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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 29th August 2011, 10:51 AM   #15501
abraxalito is online now abraxalito  United Kingdom
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If you reckon if they'd standardized the hugely complex elliptic A-A filters that were generally in use in those days (early 80s) we'd all be using DSPs applying their phase inverse to 'correct' the rather more benign phase characteristics of the digital filters used today? Or that those analog filters would have gotten set in stone preventing advances to digital ones? Either way doesn't sound like a recipe for great sound to me.
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Old 29th August 2011, 10:57 AM   #15502
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John Curl's Blowtorch preamplifier part II
If it's standardized, the pre-correction could be done at the recording end, even with early-80s technology. I put a demonstration together at the time for the management of the company I worked for, using our proprietary computers (which is what we sold); unfortunately, although it was easy to see the advantages on a scope, none of the big bosses could hear any difference. As much as I tried to convince them that whether or not they heard any improvement was a different matter than whether audiophiles would believe that they heard improvements, the project was killed. Ah, well.
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Old 29th August 2011, 11:03 AM   #15503
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Yes and if standardized it would still be built into the decoding chips even today, meaning that nobody could use the technically superior digital filtering which came along later without listening through inverse-cauer phase correction.

<edit> Brain fart - sorry didn't read your posting carefully enough! So the recording equipment could be upgraded without needing any corresponding upgrade to the replay equipment then? So why would it need to be standardized? Surely the A-A filter and the pre-correction of phase could just be a single unit?
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Old 29th August 2011, 11:15 AM   #15504
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John Curl's Blowtorch preamplifier part II
It doesn't have to be in real-time; given the slow speed of computers of that era, my demo was post processed (took all night!) before playing back.
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Old 29th August 2011, 11:17 AM   #15505
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John Curl's Blowtorch preamplifier part II
After re-reading a couple of rsdio's post I realize that I should address one point. I am simply stating that no resampling/anti-imaging algorithm that I have seen used currently even approaches the numerical limit of 64bit floats.

It is true that a real music signal sampled at 192kHz will have energy in even a 20-22.1kHz transition band. I would like to see the best a brute force approach could do on real signals. I won't volunteer to hear the difference since I can't hear a 16bit 17KHz brickwall.
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Old 29th August 2011, 11:21 AM   #15506
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So you ran some digital tape machine at 1/100th normal speed so it was correctly sync'd up to the uber-slow computer? Who did the engineering to put the tape machine into action replay mode? Sounds like a fun job
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Old 29th August 2011, 11:24 AM   #15507
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Quote:
Originally Posted by scott wurcer View Post
I won't volunteer to hear the difference since I can't hear a 16bit 17KHz brickwall.
Fortunately for us oldies, at 17kHz it don't need to be a brickwall at all. There's a full 5kHz for the transition band
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Old 29th August 2011, 11:29 AM   #15508
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Quote:
Originally Posted by abraxalito View Post
So you ran some digital tape machine at 1/100th normal speed so it was correctly sync'd up to the uber-slow computer? Who did the engineering to put the tape machine into action replay mode? Sounds like a fun job
No, we didn't use tape- we had large hard disks. You could get almost 5 minutes of music on them! The signals were processed and dumped onto another set of hard disks.
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Old 29th August 2011, 11:32 AM   #15509
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Ah, the days when a large HDD was 50MB. A bit before my time
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Old 29th August 2011, 11:57 AM   #15510
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They were flying saucer sized. Had handles.

Just to give scale, the instrument I was working on at the time was about the size of a Mini Cooper, with a full desk console and an equipment rack. I now have in my lab a functional equivalent, albeit much easier to use, faster, more versatile. It's the size of a small printer and cost 10% of the earlier unit's price in actual dollars; accounting for inflation, I suppose that would actually be closer to 3%.

Damn, I starting to feel as old as John.
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