John Curl's Blowtorch preamplifier part II - Page 3110 - diyAudio
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Old 8th December 2012, 03:42 AM   #31091
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You forgot cassette tape on your list.......
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Old 8th December 2012, 03:43 AM   #31092
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Quote:
Originally Posted by hitsware View Post
All of them exhibit usually undefined artefacts.
One of my best experiments:

Take any driver .......
In a quiet room lay it on the table in front
of you.
Drive it to just less than xmax @ ~ 10Hz
Listen carefully ..........
But ... have you tried doing that with the driver dead cold, and then compared that to the same unit after it's been installed in a carcase and driven hard for an hour or so with real music material, removed immediately and laid on the table again ...?

Frank
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Old 8th December 2012, 03:46 AM   #31093
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Originally Posted by Kindhornman View Post
You forgot cassette tape on your list.......
Because I was only talking about decent sources Steven That one's neither decent nor technically decent.
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Old 8th December 2012, 03:53 AM   #31094
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I left off the smiley face, it was a joke......
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Old 8th December 2012, 03:56 AM   #31095
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You could have faked a troll by interpreting 'tape' as 'cassette tape' rather as jcx interpreted my word 'decent'
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Old 8th December 2012, 03:58 AM   #31096
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... one of the cheap speakers in my system actually suffers from this when cold, at one stage I was fooling around a bit with the MATT track for assessing speakers and this made it obvious. The interesting thing is that driving the speaker hard effectively "lubricates" the problem area, you can hear this distortion steadily disappearing as the suspension or whatever warms up.
Frank, if it's a small speaker, get a pack of Cotton Wool from the chemist and try wedging a lump behind the cone and the chassis. Try not to move the cone forward or backward.

It's not a permanent solution cos the Cotton Wool eventually falls off.

If you play a sine wave while pressing gently on the cone surround, you can work out which way you need to nudge the cone.

On a big speaker, turning the unit round often works. What happens is that heat/humidity allows the cone/coil assembly to creep and tilt.

I know all this cos that's how I get the computer speakers I rescued from the tip to work.
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Old 8th December 2012, 04:02 AM   #31097
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Quote:
Originally Posted by jcx View Post
both vinyl and tape have clearly audible defects in addition to the numbers
Not disputing that for a moment. Current digital implementations have clearly audible defects IME too even though standardized numbers don't as yet exist for them. But I have no doubt they'll come in due course.
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Old 8th December 2012, 04:11 AM   #31098
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Don't you have to pick a decent source first? What's it to be - vinyl, tape or DAC or all of the above?
One of the most important facets of the test is that the subject picks the music and the source.

If JC, was doing the test, he uses his own CDs, vinyl, SACD etc. And he MUST be happy with the player; .. not a problem if the test is conducted at chez Curl.

But if his nominated golden pinnae wants cassettes, presumably this august person has a good cassette player he could lend us. Alas, all of mine are dead even if the termites haven't eaten them.

Quote:
Indeed - the first error they make is calling it, and treating it as, a 'test' when listening is purely for pleasure.
Abra, this is another important facet; that the subject 'enjoy' at least one presentation.

We ensure this by letting the subject listen to his preferred system while he can see what it is first so he is happy it is functioning correctly.

There is no doubt in my mind that Blind Tests are stressful. IMHO, this is the MOST important criticism of most Blind Tests. I spent nearly 2 decades working on this problem with some success.

It's only when you manage this that you have any chance of finding the true golden pinnae. If you are lucky enough to find them, be prepared to be amazed at what some people can pick out.

Last edited by kgrlee; 8th December 2012 at 04:26 AM.
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Old 8th December 2012, 04:13 AM   #31099
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OK, sounds a tad more promising than the usual tests I guess that could be because you're not (as in the case normally) expecting a null result?
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Old 8th December 2012, 04:36 AM   #31100
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OK, sounds a tad more promising than the usual tests I guess that could be because you're not (as in the case normally) expecting a null result?
Is anyone seriously interested in yet another NULL test result? At best, it would rate a single line in a Stereophile editorial. Certainly not worth an AES paper from the Dynamic Duo.

But if some people can reliably distinguish between Blowtorch and an evil 4558 device, this would be NEWS. It would answer Jay's Question 1.

Only if the answer to this is YES, can we answer his Question 2 Which one sounds better?
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