John Curl's Blowtorch preamplifier

[kamskoma]

Didden interview

Tips!

Jan Didden has done a very nice interview with the audio engineer Erno Borbely a very interesting interview, you can go to Ernos site, the site also have a link to an american audio builder who is using Ernos products.


Kamskoma

 

[jacco vermeulen]

page 500.

Ah, prime time for strapping Mr Curl in a chair and tickle his feet till he starts talking VR3.
In the meantime, new-combers to the greatest show on earth can eyeball the official Scrapbook

(even after half a mill pages, Mr Curl hasn't yet commented why the structural rigidity of the amp case is part of the trick)

 

[Joshua_G]

(even after half a mill pages, Mr Curl hasn't yet commented why the structural rigidity of the amp case is part of the trick)

He did, early in this thread.

 

[forr]

Hi PMA?

Controlled crosstalk with good effect:

From
http://www.richardbrice.net/ppm.htm

"[...] So that, when two-loudspeakers reproduce a stereo image from a standard stereo CD for example, the high frequency components of each instrument or voice emanate from one place within the stereo image and the low-frequency components emanate from nearly - but not quite - the same place. The result, to use a visual analogy, is a slight smearing or blurring of the stereo image. [...]"

Here is the simple circuit Richard Brice proposed to cure this blurring effect. It was published in his book
http://www.amazon.fr/Multimedia-Virtual-Reality-Engineering-Richard/dp/0750629878

It is permanenly switched on in my sytem.

 

[jacco vermeulen]

early in this thread.

That it matters yes, not why : here

 

[Joshua_G]

That it matters yes, not why : here

From memory, JC refereed few times to the structure of the case.
One point is RFI shielding.
Second point is the air tight structure. Air flow may modulate the input JFETs.

 

[Andre Visser]

The do a simple IM test. 60 and 6000 Hz should show up any electronic problem. Nothing mysterious about it.

OK, so this will show whether there are detail lost, very mysterious.

Originally posted by SY
How did you verify that the first amp wasn't being run into overload? Did you have a scope on the output while you were listening? How did you verify that the listening tests were conducted at the same SPL? Did you have an SPL meter or calibrated spectrum analyzer running during the listening sessions?

Well for claimed 200W monoblocks at normal listening levels, I would not think that to be a problem, especially when the second amp was 160W. Are you listening to music, on other people's systems, with SPL meters and a calibrated spectrum analyzer connected?

Originally posted by SY
If you're seriously interested in correlating measurements to audible phenomena, it's not a terribly hard thing, nor does it require very exotic gear.

Yes' I've noticed a few correlating measurements, I guess some of them will be very controversial from a scientist's viewpoint. Then, unfortunately there are a few that I don't have a clue how to measure for, luckilly it is easy to do a listening test.

 

[jacco vermeulen]

structural rigidity

= different thingy

 

[Andre Visser]

Yes. Give me two amps and a multimeter and I'll tell you which one sounds the most spacious in a specific system, that isn't changed between swaps.
Jan Didden

The SPL matching theory, it is very overrated. A good system will sound good at any reasonable volume, a bad system will sound good only at one volume.

 

[Joshua_G]

The SPL matching theory, it is very overrated. A good system will sound good at any reasonable volume, a bad system will sound good only at one volume.

A bad system may sound bad at all levels …

 

[Andre Visser]

A bad system may sound bad at all levels …

Wrong, ever heard how good a bad system sound when the volume is turned down completely?

 

[Joshua_G]

Wrong, ever heard how good a bad system sound when the volume is turned down completely?

Okay, you got me here …

 

[fredex]

I want to believe 'nothing is impossible'.

It should be possible to back up your reports with other reports.

If you invited other skilled listeners to your home and they had a choice between two amps or two cables that you know sound different in one particular aspect such as sound stage focus, they should be able to confirm your reports.

The test can be sighted, but you should be absent while they are introduced to the equipment and whilst they swap and listen. They are only told that eg "one of these has a defocussed sound stage, just identify it."

 

[myhrrhleine]

Jacco, I agree with your logic and observation, but I bet Joshua doesn't even recognise there being anything at all odd about a 65 year old having more accurate hearing than most (or he will argue that his experience enables him to make better use of what he has left). His posts read as instant responses without self observation, that come out of him as attempts to ridicule those that post logical thought. A shame really because he may have useful things to contribute, but until he works out how to participtae he won't get most of us taking him seriously.

One of the things that well grounded engineers develop is a wide range bs detector, and I think that may be missing here.

Ever notice a blind person seems to hear things others don't?
It's not that their ears suddenly improve ten fold.
It's that they learn to notice the sounds that most of us don't.
So it it with some audiofiles.
They don't have better hearing, they've just learned to notice sounds others ignore.

 

[Joshua_G]

Ever notice a blind person seems to hear things others don't?
It's not that their ears suddenly improve ten fold.
It's that they learn to notice the sounds that most of us don't.
So it it with some audiofiles.
They don't have better hearing, they've just learned to notice sounds others ignore.

Indeed.
Also, it seems to me that the time I worked as a recording 'engineer' have its' effect on training my ears to note subtle nuances.

 

[Andre Visser]

It should be possible to back up your reports with other reports.....

That is a method I've used quite a lot, mostly I would not say anything and let a friend describe to me what he hear.

 

[Andre Visser]

They don't have better hearing, they've just learned to notice sounds others ignore.

Very true, I've seen a program on TV showing a few blind guys riding their bicycles, making clicking sounds with their tongue while listening to the echo's to avoid obstacles.

 

[fredex]

.............. If one would want to express sound stage width in terms of electrical signal properties, what would they be?
Has anybody here some info on that? Jan Didden

Only that one of the most spooky stereo imaging I've heard came from a Gretz cassette portable with detactable open back single drivers sitting each side of the mantle piece. Those Germans knew what they were doing...............my ears were real good then.

 

[jan.didden]

The SPL matching theory, it is very overrated. A good system will sound good at any reasonable volume, a bad system will sound good only at one volume.

The louder the system, the wider the soundstage and the more spacious it sounds. Spaciousness depends on the audibility of the reflections in the sound which are of much less amplitude. Increase the level, and more and more reflections rise above the audibility threshold. Simple.

Jan Didden

 

[jan.didden]

It should be possible to back up your reports with other reports.

If you invited other skilled listeners to your home and they had a choice between two amps or two cables that you know sound different in one particular aspect such as sound stage focus, they should be able to confirm your reports.

The test can be sighted, but you should be absent while they are introduced to the equipment and whilst they swap and listen. They are only told that eg "one of these has a defocussed sound stage, just identify it."

You don't know that "two cables that you know sound different in one particular aspect". That's the crux. You want to do a test to find out.
Such a test you describe would be completely worthless, of course. A step forward would be to say: "I have two cables. Do you think they sound different or not?". But just a step, there's still a long way to go before such a test would be accepted by serious investigators.

Jan Didden