John Curl's Blowtorch preamplifier part II

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I'm glad - and a bit surprised - that so many of you enjoyed the Seeburg background music. It's the best background music I've found so far. I enjoy the sections with a lot of piano and vibraphone. Much better than Muzak or the old 3M tapes. Many years ago one of my tasks was to monitor the Muzak feed that was on a subcarrier of our FM station. It was a top 40 station, but owned by Muzak to broadcast their feed on the subcarrier to all the Muzak receivers around Palm Beach county. I did not enjoy it.

I usually chill to my Pandora "Exotica" channel full of Les Baxter, Martin Denny, Arthur Lyman, Cal Tjader, Don Tiki, Richard Scott, Esquivel and others. The Seeburg background is a nice change.

(For some reason, I can only appreciate Ives during the cold winter months here.
Ives is a tough one. It's taken me decades not to hate him. That's odd, because I'm a solid 20th century kinda guy. Bartok, Stravinsky, Shostakovitch, Hindemith, Ligetti, Stockhausen, Varese, Berg, Bayle, I grew up listening to those cats - I even worked for Pierre Boulez. But Ives isn't easy for me.
 
This isn't new news. We use the T&M to aid and verify designs but no one who uses them in design think it/they tell the whole story.

Maybe some do think it is all? Who? Raise your hands.


THx-RNMarsh

When you get to ppm distortions and used within their specs, the only way to keep amplifiers apart is by measuring them.

All of you who believe in voodoo aspects of electric signals that cannot be measured with present technologies, please start praying to your subs.
 
When you get to ppm distortions and used within their specs, the only way to keep amplifiers apart is by measuring them.

Which is most probably incorrect. ;)

Btw, where does the ppm distortion requirement originate?

All of you who believe in voodoo aspects of electric signals that cannot be measured with present technologies, please start praying to your subs.

There is a difference between "cannot be measured" and "can be measured but people believe that it can´t be heard" and "not knowing what exactly has to be measured under specific conditions" .
 
My understanding is that some early CD player reconstruction filters couldn't handle intersample overs very gracefully. Supposedly, it's no longer a problem.

It created problems with resampling filters as well, but isn´t that missing the core of the "majors know what they are doing" argument?
Imo apparently it was quite easy to create signals that raise problems somewhere downstream and you have to assume that the same developers who didn´t see this problem would have nevertheless ensured that no signals could be created that violate the nyquist criterium.


<snip> Intentional digital clipping is used on a lot of modern recordings now, which makes inadvertent intersample overs seem fairly mild by comparison.
 
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Which is most probably incorrect. ;)

Btw, where does the ppm distortion requirement originate?

Mainly that a number of designs posted here in recent years reach that level. Members doing stuff for fun to see how low they can get distortion. Attached is the multitone plot for the amplifiers I am (slowly) building to run my active speakers with. I personally think this is a very good test, but isn't used much as needs a very good test set. This waveform is closer to 'real music' than most tests and although steady state gives a good idea of the IMD performance.

Based on this single data point and assuming amp not driven into clipping/current limiting I cannot see anything to suggest this is anything other than transparent to the source. That is of course my personal view as grot 10dB below the best noise floor in my room is (to me) undetectable. I am happy in my clotheardness
 

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Which is most probably incorrect. ;)

Btw, where does the ppm distortion requirement originate?



There is a difference between "cannot be measured" and "can be measured but people believe that it can´t be heard" and "not knowing what exactly has to be measured under specific conditions" .

ppm is not a requirement for audio, it just so happens that this is technologically possible.

I agree that there are 'measurement' differences as you mentioned. In the order you used:

1) not so much can't be measured on an electrical signal.
2) it is my experience that many differences can be measured, but not heard. Really gross differences that is.
3) not knowing what exactly has to be measured under specific conditions is a call for further study.
 
Jan, I really haven't 'smelled' differences in sound, you must be thinking of someone else. '-)
However, we do have a bit of 'newspeak' here. SY uses the latest 'definition' of 'ears only'. I use the same technique that I have used for the last 60 years, starting with differences in acoustic guitars, and migrating to audio reproduction systems. I just listen, but I also note the opinions of my colleagues, because I might be wrong sometimes about something. I have learned that I have to use either my ears (which are aging) or the listening feedback from others to be sure that any one of my designs is really sonically OK. Unfortunately, I found some examples of my designs that really 'sucked' even though they measured OK. I happen to believe in open listening, mostly to a product (either mine or some others) over time and and gain a listening impression that I can then use to rank the products overall quality, or success relative to price point. I used to do this with guitars, before I got into hi fi, and went to great lengths to find quality guitars based on their listening quality, no matter what they looked like. Therefore, I resold several 'beautifully made' guitars because I could not live with their sound over time, and kept one Mexican 12 string guitar, that was a BEAR to play, due to a weak neck, and had an ugly cigarette burn on its face. If I was affected mostly by sight, I would have kept the guitars that I sold off. It is the same way with hi fi. I don't really care what a product looks like (although many people do) just how it sounds.

You said 50 years in a recent post on another thread!
 
Oh you guys would HATE coming over to my house. :D This is what I've been grooving to for the past couple of days. It makes me happy.
Seeburg 1000 Background Music Radio | seeburg1000.com
You need chicken soup.

Click the Playing Now and tell me how long you can take it.
About six feet.

Frankly I could listen to a 1000 versions of "The Little Drummer Boy" all year long.
Number of artists: 582
Number of different versions: 779
Total playing time: 50 hours, 56 minutes, 3 seconds.
Shortest version: 0:01 (Pavel Buechler)
Longest version: 9:45 (Outer Rhythm)


Dan.
 
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It created problems with resampling filters as well, but isn´t that missing the core of the "majors know what they are doing" argument?
Imo apparently it was quite easy to create signals that raise problems somewhere downstream and you have to assume that the same developers who didn´t see this problem would have nevertheless ensured that no signals could be created that violate the nyquist criterium.

That the majors know what they are doing is for the the most part true. However, human error is always a possibility, and technology is always advancing so things keep changing, usually for the better. Sometimes it is two steps forward and one step back.

In the case of intersample overs, apparently the problem was with the CD players. That's where it was ultimately fixed. In the interim, once people knew about the problem, they recorded to a bit less than digital zero to minimize the chances of problems.

Ultimately, it goes back to the CD Redbook spec. If a CD meets spec, then a player should play it.

Regarding the present situation with digital clipping, that occurred slowly by trial and error, as a part of the loudness wars. It seems that people can't hear occasional clips on a good CD player, so mastering engineers did what their clients wanted, pushed the levels up a little more and see if it helps record sales. It did, at least for a lot of pop music.
 
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