John Curl's Blowtorch preamplifier part II

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with listening as measurement, what happens when taste or mood changes? does the quality of the amps change also?
Probably the best test of all. Yesterday, because of unrelated issues I was in a fairly off mood, and happened to be listening to rather uncompromising music. Hence the slightest unpleasantness in the quality was intolerable, but that didn't stop me appreciating when the system was doing fine, being aware that it was largely OK - it didn't "mend" my mood, but it didn't make it any worse!! :)
 
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Bcarso, do you mean that you actually know a REAL hi fi enthusiast, who trusts himself, over the critics here? I'm glad that you know one, I know many. They contact me almost every day.

Yes, astonishingly. He has some interesting theories and preferences, some of which I could take issue with if I wanted to be contentious (which I generally do not), but I have always heard good sound at his place, and I respect him for that. Other appealing features: besides composing, he's an accomplished pianist, and his wife is a choral conductor and cellist, so they are well-acquainted with the sound of real instruments and voices in real spaces.

She however tires of audiophile talk in a hurry. Once years ago when I brought an LP, I believe it was the Chesky reissue of the Reiner/Chicago Red Seal Stravinsky Song of the Nightingale, and we were marveling at the recording, I said "And what a terrific piece!" She started practically screaming: "He talked about the MUSIC!!!"
 
There needs to be an orderly process:

1. Do something "nutty", and find it has an effect.

2. Attempt to understand the underlying process that has caused the audible change, and implement a good engineering solution to the issue.

3. If it's impossible to understand the process, because you haven't the knowledge or ability, and no-one else that you've come across has come up with a sensible explanation - then continue with the "nuttiness" but do it, or recreate it, in a reasonable manner; that is, using low cost, conventional materials and parts.
 
She however tires of audiophile talk in a hurry. Once years ago when I brought an LP, I believe it was the Chesky reissue of the Reiner/Chicago Red Seal Stravinsky Song of the Nightingale, and we were marveling at the recording, I said "And what a terrific piece!" She started practically screaming: "He talked about the MUSIC!!!"
Can be fun, too, :D. A friend, who I've got on the "right path", ;), put on an LP of British Isles bird calls, with a terribly, terribly correct, BBC voiced commentary on what we were hearing, of some of the most dreary, uninspiring bird noises one could imagine. We were all having hysterics - it was better than The Goon Show ... ;)
 
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Can be fun, too, :D. A friend, who I've got on the "right path", ;), put on an LP of British Isles bird calls, with a terribly, terribly correct, BBC voiced commentary on what we were hearing, of some of the most dreary, uninspiring bird noises one could imagine. We were all having hysterics - it was better than The Goon Show ... ;)
When Daniel Kessner was talking his final PhD oral exam at UCLA, one of the committee played a recording which, in the context of the PhD in music and Kessner's own music, could have been supposed to be something by a contemporary composer, perhaps along the lines of Penderecki or Ligeti.

Danny was a bit puzzled, but came through with flying colors: "Aren't those wolves??"

They were.

Kessner went on to become a professor of composition, and recently retired. Makes me feel a little old, which I am.
 
There needs to be an orderly process:

1. Do something "nutty", and find it has an effect.

2. Attempt to understand the underlying process that has caused the audible change, and implement a good engineering solution to the issue.

3. If it's impossible to understand the process, because you haven't the knowledge or ability, and no-one else that you've come across has come up with a sensible explanation - then continue with the "nuttiness" but do it, or recreate it, in a reasonable manner; that is, using low cost, conventional materials and parts.

Hi Frank,

That doesn't really seem orderly-enough.

If we're talking about doing engineering, and I believe that we are, then you should probably first try to identify a problem or need, which you want to be solved or satisfied.

And you would want to weight the problem or need and compare it to the potential time, costs, performance/benefits, and risks that might be involved, i.e. it should be determined to at least be significant-enough (and maybe doable-enough) to justify even thinking about working on it.

Actually, you would want to try to identify all of the problems and needs, first, and prioritize or otherwise organize them, so you'd have some idea of where your time and money would be most effective, and valuable (and would probably also want to attempt to understand or estimate and map any dependencies among them, etc.), and try to pick the "best" starting point.

Then, if you don't know how to attack the problem or need that you're working on at the time, the LAST resort would be a Monte Carlo (i.e. "random") type of approach, i.e. shot-gunning it until "something happens", which is what your "do something nutty" reminds me of (But maybe you already know what to try, from experience or insight. But that would make it not "nutty".).

Instead, I would first want to attempt to break the problem I don't know how to attack, much less solve, down into smaller and smaller pieces until I have a bunch of little things that I do know how to attack or maybe even solve. That's one definition of engineering, by the way (for any non-engineers, here).

Then you work on each small problem or need, validate and verify your solution for each one as you go (or whenever it's logical), and then eventually recombine/integrate them in the obvious logical fashion (you decomposed them to begin with) and validate and verify each clump of them, and finally the whole thing is thought of as one big system again and you validate and verify that, and then it's ready for the customer (you, in this case), or production, or LRIP (low-rate initial production), or prototyping, or putting the cover back on, or whatever stage of the process (and type of application of the process) you happen to be in, or emerging from.

That process is also to be thought of as recursive (as well as iterative), i.e. applied to any sub-item as needed. And along the way, you probably need to repetitively do a few other types of loops or V's to iteratively and recursively evaluate or assess options and their costs, performance (e.g. versus the derived requirements), and risk relationships. i.e. At each stage, possibly, you need to define (or recall) key performance parameters and system attributes, derive technical requirements from them, define and test the baseline, test during development, and then later do operational testing, document the results of each of those, assess performance/cost/risks versus requirements for each of those (at the time), and re-refine or re-define your engineering plans per all of the above, all along the way, i.e. possibly for each clump of problems/needs/system components/etc and for each item in each clump.

It's a development process. If proper adaptations are made it applies equally well to development of a system and to development of an increment of capability.

Sorry if I didn't explain it well. It's been a while since I was a systems engineer (thankfully). For a large system or project, there are a LOT more steps, and many, many required formal events and reports and decisions and entrance and exit criteria for each phase and milestone (and each sub-phase and sub-milestone, sometimes almost ad inifinitum). Thank God I'm back doing semi-technical stuff, again.

Cheers,

Tom
 
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Nice effort, Tom ... :D

I was really talking in the context here of people purchasing, or trying wacky "things" to help their sound, and indeed hearing that there was a change. So, rather than trying to force that variation to fall into a "it must be all in my mind" slot, I'm just suggesting here a general approach for dealing with the abberation. Yes, of course, one should do reasonable tests to make sure that the effect is reversible, or whatever is necessary to get a handle on it, that you can be sure you're hearing something "real".

True, from quite a bit of experience I do know generally what to try, :p, but it doesn't mean I always know the engineering solution for the situation. There are things that I still have in a 'dunno' box - I can make guesses, etc, but for true understanding I would need a level of knowledge and test equipment that I don't have ...

The most powerful tool in my arsenal is knowing what the reproduction should sound like - that is a very clear measure in my head, how capable the playback should be - either a system is up to scratch, or it isn't -- this makes life a lot easier in knowing what to do next ...

Cheers,
 
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Now an issue that many seem to have missed is the noise in the power supply even when it is unplugged.
I didn't miss it, just got caught up on the thread. I wondered why the green line wasn't much lower than the reverse polarity line (nice trick!). But hey, there's noise everywhere. I even went so far as to plug battery powered measuring equipment into the earth in my back yard. Plenty of 60Hz and harmonics, mostly odd. It's everywhere.
 
people close to the antenna have reported hearing AM radio on their speakers with the amp power off

I can do that any day with a piece of wire across the aluminum tracks on the sliding windows and power my speakers from the FM radio station above me about 150 yards away. Made me think I was nuts the first time I heard that happen and knew the speakers weren't hooked up to the amp!
 
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If you treat audio as a technical pursuit with a clear definable goal it has a rational endpoint and goalposts that can be attained through engineering. If audio is a mistress promising sensual delights that can be attained only after enduring some arduous tests and personal deprivation it fits the myth and give a purpose to the ongoing frustration that the sound is not good enough yet.

I still think that it is a bit misleading although a reasonable thought.
If we are talking (for simplicity) about the reproduction of a real acoustical event (i.e. acoustical instrument, singer ) then "hifi" could only mean in a technical sense, that we have to reproduce the original sound field in perfection.
Any deviation from the original soundfield would be an intolerable error.

But "audio" normally means that the reproduction is made for human listeners and therefore audio engineering (and its objectives) is obviously bound to human perception and the intersubject variation in thresholds, listening habits and preferences, which can be sometimes quite large.

While the rationale endpoint of audio engineering should be the above mentioned perfect reproduction (leaving aside the problems that would arise during reproduction in normal rooms/systems/situations), during the evolution we need psychoacoustic experiments and (often) kean listeners to rely on.
 
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I didn't miss it, just got caught up on the thread. I wondered why the green line wasn't much lower than the reverse polarity line (nice trick!). But hey, there's noise everywhere. I even went so far as to plug battery powered measuring equipment into the earth in my back yard. Plenty of 60Hz and harmonics, mostly odd. It's everywhere.

On the east coast usa, that is a given. We have single bushing transformers (actually, autotransformers) on the east coast. Every 2 or 3 poles, they run an earthing conductor tied to the neutral conductor feeding the houses. This neutral conductor and earth is the return for the HV at the very top of the pole. As a consequence, anywhere from 2 to 5% of the current through the wires is actually being conducted through the earth. There are 60 hz gradient fields in the dirt..

That's one of the reasons to never run an independent earthing rod for a stereo.

Another is the issue of a nearby strike, it can force very large earth gradients, and if two earthing rods feeding a stereo get caught in the middle of the earth gradient.......toast.

jn
 
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Lucy Bell had a tooth
Lucille Ball. She claimed to pick up all sorts of radio signals in her tooth.
I had a cousin who claimed the same, tho he said it wasn't loud or clear, just always in the background.

The inducted audio from FM confused me at first. What's doing the frequency to amplitude conversion? Then someone told me that there is a large AM component to the FM. If you're close enough, it has some power. Is that right?
 
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