John Curl's Blowtorch preamplifier

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#16,921
anatech said:
Hi Glen,

Clearly I was responding to a comment you made about an EF buffered Vas. Was I unclear on that? I think you are deflecting attention from your error.


You don't say? Hell, I can't believe it! You stated an obvious fact as though I had assumed something really stupid was true. Keep focused on what is actually said Glen. Respond to that and you will appear to be far more intelligent, rather than skilled in debating through deflection. 🙄


Didn't you post this...

If you look at your post, 16839, I believe you will find you are mistaken. Do I get an apology?
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This is getting utterly ridiculous. My only comment in post 16839 on EF buffered VAS's was:

"EF'ed VAS? What ARE you talking about?"

Do notice that is a question? I was talking about complementary LTP's and input bias currents. I have no idea why the person I was replying to mentioned "EF'ed VAS" or why you felt the need to interject at that point and tell me how correct he was on a issue completely non related to input bias currents and complementary long tail pairs, that was not being discussed at all!

No error on my part and no apology for you. Try reading for comprehension before commenting one someone else’s intelligence and debating skills.
 
#16,923
Yes it is, PMA, but I am retired, so I cannot further invest in better test equipment. Still, I have much more varied equipment than just THD measuring devices.
Besides, it doesn't matter that much if I can measure any lower, so long as I can signal average to remove noise.
I wish that you PMA, would design an effective FM detector that could pull out PM modulation from the equipment. You might also try to duplicate a Hirata box, to measure that sort of distortion.
It is my feeling, at this time, that extremely low numbers are meaningless, unless they correlate to other factors that we can hear, yet not directly measure at this time.
 
#16,924
syn08 said:


Incorrect. Correct would be:

Audio industry is not RATIONAL, it is subjective!
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I'd say that the audio industry is very rational. It must be to survive. It's the customers that are irrational, subjective, open to influencing. The audio industry works quite rational and methodological to make that customer shell out money for *their* product. That rationality may cause the manufacturer to put more money in esthetics or marketing or carefully building up a reputation than in circuitry, for example.

Jan Didden
 
#16,925
john curl said:
Chris, I regret that you are not getting complete input from me. However, you have shown me that you do not like my style of communication and you often take it personally, and this is not a good thing, as you are a moderator, and I don't wish to get on your bad side.
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:cop:

John, one of the unofficial rules we follow as mods is that no moderator should make decisions alone on moderating a thread in which he is involved. Any action is decided by a third party, not involved in the debate. So as long as you post according to the rules, you can say anything to Chris, (or any other mod for that matter), that you would say to any other member. Using our powers to suppress debate purely because someone disagrees with us would be viewed very negatively by the rest of the mods, and if anything, we are more strict with ourselves than with the general membership. 😉
 
#16,927
However, you were able to negate the entire effort. I have not yet heard from John himself. Just a lot of back and forth comments without his rationale in one statement.
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What's your point? It's pretty clear what Curl does and it's not difficult to gather from that what his rationale is:

He said he designs something, it measures well, he thinks it sounds right, and then he gets bunch of other people to listen to it, see what they think. If his listeners' critiques suggest to him there might be some problems, he reworks it some more. Repeat, if necessary.

Seems to me he covers the subjective/objective bases pretty well.

We can gather from his procedure that it's the collective subjectivity which is the final arbiter for him. From an analytical point of view, I think that's good procedure because there is not yet a well developed metric which indicates subjectively good sound.


He's got a slightly gnostic style but I don't think you're going to get him to change that at this date, eh?

If fish rise to the bait that's their lookout isn't it?

.................................
 
#16,928
FrankWW said:
From an analytical point of view, I think that's good procedure because there is not yet a well developed metric which indicates subjectively good sound.
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You mean as far as you and JC know.
This is the crafting process...build, listen, adjust, listen, adjust, listen. Back-fit some analytical theories to justify the final recipe, often with some shoe-horning.
The crafting process is like natural selection. It is very valuable because it provides an instance of excellent performance for reference. But it doesn't lead to understanding of the underlying principles directly. And the process can be very self-limiting when successful rules of thumb become entrenched.

If fish rise to the bait that's their lookout isn't it?
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You don't really mean that.
 
#16,929
Gents,
I find all this bickering about tiny circuit changes and absolute measurements to be a complete waste of (at least my) time to even read them.

Yesterday I went to a Swiss Hi-End hifi show, and the best sound at the show, without ANY doubt, was from Herr Schopper, who rebuilds old Thorens turntables, and refurbishes old tube gear.

Playing from vinyl through rebuilt (very old) Western Electric tube gear, the sound was very lifelike, realistic, and kept me in my seat for an hour.

A huge relief after room after room of fantastic spec solid state amps, or even worse, full digital systems!

I have to ask, where are your comparison, not from sims, but with respect to LISTENING?

Regards, Allen (Vacuum State)
 
#16,930
Re: Re: Re: Re: Re: Re: VAS fighting

G.Kleinschmidt said:
Bob, I understand exactly how the circuit works and the different values of emitter degeneration resistors are to account for the differences in Vbe between the NPN and PNP transistors.

This is one way to avoid the Slone problem, however you are missing the point. The large gain of the LTP's makes the circuit excessively sensitive to an input offset imbalance between the LTP's.
Do the experiment I showed here in post 16874 to see for your self just how small an imbalance is required to throw the VAS bias out:

http://www.diyaudio.com/forums/showthread.php?postid=1793473#post1793473


BTW, you are not the only one:

http://www.diyaudio.com/forums/showthread.php?postid=1654719#post1654719

Cheers,
Glen
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Hi Glen & Bob,

And here's another one who experienced the same problem:
thread: Bob Cordell Interview: BJT vs. MOSFET
page: 48, post: #1194
(copy post didn't work, hence the clumsy way of referencing)
If you look at the schematic (and ignore the TMC and NDFL hassle), you will see that I was using 3k3 (R15/R16) instead 20k as LTP loads. As far as my memory serves, even this much lower resistance wasn't able to cope with an input offset imbalance. So I think that the difficulties as mentioned by Glen are real.

Corollary:
Precisely for this reason, I had to look for other means to stabilize the DC operating point. In this case I added a common mode control loop (CMCL), see: Q20,21,27,28. Please notice this was my first attempt to incorporate a CMCL, so still in its infant state and far from optimal.

Cheers,
Edmond.
 
#16,934
janneman said:


I'd say that the audio industry is very rational. It must be to survive. It's the customers that are irrational, subjective, open to influencing. The audio industry works quite rational and methodological to make that customer shell out money for *their* product. That rationality may cause the manufacturer to put more money in esthetics or marketing or carefully building up a reputation than in circuitry, for example.

Jan Didden
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I fully agree Jan. I was thinking about the Audio Industry as a habitat of designers, manufacturers, equipment, customers.

OTOH, it's the Audio industry as a whole which currently finds convenient to perpetuate the statu quo. I see the current situation as a local equilibrum point, where everybody is more or less happy: designers have space to "make a difference" using Bybee devices, the manufacturers have a demand and space to minimize costs, reviewers have space to spread subjective BS, customers have always options to pick from.

The only problem is that the current situation is barely allowing space for any progress, other than opening another manufacturing site in Asia and slicing the manufacturing costs even further. And even so, the savings are not going into the customer's pocket, or in R&D, but in just in more BS marketing campaigns.
 
#16,935
I don't know what to add. It is still disappointing to me that many here are still suspicious of my and many of my associates motives in how to produce better audio, and to run our businesses, such as they are. Most of my associates share a love for audio reproduction, and that is what we direct our primary attentions too.
Sure, we try to put our designs in a pretty box. Everyone else does, and we must too. I find it a distraction, but necessary.
Frank has me 'dialed in' as well as I could explain it myself.
Joshua, your question is repeatedly answered throughout this thread, when I can get a word in edgewise over the hoots my of critics.
 
#16,936
Allen Wright said:
Not surprised, just very happy to hear this.

You should check out Schopper's site, he does some amazing work on the TD124.

http://www.schopper.ch/static/services/z_top_audio/Neutrik/Thorens_Uebersicht_EN.html

and he has perfect English.

Regards, Allen (Vacuum State)
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I've met Schopper twice now, both times at the 'Quad Musikwiedergabe' show in Koblenz, Germany. A driven man with a very solid physics and mechanical background. I found his equipment very enjoyable, absolutely, although technically you could hear some deficiencies.
That happens often, at least to me. I enjoy the music reproduction, even though I hear where it, technically, could be better for instance in terms of dynamic range, freq response coloration to name just two.

Jan Didden
 
#16,937
syn08 said:


I fully agree Jan. I was thinking about the Audio Industry as a habitat of designers, manufacturers, equipment, customers.

OTOH, it's the Audio industry as a whole which currently finds convenient to perpetuate the statu quo. I see the current situation as a local equilibrum point, where everybody is more or less happy: designers have space to "make a difference" using Bybee devices, the manufacturers have a demand and space to minimize costs, reviewers have space to spread subjective BS, customers have always options to pick from.

The only problem is that the current situation is barely allowing space for any progress, other than opening another manufacturing site in Asia and slicing the manufacturing costs even further. And even so, the savings are not going into the customer's pocket, or in R&D, but in just in more BS marketing campaigns.
Click to expand...

Indeed. You could reason that objectively, there has been essentially no progress to sound reproduction for the last 30 years or so in amplification. (Speakers is another matter).

Suppose someone finds a measuring protocoll that would exactly predict customers' preference. That would be the end of the audio industry, because within a few milliseconds someone would have figured out how to build such an amp for $ 99.95 in China. After all, it's only engineering.

But, since customers preference is only remotely related to the actual objective music reproduction of an amp, the danger of the above scenario is nil and we can all live happily hereafter 😉

Jan Didden
 
#16,939
Jan,
I agree with you about musical enjoyment.

I could have taken Schopper's system home and listened to my whole vinyl collection (2500+) and never wanted for more - and I couldn't say that about any other system at the show.

The next best was the Quad demo by 'Quad Musikwiedergabe' with rebuilt ESL57's, but they were only playing digitally sourced sounds from some music server, which would go on the blink occassionally and they had to then resort to an iPOD...

I have offered our electronics for their next show and I think we have a deal!

Simply beautiful sounding speakers.

Regards, Allen (Vacuum State)
 
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