John Curl's Blowtorch preamplifier part II

[Steve Eddy]

Or something like this.



se

[EUVL]

One set of transformer winding missing in what you posted.
So not the same.

[Soundminded]

Originally Posted by Joshua_G

Wow!
Will you please enlighten us with your amplifier design that stems from such a deep and unique knowledge? Or is it that, according to you, all amplifiers are the same?

You won't turn a donkey cart into a formula one race car by endlessly trying to make the wheels rounder. Once they are round enough, further improvement in that direction buys you nothing. It's a fruitless waste of time. The answer to the problem lies elsewhere.

What's wrong isn't the amplifier, it's the paradigm behind the system design. Given the ability of human hearing and memory, it is not possible for todays concepts of what high fidelity means in the sense of duplicating the sound of live acoustic instruments through recordings to convince the human brain it is experiencing the same stimulus.

[brianco]

That "answer" to Joshua's question is a total evasion of the question asked. You have already said what is contained in this last post....mercifully this time in fewer words.

[SY]

Problem is, Joshua's question contained a both an incorrect assumption and classic false dichotomy. If the premise of a question is incorrect, it cannot be satisfactorily answered.

[jacco vermeulen]

Try to retain some objectivity, give SM some slack to get at where he's going.

(at the least, more inspiring than ever-predictable schematic fishing ones)

[Soundminded]

Here's an unexpected answer to Joshua's question. If you walked into a room and a sound system was playing music and you didn't know what amplifier was installed, could you correctly guess which one it is? I'd have thought the answer was no. But in 2007 I went to the VTV show in central NJ which wasn't far from my home. I heard a whole building of vacuum tube amplifiers. Then late in my visit, I heard a setup with a solid state amplifier, probably the only one at the show that day. I guessed it correctly immediately. I was reminded why I was glad to see the end of vacuum tube amplifiers and why I never turned back. Perhaps todays seemingly universally shrill loudspeakers benefit from the peculiar coloration (electrical waveform distortion) that an output impedence matching transformer imparts to high frequencies. I know it did not benefit the dull sounding bookshelf speakers of the 1960s. I only learned recently on another blog site that the reason the AR3 LvR demonstrations I heard worked as well as they did, surprisingly well in fact, was that Roy Allison had turned up the treble control on the PAS3 preamp to compensate for AR3s rolled off high end and possibly the Dynaco Stero 70s coloration. You had your choice then, dull high ends from bookshelf speakers or harsh ones from large horn speakers like A7.

Hearing memory is I think better than you'd imagine, better than a what I've read would have me believe. For example, you can usually immediately identify someone you knew for a long time but hadn't seen or heard form in decades if you get a surprise phone call from them. You can also usually tell if someone you don't know has even a slight cold or sinus condition by the sound of their voice alone. While hearing can't improve with age, it can only deteriorate (mine still tests very good) I think you can train yourself to become a much better listener. You can make yourself aware of many details of sound you overlooked in the past. It's too bad I can't hear those LvR demos again. I wonder how convincing they'd sound to me now. If you can find it, watch PBS's documentary about Steinway pianos called "Note By Note." Notice how carefully prospective buyers listen to and compare the sound of different Steinway pianos. Each of them sounds different and each performing artist is looking for a particular sound that suits their performing style best. It is too bad our recording technology can't really reproduce the sound of any of them. That is still beyond the state of the art. Improving a preamplifer to get from 99.997% perfection to 99.998% perfection will not close the gap.

[john curl]

Soundminded, I appreciate your opinion on this subject, but not your conclusion. We have found that in the reproduction of music, LEAVING OUT certain distortions, makes the listening process easier and more exciting. Trying for that extra .01% in the usual types distortion that we measure, I agree, is a waste of time.

[john curl]

EUVL, your schematic does not give us any insight to the questions at hand, and is difficult for an amateur to emulate. It is true that Steve Eddy's alternate circuit is cruder in almost every way to yours, but it too, is inappropriate, although in fact, it would have been easier to design properly, as the transformer has been replaced by a choke.
Steve's circuit shows a complete lack of understanding of modern design, and that approach is virtually worthless, except for vacuum tubes.
EUVL, your schematic is 'interesting' but the transformer characteristics would have to be precisely known for the circuit to make any sense. Where and what is the transformer type?

[simon7000]

Originally Posted by john curl

EUVL, your schematic does not give us any insight to the questions at hand, and is difficult for an amateur to emulate. It is true that Steve Eddy's alternate circuit is cruder in almost every way to yours, but it too, is inappropriate, although in fact, it would have been easier to design properly, as the transformer has been replaced by a choke.
Steve's circuit shows a complete lack of understanding of modern design, and that approach is virtually worthless, except for vacuum tubes.
EUVL, your schematic is 'interesting' but the transformer characteristics would have to be precisely known for the circuit to make any sense. Where and what is the transformer type?

John,

One of the advantages of being a critic is it is easier to "Dis" things than offer a comprehensive review.

Steve Eddy's circuit is from a very early solid state design. It uses a choke because it is supposed to show how you can design audio circuits without a transformer and save money! Interstage and output transformers were the mindset of the day.

Note that it uses all PNP transistors! Probably point contact types. The heatsinks were really needed as 5 watts would have been a lot of power!

Sorry you missed the joke, the humor was if you think that is retro here is one even worse!

ES