John Curl's Blowtorch preamplifier part II - Page 509 - diyAudio
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Old 23rd July 2010, 09:18 AM   #5081
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Quote:
Originally Posted by abraxalito View Post
This is obviously false - I've read his 5th edition book and whilst he is excessively (IMO) strong on distortion he does cover other aspects of amplifier measurements - such as slew rate and noise just to give two examples.
What I was trying to convey is that he designs ONLY to satisfy criteria that he can measure with an electronic instrument. I know that he cares about noise etc, but the point is that he ignores ANYTHING that doesn't show up in measurement equipment.


Quote:



I agree, this is the primary weakness of his book. But then he gives no PCB layouts either - schematics can't be listened to. The second weakness of his book is citing Randi.
That certainly is a very big gap in a book on amplification. But if you never venture much beyond theorising, why worry about practicalities, like actually making the amp?

Quote:

I've designed and built a few amps on his principles since he first expounded on them in E&WW and have never suffered complete disappointment. So do you have any examples to offer where the disappointment can be laid at the feet of Mr. Self's principles, rather than say sheer incompetence?
Try this.

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The experimenters in this case may have been more or less incompetent, as well as misguided by Self, but numerous design decisions were made by reference to the words of the great Doug.

Actually, I suggest it would be far more enlightening if anyone can give us an example of an amplifier designed chiefly on Self principles that has actually convinced a critical audience of listeners.
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Old 23rd July 2010, 09:27 AM   #5082
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Originally Posted by Joshua_G View Post
[snip]Indeed, there is catch. I know that I can never follow blindly listening evaluations of others, since different people evaluate differently sound reproduction systems. Thus, I know in advance that I cannot take anything for granted before I'll hear it myself, on my own stereo setup. Yet, I will never spend my time and money to build an amp that all I know about it is that it measures well.[snip].
Joshua,

While I understand the wish to select your projects on some kind of trustworthy listening result, your statement above cannot be easily resolved.
You agree that anecdotal listening reports from individual listeners don't say anything about what you would like or not, yet you don't want to select your amp unless there is a listening report.

You can't escape your own conclusion: you must somehow use other parameters to select maybe a few projects, and listen for yourself, with the risk that it's not what you want. And while I agree that measurements don't tell you how an amp sounds, I DO know that an amp that measures well in a few significant areas at least doesn't add too much or subtract too much from the music. I would think that this would be a good starting point.

Inevitably, unless you go for a finished product in a shop that you can audition, there's always the gambling element in a diy project to the outcome. Actually, the fact that we are so subjective and open for influence does help in this case: selecting a project that gets rave reviews increases the likelyhood that you too will like it.

jd
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Last edited by jan.didden; 23rd July 2010 at 09:40 AM. Reason: revised wording more neutral
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Old 23rd July 2010, 09:38 AM   #5083
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Originally Posted by Rod Coleman View Post
[snip]Actually, I suggest it would be far more enlightening if anyone can give us an example of an amplifier designed chiefly on Self principles that has actually convinced a critical audience of listeners.
I don't have any type numbers but there's literally 1000's, maybe 10.000's of acclaimed amps out there designed by Mr. Self. They don't have his name on the faceplate, but he designed them nevertheless. People who's business depends on selling amps depend on Douglas to design them so that people buy them. Not a bad track record, despite what you think about him

jd
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Old 23rd July 2010, 10:06 AM   #5084
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Originally Posted by SY View Post
...................I will say unequivocally that NO ONE has ever demonstrated that they can hear the difference between two boxes of gain that have reasonably low distortion, adequate bandwidth, are not driven into overload, and have appropriate input and output impedances for a given application. To put a fine point on it, NO ONE has demonstrated that there is any audible difference between a Blowtorch and a cheap op-amp based linestage of competent design (the vast majority of commercial product).
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...................The Blowtorch is analogous to a Rolex- it is gorgeous, beautifully made and engineered, and a total luxury and status item. But a $19.95 Timex tells time just as well.
By the above statements, you are telling us that a "cheap op-amp based linestage of competent design" sounds ("tells the time") the same as a blowtorch (and other pricey but competently engineered preamp products like Pass, Ayre, Lyra, whatever...), at least that is how I understand it.

Well, then there are not much reasons
- to spend time and money developing and building diy line stages (maybe using even tubes), just to “being told the time” (NO ONE will demonstrate you anyway that your's will tell the time differently)
- to write countless posts in a long thread in an audio forum trying to illuminate a designer which has developed some of the finest gear (err, sorry, no this is an illusion, he's so good at marketing that it's all imagination) since the 70-ties, that all his work on line stages has been moot and that he could have used op-amps instead, to “tell the time” to the customers.

Isn't it?

My recommendation to all those who need the proof of a scientific DBT before buying or building something based on recommendations from JC and the likes:
- buy an Ipod (or similar).
- if applicable, stop spending hours on a thread trying to convert a bunch of stubborn DIYer’s and designers.
- if applicable, stop DIY’ing line stages.

With the time saved, you can
- load music on it with bitrates >256 kbit/s.
- attach the Ipod (or similar) directly to the (DIY?) power amp or (DIY?) active speakers.
- enjoy the music.
- feel good in the certainty that NO ONE will ever demonstrate (with an appropriate test method according to the highest DBT requirements) to you that he can hear a difference compared to a setup which uses an expensive CD Player and a high cost linestage.

Consultants are paid, but this one is for free.

Tino
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Old 23rd July 2010, 10:33 AM   #5085
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Originally Posted by janneman View Post
I don't have any type numbers but there's literally 1000's, maybe 10.000's of acclaimed amps out there designed by Mr. Self. They don't have his name on the faceplate, but he designed them nevertheless. People who's business depends on selling amps depend on Douglas to design them so that people buy them. Not a bad track record, despite what you think about him ;
jd
Jan, how do you know he designed them , if you don't even know the type numbers?
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Old 23rd July 2010, 10:51 AM   #5086
SY is offline SY  United States
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Quote:
Originally Posted by zinsula View Post
By the above statements, you are telling us that a "cheap op-amp based linestage of competent design" sounds ("tells the time") the same as a blowtorch (and other pricey but competently engineered preamp products like Pass, Ayre, Lyra, whatever...), at least that is how I understand it.
Not only am I telling you that, John has told you that- he has said again and again that he needs to peek in order to distinguish one from another. He cannot do it by ear alone.

Again, if you have ANY actual data showing that ANYONE can hear the difference between a Blowtorch (or Ayre or whatever luxury unit) and a cheap IC opamp based linestage without peeking, I'm eager to see it.

I've never heard an iPod. Does that play music uncompressed?

Appreciate your advice. I'll let the Rolex people know they can go home now.
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Old 23rd July 2010, 11:15 AM   #5087
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Originally Posted by SY View Post
.............Appreciate your advice. I'll let the Rolex people know they can go home now.
My advice was the other side around......or do you want John et al to leave the thread?


I don't know if Ipods can play uncompressed material, but I seem to recall(don't ask for refercences...) that there was an article that compressed music at high enough bitrate cannot be distinguished from uncompressed 16/44.1 in DBT's. Should do for most Non Rolex people.
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Old 23rd July 2010, 11:17 AM   #5088
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Originally Posted by zinsula View Post
I seem to recall(don't ask for refercences...) that there was an article that compressed music at high enough bitrate cannot be distinguished from uncompressed 16/44.1 in DBT's. Should do for most Non Rolex people.
Not correct. And I have personal knowledge there.
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Old 23rd July 2010, 11:23 AM   #5089
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Old 23rd July 2010, 11:24 AM   #5090
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Quote:
Originally Posted by Rod Coleman View Post
What I was trying to convey is that he designs ONLY to satisfy criteria that he can measure with an electronic instrument. I know that he cares about noise etc, but the point is that he ignores ANYTHING that doesn't show up in measurement equipment.
Given that we seem agreed that he's not too interested in listening, what other options are available to him? Its either meters or ears or some combination of the two - suggest some other way to do it as I can't see one at present. From memory he doesn't explore the whole gamut of what's available in measurements either - can't recall any results from intermod tests nor multitone tests that he's cited. Sure, he briefly discusses them but limits his treatment of design issues to the effect only on THD.


Quote:
That certainly is a very big gap in a book on amplification. But if you never venture much beyond theorising, why worry about practicalities, like actually making the amp?
Are you suggesting here that Self never ventures much beyond theorising? If so I'd say that since he's an established designer in the pro-audio field, your statement doesn't stick.

Quote:
Try this.
You linked to a particular post detailing errors on a board layout. Or did you mean to mean me to read the whole thread? If not, seems a tad churlish to lay board layout errors on Mr. Self.

Quote:
The experimenters in this case may have been more or less incompetent, as well as misguided by Self, but numerous design decisions were made by reference to the words of the great Doug.
Some examples of where Self misguides people would be helpful here - as I mentioned I've read his book and can only think of one technical error in it offhand, related to the fact that he doesn't listen. There are plenty of fallacies in reasoning in his diatribe against subjectivism but those don't count for now. So please elucidate.

Quote:
Actually, I suggest it would be far more enlightening if anyone can give us an example of an amplifier designed chiefly on Self principles that has actually convinced a critical audience of listeners.
Well I could offer one of my own designs which satisfied critical listeners in which I gladly employed the wisdom of Mr. Self. Its been out of production for well over a decade so I don't know if its very easy to find one to audition. But before I give details of it, I'd like to know what 'convince a critical audience' actually means in practice - do you mean passed a DBT for example?
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