John Curl's Blowtorch preamplifier part II - Page 961 - diyAudio
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Old 7th February 2011, 12:46 PM   #9601
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I am on a diet, myself, gaining 10 lbs from too many potatoes and 'chicken fried steak' on the road to and from Las Vegas, so I would like to talk a little about differences in phono cartridges. This is something that apparently only Joachim and I can talk seriously about, but what the heck!
About 5 years ago, I needed to replace my MC phono cartridge. I went to the local importer, Immedia, to get a replacement, as I had one of their Lyric cartridges, already, and I knew them through CES shows, etc. I was recommended to get a Helikon SL, by Allen Perkins, the proprieter, but the cost, even wholesale (remember, I am in the audio family of manufacturers and this is OK) was daunting. He then offered me a slightly used, lessor priced unit, called a Dorian, that my associate Brian Cheney had used at a recently previous CES, and one heck of a good price, because it was used, but in perfect condition. Remember, this is a shop that has the equipment and experience to inspect these cartridges for problems. I called Brian Cheney, and he said it worked well for him at CES, so I bought it.
After mounting it, and playing it for awhile, I knew I was MISSING something. The cartridge did seem to play the record alright, but it just was not at the level of the phono cartridge that I had previously used. Now, it is 5 or so years later, and I am still complaining.
No, the cartridge didn't need to be 'broken in' that had already been done at CES. If I only had to get used to it, well, it has been long enough. What is the 'magic' that is missing and WHY is there such a spread in cost for MC phono cartridges? (more later)
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Old 7th February 2011, 01:27 PM   #9602
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Quote:
Originally Posted by Soundminded View Post
Apples and oranges. Military grade hardware always requires far more testing, much tighter tolerences, more documentation, and a far more elaborate administrative and tracking process than even industrial equipment let alone consumer grade equipment including high end audio equipment.
You just regurgitated what was stated..

Um, I repeat::And even at those ratios, the profit was not very high. QA and labor was a very big chunk of the final selling price.""

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Originally Posted by Soundminded View Post
There are many factors that affect manufacturing cost and selling price of high end equipment. Small production lots means no economy of scale in many aspects such as tooling.
Again, you regurgitate what I stated..
Again, I repeat...:""Amps like JC's, wires like SE's, lots of the high end stuff has by nature, very large labor costs as a result of scale of manufacture and complexity.""

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Originally Posted by simon7000 View Post
If I still had my plots of 300B resonances and could post it then it would be clearer that the multiple metals, flexure modes, three dimensional structures and the incredible number of resonances make tubes' resonance effects non-linear to the max.
Actually, I disagree with you and agree with Scott... The level of deflection is not outside the non-linear range. What you are doing is neglecting a higher order linear model with intermodal coupling, and instead insisting that because it does not act like a simple model, it must be non-linear.

Quote:
Originally Posted by simon7000 View Post
If you look at how a grid is often a porous tube and must wiggle sideways to really change things, then you understand why I call that buckling mode.
Buckling is a non-linear term. Using it only adds confusion to the discussion. Buckling is non-reversible behaviour.

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Originally Posted by simon7000 View Post
As mentioned electric circuit theory resonances and acoustic ones may share the basic math, but they are not identical.
The order of the model is the name of the game...they are indeed the same math.

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Originally Posted by simon7000 View Post
I have presented that it may be an improvement over current practice to also have a high resolution time domain measurement. It may show something that went unobserved by other techniques. That is based on the work I do and issues that have been problems.
Your inputs may or may not actually be an improvement over current practice...the discussion however, is welcomed and may indeed improve practice..
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Originally Posted by scott wurcer View Post
I knew that for 30 years. You (soundminded) still like implying we are all fools.
Ah, so I'm not the only one who feels that way..

Quote:
Originally Posted by simon7000 View Post
Scott,

This is my test setup for resistor very low level signals.
You've put the whole kitten-caboodle into a magnetic box? It looks like you have formed a ground loop with the two boxes and the cable between them. If so, how do you control where the ground current travels? DC will go through the box....hf will go through the cable shield... And, at the levels of interest, vibration will couple to the shield cable, residual magfield will cause errors a-la faraday..

BTW, still nice work..

Cheers, John

Last edited by jneutron; 7th February 2011 at 01:30 PM.
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Old 7th February 2011, 02:10 PM   #9603
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Another point ED, you show a dead zone in an ordinary resistive divider just like one would find in an ordinary op-amp follower with feedback. So it might be worth wondering why in 35yr. with millions of amplifiers and thousands of customers, not one has ever sent me a picture of this wondering what was up. This includes physicists building photon counting cameras and folks building things like load cells or any number of ultra-low noise systems that have to be continuous through zero. Not one nada. Remember the old days when op-amps had a trim pot to zero them? Never heard of one that you couldn’t zero. How about CD players doing the -60dB at 1kHz test. Never saw one with a trail of harmonics.

Though I also think this stuff is good to do.
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Last edited by scott wurcer; 7th February 2011 at 02:25 PM.
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Old 7th February 2011, 02:44 PM   #9604
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Quote:
Originally Posted by john curl View Post
(more later)
You mean Lyra? Anyone that can get away with a $5000 mono cartridge must be doing somethig right.
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Old 7th February 2011, 02:48 PM   #9605
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My phono cartridge is ZYX R1000 Airy3. I'm very pleased with it and I cannot afford any better one.
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Old 7th February 2011, 02:50 PM   #9606
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I might as well continue with phono cartridges, as a few things are fresh in my mind.
First, a little history: Almost everyone in the USA started with a Shure phono cartridge.
This is a so called 'moving magnet' cartridge, as it is what it is. A 'moving coil' or MC cartridge is what it is called, as well, a moving coil. This offers certain advantages, and some limitations.
I used my first MC cartridge (Ortofon) in 1965 (yes, 45 years ago) and seldom if ever, looked back. In those early days, the Ortofon phono cartridge had a 100:1 step-up transformer directly attached to the cartridge. You can just imagine the compromises that poor little transformer had designed into it. YET, it still sounded better (to my ears) than the Shure, or similar cartridges available. By 1967, Ortofon had removed the transformer from the cartridge itself and put it in a separate plastic box. This allowed for a slightly better transformer (not that much better) and I think they reduced the winding ratio to 50:1. I used this cartridge with or without transformer (when I had a suitable head amp) for about 5 more years. Ortofon, at the time, was the only MC cartridge that was normally sold in the USA at that time, because Grado owned certain patents, and this discouraged importation of other MC phono cartridges, especially from Japan. However, this was challenged in the early '70's, and a 'flood' of MC phono cartridges became available: the most popular being SUPEX and DENON. These phono cartridges had somewhat more output than the Ortofon, which made pre-pre or head amps, more practical and popular. This is when the Levinson JC-1 was produced (1973), and with its 0.4nV/rt Hz noise floor, worked very well with the whole range of MC pre-preamps. This, coupled with new direct-to-disc records that really showed the capability of vinyl recording, created a mini 'golden age' of record and hi fi reproduction. (more later)
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Old 7th February 2011, 03:24 PM   #9607
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By 1974, a new age of phono reproduction was being introduced, both tube and solid state electronics, and many of these new phono cartridges were measured by John Meyer and myself, at our Swiss Lab. We had the newest and best test records and the latest B&K test equipment to make the measurements. It was amazing how SIMILAR these MC cartridges measured, especially in frequency response. At the time, we measured Supex, Ortofon, and EMT (a German MC cartridge). We found that all had an EXTENDED RESPONSE, the lowest being 30KHz (EMT) and the other two around 50KHz, or at the limit that we could measure.
We found that most MC cartridges had a characteristic 'trough' or 'suck out' due to 'scanning losses' that could be compensated for by adjusting the cartridge damping-tip resonant frequency. This, some MC and other phono cartridge manufacturers do, in order to get a 'ruler flat' response to 20KHz, conveniently ignoring anything above 20KHz. Most MC cartridges had to live with the scanning loss, only reducing it by making better scanning phono styli that worked better. This is part of the high cost of modern phono cartridges. (more later)
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Old 7th February 2011, 03:32 PM   #9608
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Quote:
Originally Posted by jneutron View Post
Actually, I disagree with you and agree with Scott... The level of deflection is not outside the non-linear range. What you are doing is neglecting a higher order linear model with intermodal coupling, and instead insisting that because it does not act like a simple model, it must be non-linear.


Buckling is a non-linear term. Using it only adds confusion to the discussion. Buckling is non-reversible behaviour.


The order of the model is the name of the game...they are indeed the same math.

You've put the whole kitten-caboodle into a magnetic box? It looks like you have formed a ground loop with the two boxes and the cable between them. If so, how do you control where the ground current travels? DC will go through the box....hf will go through the cable shield... And, at the levels of interest, vibration will couple to the shield cable, residual magfield will cause errors a-la faraday..

BTW, still nice work..

Cheers, John

John,

Linear or non-linear here we can disagree. Most of my experience is with acoustic resonances which in start up mode is non linear. I think from way back that was the issue. I agree if we suspend an aluminum bar from a string that excitation is linear, (Used to actually do that, amazing how loud you can get it.) Seems we are getting into chaos theory. But I think we all agree movement in a vacuum tube either externally applied or from internal forces can be an issue. As tube design progressed they certainly made the internal parts stiffer.

I mentioned my example of a church where adding 16 sabins of absorption changed it from bad to good for speech. I understand most folks reading that would not understand why that is so amazing. As the church was 500,000 cubic feet or so and already would have had 3000 sabins of absorption it is almost mind boggling that adding 16 more at the right place would solve a resonance (Not a slap back.) If the start of resonance were linear that would not have happened.

Buckling behavior as I used it is a motion off axis to the applied force caused by non-uniform strength of the column. An argument over semantics I think we can leave to others.

Any order of the model past first is just way over my head! Again as I am using parts not building them I want to see how they perform. Improving the product is often a level of depth I do not want to go into. So I will just stick to parts that work better for my designs.

As to the picture it started out as two AL boxes, I tried the steel overcoat to see if there would be any change, there was not. All the magic really occurs in the small cast box. This example was made out of my junk box. I consider the proof of concept to be far enough along I may build a specific gizmo to look deeper.


Scott,

So far I have tested a known bad resistor, and an off the shelf carbon film cheapie. The bad one shows lots of undesirable behavior around zero volts. The carbon film shows some behavior at the limits of my current setup. I am using a preamp with just an RF low pass filter. That is why 1/f noise is an issue.

I may build a test specific instrument. This will require an oscillator with extremely stable output level but not really low distortion. A band pass filter to follow the oscillator to reduce out of band noise. A resistive voltage divider to feed a step down transformer to feed my device under test a signal under 100nv. This will be followed by a step up transformer feeding a band pass amplifier. As I would like to get at least 100mv out to make the display easy that would require a gain of one million. Actually do-able but will require a great deal of care to not oscillate. Noise figure is easier to do, since I am using a transformer which can provide voltage gain.

You ask the very reasonable question as to why this does not show up in lots of other applications. My working model in my opinion is that the problem goes away if there is a voltage spike to punch through whatever has formed to cause the dead zone. Once voltage drops to zero the problem may re-occur with time (way more than just seconds.)

As it is my feel is that we are looking at something that for good parts my be as low as 10 picovolts and as large as 1 millivolt (clearly a defective device) I do not want to subject the device under test to any large voltage.

I also suspect if you had a dead zone of 10pv that the amp would slew right through it.

ES
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Old 7th February 2011, 03:55 PM   #9609
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Now, what about other MC cartridge characteristics? Well, tracking difficult passages on the record, is certainly one. MC cartridges always had some problems with mis-tracking, but IF the phono stage had enough 'headroom' the problem occurred so briefly, that it could be essentially ignored by most listeners, BUT if the phono stage clipped or went into slew rate limiting (relatively easy to do) the sound quality would change significantly. This was one REAL advantage to typical MM cartridges like the Shure, they usually track well, and they are intrinsically bandwidth limited by a 4 pole low pass filter, built into the phono cartridge system, itself, and they can't slew their way 'out of a paper bag!'
This makes it very easy for otherwise mediocre electronics to be happy, and sound OK.
(more later)

Last edited by john curl; 7th February 2011 at 03:58 PM.
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Old 7th February 2011, 04:11 PM   #9610
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Now, what about distortion characteristics. The very best way to compare phono cartridges, and MC cartridges in particular, is to use ONE LAB, for the comparisons. A good resource for this, at least for past phono cartridges was a hi fi magazine called:'High Performance Review'. This, now defunct publication, tried in the best possible way to correlate MEASUREMENTS with SUBJECTIVE RESPONSE. They had the equipment, they had the patience, and these measurements that they made are still the best overall comparison that I have ever found.
Now, what did they find? In truth, not much. Disappointingly, mostly because of the lousy test records available, but also the similarity between MC phono cartridges, there was nothing that really stood out to tell you whether one phono cartridge sounded better than another. In the end, except for perhaps designer opinion about what is most important, there are very little measurable differences, AND they had 50KHz response nailed down, 37 years ago, at the very minimum. So why have MC phono cartridges gone from, let's say $100, to $5,000 or more dollars? What do you get for your money, if anything? (more later)

Last edited by john curl; 7th February 2011 at 04:18 PM.
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