John Curl's Blowtorch preamplifier part II

[fas42]

Of course it's subjective - my hearing detects a difference, therefore there is a reason it. Name me a single loudspeaker designer who refuses to listen to his creation, and totally depends on instrument measuring to assess its quality?

 

[marce]

Never said that measuring only is the way to go, but have said listening without measuring and some back up is not reliable...

 

[fas42]

I agree that it would far better to have numbers for these behaviours, but if one lacks the instruments which would it straightforward to get measurements - or, there is not a clear, well defined procedure to follow even with sufficiently sensitive instruments ... then, what to do ...?

My overall solution so far has been to know what I'm after, and work backwards from that - the "measuring", so to speak, has been how close to that goal I am at any particular moment ...

 

[SY]

I recently found a paper that explains why SET amps can sound better than normal push pull amps, especially with horns. It is an AES preprint. I read it and it makes sense. It has to do with LOW LEVEL level change with frequency in the output transformer.

This was discussed a few years ago in another thread and someone (who, me?) did some measurements. With good output transformers, one doesn't see this effect to any significant extent.

 

[DavidL]

My overall solution so far has been to know what I'm after, and work backwards from that - the "measuring", so to speak, has been how close to that goal I am at any particular moment ...

Frank, you may know what you are after but the rest of us haven't a clue to what you have been sputtering about since you showed up on these forums. So you have calibrated ears now and don't need to measure I take it.

 

[DavidL]

This was discussed a few years ago in another thread and someone (who, me?) did some measurements. With good output transformers, one doesn't see this effect to any significant extent.

And by using "modern" solid state amps you eliminate the output transformer altogether.

 

[fas42]

Frank, you may know what you are after but the rest of us haven't a clue to what you have been sputtering about since you showed up on these forums. So you have calibrated ears now and don't need to measure I take it.

Tsk, that was thrashed out ages ago - have a wander around the posts here, to get the gist of it: http://www.diyaudio.com/forums/loun...ch-preamplifier-part-ii-2651.html#post3129421 ...

 

[gpapag]

Demian, the paper is:

That and two more from him
http://www.mennovanderveen.nl/nl/download/download_1.pdf
http://www.mennovanderveen.nl/nl/download/download_5.pdf
http://www.mennovanderveen.nl/nl/download/download_3.pdf

This was discussed a few years ago in another thread

The references in those papers are sadly only self references, like Scott said here

One needs to read at least Radiotron Designer’s Handbook Ch. 5
Then search for 'magnetic modulators' and 'magnetic amplifiers' theory and applications (1930-1960)

George

 

[TheGimp]

On that article about double blind testing what I got from that was that the relays used had some type of electrical problem if they could be absolutely identified by the test subjects. The silver platted switches showed they did not have this problem and they should have been substituted into the experiment and the experiment redone. That would have been the better test and could have been used to evaluate the original assumptions or to test for the preferred result. Nobody said that a double blind test can't be a failure or incorrectly implemented, experiments are often a failure due to poor setup or improper procedure. This is exactly why most test protocols are tested by multiple researchers to look for these types of systemic errors. it happens all the time in science. Peer review is a necessary evil most of the time before a real result can be proven or dis-proven. The exact procedure must be well documented so it can be duplicated and confirmed. That is what I take away from that discussion.

Or better yet, gold plated reed relays . These have existed for over 35 years (although the early ones were for the military).

 

[scott wurcer]

I have searched and have asked for pointers to credible information regarding this...repeatedly

Why don't you actually do a search. It just might turn up something. I often show my system for measuring distortion in wire and that it is directional. A search just might get you the observations from one of those folks.

I never saw any data that was not needlessly contaminated with noise and confounders. For instance if I set out to measure extremely low IM I would start with two independent precision sine wave oscillators. You could even use two high quality sound cards. Also none of jn's excellent suggestions were ever followed up on by either JC or Ed in these supposed wire distortion tests.

Any refereed controlled reports anywhere in the literature? You must have a link.

 

[scott wurcer]

The references in those papers are sadly only self references, like Scott said here

One needs to read at least Radiotron Designer’s Handbook Ch. 5
Then search for 'magnetic modulators' and 'magnetic amplifiers' theory and applications (1930-1960)

George

I wonder if any of these were invited to the AES Journal, the conference proceedings are, to say the least, weakly reviewed.

 

[SY]

I wonder if any of these were invited to the AES Journal...

The first conference paper wasn't. I don't know about the others.

I was amused by the references, since I was actually in some of those "private conversations."

 

[jneutron]

They also used a 120 volt to 125 volt step up transformer for the lighting system to allow for the voltage drop in their power switching circuit. Ever see a transformer rated for 125 volts 30 amps?
Ed

Of course. Typically they'll have taps for changing the ratio.

It's also easy enough to use a 5 volt 30 amp transformer, and just series it in the line with the equipment being powered.

Why, did they use a 4kVA transformer?

jn

 

[PMA]

The references in those papers are sadly only self references, like Scott said here

Thanks for the links, George. It may happen that one is alone with his research.

 

[SY]

It may happen that one is alone with his research.

Or one is promoting one's own products.

 

[scott wurcer]

Or one is promoting one's own products.

This research explains deviations in the reproduction of micro details at the threshold of audibility.

 

[gpapag]

Thanks for the links, George. It may happen that one is alone with his research.

Thanks Pavel.
It may happen that one carries on his own investigations, yes.
It is prudent, at least before sending a paper, to review some reference books and conduct a search in the literature using some relevant keywords.
Sitting references spread over time and authors adds credibility to -it doesn't subtract from - a technical paper.
I would feel ashamed to reference only my own work, even if I was convinced that the core of the subject was untouched by anyone else but me.
There is no parthenogenesis in technology.

George

 

[jan.didden]

I was amused by the references, since I was actually in some of those "private conversations."

Funny - I more remember it as 'private drinking'

 

[Chris Hornbeck]

Low flux density effects in transformers aren't some new Heresy. Frank McIntosh wrote about it in audio output transformers before many of us were born.

Thanks,
Chris

 

[john curl]

Try harder.