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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 9th October 2019, 03:08 PM   #29521
scottjoplin is offline scottjoplin  Wales
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Interesting, 'has' is present tense, but then I combined it with studied.... we need a cunning linguist.
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Old 9th October 2019, 03:22 PM   #29522
vacuphile is offline vacuphile  Netherlands
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'He has studied' can refer to a deceased person. 'He studies' can not.
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Old 9th October 2019, 03:26 PM   #29523
GOR3 is offline GOR3  United States
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It annoys me that your English is better than mine.
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Old 9th October 2019, 03:43 PM   #29524
scottjoplin is offline scottjoplin  Wales
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Actually...the 'has' seems redundant
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Old 9th October 2019, 04:55 PM   #29525
john curl is offline john curl  United States
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I am not a promoter of distortion. I am a promoter of best sound quality, especially from electronics, that is my specialty. I NEVER add distortion, BUT I have found that open loop designs often sound better, and that is the case with this Audible Illusions line amp that I worked around (I did not design it) that uses an open loop triode design. About 30 years ago, I actually attempted to measure the higher order distortion in this preamp. In those days I did not have a spectrum analyzer, but I added a GR wave analyzer to the distortion output of a Sound Technology THD analyzer. There was some distortion, but it was pretty low, probably below normal levels that would be directly audible, but the higher order distortion that I was looking for was virtually not there. I was surprised, but at the same time, impressed. This is a heavily 'massaged' design adjusted to perfection, over the years. Later, I lived with it for a few weeks and compared it to the CTC Blowtorch. It was pretty darn good, maybe better in some ways than the Blowtorch. In fact, the Blowtorch design concept actually followed this design philosophy: No loop feedback, simple (as much as practical) through-path, as linear a transfer function as possible, local feedback (single resistor near input) is OK, probably, and nothing much above 3rd harmonic.
The open loop triode design has the advantage of only having significant 2'nd harmonic (still pretty low), compared to the Blowtorch that has mostly 3'rd harmonic, as 3'rd harmonic is not easily reduced to zero. However, the triode requires a single (very high quality) output coupling cap, and the Blowtorch is direct coupled throughout.
I can never make a jfet as linear as a quality triode, but I can make it balanced more easily, and sometimes this is an advantage.
Now, AI now wants balanced out too, so this is why this new design challenge has come up. AI is trying to include its 'proven' design in this new line amp, but then there has to be an inverting circuit in front to make it work. The solution is not so simple, except for those of you who do not design at this level.
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Last edited by john curl; 9th October 2019 at 04:59 PM.
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Old 9th October 2019, 05:10 PM   #29526
Evenharmonics is offline Evenharmonics  United States
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Quote:
Originally Posted by john curl View Post
I am not a promoter of distortion. I am a promoter of best sound quality, especially from electronics, that is my specialty.
Loudspeakers are electronics too. Speaking of which, how does frequency response at your listening spot look?
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Old 9th October 2019, 05:36 PM   #29527
john curl is offline john curl  United States
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In my opinion, frequency response is secondary to audio quality. In fact, I doubt that a really flat frequency response at my ear is possible. A few decades ago, everybody had a 3'd octave equalizer, and so did I. I never used it. Today, I use no added EQ, but I do try to make my components as flat in response as possible. The biggest exception is the Sequerra Met 7 speakers that both Scott Wurcer and I use often, and they are optimized for TIME arrival response, and have relatively lousy frequency flatness, YET they can sound wonderful! Why?
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Old 9th October 2019, 05:48 PM   #29528
scottjoplin is offline scottjoplin  Wales
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I EQ my OB subs but not as much as "you are supposed to" and I cut a modal peak. I've tried HF boost to compensate for hearing loss but prefer the sound without. I don't measure or EQ my Jordans but listen nearfield. I make no adjustments between recordings (other than volume), but let my ear/brain combo make any necessary modification
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Old 9th October 2019, 05:58 PM   #29529
Evenharmonics is offline Evenharmonics  United States
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Originally Posted by john curl View Post
In my opinion, frequency response is secondary to audio quality.
But it is one of those things that can be shared online.

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In fact, I doubt that a really flat frequency response at my ear is possible. A few decades ago, everybody had a 3'd octave equalizer, and so did I. I never used it. Today, I use no added EQ, but I do try to make my components as flat in response as possible. The biggest exception is the Sequerra Met 7 speakers that both Scott Wurcer and I use often, and they are optimized for TIME arrival response, and have relatively lousy frequency flatness, YET they can sound wonderful! Why?
Would you mind sharing the image of your FR?
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Old 9th October 2019, 11:18 PM   #29530
johnego is offline johnego  Indonesia
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Originally Posted by Evenharmonics View Post
Would you mind sharing the image of your FR?
For you to mock around? Hehe this is the internet where anyone can share information (one who knows and one who doesn't) but unfortunately ANYone also can decide which one is priceless and which one is worthless. Imho, he is sharing priceless info and you are asking for worthless one?
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