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John Curl's Blowtorch preamplifier
John Curl's Blowtorch preamplifier
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Old 27th May 2008, 03:02 PM   #5601
john curl is offline john curl  United States
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SY must be right, he has the PhD in physics. From now on, audio transformers are PERFECT, without any tradeoffs, (except cost and size) and everyone should use them, whether they need them or not.
Now, can we move on?
"Condemnation without Examination is Prejudice"
Old 27th May 2008, 03:12 PM   #5602
macka is offline macka
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You missed the point and appear somewhat rattled and insecure.

Having a superior attitude is not an endearing quality that most well balanced people find attractive. Although it is not uncommon with technical people. I hope you don't speak to you clients like that. Its certainly not a measure of success.

Actually my standard of excellence is right up there John.

I own mostly recent model Pass Labs equipment and I am looking at acquiring an Ayre CX-7 player have having sold my Lavry DA-10 to a friend. What is just as important to me is the person behind the brand.

Parasound never really did a lot for me I am sorry.

Old 27th May 2008, 03:19 PM   #5603
john curl is offline john curl  United States
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That's OK, Macka. I just get A reviews to help Parasound make a living. Of course, I kind of like my 'Blowtorch' but I doubt that you will ever see or hear one, and it doesn't have any audio transformers, so nobody else will be interested, in future.
I am just a semi-retired old engineer who has tried to help others with audio design.
It is true that I waste my time for the most part trying to do this. They can just read a book. Why don't you recommend something? Let's compare books!
"Condemnation without Examination is Prejudice"
Old 27th May 2008, 03:35 PM   #5604
gainphile is offline gainphile  Australia
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Originally posted by macka

How many books have you written on audio engineering?

What has this got to do with anything

It's great enough that we have someone with John's calibre in our forums.
Old 27th May 2008, 04:32 PM   #5605
PMA is offline PMA  Europe
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John Curl's Blowtorch preamplifier
Please let's stay with circuit design and topologies, no need to go personal.
Old 27th May 2008, 05:50 PM   #5606
syn08 is offline syn08  Canada
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Originally posted by janneman
... and for completeness, the drive circuit itself:

Jan Didden
Exactly the same topology as in my ~1990 Amber 5500, with about -110dB residual (at 1KHz). The Amber 5500 uses a canadian Hammond transformer, shielded in a octal socket tube like enclosure, and 5534 opamps. Amber Electro Design was eventually purchased by AP, so guess who originally designed this circuit :-)
Old 27th May 2008, 06:09 PM   #5607
Variac is offline Variac  Costa Rica
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John Curl's Blowtorch preamplifier
without any tradeoffs, (except cost and size)
I doubt that anyone here wants to use transformers in everything whether they need them or not- except maybe SE BUT it seems disengenuous (sp) to argue that their biggest failings are size and cost after emphasizing that the Blowtorch and similar are made with no regard to size and cost....
"The geek shall inherit the earth"
2017 Burning Amp is November 12 in S.F. Thread here on diyAudio:
Old 27th May 2008, 06:16 PM   #5608
Nelson Pass is offline Nelson Pass  United States
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John Curl's Blowtorch preamplifier
Originally posted by john curl
I met Nelson Pass in San Francisco about 1977. The first thing that he said to me was something like 'let's drink' which is wonderful input to a heavy drinker, but in the end, unlike some other designers, such as Jon Iverson, he found my behaviour wanting.
Well, John, that's not the case at all. I am a friendly and non-
judgmental sort of guy, but I don't get out much. And then there
was the occasion when somebody played "Let's you and him fight".
Old 27th May 2008, 06:20 PM   #5609
Steve Eddy is offline Steve Eddy  United States
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Ok, I just received the copy of John's old datasheet for the Jensen JE-16-A from SY.

Because the distortion curves in this datasheet weren't nearly as good as the same curves published in Jensen's current datasheets, John leaped to conclusions and accused Jensen of being less than honest with their measurements. That Deane Jensen was an honest man and that the company had since "buried" this sort of information over the years and I was a dupe, a fool, and a shill for them.

First, the test conditions for the old JE-16-A and the new JT-16-A are virtually identical. 150 ohm source impedance and 6.2k load impedance. The only difference is that the RC damping network for the JE was 3.6k in series with 820pF and 4.5k in series with 620pF for the JT.

The overall distortion for the JE is significantly higher and the hysteresis "bump" is far more pronounced compared to the JT.

At first I thought the JE had used 50% nickel cores instead of the 80% nickel core that the JT uses. But the JE had the same rated input level as the JT.

So I called Jensen this morning. Bill wasn't available so I spoke to David who has been there since 1980. He said that the JE had in fact used an 80% nickel core. The improvement in performance of the JT over the old JE was due to two things.

Primarily the availability of better core material, and secondarily their precision CNC winding machines which allow them to wind more efficiently and get more turns on the bobbin (which probably explains the slight change in the damping network).

So there you have it. Nothing has been "buried" and Jensen is just as honest in their measurement data as they have always been. All they've done is improve the quality of their product over the years.

Given the false accusations that John has made, I think he owes nothing less than an apology.

Old 27th May 2008, 06:24 PM   #5610
john curl is offline john curl  United States
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Thank you Steve. It is interesting that Dick Sequerra told me this morning that they might have improved their core a little and perhaps added more windings. Then we went on to talk about metglas transformers that are more interesting to us, in particular.
"Condemnation without Examination is Prejudice"

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