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Old 3rd January 2014, 07:05 AM   #11301
fas42 is offline fas42  Australia
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Like most people, I've heard other systems where everything is in alignment in that particular instance, for the specific recording. But, the aim is for a setup to always be in that groove, every time you decide to play something - the ideal is for all the parameters that make that happen to be fully known, and under your control at all times. I'm steadily getting closer to having that be - not perfectly by a long shot, very much still a learning exercise, but well worth the journey so far.

At the moment I'm exploring getting a high power amp to run, in sim, at sub-ppm distortion at all powers, into impedances of 2 ohms or so ...
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Old 3rd January 2014, 07:10 AM   #11302
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You surprise me Frank, I never had you down as a sub-ppm THD-chaser, particularly not in sims.....
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Old 3rd January 2014, 07:49 AM   #11303
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Originally Posted by fas42 View Post
dvv has already given the answer, 70W/8R working correctly is 100% room filling sound - and a chip amp working correctly delivers those power levels ... QED ...

dvv, you spoken fondly of the Karan often ... so in what specific area do you feel it comes off 2nd best? You mention the AR speakers testing it - this implies that current delivery exposes a slight weakness ...

Edit: even the Karan's spec's 'give it away' - the power rating drops very significantly with double the load ...
I've never measured this because it doesn't apply to me, but I have a nagging feeling that the Karan, fabulous as it may be, does like to pick and choose speakers it will do best with.

This is because with AR94s its sound is a truly shade different than with my other two pairs of speakers, both of which are nominally 8 Ohms. I'm not even 100% sure I'm not imagining it, but if so, I must have an uncanny ability to imagine something which then comes off the same each and every time. It's just a shade, but after so many years, I hear it. Most people don't, not after a 30 minute session, or some such.

Thus far, the literally only amp which changes 0% with any speaker I own is the HK Citation 24, which is why I am so taken with it. So far, it appears literally bullet proof sound wise, in conjuction with its team mate, Citation 21 preamp. Originally, I was after the bigger model of the premp, but have in the meanwhile discovered that the two are exactly the same, onl the bigger model has a different signal switching setup and more fascilities - this means zilch to me, as I honestly don't need the added extra.
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Old 3rd January 2014, 07:53 AM   #11304
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Originally Posted by Charles Darwin View Post
I'm not producing excessive bass, I just used my bass amp as an example since my speakers are 4way active.
Since I moved house and had to place the speakers in the corners I dialled down the bass amp by about 8dB to get a flat response (+-2dB 20-20 000Hz) at my listening position.
The treble as well as everything else remains smooth, articulated and clean all the way into completely stupid levels. You only realise how loud it can get when you have to scream and shout to communicate.
I believe this completely. A snare drum will draw prodigious power levels from the amp just to stay in tune with the rest, so if you're going a bit louder than usually, 50W or more is no wonder.

And if you happen to have a rather large room, and your bass driver is not all that efficient ...
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Old 3rd January 2014, 07:53 AM   #11305
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You surprise me Frank, I never had you down as a sub-ppm THD-chaser, particularly not in sims.....
At the moment it's purely an exercise, to understand precisely what factors contribute to optimum technical performance, and what elements subtract, and to what degree. At the moment this performance is achieved in fairyland sim world, of near perfect power supplies, perfect grounding, nil extra parasitics - it will an interesting process, adding in more and more real world imperfections, and seeing if desirable levels of behaviour can still be extracted from the circuit ...
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Last edited by fas42; 3rd January 2014 at 07:56 AM.
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Old 3rd January 2014, 08:55 AM   #11306
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Originally Posted by fas42 View Post
At the moment it's purely an exercise, to understand precisely what factors contribute to optimum technical performance, and what elements subtract, and to what degree. At the moment this performance is achieved in fairyland sim world, of near perfect power supplies, perfect grounding, nil extra parasitics - it will an interesting process, adding in more and more real world imperfections, and seeing if desirable levels of behaviour can still be extracted from the circuit ...
"Fairyland sim world".

My experience is such that my sim is sometimes even wildly conservative. If it says 300 kHz, you can bet your bottom dollar the circuit will do at least 360 kHz. If it says THD is say 0.05%, you can bet it will be more something like 0.04% or less.

In the last 5 years, it has never failed me once, the actual model will perform as it says it will, only a bit better than it says it will. Its older versions, back to 2001, were exactly the same.

I will readily agree that the fact that I use 20+ years of experience PCB artwork designers has something to do with it - I am good, but they are better, so I get them to do the artwork. Their work is more compact and has less spurious capacitance than I'd get, to be sure. I try to never underestimate anyone's expertise, and I never assume friendly favors, I prefer to honestly pay for honest work. Why not, I don't work for free either as a general rule, though I'm not above friendly favors for individuals I deem as good people. That definition covers a surprisingly large number of people from this form, for example (not that many need favors).

Frank, I believe in the wide open loop bandwidth approach. I've stopped discussing this matter with others a long time ago, ever since I became aware that most audio electronics I have encountered and think of as good sounding use this approach. Obviously, it's hardly an automatic process, simply using this approach guarantees nothing but in my view a better chance of getting it right.

Much like yourself, I assume that to get it right, one needs very good power supplies. It's like our own heart, and one can't ask a man with a cranky heart (poor PSU) to run a marathon (go loud without changing its voicing). I am sometimes criticized for being a PSU glutton, but I see nothing wrong in dimensioning my PSU to the highest demands I have from the amp, plus a safety margin.

If your output stage can deal with nasty loads and not run out of breath, I feel most of your problems will never happen.

My only issue with chip amps is twofold, and I must stress I have little experience with them: they typically require what I see as a lot of global NFB (a most arguable point), and they are not very good at delivering high currents. My AR94 speakers, a nasty load with lower efficency of 87 dB/2.83V/1m, say so.

The only chip amp I was pleased with is the now long gone LM 391-100 (I think?), which was in fact a driver chip which required outside discrete driver and output tranistors, obviously because I could drop in things like MJ21193/21194, and more than one pair, too.
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Old 3rd January 2014, 09:18 AM   #11307
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"Fairyland" in that insufficient modelling has been done, that it is necessary to add in, as conventional Spice elements, devices that model more closely all aspects of the environment - the closer the Spice circuit is to the real world, the less the subtle things will bite you.

Hefty supplies are good, but I part ways on FB philosophy - I'm with Putzeys, either don't do global feedback at all, or use lots and lots of it; a halfway house is a poor compromise, IMO. Where chip amps can falter is that the PSRRs are not good enough, so very stiff, stable power supplies are necessary to get the best from them - I wouldn't try and drive very current hungry speakers with them - or only do so with heavy paralleling of units.
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Old 3rd January 2014, 09:51 AM   #11308
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Originally Posted by dvv View Post
I agree with this, Pavel, but with some reservation.

I have come across a few speakers, admittedly not many, but all were mid to high price point which simply denied any attempt to create a 3D sound image. They were driven with high quality amplification which managed that with other speakers without any particular problem except with a few. Also other amps fared the same, did well in other cases but failed here.
I agree, sometimes the design flaws in the speaker design do not allow for good imaging.
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Old 3rd January 2014, 10:16 AM   #11309
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Originally Posted by a.wayne View Post
What amp ( name) are we talking ...?
MC2 Audio. Two from their now discontinued MC series and one from the T series.
The audio circuitry is the same for all of them, they differ in the protection circuitry only.
For the super tweeter I use an Omniphonics/BeyerDynamic which is also a BJT amp but with my advancing age (50 later this year) I hear less and less from this one as it only kicks in at 15kHz.
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Old 3rd January 2014, 12:43 PM   #11310
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Originally Posted by a.wayne View Post
What about chip amps
Does half a chip amp count ?

(the Karan looks like one, two of them tied in bridged mode to reach the power level)
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