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Old 19th May 2013, 02:10 AM   #39511
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Well, if anybody has the test record, we should check it out. I don't have it anymore, but I was told that the test 'triangle wave' that differentiates into a square wave was recorded at 1/2 speed or less. This would make sense with an older Westrex or similar recording head, if they they could be adjusted for maximum bandwidth by changing the feedback on the head. this would normally cause a bump at high frequency, about 40+kHz.
I am willing to go with solid proof that a nearly perfect square wave could be generated by any 'nearly perfect' phono cartridge, but I have never found it. I have only found extreme rolloff in older Shure, Empire, and other similar cartridges, because they could not reproduce 40KHz or more, so the square wave looked pretty smooth back in the 1960's or so. My own extended sweep frequency response measurements showed a slight rise, perhaps 3dB at 40kHz or so for Supex and similar phono cartridges. 30kHz for EMT. Almost completely flat from 20-20KHz, except for scanning losses that were not completely covered by early MC cartridges, except for EMT that was almost ruler flat 20-20KHz. We used an extended response Ortofon test record for our tests. Show me different results somebody, if you can. I have already done a number of measurements showing the trend.
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Old 19th May 2013, 02:17 AM   #39512
SY is offline SY  United States
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Originally Posted by john curl View Post
Well, if anybody has the test record, we should check it out.
I do. This was our tool for evaluating cartridges and how the EPC100 got "discovered" in the US. Read the Stereophile reviews for the story (their reviewer was a good friend of ours)- it ended up being their reference cartridge, replacing, yes, the V-15.
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Old 19th May 2013, 02:22 AM   #39513
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George, you misunderstand what I was testing for with my bandwidth measurements of MISTRACKING phono cartridges. I deliberately mistracked each cartridge, by finding an almost 'impossible' to track passage on a Sheffield direct disc recording. It was the MISTRACKING that generates the bandwidth, up to 500KHZ, with mistracking. I did NOT have to try hard to make the cartridges that I used at the time to mistrack, they did it within the range of their recommended tracking force with the passage I selected. Once the stylus leaves the groove, then it must come back down and 'crash' on the vinyl surface. The bandwidth then depends on the 'intrinsic' bandwidth of the playback cartridge with both mechanical and electrical resonances, some within the audio bandwidth, but most MC's outside the audio bandwidth. My concern was the EFFECT of such a broadband signal on a phono stage designed with only 20-20kHz in mind, and no more. I believe that I made my point 35 years ago. What have you guys done lately?
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Old 19th May 2013, 07:35 AM   #39514
morinix is offline morinix  United States
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Not much, just figured out how to bring the price of LCR phono down by a factor of something like 10. Other than that, just hangin'.
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Last edited by morinix; 19th May 2013 at 07:40 AM.
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Old 19th May 2013, 12:04 PM   #39515
gpapag is offline gpapag  Greece
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Originally Posted by john curl View Post
George, you misunderstand what I was testing for with my bandwidth measurements of MISTRACKING phono cartridges
Thank you M. Curl.
Now I understand what you were doing.
I am afraid that they were many variables in the mix.

It seems that many things are predictable and explainable by theory (which I didn’t know).
Attached, some telling FR/SQW
Source: https://sites.google.com/site/zevaud...e-start-point-

If you will read this https://sites.google.com/site/zevaud...ist/shure-v15v
You will find a way to separate electrical from mechanical resonances, at least applicable for MM cartridges.

In some of the FR plots shown below, you will find cartridges with HF peaking continuing raising past 20kHz https://sites.google.com/site/zevaud...omparison-list

George
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File Type: jpg Sqw test (simulation).JPG (143.1 KB, 151 views)
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Last edited by gpapag; 19th May 2013 at 12:11 PM.
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Old 19th May 2013, 01:25 PM   #39516
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Originally Posted by gpapag View Post
Scott, I think A/D is for audio far more important than cartridges.
Is it possible to explain what you mean by “some pretty bad AD/DA chips”.
Does it have to do with multibit/one bit decision or what?

George

PS. Who is TL ?
The performance when reproducing computer generated tones. I still have one vintage external DA from MOTU that will play a 24 bit sinewave from Audition (so the source has virtually no distortion) with very low THD and artifacts, better than the EMU0204. The EDIROL was even better.

I actually have several recent devices that won't reproduce a digital sine wave that hits +-32,767 in 16bit.
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Old 19th May 2013, 01:27 PM   #39517
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Scott can probably provide more insight but I think ADI has effectively exited the premium audio ADC market. The current products are less focused on ultimate performance. The current serious players for ADC are AKM, Crystal, TI and a few boutique houses. None of the major players have released new stuff in the last 10 years it seems. From what I have been able to determine AKM has many of the pro and semipro sockets. The AKM 5394A is the best performing ADC I have found but I'm sure someone here will tell me why its no good.
I have not looked under the hood, I can't disparage by brand yet.
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Old 19th May 2013, 01:52 PM   #39518
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Originally Posted by Pano View Post

A very good analogy, Scott. We sometimes blame the medium, when it fact it's just bad gear. At the shop we still have an object of fetish, a Sony Pro SVO-5800 S-VHS deck that cost several thousand dollars new. It's simply amazing. Used as a record/playback deck it rivals DVD quality. Even playing back commercially recorded tapes it looks better than you ever thought VHS could.

VHS is not a wonderful medium, but done right, it looks better than you ever thought it could. Much better. That comes at a high price, tho.
I don't know if you ever saw them making tapes, 1X speed in a room full of Panasonic NV7200's. Remember $50 - $75 for a new film on VHS? That machine could be picked up for $1500 or so, quartz locked capstan very low chroma noise.
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Old 19th May 2013, 02:06 PM   #39519
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Scott, I'd be happy to run a Letter to the Editor....

jan
Jan, the author would have to explain figures 4 and 5 (at least provide the equation for each) before it would be worth a discussion. I'm working on an article for the next issue, a sort of digital take on Gary Galo's article. I helped one of open source folks out on biquad digital filters for RIAA and it was an eye opener. There are several small (some DIY) DSP platforms that run biquad filters for crossovers/equalizers no reason they can't do RIAA or anyone of the other choices. To my chagrin the Behringer 24/96 does not seem to support arbitrary entry of the z domain poles and zeros.

Believe it or not, it is not rocket science. PS - I'm glad you got both Dick and Erik to contribute, now we need to work on Barrie .
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Old 19th May 2013, 02:27 PM   #39520
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I don't know if you ever saw them making tapes, 1X speed in a room full of Panasonic NV7200's.
Yes, pretty much. We had a room full of VHS dup machines, the auto-loaders. Each machine did 4 tapes, IIRC. I think they were JVC. Very well built, good, solid, well engineered. It was impressive to see and hear 200 tapes load at once! We soon discovered it impressed the ladies, so they'd get a night time tour.

Back in the early 70s I used to buy music on cassette from Columbia House. They were uniformly awful, and I didn't understand why. If I recorded an LP on my cassette deck it sounded pretty darn good, way better than the prerecorded tapes I bought. That was when I learned about high speed tape duplication and cheap as possible tape and shells.

Just because something can be good, doesn't mean it will be.
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