John Curl's Blowtorch preamplifier part II

[jacco vermeulen]

Originally Posted by bear

1. Some have lost a significant part of their hearing as the result of being over-exposed to amplified music.
2. Most musicians who have significant training "hear" the music in their heads - not in the "air".

D-right, meet my half Polish cousin, deaf as a bat after 30y in the business and still at it.
=> YouTube - Brainbox - Down Man

[bear]

Jan,

I do not know the details (and by the details I mean more than a description and picture of the room) of this flunked test by some person of "standing".

This is exactly my point. Not knowing enough of the empirically determinable details puts this test or ANY test into question.

Surely, you can not suggest that (to exaggerate for clarity) a DBT performed with a mid-fi receiver and run-of-the-mill 3-way speaker as the central components will be likely to yield useful information as to something like two high-end DACs?? (assuming no gross flaws in either one?) Clearly, the specifics of the test conditions is crucial, not casual.

What some other person said or did not say is a red herring in this case. He might be right, he might be wrong. He's got an hypothetical construct, that's all. And, of course a belief.

What i am saying is that a DBT is fine as a tool, but it is only as good as the test conditions permit - and the test subjects. If the test conditions are not sufficiently well documented and tested then it is merely a statistical reflection of a specific test condition and circumstance and MAY OR MAY NOT be generalizable to ALL cases...

Let's recall we are not talking about what is "good enough for the average person" we are talking about what is possible to achieve at the limits of the current technology!

_-_-bear

[SY]

I'll ask you the same question that John has repeatedly avoided: what special insight do you get into the sound quality of electronics/wire/whatever by peeking at the nameplate?

[SY]

Originally Posted by bear

There are two main problems with "professional musicians" and sound.

1. Some have lost a significant part of their hearing as the result of being over-exposed to amplified music.

2. Most musicians who have significant training "hear" the music in their heads - not in the "air". This is especially true of those who can sight read music... it is a problem in some situations.

So you'll also tag Rod's anecdote as worthless?

[jan.didden]

Originally Posted by bear

Jan,

I do not know the details (and by the details I mean more than a description and picture of the room) of this flunked test by some person of "standing".

This is exactly my point. Not knowing enough of the empirically determinable details puts this test or ANY test into question.

Surely, you can not suggest that (to exaggerate for clarity) a DBT performed with a mid-fi receiver and run-of-the-mill 3-way speaker as the central components will be likely to yield useful information as to something like two high-end DACs?? (assuming no gross flaws in either one?) Clearly, the specifics of the test conditions is crucial, not casual.

What some other person said or did not say is a red herring in this case. He might be right, he might be wrong. He's got an hypothetical construct, that's all. And, of course a belief.

What i am saying is that a DBT is fine as a tool, but it is only as good as the test conditions permit - and the test subjects. If the test conditions are not sufficiently well documented and tested then it is merely a statistical reflection of a specific test condition and circumstance and MAY OR MAY NOT be generalizable to ALL cases...

Let's recall we are not talking about what is "good enough for the average person" we are talking about what is possible to achieve at the limits of the current technology!

_-_-bear

Well you could read up on the test about the conditions, equipment, the pre-testing, the checks and balances, it's all there, well documented. I don't want to become personal, really not, but the fact that you personally don't know the details is because you didn't look them up. That's hardly something you can blame the test or the testers for.

Of course that casual test we did in our homes with our equipment is totally in the dark, so trusting that is equivalent to buying a used car after a phone call to a used car salesman .

jd

[bear]

Jan,

Please feel free to send me via email or link the best documented "DBT" you have? I'd be quite pleased to correct my comment in your favor, if it is warranted. I said I have yet to read one that I found to be even marginally well documented. So, if I have not seen it, why not just send it along?

SY, c'mon... I never said anything about "peeking at the nameplate"!! Your reading comprehension is off - that is the opposite of what I said. I'd expect far more detailed and comprehensive empirical and scientific measurements and tests.

As far as what Rod said, I dunno... don't think I made a direct value judgement on what he said rather I commented on the overall issue...

_-_-bear

[john curl]

I do not look at nameplates. I just keep track of the components under test. I don't have to be told 'which is which'. I just need to know that this is L and this is M for example, or D and H. This nameplate thing is a 'slander' to compromise my experience, in making intelligent and correct audio decisions.

[abraxalito]

Originally Posted by simon7000

In a linear network for a perfect step you get 100% of the settling on final value in 100% of the time allowed. An RC network settles to 63.7% of the value in one time constant (R*C = 1 time constant). It then settles to 63.7% of the remainder in the next time constant. (76.9% of final value) Of course it will never actually reach the final value, so custom is to allow 5 or 7 time constants. Since you want fast settling higher order filters are use.

Its obscure to me that higher order filters necessarily provide faster settling. As far as I can see, the settling time isn't so much a function of the filter order as the Q - a higher order bessel filter will settle quicker than a somewhat lower order elliptic for example.

So if your timing accuracy is really bad say 1% then a linear system will have a 1% level error, the inverse exponent system having dropped faster at first will have less error. With zero timing error the linear system should have no error and the inverse exponent must have some.

I don't consider a level error (linear) of 1% to be particularly worrisome. Do you? The faster the settling, the smaller this level error. 5 time constants will give an error -43dB down.

So if all your steps are single bit both methods are nice, but when you do a step of 1/2 full scale linear should still be zero error and inverse exponent will have the single bit remainder multiplied by the step size.

Sorry, I'm not following here. Both methods?

[jan.didden]

Originally Posted by bear

Jan,

Please feel free to send me via email or link the best documented "DBT" you have? I'd be quite pleased to correct my comment in your favor, if it is warranted. I said I have yet to read one that I found to be even marginally well documented. So, if I have not seen it, why not just send it along?

SY, c'mon... I never said anything about "peeking at the nameplate"!! Your reading comprehension is off - that is the opposite of what I said. I'd expect far more detailed and comprehensive empirical and scientific measurements and tests.

As far as what Rod said, I dunno... don't think I made a direct value judgement on what he said rather I commented on the overall issue...

_-_-bear

I don't particularly keep track of all tests I see, but the one I brought up before is here:

Boston Audio Society - ABX Testing article

There's an interesting one on speaker relative ranking blind vs sighted by Floyd Toole here:

http://www.harmanaudio.com/pv_obj_ca...rt_science.pdf

(the whole paper is a good read but the blind/sighted part is at this chapter "BLIND vs. SIGHTED TESTS – SEEING IS BELIEVING")

Now I am sure you can and will find flaw with either of those papers, but remember: even a serious attempt at documenting and controlling tests runs rings around the usual sighted, casual anecdotal 'tests'.

jd

[john curl]

Why should they be considered 'superior' IF they usually do not reflect what people hear consistently on their own. Perhaps it is the ABX test that is at fault. I think that is so.