John Curl's Blowtorch preamplifier

[PMA]

Yes they are. This is a summary of several listening test configurations, we have not had a chance to get it all in one test , but, we compared often quite different topologies and approaches.

Frankly speaking, Terry, I do not feel much like wanting to continue in those never ending quarrels here. I had a feeling that the guy who asked me was in doubts about the test gear.

I would guess that most of those, who completely disagree with John, and probably with me as well, have probably had very little of listening experience except for their home systems.

[john curl]

'In the beginning' there was a preamp called the CTC 'Blowtorch' that got people excited in one way or another. Usually, they criticized it for being ugly, featureless, poorly wired, and way to expensive. I stepped in at some early point in the discussion to 'defend' why the 'Blowtorch' looked the way that it did, why it was wired the way that it is, etc, etc. I offered some broad hints as to what the electronics was as well.
As time has progressed, I have tried to bring out some related topics that may or may not be included in the 'Blowtorch', but are considered important in audio design, by many successful audio designers. Usually, however, my efforts are slowed or blocked by specific individuals who have some reason for putting their own interests or efforts in front of the line, so to speak, and I am powerless to do anything about it, except to ignore them, as mandated by the moderators, and attempt to move forward with my own efforts at presenting some newer and somewhat interesting design concepts of my own choosing.
This seems to cause friction, and even insults to my character, but I am blocked by refuting in kind, by the general policy of the website. I will try to weave through the 'minefield' as best I can.
For the record, when I speak of open loop design toplogies, I personally am referring to preamps, prepreamps, electronic xovers, studio boards, microphone electronics, master recorders, and maybe some other components in the audio chain. I am NOT at this time speaking about power amplifiers of my own design, although Charles Hansen, my colleague and competitor, as beat me out, sonically, with at least one learned audiophile, with an open loop design, that competes with my stuff in the audio marketplace.

[Edmond Stuart]

Originally posted by PMA
10 years ago I would probably agree with Glen and Edmond on most of their points. After having passed many listening tests in the last 6 years, I do not agree, and my experience comes more and more close to that of John.

Hi Pavel,

How on earth can you agree or disagree with my points? You don't know nothing about my latest design. Either you don't know how much of John's wisdom I've put in that design.

Cheers,
Edmond.

[PMA]

Yoa answered me with OLG rolloff corner, loopgain and fT, Edmond.

[Edmond Stuart]

Originally posted by G.Kleinschmidt .........
..........................
In fact, the only significant thing I see (WRT to the nfb debate) is a resistor or two bunged onto the VAS collector(s) to ground so that the open loop gain plateau extends high up into the audio spectrum.

Hey Glen, finally you got it!
Load the VAS output as much as you can (using only sonical approved resistors, of course) and you will get a very high corner frequency of the open loop gain. And please, no whining and moaning about the added distortion, as the golden ears are totally immune for such trivial artifacts.

Cheers,
Edmond.

[Edmond Stuart]

Originally posted by PMA
Yoa answered me with OLG rolloff corner, loopgain and fT, Edmond.

Hi Pavel,

These figures say nothing about the topology and implementation, let alone listening tests. Remember, my design is new, so any comparison with other designs (with high or low global NFB, whatsoever) is highly prone to erratic conclusions.

Cheers,
Edmond.

[KBK]

Originally posted by Edmond Stuart


No, because the majority of audiofools prefer to spent their money on "directional interconnects" or comparable BS like that, instead of a really good amp.
Besides, this DIY, not business.

Cheers,
Edmond.

Directionality, with regards to 'sonics heard' definitely does exist. I would like to explain it to you Edmond (in detail), and I might do that some day soon. Perhaps in a year or so. The science to explain what people hear is definitely out there in the world. The trick is knowing what it is and the root causes-finding and making those connections. However, like some in the business, I make my money from others not knowing those considerations. I know it sounds like some sort of bunk, but the reality is otherwise. Please do not allow your 'known facts', at this time, skew your view. Investigate. The answers are there. As for the answers themselves, one of the reasons for the lack of the delivery of such, is the Pandora's box of understanding it opens up for the individual. I'm not finished musing in that area and might find more interesting things to produce and sell before someone else get to them. Which is the true reason for a lack of forwardness on the root situation.

The real problem for those who know the subject, is the ignorance of those who do not..and those in ignorance producing product and promoting it. Ie, the real doctor forced to stand and hawk right beside the snake oil salesman who is there to do his 'thing' in total ignorance. We get thrown down the same hole due to the ignorance of the buying public..and that definitely includes more than a few engineers. But, one again, we cannot offer clarity without sacrificing the very core knowledge that puts bread on our tables, and pays our bills. I wish you luck in telling the difference between the two. When it's something one does not understand... obviously....confusion abounds.

I mention this as John suffers under this umbrella..as do other designers, producers of audio gear, various loudspeaker companies, as well as many other types of gear and areas of endeavor.

[Bob Cordell]

Hi Edmond. Yes, it's just a guess of mine that doing an AC analysis with different DC offsets would reveal PIM. I have not tried it yet. The idea is that the phase data in the AC analysis can be read with very good precision. I believe that 1/1000 of a degree of the 7 kHz sinusoid used for PIM testing corresponds to about 0.39 ns, which should be pretty good PIM resolution. That is on the order of the resolution of my PIM analyzer, IIRC.

Of course, PIM is measured with a 60 Hz large signal, so measuring it with SPICE using a varying DC offset means that we are assuming that DC behavior is similar to 60 Hz behavior.

Cheers,
Bob

Originally posted by john curl
Guess? We don't need no stinkin' guesses around here! Put up or get out of the way!

Hi John,

I was just trying to be honest. I think that diverse views, presented honestly, are the sort of thing that make these threads interesting to read. One person may post a hunch or a guess, and another, reading that, may be inspired to take it a step further.

You need to lighten up and be a bit more tolerant and hospitable toward views expressed that are not quite the same as yours.

As my time permits, I'll try to further clarify some of the issues surrounding PIM.

Cheers,
Bob

[Bob Cordell]

Originally posted by KSTR
Maybe you missed my Post #6530, where I just tried that, showing only the closed-loop amplitude response vs bias. Now here, for the same test conditions, the phase plot from 1kHz to 20kHz, showing some 1deg max delta between different DC bias values.

- Klaus

Hi Klaus,

Nice work! I apologize for having missed that.

Cheers,
Bob

[Edmond Stuart]

Originally posted by KBK
Directionality, with regards to 'sonics heard' definitely does exist.
......................

Hi KBK,

I guess you also believe in the existence of a perpetuum mobile.

Cheers,
Edmond.