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Old 1st December 2012, 10:23 AM   #7721
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The Quad 405 would hardly be described as a high slew rate amplifier . It's rather special use of feed-forward and feedback was said to make it imume to problems caused by the output filtering of CD players to the extent some removed the filters . It was said the Quad wasn't in the least bit troubled if doing so . I know Quad did use a far bit of bandwidth limiting , does anyone here believe feed forward would eliminate some slewing problems ? Some argue around that whilst not saying it categorically .
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Old 1st December 2012, 12:17 PM   #7722
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We measured the Quad at 35V/us.
However, the most interesting point made here (to me), is the mention of Keith Johnson, and his design philosophy. Just yesterday, I told my new tech (19 years old) that if there is someone I fear will beat me in the audio design race, it is Keith Johnson. He is DRIVEN, like I am, to make the best audio possible. Most either do it to make a living, or just for fun. I have known Keith (distantly) for more than 40 years. He is VERY competitive with me, a little too much for comfort, sometimes.
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Old 1st December 2012, 01:01 PM   #7723
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The Lifelong Quest For Musical Realism: Spectral Audio's Rick Fryer & Keith Johnson Talk With Robert Harley

what's more interesting is that they seem to avoid sending review units to magazines, probably to avoid the scrutiny of the AP2 judge
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Old 1st December 2012, 01:06 PM   #7724
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I don't think that Keith is afraid of a component review, but it would probably not get him any further sales, and MIGHT cause harm, especially if you get a reviewer who, for some reason, takes a dislike for the product. Charles Hansen is like that with TAS, at the moment.
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Old 1st December 2012, 01:11 PM   #7725
a.wayne is offline a.wayne  United States
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TAS doesn't measure , making their reviews irrelevant to me , i do like the pics ...

Send it to JA ....!!

Keith Johnson is serious business and i do favor the sonics of the Spectral amplifiers i have heard ...
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Old 1st December 2012, 02:18 PM   #7726
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Quote:
Originally Posted by john curl View Post
but it would probably not get him any further sales, and MIGHT cause harm, especially if you get a reviewer who, for some reason, takes a dislike for the product.
I was thinking just that.

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Originally Posted by john curl View Post
Charles Hansen is like that with TAS, at the moment.
interesting, that's why I don't take reviews too seriously.
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Last edited by mr_push_pull; 1st December 2012 at 02:22 PM.
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Old 1st December 2012, 03:39 PM   #7727
bcarso is offline bcarso  United States
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Originally Posted by john curl View Post
I don't think that Keith is afraid of a component review, but it would probably not get him any further sales, and MIGHT cause harm, especially if you get a reviewer who, for some reason, takes a dislike for the product. Charles Hansen is like that with TAS, at the moment.
Spectral's systems approach flies in the face of a lot of audiophiles who want to play with mixing and matching, and generates resentment. I know a few who are quite negative about Keith and Spectral as a result, although even they have to acknowledge that he's made great recordings.

It is nice, though, to see Keith having been otherwise recognized, and presumably well-off after the sale of Pacific Microsonics to Microsoft. He was quite paranoid about his ideas being stolen back when I met him, through an acquaintance, circa 1979. I may have even put a bug in his ear then about settling time, or when I discussed it he may have merely been coy. I hasten to add that my application of it, of the settling behavior in general rather than just the speed/accuracy, to audio, was purely speculative then --- I wasn't doing audio other than incidentally. I made the distinction between data acquisition apps where one just had to be sure of the signal just before and during digitization, and what I presumed was true of audio, where the details of "getting there" were also of importance, in the sense that we may hear them.

Brad
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Old 1st December 2012, 04:08 PM   #7728
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you have no idea how fascinating this is to me.
if there is any audio brand I'd buy before listening it's Spectral. IDK, maybe some subliminal marketing techniques are having an effect on me but...
talking about fetishism LOL
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Old 1st December 2012, 06:21 PM   #7729
dvv is offline dvv  Serbia
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funny you should mention Keith Johnson, I found about Spectral only recently. haven't listened to their amps but my gut tells me there must be something special about them.
Yeah - their astronomical price. Just kidding, although their prices are, shall we say, steep?

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concerning settling time it would make all the sense in the world. but there's one thing that negates that (again I have to agree with Mr. Curl wrt that aspect): oversampling filters in most DACs seem to do way more harm with their pre- and post-ringing. some filter types minimize those artifacts but still you can't eliminate them completely. my DAC is based on the WM8742 and it has user-selectable filters (5 of them). I was curious to look at the output of the DAC on a scope with square waves and none of the 5 filters looked nice in this respect. yes, I know, what one actually sees there is a band-limited square wave that can't possibly look any other way once it's band-limited. but what should be noted is that (correct me if I'm wrong) I think settling time-related artifacts in an amp are generally much less severe.
Well, it's not like you HAVE to use them, you know. You can buy real time DACs, which use 8 parallel DACs and have no oversampling and no digital brickwall filters. I won one, not at all very expensive, but sounds way better than most CD players I have heard.
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Old 1st December 2012, 06:44 PM   #7730
dvv is offline dvv  Serbia
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Originally Posted by john curl View Post
We measured the Quad at 35V/us.
However, the most interesting point made here (to me), is the mention of Keith Johnson, and his design philosophy. Just yesterday, I told my new tech (19 years old) that if there is someone I fear will beat me in the audio design race, it is Keith Johnson. He is DRIVEN, like I am, to make the best audio possible. Most either do it to make a living, or just for fun. I have known Keith (distantly) for more than 40 years. He is VERY competitive with me, a little too much for comfort, sometimes.
Well, if I am anything to go by, I have heard one of yours and one of his, both power amps, and by chance, both driven from the same source, at the time a darn expensive Luxman preamp, I forget the model designation. I know I got a headache when I heard the price.

Frankly John, I'd be hard pushed to declare a winner. I think those were two takes on the same theme, each with its strengths and small shortcomings, at least the way I heard them in that particular system (not mine, but one I do know rather well).

I didn't have to choose, so I was spared the soul stretching making of a choice between two products I both liked.

My point is, I don't think it's about either of you being better than the other, you are simply two men with a personally clear cut take on what you want, and you go for it. I find this to be of crucial value, I've seen and heard far too many designs with which it was not at all clear what the designer actually wanted. Indecisive, so to speak.

You know what I mean - some sound subdued, others sound bold and forthcoming, some sound like they don't give a hoot about music, others are almost begging for more, some try not to offend, other try to sound full of energy and forthcoming, etc. It's that somewhat vague feeling you get in your gut when listening critically (meaning only listening and doing nothing else besides except sipping good coffee and puffing a good cigar), one which you can't put into simple words because true quality products can NEVER be described in a few words.

So, I agree that Keith Johnson is in your league and is therefore true competition, but I don't think you need to worry just yet. On the other hand, aren't James Bongiorno (Ampzilla 2000, unfortunately haven't even seen it) and Dan d'Agostino also your true competition as well? Can you name just one field of human economic activity where there is no competition?

I have never met in person any of these folks, but I have corresponded with James Bongiorno for some time a few years back, and I can tell you that just like you, he is a man with a very strong opinion and a clear cut outlook on things audio - which, just like with you, includes some looks at some of the "new fangled" ideas of today. Heck, I even got a via-Internet interview from James, something that not many have managed to do, as far as I know.

I have to say this - he has NEVER ONCE left me without a complete and timely answer to any question I had. Why should he? He knows that I will never know what he knows about the subject, by the time I get to his level, he'll be light years ahead of me. Of course, out of respect, I tried very hard not to ask anything regarding his current models, or things which need a book to be explained. But I am grateful for his time and goodwill.
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