John Curl's Blowtorch preamplifier

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#3,541
If it comes down to a choice of keeping you happy and keeping John happy...it's a no-brainer. I've learned more from him than from you.
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Grey, it might appear that I'm against you, but I'm not. In fact I'm not for or against anyone. We've all seen what admiration can bring about in the world. I give John credit for his shared knowledge and insights, from which I have learned, but no more than that. You don't have to be the spokesman for the major designers on this forum. It becomes boresome everytime you start your self-explaining posts as if you want to convince the rest of how well you understand John or others and what they actually mean.

John's knowledge and insights have lead to a basic schematic which has advanced over time and has provided material for learning and understanding. I and others will not disclose this information which has evolved to something worthwhile. It has been a challenge and still is. The most rewarding part of the process is, that it leads to new insights and ideas to take things a step further.

If you feel you haven't learned from me, it's ok. I have never pretended to know more than others or presented myself as a teacher.
 
#3,542
john curl said:
I give up, you win. I don't know what you have won, except to confuse a number of other people, but let us move on. What do I care? I have NEVER designed a tube power amp in my lifetime, even though I have 7 on hand. I was just trying to help others understand one of the differences between solid-state and tube amps and why the OP AMP concept became popular.
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But wasn't the first op-amp introduced in 1952? (tubes of course). BTW I mentioned that other amplifier thread because it was NOT just another TL071 or 741 on steroids. Fully complimentary VAS with CMFL is the way we (and most others) have been designing low distortion amplifiers lately. Error correction doesn't cut it at 50MHz. If you choose to feel that a few mico-Henrys of inductance in the output negates all the rest of the merits of the work, that's certainly your perogative.

BTW our young guys (younger than my sons) are blowing me away lately. They're so facile with the latest simulation tools yet at the same time doing fundamental new circuit architectures. New ways to make inherently linear open-loop stages. Us old guys must have done something right.

Please don't take my criticism of Bybee personally, I find his 'prose' hard to take seriously so what?
 
#3,544
Resistors

Hi Mr. Curl,
another question.

Besides your preference on screws.

How about resistors?
Not too long ago, Cyril Bateman did some work testing capacitor distortion.
In his articles, he discussed an analyser to test with.
In the article, he discussed resistors for the analyser.

He had a preference for one resistor design over another design (all metal film).

Have you found differences in resistor sounds?
Do you have a preference or advice on resistor selection?
 
#3,546
Everything John Curl teaches us is controversial 😉
"When you're one step ahead of the crowd you're a genius.
When you're two steps ahead, you're a crackpot."

-- Rabbi Shlomo Riskin, (Feb. 1998)

"When you're three steps ahead of the crowd, you're John Curl" 😉

But thank you.
I'll just trust my ears for now.
My Mach-1 precision ears tell me quite a bit.
 
#3,557
john curl said:
I give up, you win. I don't know what you have won, except to confuse a number of other people, but let us move on. What do I care? I have NEVER designed a tube power amp in my lifetime, even though I have 7 on hand. I was just trying to help others understand one of the differences between solid-state and tube amps and why the OP AMP concept became popular.
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Hi John,

I'm surprized that you never did tubes. I did several tube amps in my teen years and had a lot of fun with them. I remember at the age of 15 obsessing over how to do a better phase splitter. I also remember running 6550's pretty hot, to the point where if you darkened the room you could see them "blushing". I was naive about reliability back then. I got 90 watts out of a pair of 6550's with about 550V on the plates.

Anyway, I do indeed remember some cases of motorboating. However, it was largely my experience that the HF oscillation issue caused by output transformer excess phase usually whacked me first. I also remember that some tube amp topologies had more ac coupling points in the loop than others, and of course that some amps had those frequency corners much higher than others. Those aspects made a very big difference in the tendency to motorboat. Fewer LF corners placed at frequencies well below the corner frequency of the output transformer usually seemed to work best.

Ever curious, about two years ago I gutted and re-built one of my VT amplifiers from the old days so that I could try to hear for myself the differences between well-designed SS amps and well-designed VT amps. The design was a classic KT88 one that produced about 35 wpc (the KT88's were loafing).

Quite surprizingly to me, the differences between the VT and solid state amps were more subtle than I expected. I took the VT amp to a bottlehead gathering and the tube guys there loved it. I also have to say that I could not for the life of me understand what these guys saw (or heard) in 300B SET amplifiers.

That VT amp is also the one we used at RMAF and HE2007 in our SS/VT listening comparisons.

Cheers,
Bob
 
#3,558
john curl said:


Grey, it might be time for plan B. :mafioso:
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MikeW said:


Why don't you and Grey do a tube design? 😀
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John needs me as a design collaborator about the way he needs a flat tire on his car. I suspect he meant Plan B in the sense of shedding the bird poop that seems to be accumulating on this thread.
My love for tubes is well known, but I'm afraid that tube pricing, availability, and most especially consistency/quality have all been going in the wrong direction for me. That's the whole reason I went to solid state. At least with silicon (if you can avoid the fakes) you're generally going to get fairly predictable consistency. The irony of the availability question became evident when Toshiba pulled the plug on the 2SK389/2SJ109 & 2SK170/2SJ74. If I'm reading the smoke signals correctly, they won't be satisfied until they've discontinued all small signal through-hole parts. Bummer. For a while there, I was encouraged by the introduction of the Lovoltech/QSpeed power JFETs...then those went away, too. LU1014D, we hardly knew yeh!
Maybe I should go back to tubes, after all...
For what it's worth, I've still got a few tubes on the shelf. I haven't decided what to do with them yet. Maybe a preamp. Maybe an amp. Maybe a hybrid phono circuit (the one I've been fiddling with recently is all solid state). It would be a bittersweet thing to go back into tubes--kinda like Led Zeppelin's presumed last concert a few months ago. (It's my understanding that Plant doesn't want to do more Zep stuff, although the others are willing. At least I got to see them a couple of times back in the '70s.)


lumanauw said:

I tought almost all circuit permutation have been known by now.
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Patents for new stuff (even with tubes, believe it or not) are being granted all the time. Even if you discount some arbitrary percentage as not being valid patents for one reason or another, there are still new ideas waiting to be discovered. Some will even be applicable to audio.
John has at least one patent that I'm aware of, possibly more. Nelson has been gracious enough to let us play with his patents. Analog Devices (represented here by Scott Wurcer) has patents.
Speaking of Scott (who thinks I hate him, but it ain't true), it'd be fun to see what he could do if he were to do a clean-sheet design--something discrete.

Grey
 
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