As a former physical geography student, and magnifying glass starer of mica/silicate at the A'dam geology faculty, may I suggest a read-up on the definition of ''erosion''
(Also look up the term silicon/silicate passivation)
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Don Johnson in "a boy and his dog" (1975) : small, crooked, and with a serious teeth gap.
Couple of years later he had his entire front lawn recapped and closed up.
As goes for 2/3d of Hollywood (after they made some cash), Clooney, Michael Douglas, the works.
Most authentic actor is Steve Buscemi, and one of the best.
The former Tom Cruise : http://db2.stb.s-msn.com/i/EE/5AD3F363D4577AD3DECD371C5E3266_h338_w464_m2_q80_cQqyQyZbe.jpg
Afaig, of the less fortunate in the US, about a million a year book a dental holiday leave of (N2O) absence in Cancun, Tijuana and the likes.
(it's said that cheap beer is bad for teeth. Marriage on the other hand is good for an increase of dentist's revenue.
Before : http://www.fotosmulders.nl/500px/December 2003/Prins Willem Alex 24010144.jpg After : http://sphotos-b.xx.fbcdn.net/hphotos-prn1/p480x480/935049_165780600252528_341016860_n.jpg )
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Yes. I remember going through math classes wondering what the hell all this stuff was about. No one explained the big picture to me i.e. how you start with simple algebra, how that progresses onto geometry, trig, then solids, limits and the calculus. The result is I drifted through a lot of my math education in a 'dwaal' which is South African for in a daze and passed exams through rote learning. With high level math, you really need to be able to abstract, much like software coding. Anyway, my linguistic skills were always ok. My spelling is remains crap. Thank goodness for spell checkers and LTSpice!
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Wow, you know what, I learn at least one thing here most days, but the comments here from other autodidacts further along the path to enlightenment (or is it just a deeper state of confusion?) are extremely encouraging.
these days when i'm less addled and things tend to stick more readily, even moreso. I had the very same experience re maths, my 'educators' had a lot of trouble showing where the progression of math and its abstraction was leading towards a practical outcome. maths simply for the sake of getting the correct answer starts to lose its shine after a while.
these days when i'm less addled and things tend to stick more readily, even moreso. I had the very same experience re maths, my 'educators' had a lot of trouble showing where the progression of math and its abstraction was leading towards a practical outcome. maths simply for the sake of getting the correct answer starts to lose its shine after a while.
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I hope to help with this transformer commentary:
Transformers have been with us for many, many decades.
Some of the finest musical reproduction has been made with tube equipment going through good transformers, especially recordings made in the 1950's and early 1960's.
However, tranformers, even the best, at the time at least, were not perfect.
They were heavy, expensive, prone to SIGNIFICANT bass distortion, limited bandwidth, and hum pickup.
Most REAL manufacturers like AMPEX did NOT use the very best transformers for all of their audio products. They could not justify them, cost-wise, and the transformers they used, allowed them to met the professional specs that the industry set.
Now, let me give you an example of the REAL difference, both in cost, but also in performance in transformers from 40-50 years ago.
Ampex produced two MASTERING QUALITY analog multitrack tape machines in the 1960's. First, the MR-70, a true mastering recorder with tube electronics by Erling Skov. The second, the AG-440, a practical machine with solid state electronics.
Now which of the machines actually had a QUIETER reproduce stage?
The TUBE unit, does this surprise you?
Now, why?
Much of it had to do with the input transformers for the two machines.
The tube based transformer was a toroid, specially made, and cost Ampex about $30 OEM in the 1960's. The solid state AG-440 had a transformer made by Beyer that OEM'd at about $5 in 1968.
I was put to the task of personally measuring the AG-440 transformer with what is called a GR 'Q' meter, and I found some interesting stuff.
Specifically, the eddy current losses due to the rather thick laminations in the transformer caused a measurable loss in S/N at high frequencies.
Removing the need for a transformer, even at that time would have been a good thing, and it was removed, with time.
However, there are other things about transformers that many people overlook, and even ignore. They can increase in distortion at lower output levels in the bass. Yes, just where you are listening.
In all, over decades of listening through transformers and adding or subtracting transformers, we found that we could normally live without them, AND we made it so.
Now, what about today? It is true that SOME transformers, usually the most expensive ones are better than the earlier transformers, in this low level bass distortion, BUT NOT ALWAYS! Metglas transformers from Lundahl, OEM'ing at about $200 each, distort significantly at low levels and low frequencies. That is why I decided to drop the use of an input transformer in the Constellation phono stages. Too much distortion, OR a recognized difference in mid-range sound quality, even by the manufacturer.
I have posed questions to some of the best transformer designers in the business, and the transformers that they design are very good, but not necessarily better than a transformer-less design in consumer products.
Transformers have been with us for many, many decades.
Some of the finest musical reproduction has been made with tube equipment going through good transformers, especially recordings made in the 1950's and early 1960's.
However, tranformers, even the best, at the time at least, were not perfect.
They were heavy, expensive, prone to SIGNIFICANT bass distortion, limited bandwidth, and hum pickup.
Most REAL manufacturers like AMPEX did NOT use the very best transformers for all of their audio products. They could not justify them, cost-wise, and the transformers they used, allowed them to met the professional specs that the industry set.
Now, let me give you an example of the REAL difference, both in cost, but also in performance in transformers from 40-50 years ago.
Ampex produced two MASTERING QUALITY analog multitrack tape machines in the 1960's. First, the MR-70, a true mastering recorder with tube electronics by Erling Skov. The second, the AG-440, a practical machine with solid state electronics.
Now which of the machines actually had a QUIETER reproduce stage?
The TUBE unit, does this surprise you?
Now, why?
Much of it had to do with the input transformers for the two machines.
The tube based transformer was a toroid, specially made, and cost Ampex about $30 OEM in the 1960's. The solid state AG-440 had a transformer made by Beyer that OEM'd at about $5 in 1968.
I was put to the task of personally measuring the AG-440 transformer with what is called a GR 'Q' meter, and I found some interesting stuff.
Specifically, the eddy current losses due to the rather thick laminations in the transformer caused a measurable loss in S/N at high frequencies.
Removing the need for a transformer, even at that time would have been a good thing, and it was removed, with time.
However, there are other things about transformers that many people overlook, and even ignore. They can increase in distortion at lower output levels in the bass. Yes, just where you are listening.
In all, over decades of listening through transformers and adding or subtracting transformers, we found that we could normally live without them, AND we made it so.
Now, what about today? It is true that SOME transformers, usually the most expensive ones are better than the earlier transformers, in this low level bass distortion, BUT NOT ALWAYS! Metglas transformers from Lundahl, OEM'ing at about $200 each, distort significantly at low levels and low frequencies. That is why I decided to drop the use of an input transformer in the Constellation phono stages. Too much distortion, OR a recognized difference in mid-range sound quality, even by the manufacturer.
I have posed questions to some of the best transformer designers in the business, and the transformers that they design are very good, but not necessarily better than a transformer-less design in consumer products.
You're right, John. Transformers are not for those who are engaged in a soulless pursuit of numbers.
se
Now, while I'm soullessly pursuing the numbers in my pocket, I can't afford transformers. When I'll be rich and famous, and soullessly pursuing the sound quality numbers, I will afford to say they suck.
Yes, including mine <cough>. The switchon-switchoff one is particularly interesting to me, as well as the insistence that wirewound R have no excess noise. There is also the suggestion that chopper-stabilized devices have none. Rubbish --- although it's a fine strategy to minimize drift as such, and has been with us in various forms for a long time. Recent devices are vastly superior to old ones, especially in terms of reducing deterministic switch artifacts.
Once at my former client Harman years ago an outfit whose name I've forgotten, but probably had some twist on "analog" in their name, gave a presentation. In the group thus was the CTO. The company was pitching their programmable analog ICs, or more descriptively their switched-capacitor-based analog ICs, for those folks who found analog baffling and off-putting and wanted to get to market in a hurry. I wasn't in a particularly hostile mood (these are rare, though some might disagree lately), but I wanted to know some very key details about cost and performance.
The theory of switched-capacitor circuitry is probably pretty well-developed now, although it's hard to track down certain key material. I bought a whole expensive book on the subject with no mention of noise! Among the less-well-covered items anywhere, at least the last time I looked, was noise, beyond the simple assumptions of perfect switches and complete achievement of thermodynamic equilibrium within a switching cycle, which shows that the uncertainty of charge on a reset capacitor is not a function of the resistance of the switch and circuit, but merely the effective temperature and capacitance.
But there is excess noise in the MOSFETs generally used for switched-capacitor topologies. I asked the CTO about this and how quiet their devices were. He straightfacedly asserted that there was none, for in his recollection (I detected the hint of a sneer, but bear in mind his boss was listening) you only got 1/f-type noise when current flowed (!)
Having had direct experience with the reset switches in self-scanned photodiode arrays, and knowing well that the textbook thermodynamic argument for their reset noise was far from accurate, I was singularly disappointed.
In any event their stuff was way-expensive, and given our core competence in analog circuits (before upper management dismantled whole divisions) simply not remotely viable. I tried to be conciliatory about what markets they might still find for their stuff, but suggested that we probably weren't very interested.
Can anybody comment on the flat spot through zero crossing of the B-H curve? Is this real and if so doesn't it mean that transformers introduce some "crossover distortion" (or at least are not monotonic)? Frank McIntosh mentioned this in his amplifier papers before I was born, in the context of output transformers, so it's not new ("audiophile") stuff.
Thanks for any thoughts,
Chris
Thanks for any thoughts,
Chris
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Regarding transformers and other magnetics
I found it curiously satisfying to tell my audiophile friend, who believed transformers to be somehow essentially perfect, about some other noise he might not have considered: Barkhausen effect - Wikipedia, the free encyclopedia
I like the description of Barkhausen noise as unwrapping a candy, eerily similar to the late Terence McKenna's account of the third deep hit of some concoction, before he began to see his little critters, keen on telling him something of tremendous importance. I think this is excerpted on a Shpongle recording.
I found it curiously satisfying to tell my audiophile friend, who believed transformers to be somehow essentially perfect, about some other noise he might not have considered: Barkhausen effect - Wikipedia, the free encyclopedia
I like the description of Barkhausen noise as unwrapping a candy, eerily similar to the late Terence McKenna's account of the third deep hit of some concoction, before he began to see his little critters, keen on telling him something of tremendous importance. I think this is excerpted on a Shpongle recording.
it is indeed...I think its on 'nothing lasts, but nothing is lost'? my head feels like a frisbee hehe
what did I say about mispent youth?
nope, 'A new way to say hooray' on 'tales of the inexpressible'. 'but that is not what arrests my attention....what arrests my attention is that this ...SPACE...is inhabited...'
now that there is some well produced electronic music... its one of my various test albums. there is some really excellent tabla on there too.
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I would think that would result in a rather dramatic rise in distortion at lower and lower levels, much like with an amplifier in class B. Can't say I've ever seen anything that bares that out.
Here's a plot of distortion at fixed frequencies versus input level for a 1:10 microphone transformer. There is a slight rise as level goes down, but looking at the 50Hz plot, it starts trending back down again.
se
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But does Barkhausen noise rise to the level of audiblity in a good quality transformer?
se
Those two comments seem to fit together. I'm wondering if it would be a good idea to use some DC bias current with small signal transformers. Not enough to get near saturation, but enough to move the operating range away from that "crossover" area. Something like the way SET output transformers are used.
I dunno. I haven't done much listening to transformers as such. However based on the enthusiasm with which tiny effects are embraced among some, I thought it worth a mention. I'm sure it is very materials-sensitive in any event.
Yes I think I bought that on LP at the now-defunct Tower Records, and it is a very good pressing as well. I used to chat online with the flutist of the group when I frequented the deoxy.org website, run by the enigmatic "dimitri". "Those days are gone forever, over a long time ago..."
If it were audible, I'd guess it would only be with extremely low level signals, such as the output of a moving coil phono cartridge. But then I'd also guess it would likely be pretty well swamped by the record's surface noise.
se
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