John Curl's Blowtorch preamplifier part II

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The underlying problem is that at each stage efforts can be made to "improve" the perceived sound. They are all independent and still interactive. .

Sometimes one engineer does all recording and mixing. However, it is the producer's job to make sure everything is optimized in an overall coherent way. That starts with the song, arrangement, instruments, mics, recording medium, and so on down the line. If anything is done poorly at any one stage, it often can't be fixed later.
 
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...An old analog trick for doing it is to apply half the EQ and record to tape. Turn the tape over so it it traveling backwards over the recording heads and add the other half of the EQ. Either way, you end up with "pre-ringing" type effects since you are applying some of the EQ backwards in time.

Wow! Analog FIR (sort of)! I never heard of that trick before. Mark, do you know any examples of commercially available recordings where this was done?

- Jim
 
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It does look like that monitor has a dip from 1-3K, at least off axis.

45 degrees off axis is pretty severe though, esp as the 1976 WW article was referring to on axis dips in response. But intrigued me to revisit some of the Zaphaudio designs. Interestingly some of those are designed with off-axis listening in mind* and across the board they show how flat you can get off-axis if you think about it and design wisely.

*fully aware that those versed in the art will scoff at why I wasn't aware of the advantages of optimising for 15degrees off axis.
 
It is my understanding that there are different frequencies for different sample rates. In fact, I remember the AP folder to have separate files with names preceded by 44k or 48k or 96k.
Can't find it anymore..!

Yes I did find it! See attached some sample sweep tables.


Jan

Thanks Jan that's what I remember seeing. Take the 48k file for instance bin 3 and 4 imter-modulate into bin 7 (f1 + f2) and is masked because there is an input tone there so I just have a different understanding of exactly what is trying to be achieved. This is not true for the 44.1 file (for bin 3 and bin 4). My understanding was the Excel numbers were generated by some algorithm and you picked the closest match for your FFT size and sampling rate. If you allow unlimited orders of distortion for all 31 frequencies there simply are not enough unique bins.

EDIT - on some thought an algorithm that guaranteed >some< bins were always empty would be useful ( I guess?).
 
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Thanks Jan that's what I remember seeing. Take the 48k file for instance bin 3 and 4 imter-modulate into bin 7 (f1 + f2) and is masked because there is an input tone there so I just have a different understanding of exactly what is trying to be achieved. This is not true for the 44.1 file (for bin 3 and bin 4). My understanding was the Excel numbers were generated by some algorithm and you picked the closest match for your FFT size and sampling rate. If you allow unlimited orders of distortion for all 31 frequencies there simply are not enough unique bins.

EDIT - on some thought an algorithm that guaranteed >some< bins were always empty would be useful ( I guess?).

If you have high enough resolution FFT (I usually use 128K or 256K) and a suitable window pretty much everything has its own bin I would think, making the issue of finding optimum frequencies less important. I have used as high as 16M but you go out for lunch while its taking a measurement and then frequency stability becomes a real issue.
 
The choral pieces in "Bambi" are spectacular. I miss the classic mixed male female choruses of the 40's, 50's though I think the mics of the time had something to do with it.

Hi Scott, I miss them also. It's not the mics. They sounded like that live!

Those film studio choruses, the Robert Shaw Chorale, Roger Wagner, all had one thing in common - the singers were really good and even if they were not classically trained, probably all could sing classical repertoire.

Robert Shaw, when asked how he got his wonderful results, down played his own talents somewhat when he said something like, 'I find the best singers I can, and let them sing.'

He and those directors of that time all let their artists sing with their natural vibrato and formant and the blend is that gorgeous sound.

I can say this confidently because I sang in a very small amateur choir in the 1960's under a talented American conductor who thought Shaw was the bee's knees and in a very short period we started producing the same sort of sound. (Not as good, though).

Here ya go Shaw, 1948. Noise and all, still sounds good.
https://www.youtube.com/watch?v=siYf8YIlY3Q

1956, this is exquisite

https://www.youtube.com/watch?v=Oc22Vfzl1Kg

Living Stereo

https://www.youtube.com/watch?v=Mbf5CuabIlY&list=PLD02C2991130D9839&index=30

I just stumbled over this and you get it because Doris is a doll and in 1954 I think my wiring got connected right listening to her. The back up is Norman Luboff singers.

https://www.youtube.com/watch?v=Lc5xknlOl3c
 
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The phase shift comes from the math. One change necessitates the other. Good DSP UI will show both. However I doubt you could hear the phase effects unless the frequency effects are huge.

Did someone already point out that with FIR filter eq you can manipulate the amplitude response and the phase response completely separate. You can have say a 100dB/oct roll off yet flat phase response throughout that.

Jan
 
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Thanks Jan that's what I remember seeing. Take the 48k file for instance bin 3 and 4 imter-modulate into bin 7 (f1 + f2) and is masked because there is an input tone there so I just have a different understanding of exactly what is trying to be achieved. This is not true for the 44.1 file (for bin 3 and bin 4). My understanding was the Excel numbers were generated by some algorithm and you picked the closest match for your FFT size and sampling rate. If you allow unlimited orders of distortion for all 31 frequencies there simply are not enough unique bins.

EDIT - on some thought an algorithm that guaranteed >some< bins were always empty would be useful ( I guess?).

I was indeed under the impression that IM tones would fall in empty bins, that that was the whole deal with the special algorithm. I never actually looked at it the way you did (which is yet more proof that you are much smarter than I am of course ;-).
I do remember that there was a limit to the number of harmonics this would show, depending on FFT size and such.

I have a folder of more than a dozen with this type of files, if anyone is interested.

Jan
 
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The average British 'salon' appears just large enough to fit seating for four, in which the lord of the manor leap jumps over the furniture in the absence of visitors to entertain. (aka, my home is my storage room)

Yes, I know what you mean.

They are selling strong chandeliers here as well so you can swing from them with one arm whilst scratching your armpit with the other.

After that, you go out and buy 2 litres of warm beer and the Sun for a relaxing morning sitting on the doorstep.

:D
 
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If you have high enough resolution FFT (I usually use 128K or 256K) and a suitable window pretty much everything has its own bin I would think, making the issue of finding optimum frequencies less important. I have used as high as 16M but you go out for lunch while its taking a measurement and then frequency stability becomes a real issue.

:cool::) THx, I can use that... good practical directly useful solutions.


-RNM
 
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