. So that's bands, DJs, nightclubs, bars, concerts. I'm all for it and I'll bet the roadies are happier (less weight).

The only area it is meeting stiff opposition is the high end of home audio. And even the medium end, where tradition still wins in some respects. Just as tubes are still around and turntables, RTRs and other obsolete technology, it will be a long time, if ever, before Class D amplifiers are fully accepted.

Look at Yamaha. They built a few high quality Class Ds before quietly scrapping the idea and going back to what their customers wanted.
Sony did it back in 1978, ran the model for about 5-6 years and unceremoniously killed it until they tried again in the early 2000s with their S-Master amplification. Killed that too.

 

[Doodski]

Class D has already won the consumer electronics amplification war.

It's in every flatscreen television, every bluetooth loudspeaker, every mobile phone, pretty much every modern OEM car audio system, they even run the audio amplification in self serve checkouts at the supermarket.

Most new professional sound reinforcement gear is now Class D. So that's bands, DJs, nightclubs, bars, concerts. I'm all for it and I'll bet the roadies are happier (less weight).

The only area it is meeting stiff opposition is the high end of home audio. And even the medium end, where tradition still wins in some respects. Just as tubes are still around and turntables, RTRs and other obsolete technology, it will be a long time, if ever, before Class D amplifiers are fully accepted.

Look at Yamaha. They built a few high quality Class Ds before quietly scrapping the idea and going back to what their customers wanted.
Sony did it back in 1978, ran the model for about 5-6 years and unceremoniously killed it until they tried again in the early 2000s with their S-Master amplification. Killed that too.

I think once the general population of home audio amp seekers understand a little more about class D operation/efficiency that they will be accepted for high end home audio. No telling how long this will require but the sooner the makers of class D get to educating the people the faster their class D product will be a leading contender. People need to know how they are more efficient and space saving in order to accept the small size and decreased weight.

 

[restorer-john]

I think once the general population of home audio amp seekers understand a little more about class D operation/efficiency that they will be accepted for high end home audio. No telling how long this will require but the sooner the makers of class D get to educating the people the faster their class D product will be a leading contender. People need to know how they are more efficient and space saving in order to accept the small size and decreased weight.

I will never recommend any Class D amplification made by any manufacturer who goes out of their way to prevent their customers repairing or being able to obtain spare parts and crucial documentation (schematics). Amplifiers die and need to be fixed.

I don't care who they think they are or how important they think their IP is. It's disgusting.

Did Sony lock up their IP with the world's first Compact Disc player? Nope. They provided comprehensive service manuals to every Sony approved repair facility before the players were even in the stores.

 

[Doodski]

I will never recommend any Class D amplification made by any manufacturer who goes out of their way to prevent their customers repairing or being able to obtain spare parts and crucial documentation (schematics). Amplifiers die and need to be fixed.

I don't care who they think they are or how important they think their IP is. It's disgusting.

Did Sony lock up their IP with the world's first Compact Disc player? Nope. They provided comprehensive service manuals to every Sony approved repair facility before the players were even in the stores.

Good point. Without a schematic and PCB layout servicing them will be a severe drag and they will most likely end up in landfill..

 

[AudioJester]

Good point. Without a schematic and PCB layout servicing them will be a severe drag and they will most likely end up in landfill..

Yeah, not good. Like smart phpnes, laptops etc. Way too much waste

 

[John Atkinson]

Not sure what is going on with @John Atkinson and his dBW numbers...

DBW is decibels with reference to one Watt. Since when was dBW only a reference to 2.83V@8R? That makes no sense.

His 4R and 2R dBW numbers in the review are incorrect in my opinion.

Technically you are correct. But since the early 1980s, first in Hi-Fi News then in Stereophile, I decided to modify the formal definition of dBW. Adding a -3dB correction factor every time the load impedance halved would indicate the quality of an amplifier's power supply. An amp that, on this basis, delivered 20dBW into 8, 4, and 2 ohms would be clearly superior to one that managed 20, 17, and 14dBW, respectively. This would be an easy paradigm for non-technical readers to understand.

John Atkinson
Technical Editor, Stereophile