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Trevor Wilson[_3_] Trevor Wilson[_3_] is offline
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Default High End Class D

On 17/07/2020 7:34 pm, Howard Stone wrote:
On Thursday, July 16, 2020 at 10:52:37 PM UTC+1, Peter Wieck wrote:
John:

I see that, once again, you are nibbling around the edges of the "Brute Force Amp" concept. I kinda-sorta figured you would get there eventually. And, coincidentally, you missed out on a Harman-Kardon Citation 19 that I tripped over at a yard sale - my son-in-law laid claim to it the moment he saw it on the bench.

But, getting to your question directly: If you choose to move to Class D amplification do go for the most recent designs and do pay attention to how the signal is filtered to the speakers. Put as simply as possible: "Good Audio Quality" class D was only a concept as recently as 4 years ago. Today, distortions (all components) of less than 0.05% are routine. A few years ago, damping in Class D was very nearly non-existent. Today, it is approximately that of a 30-50 watt tube amp. Low, but definitely there.

A few things:
a) Class D amps do not like being run at/near rated output for long periods. They do not 'blow up' but they do get quite warm.
b) Based on the nature of sound and the decibel scale, if you are going to go to Class D, go BIG - Given that the next step after a 20 watt amp is a 200 watt amp, start there. Really. Do not try to gang them up, start with the highest power module you can afford and work from there (The 686 in Neurochrome, or any of several other brands:

https://www.parts-express.com/icepow...-500w--326-200

https://www.diyclassd.com/diy-amplifier-modules/

https://www.dhgate.com/wholesale/cla...rs+module.html

As you can see, prices are all over the place and largely depend on how user-friendly and/or complete the various parts will be on arrival. But the overall audio quality will be largely indistinguishable **!IF!** you purchase an audio-purposed module initially vs. something for sound reinforcement.

My 'audio-snob' neighbor down the block built a Class D amp recently in a COVID-related fit of boredom to compare to his 300B-based flea-powered SET tube amp - he used the 150-watt mono modules, with separate power-supplies. I am not sure he is going back to tubes.

Repeat: GO BIG, or not at all - no need for extremes (1,100 watts, for example), but getting those transients is worth something.

Peter Wieck
Melrose Park, PA


That's really helpful Peter, thanks.

How serviceable are these amps. I mean, in 10 years, and Neurochrome no longer exists, and my expensive amp has a fault, is it going to be impossible to service because the parts (the chips?) are no longer available?


**In general, Class D amps are unservicable. Or at least they will be.
And here's the irony: Around 6 ~ 8 years ago, I was considering a
different occupation (apart from servicing audio equipment). I was in my
late 50s and found that the preponderance of surface mount components
and, in many cases, the complete lack of schematics for some products (I
had an NAD on the bench, that used an ICEPower module, for which no
service data was available, thus requiring an entire module
replacement). In the last few years, I've seen these trends accelerate.
Given the cost of Class D implementation is rapidly falling in cost, I
predict several things:

* Class D amps will not be worth repairing. Even expensive ones.
* High end manufacturers (like Rowland) that have embraced Class D will
disappear.
* High end companies like ARC will likely survive, because sufficient
listeners will continue buying linear amplification.

The upshot for me is that, despite being at the end of my working life
(I'm 67 years old next month), I have never been busier. Most of the
guys in my business have switched to more profitable pursuits, or
retired. I get repair jobs in from all over the country (Australia).

I reckon that Class D amplification will sweep all before it. EXCEPT for
niche stuff. And there will likely be demand for that for a very long
time. Hell, I've started repairing cassette decks again! YIKES!

Postscript: Ya gotta love hipsters. As a group, they have pushed the
revival of old stuff along very nicely. I tips me hat to them.

--
Trevor Wilson
www.rageaudio.com.au

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