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# Are audio companies all involved in a huge conspiracy? - Page 101

Quote:
Originally Posted by arnyk

The laws of physics and actual test bench results say that it is impossible to build a real world amplifier that "doubles down!.

Which law of physics!

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Quote:
Originally Posted by wse

Quote:
Originally Posted by arnyk

The laws of physics and actual test bench results say that it is impossible to build a real world amplifier that "doubles down!.

Which law of physics!

Ohm's Law, Law of Conservation of Energy and 2nd Law of Thermodynamics
+1 to Arny and Ethan. An amp will only "double down" so far... Most manufacturers only spec at 8 and 4 ohms, a very few take it down to 2 ohms. Eventually you run out of current as building an ideal voltage source is a challenge, and of course not everyone has Hoover Dam to draw from (and that would not be enough as the impedance got very low). As impedance goes to zero, power goes to infinity.
Quote:
Originally Posted by arnyk Ohm's Law, Law of Conservation of Energy and 2nd Law of Thermodynamics

You mean these?

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,[1] one arrives at the usual mathematical equation that describes this relationship:[2]

$I = \frac{V}{R},$

where I is the current through the conductor in units of amperesV is the potential difference measured across the conductor in units of volts, and R is the resistanceof the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[3]

The law of conservation of energy, first formulated in the nineteenth century, is a law of physics. It states that the total amount of energy in an isolated systemremains constant over time. The total energy is said to be conserved over time. For an isolated system, this law means that energy is localized and can change its location within the system, and that it can change form within the system, for instance chemical energy can become kinetic energy, but that it can be neither created nor destroyed.

In 1856, the German physicist Rudolf Clausius stated what he called the "second fundamental theorem in the mechanical theory of heat" in the following form:[10]
$\int \frac{\delta Q}{T} = -N$

where Q is heat, T is temperature and N is the "equivalence-value" of all uncompensated transformations involved in a cyclical process. Later, in 1865, Clausius would come to define "equivalence-value" as entropy. On the heels of this definition, that same year, the most famous version of the second law was read in a presentation at the Philosophical Society of Zurich on April 24, in which, in the end of his presentation, Clausius concludes:

The entropy of the universe tends to a maximum.

Quote:
Originally Posted by wse

Quote:
Originally Posted by arnyk

Ohm's Law, Law of Conservation of Energy and 2nd Law of Thermodynamics
You mean these?

Ohm's law states that the current
through a conductor between two points is directly proportional
to the potential difference
across the two points. Introducing the constant of proportionality, the resistance
,[1]

one arrives at the usual mathematical equation that describes this relationship:[2]

$I = \frac{V}{R},$

where I
is the current through the conductor in units of amperes
V is the potential difference measured across the conductor in units of volts
, and R is the resistance
of the conductor in units of ohms
. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[3]

The
law of conservation of energy
, first formulated in the nineteenth century, is a law of physics. It states that the total amount of
energy
in an
isolated system
remains constant over time. The total energy is said to be
conserved
over time. For an isolated system, this law means that energy is localized and can change its location within the system, and that it can change form within the system, for instance
chemical energy
can become
kinetic energy
, but that it can be neither created nor destroyed.

In 1856, the German physicist
Rudolf Clausius
stated what he called the "second fundamental theorem in the
mechanical theory of heat
" in the following form:
[10]

$\int \frac{\delta Q}{T} = -N$

where Q is heat, T is temperature and N is the "equivalence-value" of all uncompensated transformations involved in a cyclical process. Later, in 1865, Clausius would come to define "equivalence-value" as entropy. On the heels of this definition, that same year, the most famous version of the second law was read in a presentation at the Philosophical Society of Zurich on April 24, in which, in the end of his presentation, Clausius concludes:

The entropy of the universe tends to a maximum.

The bottom line is that when you put a lower impedance load on an amplifier, you increase its internal losses. The increased internal losses make it impossible to maintain the same output voltage output with the doubled current load.
As I like to opine, in the case of "doubling down" amps they are not built to double down, per se, but are instead rated to "half-up".

IOW, the amp isn't designed to produce -
8 ohms = x, then
4 ohms = 2x and
2 ohms = 4x.

They are designed to produce -
2 ohms = x, then rated to
4 ohms = x/2 and
8 ohms = x/4.
Edited by whoaru99 - 4/14/13 at 8:57am
Quote:
Originally Posted by arnyk

The bottom line is that when you put a lower impedance load on an amplifier, you increase its internal losses. The increased internal losses make it impossible to maintain the same output voltage output with the doubled current load.
It's impossible with passive power supplies. Not with a regulated power supply (where the supply measures its output and with feedback adjusts its operation). It's pointless, but not impossible.
Are power conditioners worth it? I think not what do you think?
Quote:
Originally Posted by wse

Are power conditioners worth it?

Not usually, though they can help reduce clicks and pops if you get that when your refrigerator or furnace turns on and off. Claims of "increased clarity" and "improved width and sound stage" etc are total bull.

--Ethan
Quote:
Originally Posted by Roger Dressler

Quote:
Originally Posted by arnyk

The bottom line is that when you put a lower impedance load on an amplifier, you increase its internal losses. The increased internal losses make it impossible to maintain the same output voltage output with the doubled current load.
It's impossible with passive power supplies. Not with a regulated power supply (where the supply measures its output and with feedback adjusts its operation). It's pointless, but not impossible.

That might solve (or at least mitigate) the supply rails, but does not help reduce the drop across (inside) the output devices and/or ballast resistors. Or am I misunderstanding? Of course, feedback helps with the output IR drop, but eventually it runs out of steam... I suppose a supply that was able to raise the rails (class H in some fashion) would help. In any event, in practice I don't think any amp can double down forever, but there are some durn good amps out there.
Edited by DonH50 - 4/14/13 at 2:34pm
I love it when nerds argue.....

Whether an amp can double down into real world loads, depends upon the engineer's brief and potential customers.
An engineer at QSC will try to find the best power into 8, 4 and maybe 2 ohms to meet a price, reliability, size and weight spec that they feels will be viable in a very competetive marketplace. This would I assume also be based upon feedback from actual professional users about what they need. For him, having an amp that doubles down sucessively into 2 from 8 is probably not going to meet all the other criteria and make it a seller. A pro user with a system more complicated than a couple of 15" + 1" boxes on sticks will likely know the exact load and power desired at that load and will select from the catalogue, the appropriate item.

An audiophile amp is somewhat different. Because it will be in the hands of users that tend to the left of the Bell curve in competence, having a vastly over engineered amplifier can have several advantages. Boast factor (of being able to double down) even if it's never used in practice, massive size and weight, which are impressive to someone that only has to place it once and thick machined faceplates. Add a 'name' and a stupendous pricetag and you'll have all the local and internet 'phools gushing over how awesome you are for buying it. Even if they could never pass a Zipser test.

If I were to begin to design either type, I would still set the rails first and work from there, adding extra parallel output devices to get the required Iout into the worse case design loads, iteratively and work through the issues such as minimising any series impedances to reduce Vdrop and I²R until I had met spec.

After you drink they sound better :)

Quote:
Originally Posted by A9X-308

I love it when nerds argue.....

Whether an amp can double down into real world loads, depends upon the engineer's brief and potential customers.
An engineer at QSC will try to find the best power into 8, 4 and maybe 2 ohms to meet a price, reliability, size and weight spec that they feels will be viable in a very competetive marketplace. This would I assume also be based upon feedback from actual professional users about what they need. For him, having an amp that doubles down sucessively into 2 from 8 is probably not going to meet all the other criteria and make it a seller. A pro user with a system more complicated than a couple of 15" + 1" boxes on sticks will likely know the exact load and power desired at that load and will select from the catalogue, the appropriate item.

An audiophile amp is somewhat different. Because it will be in the hands of users that tend to the left of the Bell curve in competence, having a vastly over engineered amplifier can have several advantages. Boast factor (of being able to double down) even if it's never used in practice, massive size and weight, which are impressive to someone that only has to place it once and thick machined faceplates. Add a 'name' and a stupendous pricetag and you'll have all the local and internet 'phools gushing over how awesome you are for buying it. Even if they could never pass a Zipser test.

If I were to begin to design either type, I would still set the rails first and work from there, adding extra parallel output devices to get the required Iout into the worse case design loads, iteratively and work through the issues such as minimising any series impedances to reduce Vdrop and I²R until I had met spec.

Which basically means you'd design as I previously described for the lowest target load, then just "half-up" the ratings if you wanted to play into the "double down" mindset, or rate them more realistically for a crowd like pro audio that wouldn't buy an amp with low stated wattage and high price compared to the competition (nor buy into the double down facade).

Or, put another way, you're not going to design an amp for 200W @ 8 ohms then just overbuild it through multiple iterations until it does 800W at 2 ohms. You're going to build an amp to do 800W @ 2 ohms then simply derate it into higher impedances for the double down crowd, or measure what you get and rate it accordingly for someone that understands if the amp can do 300W @ 8 ohms that it can also do 200W @ 8 ohms.

Every amp I own can be shown to "double down" when you take the lowest rated impedance and half it up.
Edited by whoaru99 - 4/15/13 at 9:12pm
Quote:
Originally Posted by wse

After you drink they sound better

Yeah, looking at that sort of stuff gives me a sort of deep nagging feeling of unease in the guts... difficult to describe (I'm being serious BTW). I feel the same way when I see a story about gross injustice in the newspaper. Anyone else feel this way, or am I weird?

I reckon it's the thought that otherwise intelligent, rational people can fall into the rabbit hole and line the pockets of the people who push this overpriced stuff that makes zero difference. I just wish they would think about how much nice red wine they could buy - and enjoy while listening to music - for the price of that battery powered DAC or pair of monoblocks.

Ah... that's better. Time to go crank up some tunes!
Quote:
Originally Posted by A9X-308

I love it when nerds argue.....

Whether an amp can double down into real world loads, depends upon the engineer's brief and potential customers.

Here's a funny story from Douglas Self's power amplifier design book:
Quote:
Originally Posted by Douglas Self
I was once faced with this situation: the managing director wanted exact power doubling in a high-power design, but I was less than enthusiastic about trying to make heavy-current regulated power supplies work dependably. Time for some thought. If you accept that there is no problem in making a hum-free amplifier that runs from unregulated and ripply rails – which is emphatically true, as demonstrated in the second half of this chapter – then the function of the regulators is simply to keep part of the supply voltage away from the amplifiers. In effect, the output stage is a giant clipping circuit. So why not do the clipping at the input of the amplifier, where it can be done with a couple of diodes, and go back to an unregulated power supply? The idea is shown in Figure 9.1 . The electrical power previously wasted in the regulators is now absorbed by the output devices, perhaps necessitating a bit more heat-sinking, but all the complications of regulators disappear. As with a regulated supply, the clipping will be clean and uncontaminated by ripple – in fact probably cleaner because a small-signal clipping circuit will have no time-constants that may gather unwanted charges during overload. Now you may think that this is cheating – the managing director certainly did, but even he was forced to admit that what I proposed was functionally identical to an amplifier with regulated supplies, and much cheaper. However, the idea of deliberately restricting amplifier output – and this new approach simply makes it obvious that that is what regulated supplies do – did not appeal to him any more than it does to me, and the project went forward with unregulated supplies. And no hum.
Quote:
Originally Posted by whoaru99

Which basically means you'd design as I previously described for the lowest target load, then just "half-up" the ratings if you wanted to play into the "double down" mindset, or rate them more realistically for a crowd like pro audio that wouldn't buy an amp with low stated wattage and high price compared to the competition (nor buy into the double down facade).
No. You need to set the rail voltages first as that will determine the voltage swing and therefore power into the highest Z load before clipping. Then if you want more current into lower Z loads, you add more or different outputs to get the desired result.

Design iterations once you had a rough design for higher power at low Z designs would include details such as layout and placement of devices and cooling and PSU to minimise any series Z to reduce loss and heat. Many more considerations too such as layout affecting stability but that would take a book or two to cover more than generalities. I'd suggest Cordell's latest if you want to know more.
Quote:
Originally Posted by DonH50

Quote:
Originally Posted by Roger Dressler

Quote:
Originally Posted by arnyk

The bottom line is that when you put a lower impedance load on an amplifier, you increase its internal losses. The increased internal losses make it impossible to maintain the same output voltage output with the doubled current load.
It's impossible with passive power supplies. Not with a regulated power supply (where the supply measures its output and with feedback adjusts its operation). It's pointless, but not impossible.

That might solve (or at least mitigate) the supply rails, but does not help reduce the drop across (inside) the output devices and/or ballast resistors. Or am I misunderstanding?

I think that your understanding is very clear and correct. Yes, there are losses in the power supply which the regulator would mitigate by throwing away less power, but there are also losses in the output stage and internal wiring which the regulator can't help unless you give the regulator a negative source resistance characteristic.
Quote:
Of course, feedback helps with the output IR drop, but eventually it runs out of steam... I suppose a supply that was able to raise the rails (class H in some fashion) would help. In any event, in practice I don't think any amp can double down forever, but there are some durn good amps out there.

The problem with regulators is that they are bound by the law of conservation of energy. When they regulate heavy loads they accomplish this by wasting less energy than they do under light loads. A reasonable designer would prefer to put the full capabilities of the power supply under the control of the output stage instead of wasting part of it for the sake of a silly spec.
Quote:
Originally Posted by A9X-308

I love it when nerds argue.....

Whether an amp can double down into real world loads, depends upon the engineer's brief and potential customers.
An engineer at QSC will try to find the best power into 8, 4 and maybe 2 ohms to meet a price, reliability, size and weight spec that they feels will be viable in a very competetive marketplace. .

One irony being that the producers of amps for the professional markets have placed far more power amps in customer hands that can actually work well with 2 ohm loads.
Quote:
Originally Posted by DonH50

That might solve (or at least mitigate) the supply rails, but does not help reduce the drop across (inside) the output devices and/or ballast resistors. Or am I misunderstanding? Of course, feedback helps with the output IR drop, but eventually it runs out of steam... I suppose a supply that was able to raise the rails (class H in some fashion) would help. In any event, in practice I don't think any amp can double down forever, but there are some durn good amps out there.

NAD 208 is a great example of a well working class-H amp. One can only hope the new Emotivas can get reasonably close to it.

How about Bob Carver's tracking downconverter?
Quote:
Originally Posted by Nightlord

Quote:
Originally Posted by DonH50

That might solve (or at least mitigate) the supply rails, but does not help reduce the drop across (inside) the output devices and/or ballast resistors. Or am I misunderstanding? Of course, feedback helps with the output IR drop, but eventually it runs out of steam... I suppose a supply that was able to raise the rails (class H in some fashion) would help. In any event, in practice I don't think any amp can double down forever, but there are some durn good amps out there.

NAD 208 is a great example of a well working class-H amp. One can only hope the new Emotivas can get reasonably close to it.

QSC's RMX 2450. 500 wpc, about $750 NAD 208 - seems to have been replaced by the M2 which is switchmode. Quote: Originally Posted by arnyk NAD 208 - seems to have been replaced by the M2 which is switchmode. Well, there was many years inbetween, so I wouldn't call it a replacement. The S200 was the biggest one for many years and that's identical to the previous 218 model. The 208 was a one off - it wasn't designed by NAD, but a purchased construction from an unnamed British(?) company. I have still not come across anyone who knows who it was, but I'll keep asking... Quote: Originally Posted by arnyk Yes, there are losses in the power supply which the regulator would mitigate by throwing away less power, but there are also losses in the output stage and internal wiring which the regulator can't help unless you give the regulator a negative source resistance characteristic. Which is easily done. Think of it, a power amp that not only "doubles down" but actually delivers more than 2x the output power as the impedance drops in half. It's a miracle! Quote: A reasonable designer would prefer to put the full capabilities of the power supply under the control of the output stage instead of wasting part of it for the sake of a silly spec. Exactly. Quote: Originally Posted by Roger Dressler Quote: Originally Posted by arnyk Yes, there are losses in the power supply which the regulator would mitigate by throwing away less power, but there are also losses in the output stage and internal wiring which the regulator can't help unless you give the regulator a negative source resistance characteristic. Which is easily done. Think of it, a power amp that not only "doubles down" but actually delivers more than 2x the output power as the impedance drops in half. It's a miracle! Not only that, but there would be an impressive collection of power transistors and heat sinks for the voltage regulator. Ironically, they would be there to detract from the actual usefulness of the power amp. I think we may have stumbled onto the next big thing in audiophilia - even bigger than tubes, vinyl, magic cables or bricks! ;-) This kinda reminds me of radios during the 1930s when people judged radios by how many tubes they had, and manufacturers started adding tubes to up the count and not get in the way of how the radio actually worked. Edited by arnyk - 4/16/13 at 11:30am ...and in the 70's and 80's through today when people count the number of output transistors. Never mind that 20 of one type may only be worth 1 of another type, it's all about the quantity! Reminds me of a tale I have related before about a preamp designer way back when who added a little board filled with metal-film resistors. He resisted using them in the signal path because carbon film Rs actually had lower noise than metal film in the audio band, but The Market demanded metal film. So he built a little daughterboard prominently showing the metal-film Rs. Which, IIRC, served as leak resistors across the power supplies caps to drain them down when the preamp was turned off... Hmmm, perhaps I should build a tunnel diode into my next design... Quote: Originally Posted by DonH50 ...and in the 70's and 80's through today when people count the number of output transistors. Never mind that 20 of one type may only be worth 1 of another type, it's all about the quantity! . It's all in how you spin it. Danish GamuT make it a selling point to get 200W from a single transistor (pair, I assume) Quote: Originally Posted by A9X-308 No. You need to set the rail voltages first as that will determine the voltage swing and therefore power into the highest Z load before clipping. Then if you want more current into lower Z loads, you add more or different outputs to get the desired result. Design iterations once you had a rough design for higher power at low Z designs would include details such as layout and placement of devices and cooling and PSU to minimise any series Z to reduce loss and heat. Many more considerations too such as layout affecting stability but that would take a book or two to cover more than generalities. I'd suggest Cordell's latest if you want to know more. Naw, I don't need to read an amplifier design book (or whatever it is) to know my Levinson and Audio Research amps both sandbag their higher impedance ratings. Accordingly, both are stout amps relative to their rated power, and don't have the regulated PSU rails for the output stages to truly approach doubling down without sandbagging at the higher impedances. The Levinson, for example, is rated at 200wpc (@8) but puts out roughly 300wpc on the test bench. Edited by whoaru99 - 4/16/13 at 3:51pm ^^ I wasn't speaking from the standpoint of what some company may do to make their specs look more marketable, but rather from the basic EE design approach. Levinson etc sell a miniscule number of amps in the world market, so I consider their approach irrelevant. Luxury items for people who have more money than they know what to do with! Louis Vitton plastic bags for$5,000!!

Quote:
Originally Posted by Nightlord

Quote:
Originally Posted by DonH50

...and in the 70's and 80's through today when people count the number of output transistors. Never mind that 20 of one type may only be worth 1 of another type, it's all about the quantity!
.

It's all in how you spin it.
Danish GamuT make it a selling point to get 200W from a single transistor (pair, I assume)

It is all about which transistors you choose. The same case style hide an undersized silicon chip that was diffused in a hurry, or it can have a number of heavy-duty chips stitched together to looks like one transistor but it is actually 4 in parallel.

A friend was a competitive regional builder of power amps for pro audio who had worked out a good robust design. Unbeknownst to him, his supplier, a well-known and up until that point reliable source suddenly changed the output devices they were selling to him in the thousands to use a smaller chip. His amps started blowing up all over the place and it eventually put him our of business. He ended up grinding the tops off of the transistor cases, and the smaller chips were obvious.

Today counterfeit parts are endemic and a constant threat to power amp builders.
Quote:
Originally Posted by whoaru99

Quote:
Originally Posted by A9X-308

No. You need to set the rail voltages first as that will determine the voltage swing and therefore power into the highest Z load before clipping. Then if you want more current into lower Z loads, you add more or different outputs to get the desired result.

Design iterations once you had a rough design for higher power at low Z designs would include details such as layout and placement of devices and cooling and PSU to minimise any series Z to reduce loss and heat. Many more considerations too such as layout affecting stability but that would take a book or two to cover more than generalities. I'd suggest Cordell's latest if you want to know more.

Naw, I don't need to read an amplifier design book (or whatever it is) to know my Levinson and Audio Research amps both sandbag their higher impedance ratings. Accordingly, both are stout amps relative to their rated power, and don't have the regulated PSU rails for the output stages to truly approach doubling down without sandbagging at the higher impedances. The Levinson, for example, is rated at 200wpc (@8) but puts out roughly 300wpc on the test bench.

Or, you can buy a Behringer EP2500/4000 and get

http://forum.blu-ray.com/showpost.php?p=3240546&postcount=2
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