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Offline Peter M  
#1 Posted : 03 May 2020 13:44:27(UTC)
Peter M


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Back in 2007, a very early edition of HFC carried an article on digital power amps and came to the conclusion that they were, at that time, distinctly inferior. Many years have now passed and I wonder if things have changed. Is there now such a thing as a digital power amp approaching Audio Excellence?
Peter M
Offline kengale  
#2 Posted : 03 May 2020 16:34:05(UTC)
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Originally Posted by: Peter M Go to Quoted Post
Back in 2007, a very early edition of HFC carried an article on digital power amps and came to the conclusion that they were, at that time, distinctly inferior. Many years have now passed and I wonder if things have changed. Is there now such a thing as a digital power amp approaching Audio Excellence?
Peter M

Well... you can certainly get power. One of the underwater setups I have worked with uses back-to-back 900mm (yes you've read that right) dome drivers driven by a single 60kW amplifier. Don't think you could do that with an all-analogue amplifier!
Offline Pete_w  
#3 Posted : 04 May 2020 14:59:09(UTC)
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Hi Peter

Originally Posted by: Peter M Go to Quoted Post
Back in 2007, a very early edition of HFC carried an article on digital power amps and came to the conclusion that they were, at that time, distinctly inferior. Many years have now passed and I wonder if things have changed. Is there now such a thing as a digital power amp approaching Audio Excellence?
Peter M


Compared to your current room-heater, perhaps not BigGrin

I've kind of followed this a bit as I used to have a pair of home-assembled "digital" amps. I use the quotes because they were amps with a switching output stage fed from an analogue input stage, that's an important differentiation as very few amps are (or were) digital throughout. I loved mine, despite their limitations; they were a bit rough'n'ready to say the least, but their ability to find the heart of musical timing was awesome.

Suspect your best bet is to find a company who are boxing-up Bruno Putzeys' Ncore/Hypex modules, they seem (in their more expensive incarnations) to have a rep for being the best bet around for top-end switching amps. And Putzeys is, after all, the man who once said to an interviewer something along the lines of "No, my amps don't sound good because they're Class D, they sound good despite being Class D". That's the spirit :-). Putzeys himself seems to have got himself a bit distracted by putting his amps into speakers (Kii Audio), unless any of our Danish readers knows whether he has a sister company building ready-to-use amps...?

There's also always the french lot, isn't there, Devialet, but on the (only 2 or 3, I think) occasions when I've heard them I've been distinctly underwhelmed. They may have improved, it was quite a while ago. I know some people love 'em, and we're all different, but having heard *your* system I think I know where you're coming from, and I'd suggest it's the more musical rather than hifi side of the great divide.

Best regards
Pete


Offline Peter M  
#4 Posted : 05 May 2020 07:55:29(UTC)
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Thank you Pete. You hit the nail on the head in your "room heater" remark, but it is worse than that. I am concerned by the way in which my Krell cooks equipment on the shelf above the amp. But I do not want to compromise on sound quality. Hence my wondering about the state of the art in class D.
I had a "Deviant" on dem a while ago, and although it is clearly an incredible lifestyle package, it set my teeth on edge.
I will keep on looking, perhaps for a cool-running conventional amp.
Peter M
Offline Pete_w  
#5 Posted : 05 May 2020 19:57:17(UTC)
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Hi Peter

I had the same problem when I got rid of my switching amps. I'd built furniture around them, I needed not-too-large and cool running, because there was almost no ventilation. It's not a crowded market sector.

I settled on a pair of Benchmark AHB-2 amps. When I bought them they were six grand for the pair, that now seems to have risen to 7. They've had mixed press reviews (Absolute Sound liked 'em, HFN/RR over here liked them (might have been Andrew Everard), 'CRITIC hated em). They're a stereo amp, but I run 2 of 'em bridged-mono, and with your speakers you probably will too :-).

I found - very disappointingly, and I wrote about it on here at the time - that they were incredibly sensitive to mains cables. And this is despite having a SMPS on board to drive them (they're a linear amp, but with a SMPS). Thin mains cables can make them sound like they have their feet mired in treacle, which I think is more or less what CRITIC said about them. Mine have got thick shielded cables into the back of the PS Audio Power Plant, and they're as fast and upbeat as you'd wish - no treacle at all.

I've only just seen this Absolute Sound Review but I think it pretty much covers my ground for me.

Cons? Well, there's the mains issue. I did complain, direct to the designer. Maybe he's tweaked it. The binding posts on mine are the most godawful things I've used. Fine if you're on bananas, but I'm biwired on spades and ...aaargh. I got there in the end. Basic problem is that it's a small box and the back panel is very cramped. They're balanced XLR input only, but that shouldn't be a problem. And they turn themselves off after 40 minutes of idle. But musically, for me, they deliver. Straight wire with gain :-)

Running a pair in bridged-mono, the claimed maximum output is something like 380W. I've got a pair of Martin Logan Prodigies hung on mine, which are probably about as evil as loads get, and I now know (thanks to my darling son winding the knob all the way to the right) that they remain calm and just sound "magisterial" when driven far louder than you could possibly tolerate. I was just delighted that nothing went bang!

I didn't try lots of other amps. The "good, small, cool" sector is not crowded. At the time, my alternatives seemed to be the Benchmarks, or to buy some of Bruno Putzeys' eval modules (google Purifi Audio) and put them into the same boxes that my old amps had inhabited. But the voltages didn't quite match so I'd have been having to commission some more "audio-grade" mains transformers from Antrim and they have a minimum order of 10 and, blah, I'm tired and I just wanted a turnkey solution....

If Lockdown ever ends I'll be happy to bring my amps over. Or there may be some more alternatives on the market by now...

Cheers
Pete

Offline Peter M  
#6 Posted : 06 May 2020 10:05:21(UTC)
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Thank you once again, Pete.
I measured the temperature of the shelf above my Krell and it is around 36 degrees C when the amp warms up. I have no idea of the total heat output of the Krell but I guess that it must be a few hundred watts or so. Anyway, my solution for the present is to leave that shelf empty. And that will have to do until funds allow otherwise, because meanwhile, I have purchased some other goodies. I blame MC!
Peter M




































Offline Martin Colloms  
#7 Posted : 06 May 2020 16:52:20(UTC)
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Originally Posted by: kengale Go to Quoted Post
Originally Posted by: Peter M Go to Quoted Post
Back in 2007, a very early edition of HFC carried an article on digital power amps and came to the conclusion that they were, at that time, distinctly inferior. Many years have now passed and I wonder if things have changed. Is there now such a thing as a digital power amp approaching Audio Excellence?
Peter M

Well... you can certainly get power. One of the underwater setups I have worked with uses back-to-back 900mm (yes you've read that right) dome drivers driven by a single 60kW amplifier. Don't think you could do that with an all-analogue amplifier!


there has been substantial improvement, viz the Excellence rating acccorded the Kii THREE active loudspeakers: all 'switch mode' supplies and amplification.

High powers are possible with keen pricing.
Martin.
Offline Pete_w  
#8 Posted : 08 May 2020 15:47:29(UTC)
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Originally Posted by: Peter M Go to Quoted Post

I blame MC!


I blame MC for everything. Particularly Alabama 3! BigGrin
Offline Martin Colloms  
#9 Posted : 09 May 2020 13:31:07(UTC)
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Originally Posted by: Pete_w Go to Quoted Post
Originally Posted by: Peter M Go to Quoted Post

I blame MC!


I blame MC for everything. Particularly Alabama 3! BigGrin


Why Alabama 3 ?

MC
Offline phil page  
#10 Posted : 09 May 2020 23:49:53(UTC)
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Yeah, I wondered that
Phil
Offline Pete_w  
#11 Posted : 10 May 2020 16:10:45(UTC)
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I think MC introduced it to PeterM. PM played it to me. And I was taking my poor son out for a walk the other day and found myself singing "U don't dans 2 tekno any more" to him. No-one deserves that!

(We do all realise I have my tongue in my cheek here, don't we? )
Offline Andrew Everard  
#12 Posted : 10 May 2020 22:12:09(UTC)
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Originally Posted by: Pete_w Go to Quoted Post
Putzeys himself seems to have got himself a bit distracted by putting his amps into speakers (Kii Audio), unless any of our Danish readers knows whether he has a sister company building ready-to-use amps...?


www.mola-mola.nl
Offline phil page  
#13 Posted : 11 May 2020 02:47:46(UTC)
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Fishy...
Phil
Offline Peter M  
#14 Posted : 11 May 2020 07:51:23(UTC)
Peter M


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But, “back to our muttons” as a french shepherd might not say, I have found that Krell kindly publish the heat output of their amps. Mine runs at over 300 watts at idle and over 1600 watts at maximum. I was a bit shocked.
Peter M
Offline Martin Colloms  
#15 Posted : 11 May 2020 11:34:13(UTC)
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From a very long time ago I have travelled a sonic road for audio systems which began with a search for broader frequency response, then greater flatness over frequency, then lower colouration, then sharper image focus.

Tagging along in retard was image depth, transient definition and dynamics, or lack of compression, even if these were considered dangerously subjective. Subjective rhythm assessment followed, to much industry consternation.

For decades Hi Fi News did not permit subjective characterisations of sound quality and I was determined to break out of this industry wide straightjacket.

Exercising my freedom of speech, at first this practice made me some enemies, and not least several threatened lawsuits.
As a tech boffin, listening was initially harder for me because you must learn to disconnect from the product technology and just enjoy the music.

You also must learn to ignore appearances, specification and price.

And the penny dropped. Many aspects of design, technology and specification did not correlate at all well with sound quality. And a new vocabulary was required for the growing field of subjective quality judgments.

And serious designers listen critically to their creations from an early developmental stage.Designers are judged not only on their technical expertise but also their judgment of sound quality.

Martin Colloms
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