John Curl's Blowtorch preamplifier part III

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At the end, it is boring. This permanent aggression from this team of defenders of the holly truth of what that they consider as a "science" or a religion is annoying.
On my point of view, audio design is not different than cars design. Both are fighting with the laws of physics, both industries produce imperfect gears, assembling imperfect components the best they can to produce the best products they can for the money, both are a mix of technology, performance, compromises ... and a lot of fantasies ...
Who is talking about "truth" in car's fora ?

This permanent war against supposed snake oil makes me think of these films where the heroine is pursued by a clown armed with a chainsaw. The moment I start looking for my remote.
 
Tournesol said:
Music is not a religion. Its art.
True, but irrelevant.

Audio design is not a science, it is technology.
Technology is applied science, and therefore depends on truth.

If it is DIY, you are free to do and believe what you want: it hurts nobody.
Why this strange notion of "truth" ?
Truth only seems strange to those who do not value it. I am unclear whether you regard truth itself as a strange notion, or truth in the context of audio design as strange.

Commercial success tells us almost nothing about the quality of audio design. Huge but elementary design mistakes can be made yet if accompanied by a good story then journalists will fall over themselves to praise the product.
 
Radio reception is a very interesting topic technically and context wise and I may be one of the last to deny the technical beauty of analog receivers both tubes and transistors.
Now, the RF spectrum survey, radio station reception conditions, antenna/feed line performance, the all important IF bandwidth requirement and much more can be monitored with the use of a Software Defined Radio (SDR) unit (*) and some freeware software...

Hi George!
You are on track re: SDR, I have a number of small SDR dongles and use the HD-SDR freeware, and you can have a lot of fun with them. Indeed, a marriage of traditional and DSP RF techniques makes for an even more competent RF platform. I've been a radio amateur since 1970 and have built and owned first tube, then SS ham equipment. I currently use a line of DSP-based equipment made here in the USA by Elecraft which has the best of both technologies and it's performance is within a few dB of theoretical, indeed outperforming the pure DSP transceivers on the market:Elecraft(R) Hands-On Ham Radio™
It's ultimate sensitivity exceeds that of a raw 24-bit SDR by employing low-noise linear amps and filters before the ADC, achieving a -145dBm noise floor and 106dB dynamic range.

Just like the people who enjoy listening to audio equipment based on older, obsoleted circuitry, it can be fun to go back to using old ham equipment for a nostalgic fix. However when I an doing serious contesting I always reach for the most competent radios which include SDR features.

Combining the best of proven and new technologies can be beneficial...

Cheers & 73,
Howie - WA4PSC
 
Truth only seems strange to those who do not value it.
How to qualify the believes of those that imagine our actual 'science' knows everything about everything ?
And worse if we consider the little part we all know about this "science".
Specially when we can measure flaws (distortions, bandwidth, phase turns etc.) while we have no idea of the threshold of audibility.
Why don't you try to be a little more modest with your certainties about "truth". Even planets are not exactly spherical. No one.

Contrary to what you seem to think, I am rather on the side of the "scientist", because it is reassuring, but I leave a place for my "feeling", my perceptions and my intuition, with modesty and suspicion.
A matter of balance.
I believe nobody will never succeed to sell-me the snake oil of your nightmares. Because I tend to verify and *experiment by myself*.

And if I'm more interested by those that have a different point of view than the parishioners of my chapel who do not teach me anything, don't you think it is more productive ?
 
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And if I'm more interested by those that have a different point of view than the parishioners of my chapel who do not teach me anything, don't you think it is more productive ?

That's just it, I'm interested in learning, but don't have the patience to deal with opinions built on misinformation. That also teaches me nothing, actually, it teaches me things I have to then unlearn and relearn. Which in the end is most productive?
 
Pavel,

Been busy, but surprised to learn you listen to sine waves, I thought you like classical music. For example some guy named Bach wrote a bit for pipe organs.

Now pipe organs are interesting, at least 40 years back one of the IEEE publications did a bit on a new chip that was an organ tone synthesizer. A letter to the editor asked about frequency stability and the reply was that being crystal controlled it was perfect!

Now as I am sure you know a pipe organ works based on a resonance of the column of air in the pipe. ( How the Flue Pipe Speaks ) What is of importance is that it is neither a pure sine wave nor a stable frequency. Even after sounding a bit to allow things to settle down there may still be a small frequency variation below human critical band perception.

So why don't you try your distortion test with a warbled tone of one or two cents. Failing that try something simple like dual tones at 219 and 221 hertz. Also as an FFT analysis is really different from that of human perception so try a bandwidth of 1 to 450 hertz. I suspect you will see low frequency components differ with capacitor type.
 
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So DA introduces an error component that is essentially linear. Big day today. John and Scott agree.

Edit: it is almost at the end of the article, but it is really there.

Thanks Vacu, I read it again because it was long ago that I first saw it. Good refresher.
BTW The mention of 'impuls response changing shape' also at the end is that not just the result of inserting a capacitor in the circuit? You know, phase shift and all that?

Jan
 
Tournesol said:
How to qualify the believes of those that imagine our actual 'science' knows everything about everything ?
I'm not certain I have ever met someone who fits that description. I have come across people who say silly things like that and believe that this is a way of diverting discussion away from matters of truth.

And worse if we consider the little part we all know about this "science".
You speak of yourself?

Specially when we can measure flaws (distortions, bandwidth, phase turns etc.) while we have no idea of the threshold of audibility.
We have very good ideas about the threshold of audibility. If not, hi-fi would not have been possible for the last 50 years. Our ideas doubtless need refining, but to say we have "no idea" is simple false.

Why don't you try to be a little more modest with your certainties about "truth". Even planets are not exactly spherical. No one.
It is good science which tells us that planets are not exactly spherical, and science which tells us why this is the case.

And if I'm more interested by those that have a different point of view than the parishioners of my chapel who do not teach me anything, don't you think it is more productive ?
Listening to others is helpful, unless they are talking nonsense.
 
regarding FM broadcast, the biggest problem is lack of quality sources.

Here in Portland, I can't think of one that I would call a quality source anymore. There are some programs that I generally like to listen to, but I have learned to ignore the quality.

I know most of the radio engineers here in town, having been one for 25+ years. They generally care about their craft, but the environment in which they work is limited, most are using multiple generation of lossey compression in their chain, its just a fact.

its one of the reasons I quit working for broadcast, that and the fact we have just 3 owners of the broadcast spectrum here in Portland. "We'll open up the radio spectrum to competition and better serve the public!" Ha. Thank you Regan and Clinton.

oh well.

Cheers
Alan
 
regarding FM broadcast, the biggest problem is lack of quality sources.

Here in Portland, I can't think of one that I would call a quality source anymore. There are some programs that I generally like to listen to, but I have learned to ignore the quality.

I know most of the radio engineers here in town, having been one for 25+ years. They generally care about their craft, but the environment in which they work is limited, most are using multiple generation of lossey compression in their chain, its just a fact.

its one of the reasons I quit working for broadcast, that and the fact we have just 3 owners of the broadcast spectrum here in Portland. "We'll open up the radio spectrum to competition and better serve the public!" Ha. Thank you Regan and Clinton.

oh well.

Cheers
Alan

I feel your pain, Alan. The only decent fidelity stations around here are college stations which don't compress the crap out of the mix to make themselves loudest on the dial. If you took a listen to my station on line (I can give you the 320K stream URL if you are interested) you would get a good idea what we sound like on FM: there is only linear AGC between the board and both FM transmitter and stream generator, no spectral compression.

An engineer who does a great job is John Ramsey of WWUH in Hartford, CT. Their FM signal fidelity is excellent, and their stream is pretty decent for a compressed bunch of nonsense...

Cheers,
Howie
 
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