John Curl's Blowtorch preamplifier part II

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There is nothing to "believe". And the sonic difference of the same AMP with two input stages (VFA/CFA) with the same gain will not be so obvious. You may even prefer the VFA at first sight. Like you could prefer a photography with slightly enhanced sharpness and color. But there is something common to all the CFA amps that i had and that made me chose them even when i did not knew what they were. better details separation, more fluid trebles, less fatigue on the long time (And in recording studios, you spend long hours each day). Not day and night, as I said, it is very subtle.
Your subjective description points to CFA improved VLF noise behaviour.
The VFA effective NFB path incorporates two more transistors to add 1/f noise.

Dan.
 
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Exists some comparative measurements (not only race for SR, but distortions spectra for various levels and frequencies, PSRR-mains background and intermodulation products, noise and others) of those different approaches (VFA/CFA with the same VAS and output stage)? I saw no measurements. Or conclusions about CFA superiority for audio power amplifier are stated only on basis of subjective (biased )testing and simulations?
I think this "junk" (electronic) is made for exact reproduction, not for pleasure. Pleasure should be the music itself, as is, it must be contained .
 
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The whole point of a DCOE was one barrel per cylinder for max power. Doing anything else with them is sub optimal. If you really needed flow you could sometimes find a 50DCOE for sale, but not recommended for normal use.

Not true for my conditions... turbo charging the engine. A carb will flow a lot more air thru it if when connected to draw-thru a turbo. Just the cal is all off if you do. I had run the whole engine just fine on a single 45dcoe opened way up and recal'ed internally, up to 12 psi.

With very low distortion speakers, really clean HD Mastered music files, and listening in the near-field with minimal room interaction (doesnt everyone do this?) the VFA and CFA difference is pretty large.... sonically. That is in MHO, of course.



THx-RNMarsh
 
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Look here

The sickids here play simulation knife & sword fights all day long.

(the Dungeons & Dragons ruling superstar is currently seeing a therapist to learn to accept that he can't be no1 in everything. Has a photographic memory, boinked his first chick at age 15 and goes by the name Sex-Guru at his faculty, turned 21 yesterday)

I believe it was about the enjoyment of audio, and the way(s) of achieving divine sound.
 
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Speakers: horribly non-linear
ears: easily damaged poor frequency response (level dependent)
Brain: easily confused

Doesn't stop me enjoying music though and having lots of fun.

Speakers: horribly non-linear
Perhaps yours are, mine are blissfully linear
ears: easily damaged poor frequency response (level dependent)
Probably so, but that's what decently judged loudness correction is for
Brain: easily confused
I don't feel confused, perhaps your yorkshire pudding has gotten to you.

The way you describe it quality audio is total waste if time, effort and money, there's too much working against it all around. I do not share your sentiments.
 
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Perhaps yours are, mine are blissfully linear
Probbaly so, butthat's what decently judged loudness correction is for

Specs? measurements? Normal speakers are 10-100 times higher in distortion than the amplifiers driving them. In the case of the amplifiers OS has designed maybe 1000x. Compared to the amplifiers they ARE horribly non-linear.

Oh and I'm not from Yorkshire. :p
 
the VFA and CFA difference is pretty large.... sonically.
That is my point of view too. But on details many people are not used to 'notice'.
Separation between instruments, both in the space and in the "wall of sound", very short details in the dynamic, this mysterious 'presence' that make you feel an instrument is in your room in 3D, like the subtle 3D effect with very little bokeh of some photographic lenses etc.
But, globally, distortion, balance, global dynamic is the same, don't you think ?

What i mean, is there is not so much a difference when you do a A/B immediate switch (blind or not). You need to listen alternatively to something like at least 10s of the same samples to figure out the differences. And to repeate severall time to can concentrate on the detail's differences involved. That what I called "Subtle".
 
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2 Esperado
These are simulations only, not real measurements.
Real measurements are not so different. Ask OS, or Richard. Distortion's absolute values can change depending of the accuracy of your models, but only in absolute values, relative stay the same order. For everything else, simulations are good enough.
And both don't figure out real behavior with transients signals and with your real speaker load, anyway.

I believe those sims are good enough to explore the differences between the 2 topologies.
 
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Your subjective description points to CFA improved VLF noise behaviour.
The VFA effective NFB path incorporates two more transistors to add 1/f noise.

Dan.

Except CFA op-amps have poor current noise, do a survey of datasheets and CFA's will not come back as exemplary for 1/f.

This thread needs an "ignore car talk" button.
 
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Esperado ---- I agree that so far it is better but not greatly so. But consistent as always an improvement in the right direction. The new CFA power amp circuits done here is in a new league. I have a CFA model from Marantz (150W) and its qualities show same description you have given.

BUT Dadod's is in on a whole other level above it. It is easy to hear these life-like qualities now. It is just right and it is there for the fisrt time in my life. Others have heard my sample of it as well here in Asia with same results.

If the work by OS and others is like this CFA PA then, gentle men, we have a new ball game !!


THx-RNMarsh
 
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Just before Scott activates the "ignore car talk" button.

The ignition system was a whole another project to keep pressures from killing the spark

It's not only high static pressure :)

George
 

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For the record, I am not a CFA fanboy.

The long and torturous CFA vs. VFA thread that I kicked off certainly bears witness to that - I remained scrupulously neutral throughout. I've designed and built both types and listen to both regularly.

As I have said many times before, CFA topology amps are another string in my bow - I am glad I made the effort to understand and design with them, and hopefully encouraged a few others to do the same.

If someone trashes 'em, or claims they are inferior, I'll continue come out slugging.

I'll step away from this subject now - clearly its as emotive as ever . . . nothings going to change.
 
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