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Quality Power

25K views 636 replies 43 participants last post by  arnyk 
#1 ·
Besides distortion, what else can influence the quality of power? If 10 amplifiers deliver 100 watts at 0.1% distortion then can one say the power is equally clean?


Is it really all about distortion or the lack of it, or is there some other variable that influences how clean the power is?
 
#527 ·
Was it Proton and or NAD that used to advertise some of their amps had big dynamic headroom specs, like 6dB, or maybe more?


The numbers I've seen, generally, have been 1.5dB, give or take.
 
#528 ·

Quote:
Originally Posted by whoaru99  /t/1485846/quality-power/510#post_24389896


Was it Proton and or NAD that used to advertise some of their amps had big dynamic headroom specs, like 6dB, or maybe more?


The numbers I've seen, generally, have been 1.5dB, give or take.

Yes, both, and NAD to this day puts IHF ratings in their specs as part of their "full disclosure power ratings".


I recently recapped and fully bench tested my old NAD 2100. The supply rails commute at about 60 watts, and it really does hit >200w@8ohms (matching the claimed 6db dynamic headroom spec, at least based on it's "50 watt" rating). I've been lugging that amp around since college. Some day the old lady will make me sell some stuff.
 
#529 ·
Thanks guys, I must have been thinking of one of the other manufacturers and not Bryston. I was sure, but surely wrong this time!


Improved films and multilayer designs have done a lot for capacitors over the years in capacity and bandwidth. Regarding transistors, packages are shrinking and in some cases the devices themselves (inside the package), but thermal management is as big a problem as ever for A and AB. All the new amplifier classes and flavors (D, E, F, G, H...) have helped that a lot, of course, and made smaller devices more practical. Don't think the underlying device physics has changed much, though I wonder if SiC and the like are or will soon appear in audio amps. From a practical standpoint, I don't think Tjc is that different for a TO3 vs. a TO-220, just a matter of getting from the Si (SiC, SiGe, GaAs, whatever) to the heatsink as fast as possible. Don't know for sure, power devices are not my specialty.


Shrinking transformers and power supplies probably have a lot to do with it as well.


Does the IHF still publish their "encyclopedia" series for audio licensure? Used to be a bunch of thick books in different colors...
 
#530 ·

Quote:
Originally Posted by arnyk  /t/1485846/quality-power/510#post_24389531



Power supply capacitors have undergone a similar or even more extreme transformation. A 10,000 uF 80 volt power supply capacitor used to be about the same size as a 303 can of beans,




but now its more like an inch in diameter and two inches long, and it is technically a better part as well.

I wouldn't be so quick to say better across the board. The AC ripple current rating was much better in those old screw terminal "computer grade" caps. While the newer caps are smaller for the same capacitance, the ripple current handling is lower. But as the cost is as well, you just parallel several lower UF values to solve that problem. And of course this is only a problem when you get up into the 10amp area - big power amps.


And on the TO3, they have much better thermal transfer than a TO220 because they are attached more securely to the heat sink. The newer TO143 sizes are often held down by an angle bar across the heat sink for this reason. I'll try to find the paper I read on this but when a TO220 is bolted down, the metal acts like a bourdon(sp?) tube in a gauge, that is it tends to bend upwards on the opposite end of the screw from the metal stress. And that's the end where the junction is! This is why they often clamp the device in higher power applications.


The old component styles still have their attributes but nevertheless that are obsolete.
 
#532 ·

Quote:
Originally Posted by DonH50  /t/1485846/quality-power/510#post_24390063


Wonder how long before audio starts producing diamond substrates and packages... Great for heat transfer, a little pricey for other than military and down-hole use.

I think that the last important new technology that was developed by the audio business was the transistor. It was what, 1949?


Expect to first see a new technology in pure communications plays such as, umm maybe cell phones, and not in dedicated audio systems.
 
#533 ·

Quote:
Originally Posted by arnyk  /t/1485846/quality-power/510#post_24390492


I think that the last important new technology that was developed by the audio business was the transistor. It was what, 1949?


Expect to first see a new technology in pure communications plays such as, umm maybe cell phones, and not in dedicated audio systems.

Digital music was a big one.
 
#534 ·

Quote:
Originally Posted by DonH50  /t/1485846/quality-power/510#post_24390063


Wonder how long before audio starts producing diamond substrates and packages... Great for heat transfer, a little pricey for other than military and down-hole use.
Never mind about the diamond, the moon alloy or something like "Lunalloy" sounds much more high tech. http://www.theverge.com/2014/2/9/5395684/nasa-begins-hunt-for-private-companies-to-mine-the-moon-catalyst

You'll see the boutique cable vendors jumping on this with all sorts of poems on the listening impressions.
 
#535 ·

Quote:
I think that the last important new technology that was developed by the audio business was the transistor. It was what, 1949?
1947, but do you really consider Bell Labs part of the audio industry?
 
#537 ·
Actually, a lot of early audio research was done by Bell Labs (and a whole lot of other stuff). Until the last decade or two the stuff they were into was incredibly wide-ranging.


mcnarus, where you there?
(old farts joke, no offense, it was too tempting a target!)


I've worked with radar and other RF systems using superconducting mW filters, wonder how long before somebody sells superconducting cables (and a dewar for them)?
 
#539 ·
Well, almost... High temp SC only need go down to 77 K (-196 degC, -321 degF). Low temp, 4 K (-269 degC, -452 degF). Not quite 0 K, but pretty chilly...


That's OK, everybody exaggerates.
 
#540 ·

Quote:
Originally Posted by FMW  /t/1485846/quality-power/510#post_24390664

Quote:
Originally Posted by arnyk  /t/1485846/quality-power/510#post_24390492


I think that the last important new technology that was developed by the audio business was the transistor. It was what, 1949?


Expect to first see a new technology in pure communications plays such as, umm maybe cell phones, and not in dedicated audio systems.

Digital music was a big one.

I'll play the "Derivative Technology" card against that one. ;-)


I saw my first 16 bit 44 KHz capable ADC/DAC in 1971 and the application had nothing at all to do with audio.


It also cost about a half million dollars so I knew for sure it was never going to be used for audio. BTW it was acutally capable of a true 16 bits and 200 KHz sampling and had analog multiplexors in and out.


It was attached to this:





and somone snuck in one night and did use it to digitize a LP... ;-)
 
#541 ·

Quote:
I saw my first 16 bit 44 KHz capable ADC/DAC in 1971 and the application had nothing at all to do with audio.
IIRC, AT&T was using digital sound even earlier than that.
 
#542 ·

Quote:
Originally Posted by mcnarus  /t/1485846/quality-power/540#post_24393483

Quote:
I saw my first 16 bit 44 KHz capable ADC/DAC in 1971 and the application had nothing at all to do with audio.
IIRC, AT&T was using digital sound even earlier than that.

May be true. A good cite or date or some darn thing would nail down that part of the discussion.


But what about the other uses of digital coding/decoding? It is clear that most if not all that was written about digital encoding in the 1930s was coming out or near to Bell Labs. But that was before the transistor so it supports my claim, not detracts from it.
 
#543 ·

Quote:
May be true. A good cite or date or some darn thing would nail down that part of the discussion.
Does "I read it on the Internet somewhere" count?



At any rate, pulse code modulation was patented in the 30s (in Britain), and Bell Labs was synthesizing sound by the 50s. (Remember "Daisy"?) The "audio industry," as we know it today, was just getting started then. All the key work, at least post-Edison and Tesla, was being done in the telecommunications field.
 
#544 ·

Quote:
Originally Posted by DonH50  /t/1485846/quality-power/510#post_24392003


Well, almost... High temp SC only need go down to 77 K (-196 degC, -321 degF). Low temp, 4 K (-269 degC, -452 degF). Not quite 0 K, but pretty chilly...


That's OK, everybody exaggerates.

I knew someone would be bust my chops on that. But a) too lazy to check the correct number and b) the exaggeration seemed funnier to me.
 
#545 ·
Sorry, wasn't meant to bust your chops, and I thought it was hilarious, except somebody will do it...
Long week and working on tax stuff makes me cranky.


Actually, given the prices for some cables, I am surprised somebody isn't already. However, I have not seen anything so far that is long enough to use for speaker cables. Maybe too costly, maybe not needed, maybe technical issues with the films and cooling, I don't know (not my field). There have been large efforts to extend SC lines for power delivery but I have not read anything recently. Funding probably got cut; global warming will make it harder to cool the lines, so we'd better focus on fixing that first, eh?



It'd be great if we could get some of the folk together for dinner and a beer (or whatever) sometime.
 
#546 ·
No offense taken at all. I just like the mental picture of some fool freezing himself to death to improve speaker wire conductivity. Presumably the voice coils would be immobile at those temperatures with any humidity at all.


As far as global warming, didn't you see The Day After Tomorrow (hope I am remembering the title right). Grab a bottle of whisky and wait. . .
 
#547 ·
Voice coils and other things immobile, yes, but the noise floor would be incredible...
I think it was Arny who said cables make a huge difference, just try removing them.



If I remember that movie rightly, tequila might be a better choice...
 
#549 ·
Oh, Christmas, this thread was dead in the road. Couldn't you just leave it there?
 
#550 ·
So you guys are still here???
Quote:
Originally Posted by arnyk  /t/1485846/quality-power/510#post_24393286


I'll play the "Derivative Technology" card against that one. ;-)


I saw my first 16 bit 44 KHz capable ADC/DAC in 1971 and the application had nothing at all to do with audio. It also cost about a half million dollars so I knew for sure it was never going to be used for audio. BTW it was acutally capable of a true 16 bits and 200 KHz sampling and had analog multiplexors in and out. It was attached to this:




and somone snuck in one night and did use it to digitize a LP... ;-)
Someone did? Hmmm. This technology is before my time
. Your comments that it was able to digitize audio with such high resolution and the ADC/DAC cost half a million dollars got my antenna up
. So I did some research. This is what I found.


The picture is that of Electronic Association Inc (EAI)'s 680. This was a hybrid computer that was analog but had a set of analog to digital and digital to analog converters that would let it interface with a separate digital computer. I assume this is the interface you are talking about. The interface was called the EAI 693 Hybrid Linkage Interface. I found a CMU 1971 document that was offering the 680 and 693 for sale. In there, they provided the original costs for each. The analog computer was $161,000 and the Linkage interface was $81,000. In the above you say that the cost of the ADC/DAC was $500,000. Even I throw the cost of the analog computer in there, we are at half the dollar amount you state. So that math doesn't add up, especially if one considers the cost of the ADC/DAC module along.


You next say that it was capable of 16 bits and 200 Khz sampling. That is remarkable resolution for its time. I researched this further and found a couple of university papers that had built FORTRAN libraries to access the 680/693 combo. One reference there set a limit of 30 Khz for the ADC the other said this:

"the A/D conversion system consists of a fifteen channel multiplexer and a single high-speed analog-to-digital converter. The settling time of the multiplexer is 10 usec. The ADC converts signals between +- 10 volts to 13 bits (plus sign bit) resolution; conversion time is 20 usec."


So clearly this was not a 16 bit converter. 13 is a far cry from 16. 20 usec conversion times translates to 50 Khz. Adding the MUX time of 10 usec, we get down to 33 Khz -- pretty close to the other reference (not sure if the MUX had to be programmed every time or not). Either way a far cry from 200 Khz that you state in your post.


Then there is the issue of voltages and feasibility of hooking up a turntable to this system. You would have to build a level translator to drive an ADC that wants +- 10 volts. Hard to imagine you building such a thing just for this overnight adventure
. Then there is a matter of getting access to a computer system of this cost and screwing around with it. Even if you had, this is not a stand-alone ADC. It simply generates data that must be captured by the digital system. You would have had to write a program to capture that data. But where would you have put it? I am sure no one was giving you permanent storage to put the bits there for the data rates you are talking about. The "Winchester" IBM hard disk of 30 megabytes was not to be invented until a few years later after your experiment.


And what would you have done if you did record the digital samples anyway? The DAC would not have had the proper anti-aliasing filter if your 200 Khz spec is right.


Maybe you say that this was some other ADC/DAC. So I went searching for evidence of people having such capabilities. This is the reference I found on AES web site: http://www.aes.org/aeshc/docs/recording.technology.history/digital.html

"1976 - The first 16-bit digital recording in the US was made at the Santa Fe Opera on a handmade Soundstream digital tape recorder developed by Dr. Thomas G. Stockham."


So what you are saying is that this bit of history on AES web site is wrong and that you had done this five years earlier in 1971. Quite amazing if true.


So.... how do you reconcile this data with your recollection? Is it possible you were mistaken about most of this? It is a long time ago so it would be understandable if so.
 
#551 ·
...And that is why I don't post pictures of memories here...


Arny didn't say he built it, he said he saw it.


13 + sign = 14-bit equivalent (a lot of early ADCs were treated as sign-magnitude instead of the 2's complement most processors use today).


The mux settling time should not be included when calculating the sampling rate. It probably switched, then sat whilst conversion took place. It represents a delay before conversion can start, then conversion proceeds at whatever rate the ADC can do.


I hooked my turntable up to a similar system in college, using a (tube) amplifier to get up to +/-10 V. Not much different in gain than the chain from cartridge to speaker today.


I'd have to look and it ain't worth it to me, but while the first official 16-bit audio recording may have been made on the Soundstream, there were tons of other IEEE papers on various digitizers well before then.


Storage on analog computers is something I know little about despite having worked on one in college. The one I worked on did not have storage in the way we think of it today; rather, it stored charge on capacitors for intermediate results. The answer was immediately used (it was part of an industrial power plant) and recorded on tape (paper tape!) There was also a strip chart recorder we could hook up for tracking key variables and debugging. Seemed like something in the middle of the beast was always out of whack. It was one of the most frustrating and yet fun things I have worked on. Worked on a (very) few since but the first one sticks with you...


Good for you finding the info on that old beast, that is really cool! I wouldn't beat anyone over the head with a 40'ish year old memory, however. I have many times said "I may be wrong, but I'm not uncertain." And I have been wrong!


It'd be interesting to have an antique audio forum someplace where stuff like that could be posted and discussed. A lot of history is lost every day, maybe we could capture some of it. I have found sites with pix of old components, but rarely (can't really recall any) in a forum environment.
 
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