John Curl's Blowtorch preamplifier part II - Page 3639 - diyAudio
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Old 7th March 2013, 08:41 AM   #36381
gk7 is offline gk7
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The "1931" transformer mentioned is the Lundahl LL1931:
http://www.lundahl.se/pdf/1931.pdf

Not from the year 1931 of course.
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Old 7th March 2013, 09:04 AM   #36382
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Quote:
Originally Posted by Chris Hornbeck View Post
Looks to quadruple per octave, so 40dB/decade. 2.2% at -40dBu, 6.5% at -10dBu. Maybe 0.6% at -60dBu, using "typical" values.
OK, and (putting aside why anyone would care about 2 Hz distortion), what do you get at -100dBU, which is already considerably higher than worst-case for an MC cartridge? And how does this number compare to the modulated distortion in the audible range from the gross (1mm) stylus displacement?
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Old 7th March 2013, 10:45 AM   #36383
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Quote:
Originally Posted by gpapag View Post
One step further
You definitely need a set of Kopenhager hull-drafting templates

Quote:
Originally Posted by SY View Post
edit: For a more typical warp frequency, 0.3 Hz (once per revolution), we're now talking under a microvolt.
Anyone notice that this is also rather amusing ? (0.555 Hz)
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Old 7th March 2013, 10:53 AM   #36384
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Quote:
Originally Posted by john curl View Post
Let's look at a typical MC transformer:
Pretty impressive set of specs in my view. Any idea on the cost?
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Old 7th March 2013, 11:12 AM   #36385
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$250-€250

(the 347-axt is an oldy)
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Old 7th March 2013, 12:38 PM   #36386
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Quote:
Originally Posted by jacco vermeulen View Post
You definitely need a set of Kopenhager hull-drafting templates

LOL

George
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Old 7th March 2013, 01:12 PM   #36387
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Originally Posted by gk7 View Post
1 Hz distortion ? Why would it matter ?
Electrically at the levels sy gave, nothing.

I would be more concerned with the cantilever nonlinear modulus. The further off center the motion goes, the more the elastic is compressed. I would expect warp modulation of the resultant audio. (actually been there done that, some of the records I played in the disco were warped to about half an inch height off the platter, occasionally one was so warped it hit the cantilever, some of the 12 inch 45's the tonearm would lift off the record and were unplayable.

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Old 7th March 2013, 01:17 PM   #36388
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Originally Posted by RNMarsh View Post
Here is some data which helps put things into a proper context and perspective re. cable and interference rejection; data regarding electrostatic and magnetic -test freq is 100KHz: Note how grounding - as well as cable configuration - can affect the performance -

Attachment 334427

Attachment 334429


[data from my library -> Electromagnetic Interference and Compatibility VOL.3. EMI Control Methods and Techniques. By Don J.R.White and Assoc]

Thx-RNMarsh
Very nice, thank you.

What is missing is the relationship between two independent twisted wire pairs, such as line cords and balanced mike runs. If the twist pitch of one is an integer multiple of the other, near field coupling will occur. If the twist pitches are non integer related, there will be almost complete cancellation. This is how cat5e was designed. I used this to my advantage when I bundled a 125 foot line cord to a 125 foot balanced mike run AND a pair of 125 footunbalanced line out runs on one snake.

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Old 7th March 2013, 01:24 PM   #36389
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The problem for me is that I have to make the best possible design, and even the 'best' transformers have real problems. In fact, there are sonic tradeoffs between metglas and mumetal, and metglas wins for the midrange and mumetal wins for the bass. That's why I quit trying. Well I guess I could use 2 transformers in parallel with a crossover above 100Hz to the metglas one. Kind of expensive, even for me.
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Old 7th March 2013, 01:36 PM   #36390
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Quote:
Originally Posted by jneutron View Post
I would be more concerned with the cantilever nonlinear modulus. The further off center the motion goes, the more the elastic is compressed. I would expect warp modulation of the resultant audio.
This was exactly Scott's and my point- the transformer is the least of your worries.

I see, though, that John has now abandoned that particular handwave and moved on to another.
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