Impossible to answer with any precision, one would have to know how all the amps on the market are made.
However, in terms of concept, I think it's safe to say that Harman/Kardon, who emplyed Otala for several years in the late 70ies, is still closely adhering to his concepts of wide open loop bandwidth and low global NFB.
For example, my 6550 integrated amp from December 1993, and my wife's newer 680 integrated amps from 1999, both have less than 20 dB of global NFB (17 dB for the 6550, 12 dB for the 680), and my Citation 24 power amp (12 dB), are some of the typical examples. Despite low global NFB factors, they still have responses out to around 240 kHz.
If you look at it all from the aspect of paying more attention to details, I think one could say most amps made today are more or less influenced. For example, his stipulating of a large voltage slew rate started a genuine slew rate war among the Japanese manufacturers, mainly between Kenwood and Sansui, who bent over backwards to have as large slew rates as possible in the second half of the 70ies. Some companies, such as say Spectral, have taken his basics and evolved them a long way, if memory serves they had power amps going over 1 MHz, with slew rates of like 1,000 V/uS.
Thank you, that entire post is complete news to me, most likely since I've spent most of my life in portable audio.
You may have missed my controversial posts in the other thread, but I found another theory for high slew rate, let me find the link
http://www.positive-feedback.com/Issue66/dsd.htm
I find their theory really quite relevant, but only in listening / experimenting with a DAC I have.
My DAC uses the video op-amp AD828 in LPF, I replaced it with various "normal" slew-rate / settling time IC's and the sound changed vividly.
This is really too vivid for expectation effect.
Naturally it could be something else as well which I'm not aware of.
You may have missed my controversial posts in the other thread, but I found another theory for high slew rate, let me find the link
http://www.positive-feedback.com/Issue66/dsd.htm
I find their theory really quite relevant, but only in listening / experimenting with a DAC I have.
My DAC uses the video op-amp AD828 in LPF, I replaced it with various "normal" slew-rate / settling time IC's and the sound changed vividly.
This is really too vivid for expectation effect.
Naturally it could be something else as well which I'm not aware of.
Last edited:
AFAIK, there is still no clear cut agreement on the voltage slew rate of power amps.
Some (e.g. Nationa Semiconductor Radio Data Book) feel that as long as the amp's overall voltage slew rate (input to output) equals 0.5 V/uS per peak output volt, you'll have no trouble with that. Nominally 100W/8 Ohms is 40 Vpeak, so with 20 V/uS they feel you're all right.
Others prefer to double that to 1 V/uS per every peak volt. John Curl and I feel this should be 100 V/uS simply because it's relatively easy to achieve, and more will never hurt. This assumes a full power bandwidth of around 300 kHz for the above amps, and, given the speeds of current BJT output devices, not to even mention MOSFETs and IGBTs, really shouldn't present too much of a problem.
Still others, say reVox and Sony, use twin specs. Internally, which means with unlimited bandwidth, they have something like 200 or 300 V/uS, but limit this with an input filter down to 80-120 V/uS, reasoning that there's nothing for a power amp to do at say 300 kHz.
There are sure to be yet more theories on this.
Some (e.g. Nationa Semiconductor Radio Data Book) feel that as long as the amp's overall voltage slew rate (input to output) equals 0.5 V/uS per peak output volt, you'll have no trouble with that. Nominally 100W/8 Ohms is 40 Vpeak, so with 20 V/uS they feel you're all right.
Others prefer to double that to 1 V/uS per every peak volt. John Curl and I feel this should be 100 V/uS simply because it's relatively easy to achieve, and more will never hurt. This assumes a full power bandwidth of around 300 kHz for the above amps, and, given the speeds of current BJT output devices, not to even mention MOSFETs and IGBTs, really shouldn't present too much of a problem.
Still others, say reVox and Sony, use twin specs. Internally, which means with unlimited bandwidth, they have something like 200 or 300 V/uS, but limit this with an input filter down to 80-120 V/uS, reasoning that there's nothing for a power amp to do at say 300 kHz.
There are sure to be yet more theories on this.
Not clear on this - changed the sound how, for the better, or for the worse)?
Theoretically, and judging by the views on this forum, we should know how to make a perfect amp by now. Yet, so few are even worth remembering, and then mostly by their astronomical prices.
Technicher Rundschau, Switzerland, 1969:
The difference between theory and practice
THEORY is when everyone knows how it should work, but it doesn't.
PRACTICE is when nobody has any idea of how and why, but it works just great.
Technicher Rundschau, Switzerland, 1969:
The difference between theory and practice
THEORY is when everyone knows how it should work, but it doesn't.
PRACTICE is when nobody has any idea of how and why, but it works just great.
Actually, the "answer" is a perfect system. The amplifier is just a part, in the same way a transistor is just a part of an amplifier - there is no point in having a 'perfect' amplifier - to continue the analogy, a 'perfect' transistor is a meaningless concept when talked about in the context of audio sound, it's whether it's used intelligently within the whole, being the amplifier, that counts ...
Interesting find ... now the thread where there was much PRaTishness has been closed, , I went on a hunt for threads where general audio behaviour was also discussed, and found this gem of a post, http://www.diyaudio.com/forums/multi-way/120101-problem-hi-fidelity.html#post1466205.
What I'm all about is completely eliminating that moment of "awfulness" - that's the behaviour which infests most of what occurs at audio shows, etc - you must be able to go from the "real thing", to reproduction without that reaction ...
, I went on a hunt for threads where general audio behaviour was also discussed, and found this gem of a post, http://www.diyaudio.com/forums/multi-way/120101-problem-hi-fidelity.html#post1466205.What I'm all about is completely eliminating that moment of "awfulness" - that's the behaviour which infests most of what occurs at audio shows, etc - you must be able to go from the "real thing", to reproduction without that reaction ...
The moment of "awfulness" occurs because all the subtle things that are very wrong with normal reproduction strike one on first exposure - it seems as if whole chunks of the elements that characterise natural sounds are not there, or are completely askew - it's just wrong, wrong, wrong. As Lynn implies, you must be able to stand back, apart from what you're listening to, and always be conscious of that "awfulness", if it's there - because that's what you have to 'fix', everything else is much less important ...
Last edited:
From the ridiculous to the sublime, nice find Frank
Its always encouraging to me to read posts from people who listen.
I'm on a roll, Richard ... I was triggered by a post on another thread to check out out the "notorious" Yamaha NS10 monitor, and found this, The Yamaha NS10 Story. Again, some real gems of info and sharp understanding within, including this bit:
...
... I was triggered by a post on another thread to check out out the "notorious" Yamaha NS10 monitor, and found this, The Yamaha NS10 Story. Again, some real gems of info and sharp understanding within, including this bit:Every time I see people thrash on about FR, and bass end performance I just
...
Ah I'm just (in the past day) embarked on a quest to extend the LF bandwidth of my system after just a very short trial with a much larger unit. There's more addictive sound to come, not sure what the neighbours'll think though....
<edit> I hasten to point out that the LF amps for this task will have supply capacitance measured in the 100s of F. Just because with supercaps, I can
<edit> I hasten to point out that the LF amps for this task will have supply capacitance measured in the 100s of F. Just because with supercaps, I can
Last edited:
I really wonder about that at times - the Yamaha keyboard I'm playing with at the moment has very nice samples of grand piano bass notes, and reproduced via the twiddly inbuilt amps and speakers does a remarkably good job of conveying the "weight" of those notes; note though, only 76 keys - if the higher harmonics are nicely done it seems to me that the brain "fills in the gaps" pretty well ...
I'm on a roll, Richard
Every time I see people thrash on about FR, and bass end performance I just
This is what I call "neutral".
No speaker is perfect, but to me, some are clearly better balanced tonally than others.
No speaker, in my view, can ever be fairly judged by reducing this judgement to one or two things it does well and perhaps poorly; in my view, one should look and listen to them as a whole. Ultimately, as the user, what do I care how it was done, with what slope of crossovers, with which drivers, etc, all I care is how well does its balance sit with my hearing.
I could now quote the specs of my own speakers, which were developed very much along studio monitor lines, but I believe it's not just this or that good spec, but how it was all out together or not that matters.
In fact, my key crtirion is to have the speakers disappear as an obvious factor, meaning that I don't want to listen to two boxes, I want the sound to be there and not come from obvious boxes. Whether this will happen or not also depends on the quality of the electronics and of course the source; if it was poorly recorded and/or produced, it will never sound good no matter what.
So, I spent like 20 years collecting what I feel are excellent recordings so I have something reliable to judge with. This includes many types of music, from symphony orchestras to folk and pop because, as I see it, a truly good speaker should not discriminate, if it's truly good it must be good with everything. Damn speakers good for heavy rock but poor with melodic music, or vice versa.
Once I nailed that down and got such speakers, certainly not perfect but way above the avreage even for its price class, I set about trying them out with electronics from various sources, much of it borrowed for a week or two. This eanbles me to create a short list of items it really comes to its own with. The amplification came first, I acquired those items it was best with (in my view). This was followed by a similar process of acquring a tuner and a CD player. My Sony TC-K808 ES does well in general, but I don't really use it much as a source any more, I keep it just because I love it and because I refuse to be without a tape recording machine. I'm kinda used to having one, had one since I was a kid of 11, since 1964, or 50 years even.
And while I'm always on the lookout, I must say I am not a regular upgrader. My still perfectly functional Yamaha CDX 993 CD player was retired after 11 years of faithful service. And this was done only after the new NAD C 565 BEE proved its worth, which it did, to my surprise, with flying colours.
As a result of all that, today I have a system which will sound better than many systems costing a lot more than mine does. I believe it to be better balanced overall than most. I support that claim by the simple fact that it will show up any deficiencies in the recording ruthlessly, but on the plus side, if it's a good 'un, you will hear that as well. What you also will hear is the perhaps some recording you thought to be mediocre is in fact much better than that, but you will need to review your own system.
That said, I am dying to hear it when driven by the Otala/Lohstroh amp, which I was stupid enough to sell way back, and which I now have to do all over again. Some may say that since acoustic memory reliably lasts about 15 minutes only, after which we remember our impressions of the sound and not the sound itself, but to them I say that even if that is true, my impression memories have thus turned out to be damn good so far. Haven't retired anything that I remember as good from 30 years ago which did not more or less justify that conclusion even today.
As you can see, I haven't invented anything new, nor am I any hitherto unseen talent - it simply takes a lot of patience, a lot of time and some muscle, because you will need to lug around many kilos/pounds of gear from there and back while researching.
- Status
- Not open for further replies.