Sound Quality Vs. Measurements
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 19th October 2012, 12:18 PM #7471 nigel pearson   diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire Hi Andrew . Think it is circa .0.02025 % of 31 . Know what you mean and you are probably right . 31.0063 ish . 22/7 is not bad . A lady in the pub tried to convince me that 22/7 is correct and 3.1415927 an approximation . She is sort of right . We were told at college 22/7 would be more correct as we might have an opportunity to cancel 22 or 7 in the calculations . I built my first calculator £14.95 and it save £5 on ready built . The other nice number is the so call Fibonacci no of 1.6180339887 Squared is 2.6180339887 Reciprocal is 0.6180339887 Nice thing with that one is it can be calculated if you forget the number very simply by doing the sequence . 1 , 1 , 2 , 3 , 5 ,8, 13, ............. 4181 , 6765 ( i.e . 6765/41812 = 1.618034 ) . I love irrational numbers .
 21st October 2012, 06:31 PM #7472 benb   diyAudio Member   Join Date: Apr 2010 Also, golden ratio (and isn't this the "best" Measurement for a rectangular speaker box of the "best" Sound Quality?) = (1 + sqrt (5)) / 2 or in keystrokes for the Windows calculator: 5y2r=+1=/2= (copy-and-paste into the calculator!) Pi = alt-227 (thanks to Google) = π, but to me it's not "real" ASCII, as ASCII was originally only a 7-bit code. Lots of terminal and microcomputer displays used the highest eighth bit to double the number of displayable characters, but each manufacturer used different codes until the IBM PC sold a few million and its extended character set became a de facto standard, and then part of the real Unicode standard (or maybe there really was an 8-bit extended ASCII standard somewhere in there). It always bugs me when those high-bit characters are called ASCII. It's the danger of knowing too much history, er, obsolete info.
 21st October 2012, 08:45 PM #7473 tvrgeek   diyAudio Member   Join Date: Dec 2009 Location: Md Anyone remember the old AR research that said we need a minimum of 16 channels to have realistic surround? I believe the two low rear channels in 7.1 are actually mono, so it is really 6.1
 22nd October 2012, 06:25 AM #7474 nigel pearson   diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire Michael Gerzon had the ideal as 9 speakers . That would be 8 , one at each corner of a cube and a central speaker . I suspect the centre one would be difficult as if I understand it correctly that would not be just a subwoofer . The system worked by using the speakers as a decoder . Difference signals fed to each speaker . This would allow the sound to be rotated and create real stereo images in every position . That being true any image in any position is possible . I thought the 8 speakers could be electrostatic as in the middle section of Quad ESL 57's or Magnaplanar . I would imagine polar response to be important and might need something special . My friend Paul Stewart who was at JVC said CD4 was very convincing ( tape source ) . During a demonstration a lady offered him a drink . She wasn't there ! He said the big deal was he felt her approach . That should be possible and would be very realistic . This is how it started . http://www.audiosignal.co.uk/Resourc...phonics_A4.pdf I found Hafler decoding preferable . If a vinyl record was played through Hafler it generally sounded more relaxed . The surface noise seemed outside of the listening area ! Using a Dolby decoder to do the same made the noise more noticeable . Friends and I got use to using Hafler and liking it . That would be for films also . Sources then were VHS / FM / LP / CD . BBC Radio 3 was always good . The speakers need to be matched and of good quality .
 22nd October 2012, 04:21 PM #7475 benb   diyAudio Member   Join Date: Apr 2010 Now I'm reminded of another magazine article around that time (early to mid 1970s) describing a new technology, what equipment was needed, and whether the current stereo sources were compatible with the "New Monophonic Sound Technology."
 22nd October 2012, 05:47 PM #7476 nigel pearson   diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire Funny thing is mono comparability was and is still a very serious requirement of the more professional radio stations . The cheapest CD players had problems in the early days , they sounded dull in mono due to time delay . That was just a case of spending money . Denon DCD 300 was one that dealt with it . Philips also although taking different routes at that point . I still remember the DCD300 as an exceptional low cost CD player . I seem to remember Michael Gerzon was obsessed with mono compatibility . Perhaps he felt that the BBC would need convincing .
 24th October 2012, 02:59 PM #7477 nigel pearson   diyAudio Member   Join Date: Mar 2007 Location: Oxfordshire Advice please . A friend is trying to upgrade a Rotel CD965 . Rotel UK not only helped with a technical manual they also supplier an extensive upgrading guide ! They mention changing the clock . I have always fancied making a clock from a CD4060/ 74HC4060 and RC astable . I have a digital frequency meter so can get it right by tweaking resistors . Even if the Rotel can be configured that way I fancied the clean output of a 4060 an advantage . I will use COG caps and perhaps the full 14 divisions . I suspect caps are more stable in the nS ? 74HC4060 will drive LED's well . If over 20 mA they do the MOSFET self limiting very well . A White LED runs directly without harm to itself nor chip if 5V is used . 4060B counter/divider and oscillator
 24th October 2012, 08:37 PM #7478 tvrgeek   diyAudio Member   Join Date: Dec 2009 Location: Md A crystal is far more stable. To do better, it has to go into a controlled oven for precise temp control. I know of no cap with a small enough temp coefficient for this use. Even humidity and small variations in voltage change caps basic parameters too much.
dvv
diyAudio Member

Join Date: Sep 2004
Quote:
 Originally Posted by tvrgeek A crystal is far more stable. To do better, it has to go into a controlled oven for precise temp control. I know of no cap with a small enough temp coefficient for this use. Even humidity and small variations in voltage change caps basic parameters too much.
I agree.

Caps should not be used for any precision function, unless absolutely unavoidable. They are too fickle overall, from delivering precise capacitance, via thermal behavior, to loss of precision over time. They are THE weak link of any circuit, and while they are irreplacable for power supplies and PSU decoupling, they should be avoided elsewhere.

I'd also go for crystal.
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dvv
diyAudio Member

Join Date: Sep 2004
Quote:
 Originally Posted by nigel pearson Advice please . A friend is trying to upgrade a Rotel CD965 . Rotel UK not only helped with a technical manual they also supplier an extensive upgrading guide ! They mention changing the clock . I have always fancied making a clock from a CD4060/ 74HC4060 and RC astable . I have a digital frequency meter so can get it right by tweaking resistors . Even if the Rotel can be configured that way I fancied the clean output of a 4060 an advantage . I will use COG caps and perhaps the full 14 divisions . I suspect caps are more stable in the nS ? 74HC4060 will drive LED's well . If over 20 mA they do the MOSFET self limiting very well . A White LED runs directly without harm to itself nor chip if 5V is used . 4060B counter/divider and oscillator
Perish the thought that I'm trying to dissuade you in any way, Nige, but my experience has taught me that the best way to tune a CD player is to buy a Real Time DAC.

Esentially, it has 8 DACs working in parallel, and thus eliminates the need for oversampling and brick wall digital filters, with their associated phase shifts, good as they may be.

When I bought mine from the Land of Oz, for something like US\$250 including shipping (that's about 150 quid), and when I connected it with my Yamaha CDX 993 CD player, it's original very musical character moved up a notch or two. It's a whole new ball game, and it's rather obvious from second No.1.

A clarity I think must be very hard to achieve by classic methods (though certainly not impossible), or at least, I have heard it done only once or twice, and in devices which did cost an arm and a leg.

Mine uses an AD 847 op amp for its output stage, but you could exchange it for tubes or discrete op amps if you like. In your case, even with MOSFETs.

Overall, my feeling is that this will bring about greater changes than using classic methods of tuning, but I hasten to add this is based on my sample only, not a comprehensive research project.

The additinal benefit is that such an outboard DAC can also be used to do its work on signals from your PC.
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