$300 "Krell killer" digital amp?

[dunkyboy]

Anyone here have any experience of the new wave of high-quality digital amps? There's a recent thread over at AVS Forum (can I mention this forum by name..?), http://www.avsforum.com/avs-vb/showthread.php?s=&threadi d=304368&highlight=krell+killer, (http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=304368&highlight=krell+ killer,) about how the $300 Panasonic XR-45 6-channel all-digital receiver sounds in the same sound quality league as the likes of Bryston, Classé, etc.



These claims sound outrageous, but the article in question seemed reasonable enough, and it seems there are a number of other amps using similar technology that are taking the States by storm (e.g. Carver ZR1000, and a Sony all-in-on DVD/SACD player + receiver).



So has anyone here had any experience with such things? What do you think? Is this truly a revolution in amplifier design and sound quality? Should we all be flogging our expensive amplifiers now while they're still worth something?



The Panasonic can be had from online retailers here in the UK for just over £300, so I'm seriously tempted to just by it and find out. If I sold my Yamaha processor, I could replace it with the Panny, and have a chance to compare it with the Classé power amp I'm getting in a couple of days. After reading some of the abovementioned threads/reviews, anyone else feel like doing some [relatively] inexpensive experimentation with brand new technology? Sounds like fun to me! Sadly, I'm extremely low on funds ATM......



If I do go for the Panny, I'll be sure to report back here with my findings!



Dunc

[Madge]

Don't know about $300 but for £2495 you can get an ESLab DX-S4 or whatever the new model is called - and that is a Krell killer.



As with any amp, if all you need to drive is an 8Ohm load, then the cheapies are fine. For real speakers you have to pay for a power supply, and even things like the TaCT M2150 can't drive low impedance loads that well.

There are two related technologies, Tripath Class-T, which uses a very high speed A-D then works out what the output transistors have to do magnify the signal and Equibit, which does much the same thing but uses digital inputs. Of the two, Tripath supposedly sounds better.

[dunkyboy]

I really like the idea of taking the digital out of my CD player and feeding it direcly into the amp, doing away with the preamp entirely, and only doing the DA after everything else is done. Sounds really neat and sensible to me, and means the only bit of analogue cabling is the speaker cable...



Dunc

[Uncle Eric]

Guys,

All sounds good and I've no doubt it's great value but I really doubt that a $300 dollar amp will be a so called Krell killer :(

[Slartibartfast]

I assume this is the same amp we were talking about in this (http://www.avtalk.co.uk/forum/index.php?t=msg&th=2558&rid=14&S=077c873fb45730111 8bee4e0bae13749&pl_view=&start=0#msg_26296) thread. In which case, the amp was reviewed in September's issue of HCC if you want an opinion on it. The specs have to be taken with a large pinch of salt. I don't think it would have much chance of driving my speaker set for example, so on that basis it is certainly no Krell killer.

[nicolasb]

So what exactly is a "digital amplifier"?

[dunkyboy]

Yeah, Charlie, I don't think anyone thinks it's likely to have the "drive anything" power of a Krell, but it just supposedly has the sound quality of a very high end amp.



And yes, some clever person please answer NicB's question, as I'm wondering the same thing m'self.



Dunc

[Madge]

So what exactly is a "digital amplifier"?


Ever seen one of those big finger foam hands you can buy at rock concerts? ;)~;-)~:wink:





<u>What?</u> :lol:

[Jase]

Digital Amplifier Info:



http://www.puredigitalaudio.org/digitalamplifiers/index.shtm l (http://www.puredigitalaudio.org/digitalamplifiers/index.shtml)

[dunkyboy]

Mudge, that was just .... wrong! :(



:lol:

[Madge]

Digital Amplifier Info:



http://www.puredigitalaudio.org/digitalamplifiers/index.shtm l (http://www.puredigitalaudio.org/digitalamplifiers/index.shtml)


Ahem, some major BS been flung around at that site. :(

Especially:

<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Quote:</td></tr><tr><td class="quote">
Digital amplifiers sound great. They have all the all the great attributes of the Vacuum Tube Amplifiers audiophiles love to listen to with un-beleivably low distortion at a bargain price. And a Pure Digital System sounds even better.


:P~:-P~:razz:

[Jase]

<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Jase wrote on Thu, 23 October 2003 15:16</td></tr><tr><td class="quote">
Digital Amplifier Info:



http://www.puredigitalaudio.org/digitalamplifiers/index.shtm l (http://www.puredigitalaudio.org/digitalamplifiers/index.shtml)


Ahem, some major BS been flung around at that site. :(

Especially:

<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Quote:</td></tr><tr><td class="quote">
Digital amplifiers sound great. They have all the all the great attributes of the Vacuum Tube Amplifiers audiophiles love to listen to with un-beleivably low distortion at a bargain price. And a Pure Digital System sounds even better.


:P~:-P~:razz:






LOL. I can't argue with that as I've not heard either system.

[nicolasb]

Okay, so we're basically talking about a DAC that outputs a speaker-level signal rather than line-level? Is that a fair summary?

[Madge]

Yes, the Equibit version is basically that, although it is a PWM DAC rather than PCM.

Tripath is a little more advanced in that it directly samples the analogue waveform and then uses a learning DSP to switch it's output on and off to create a magnified version of the original analogue signal.



Both are a fair bit more advanced than good old class D switch mode amps, thanks to the built in DSP power. They still have problems with ultra-sonic noise though.

[nicolasb]

Sounds like it would work well using active speakers with a digital cross-over, but I am less convinced of the advantages with passive speakers....

[Slartibartfast]

Yeah, Charlie, I don't think anyone thinks it's likely to have the &quot;drive anything&quot; power of a Krell, but it just supposedly has the sound quality of a very high end amp.




Duncan,



I don't really buy into that. To get the best out of an amplifier you are going to need some decent speakers. And the fact remains that most high-end speakers end up being pretty tough loads for amplifiers to drive. Budget speakers are compromises, and one of the critical factors is that they present a benign enough load that a budget amplifier can drive them. High-end speaker designs are not so constrained, and therefore typically require decent amplifiers with respectable power supplies to drive them properly. If you check the figures measured by HCC for the Panny, you will find it was pretty pitiful really. If it can't drive decent speakers to a reasonable level, then the sound 'quality' is academic. IMHO. ;)~;-)~:wink:

[dunkyboy]

What you say is very true, Charlie, but the fact remains that the primary proponent of the Panny was a speaker designer who makes [what I would consider] high-end speakers. For me, this is a very convincing person to be proclaiming the virtues of an amp - and he even goes so far as to offer the Panny in a bundle with his speakers, along with a Behringer digital EQ configured to drive his speakers actively, saying the resulting sound quality rivals his same speakers driven by much more expensive amplification (he specifically mentions Bryston, Classé and one or two others).



Now, if you made and sold high end speakers, particularly speakers that are difficult for your customers to audition before buying, would you even DREAM of bundling them with an amp that didn't perform VERY well with them? Surely that would be a Very Bad Idea.



Anyway, I'm not saying it IS great - I haven't heard the thing. :)~:-)~:smile: But it seems that no one else here has either. I'm still contemplating getting one as a replacement for my Yammy processor, but I'm really not in a very good way financially ATM, so it'll probably have to wait.



But surely it would be a worthwhile experiment for you more financially comfortable members. :)~:-)~:smile: I mean, if it's \*\*\*\*e, you can always just sell it on, or perhaps use it in a secondary system? The most you'd lose is about, what £150? Not a small amount, but in high-end hifi terms, 'tis but a pittance! The sort of money audiophiles spend on a pair of banana plugs. w)



In any case, I'm mostly wondering about the digital amplifier technology, and its potential, rather than the Panny XR-45 specifically. If the XR-45 even lives up to a small percentage of its hype, it bodes very well for pure digital amp technology in the long run. The Panny was designed by a large, mainstream consumer electronics company with a brief that (I imagine) prioritised slim size, low weight, low heat, and low price! If THAT'S anywhere NEAR as good as some people are saying, then what happens when a really good hifi company does their own version for 5 or 10 times the cost, without all the compromises? That's what I'm most curious about. :nod:



Dunc



(Edit - Look here: http://www.newformresearch.com/whats-newfr.htm, go to the 'Research Update August 2003' link.)

[Madge]

Those ES Labs are as close to perfect, other than exceptionally low load handling and ultrasonic noise as any amplifier gets. They are the proverbial piece of wire with gain that many search for. They also cost nearly £3000 and most of that is probably the power supply.

There is something to be said about buying things on weight. :thumbup:

[Slartibartfast]

Anyway, I'm not saying it IS great - I haven't heard the thing. :)~:-)~:smile: But it seems that no one else here has either. I'm still contemplating getting one as a replacement for my Yammy processor, but I'm really not in a very good way financially ATM, so it'll probably have to wait.



But surely it would be a worthwhile experiment for you more financially comfortable members. :)~:-)~:smile: I mean, if it's \*\*\*\*e, you can always just sell it on, or perhaps use it in a secondary system? The most you'd lose is about, what £150? Not a small amount, but in high-end hifi terms, 'tis but a pittance! The sort of money audiophiles spend on a pair of banana plugs. w)




Duncan,



Unfortunately, this particular audiophile is currently cash-strapped, having bought a Lynx 2 soundcard in the last month. :?~:-?~:???: Also, if things go according to plan this afternoon, cash is going to be in even shorter supply if I shell out for a Vel DD-18 and a couple of Gramma's! :o~:-o~:eek: :nod:



I've skimmed through the original AVS thread (there are only so many hours in the day - those guys can certainly spout words in abundance!) and your link to the original Newform Research article. Don't get me wrong, I am not disputing the potential for this technology. It is coming on in leaps and bounds and I don't doubt that these things will, if they haven't already, overtake purely analogue amplifiers. If something is released that is demonstrably better at a reasonable price, I will happily consign my Krells to the scrapheap. I just find the $300 Krell killer claim a bit too provocative. It would seem that a number of contributors to the AVS thread are confirmed Krell-haters anyway, so the opportunity for some Krell-bashing is probably too tempting for them.



Personally, I wish someone like HFN would get Paul Miller to do an objective test on the XR-45 in the same configuration as being talked about here (bi-amped stereo, rather than AV multi-channel) and give a fair appraisal of its real performance level. The HCC review gives some key specifications and observations on sound quality when used in an AV multi-channel context, a HFN review could explore its true audiophile potential. :)~:-)~:smile:

[avanzato]

You can build your own Digital amp using some ZAPpulse modules from http://www.lcaudio.dk



I was interested in the Harman Kardon DPR 1001 which is supposed to be digital from Disc to output but don't know if it ever got a UK release.

[Madge]

Sounds like it would work well using active speakers with a digital cross-over, but I am less convinced of the advantages with passive speakers....


A pair of Tripath reference boards, RB-TK2150-2 and RB-TK2350-2 are winging their way to me right now, for this very purpose. :thumbup:



When I've bodged together a suitably overengineered power supply and stuck them in a box, I'll report back on their SQ :nod:

[deckard]

Hardly a $300 Krell killer at £3k but did anyone else notice Yamaha's MX-D1 digital power amp (http://www.yamaha-audio.co.uk/homehifi/amplifiers/mx-d1/) at Bristol? It looked gorgeous but unfortunately wasn't demonstrated to my knowledge.

[Madge]

Well, the boards are about £180 each, and I'm anticipating not having to spend more than £300 on a ridiculously stiff power supply, including enclosure and all sorts of RFI screening, so no need for an expensive mains lead. The cost of adding a decent common-rode rejecting debalancer to give it XLR inputs is also reasonable, maybe another £60 to do it really well, using flat and wide Op-amps.



Still, over $300 but under £1000. Modifying the boards to take higher current rated MOSFETs is a simple enough job, total cost maybe another £100. A Krell level PSU + Current capability might take the cost over £1000, but this kind of power shouldn't be so cheap.



I could seriously get into this DIY audio lark :lol:

Of course, it might sound crap :roll:

[kwisatz haderach]

on US forums they state that quite a few of the digital amps will not drive difficult loads for example the original first post of this thread mentioned the panasonic model

several people have stated it cant drive speakers with a 4 ohm nominal impedance. The S master award wining sony digital amp is in quite a few cruddy all in one systems and is quite clearly poor (even though the all in ones get good reviews).It is a way of sticking a amp on one chip(even cheaper and more profit for the companys) krell beater im with jim royal on that one My ar*e :lol:

[Madge]

Paul/Usul ;)~;-)~:wink: ,

there are two issues involved here. One is the lack of current drive ability into low frequencies at low impedance loads. The other is the interaction between the inductors in the output stage and a low impedance tweeter. The crappy amps have both problems.



Thankfully the Tripath solution allows you to use any output MOSFETs you like, so you could theoretically build a 1 Ohm stable amp using their solution, by subsituting the already capable output devices with 100A rated designs and upping the power supply rating to compensate.

[kwisatz haderach]

your obviously quite right a well designed digital amp is and can be excellent.BUT the A.V. industry just loves the D word and people buy things just because they have Digital written on them.



Just look at the Argos catalogue to see Headphones ,composite cables etc with the D word on them (i just love listening to those 0and1 through my headphones :lol: ).

I am not a vinyl hugging ,cardigan wearing, Analogue only freak. :lol: but people often assume just because it has digital written on it it must be good.



Major manufacturers Sony,Panasonic etc are driving this Digital amp revolution Panasonic/Technics have a history of trying to get the amount of components down in a amp to make it cheaper Class AA anyone ? they went on and on how this was the best solution between a class A amp and a class B but every review said they were not that good only when they used better power supplies (R core Transformers and better Capacitors)and MosFet transistors did they start to sound better and get average reviews.



My opinion is that major Japanese companys are just trying to cut costs and are not taking a audiophille driven stance.



A well designed Digital amp is fantastic and i am looking forward to the future of these designs but as with many things all digital amps are not equal.



Just my opinion for what its worth ;)~;-)~:wink:

[lovegroova]

<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Quote:</td></tr><tr><td class="quote">
title=Slartibartfast wrote on Sat, 25 October 2003 10:25 If something is released that is demonstrably better at a reasonable price, I will happily consign my Krells to the scrapheap.


Charlie, I think I live quite near to you (I remember your location as previously given on AVForums) so please feel free to drop the Krells off at my house on your way to the scrapheap :lol:

[Madge]

Charlie,

just so I know what I'm shooting for, exactly which Krells would you be dropping off :lol:



BTW I think I can make the Tripaths stable into 1Ohm loads, N-channel MOSFETs with 1V/1A style ratings aren't too dificult to find, even up to 100V.



Ferrite bead inductors are a little harder to come by at that sort of rating :lol:

[Slartibartfast]

Charlie,

just so I know what I'm shooting for, exactly which Krells would you be dropping off :lol:



BTW I think I can make the Tripaths stable into 1Ohm loads, N-channel MOSFETs with 1V/1A style ratings aren't too dificult to find, even up to 100V.



Ferrite bead inductors are a little harder to come by at that sort of rating :lol:




OK, the Krell KSA-200S is 200W rms continuous per channel into 8 ohms, 400 into 4, 800 into 2 and 1.6kW into 1 ohm. Frequency response (-3dB) is from 0.1Hz to over 200kHz. :o~:-o~:eek:



Some people don't rate the S (sustained plateau bias) series Krells. They reckon they were a backward step from the earlier full-bias class A jobs. Personally I don't agree. The S series are 'nicer' sounding (less jackhammer!) with some systems. They won't suit all, and the FPB series or the earlier pure class A amps may work better in those systems, but it really annoys me when people write off the S series as not worth considering. They are still extremely good amps. Perhaps why you don't see them for sale very often. Totally bombproof! :thumbup:



The little KAV500/4 is rather more modest in its specs (mere 120W per channel into 8 ohms and 240 into 4) and it can't really compete with its big brother in absolute grunt but it's still a great little performer. :D~:-D~:grin:

[Madge]

Any idea how low the panel on the ML's drops in impedance terms? I know the Quad 63s hit 1.8 Ohms at one point.

[Slartibartfast]

As far as I know the ones with panel mid-range/tweeter behave like (physically) big capacitors so impedance drops as frequency increases. Precise values vary by model. The Prodigies are nominal 4 ohm dipping to 1 ohm at 20kHz. The Sequel II's are 6ohm dipping to around 2 and the Logos centre is 5ohm dipping to 2 IIRC. :nod:

[Madge]

So, realistically, one has to use either the Krell or some other voltage source type power supply with them all. The only saving grace is that this behaviour is due to a stepup transformer, so the panel actually behaves like a giant LC circuit.



In point of fact, a 4x drop in the input impedance of the circuit at high volumes make the output impedance of the Class-T circuit too close to that of the panel-transformer.

Therefore I don't believe it is possible to use any form of switch mode amplifier with electrostatics, unless you go down the path suggested by Tripath themselves, which is to use the transformer of the panel as the reconstruction filter :o~:-o~:eek: 8)~8-)~:cool:

[Slartibartfast]

Phew! lovegroova and/or Wiggenhall Depot will have to wait a bit longer! :lol:

[lovegroova]

Phew! lovegroova and/or Wiggenhall Depot will have to wait a bit longer! :lol:




Bum. That mean Acoustic Arts will be receiving even more of my hard earned.