Efficiency, where's the data?

[KeithL]

Transformers are somewhat expensive; although possibly less than you think.
Of course, a lot of those cute little parts used in a modern SMPS are also expensive (because they're more specialized).
And an SMPS is a lot more expensive to design, develop, and manufacture.

Oct 2, 2017 11:53:00 GMT -5 DYohn said:

Transformers are expensive. It is 1/3 the parts cost to manufacture SMPS versus a linear supply.

[DYohn]

Oct 2, 2017 12:26:57 GMT -5 KeithL said:

Transformers are somewhat expensive; although possibly less than you think.
Of course, a lot of those cute little parts used in a modern SMPS are also expensive (because they're more specialized).
And an SMPS is a lot more expensive to design, develop, and manufacture.

Oct 2, 2017 11:53:00 GMT -5 DYohn said:

Transformers are expensive. It is 1/3 the parts cost to manufacture SMPS versus a linear supply.

I am basing my cost statements on products that my company manufactures. SMPS is at most 1/3 the BOM cost of a linear P/S for the same ratings. Your mileage may vary.

[leonski]

Oct 2, 2017 11:53:00 GMT -5 DYohn said:

Transformers are expensive. It is 1/3 the parts cost to manufacture SMPS versus a linear supply.

Surprise!      That's pretty $$$, isn't it?    Good news is the failure rate SHOULD be nearly Zero unless somehow abused / zapped.

[KeithL]

I'm inclined to agree with you about what an amp draws at idle.

However:
1) as I get older, I've started avoiding equipment that I can't lift without risking a trip to the chiropractor
2) nobody likes to fill out all that paperwork and wait for the replacement when their new amp gets damaged in shipping
3) and we all know that, one way or the other, the customer is going to end up paying for the increased shipping cost
4) our SMPS is REGULATED, which is a big step up in performance (and, even if you could afford an XPA amp with a regulated linear main power supply, you couldn't lift it)
5) maybe you just don't like the way Outlaw products sound  
(I don't remember too many people having bad things to say about how our XPR amps sounded, and the same is true for the XPA Gen3's)

Oct 1, 2017 19:00:31 GMT -5 teaman said:

I know personally I couldn't give a rat's azz about how much the amp draws at idle. I own four plasma televisions that I am sure cost more than any idling amp in my home. I still use a Technics SU-V90 integrated amp with a huge toroidal transformer that is forty years old and still sounds fantastic. I have never used or owned a SMPS amp and probably never will. I will continue to stick with what is tried and true. Big azz amps that weigh a ton and present a longevity untested as of this time. I have a pair of Class G or H Outlaw Audio mono blocks and I didn't like the sound of them. If it costs manufacturers less to ship the SMPs, then who cares as far as we the consumer.

[AudioHTIT]

Oct 2, 2017 16:34:06 GMT -5 KeithL said:

I'm inclined to agree with you about what an amp draws at idle.

I’m sorry to hear there’s such little support for such a simple spec to include, it should add virtually no extra work or cost. Why would you (or Emotiva) be opposed to adding information, that some could find very useful? (other than some don’t care)

Edit: After all this thread is about data!

[Gary Cook]

Please indulge me while I pick up on a couple of points;

Oct 2, 2017 16:34:06 GMT -5 KeithL said:

2) nobody likes to fill out all that paperwork and wait for the replacement when their new amp gets damaged in shipping
3) and we all know that, one way or the other, the customer is going to end up paying for the increased shipping cost

I've personally had 6 x XPA power amplifiers sent to me half way around the world (that's 16,000 k's each = 96,000 k's) with not one bit of damage. Credit is due of course to Emotiva's high quality double layer packaging and maybe I'm just lucky since we use pretty much the same freight suppliers here, UPS, Fedex, etc. I've also installed about half a dozen Emotiva amplifiers (and other gear) for locals before there was distributor and not one of them has been damaged in transit either. Not in any way saying that shipping damage doesn't occur, just that in my experience it's not a big deal.

I'm not seeing any reduction in price for shipping to Australia of Gen 3 amps over Gen 1's or 2's. The highest price difference (Gen 1/2 XPA-5 versus Gen 3 XPA-5) I can find is $30 using my reshipper (less than $0.002 per kilometre), but that's a worst case scenario. The best case is no difference due to the dimensions being the major factor in determining freight cost and over ruling the weight.


Cheers
Gary

[leonski]

People would probably be surprised if the power to efficiency curve were published. And still wouldn't know how it sounded. Or reliability.

[Gary Cook]

Oct 2, 2017 18:09:10 GMT -5 leonski said:

People would probably be surprised if the power to efficiency curve were published. And still wouldn't know how it sounded. Or reliability.

Couldn't the same be said of every other measurement supplied to support the amplifier manufacturers' claims?
Why should efficiency be exempt?


Cheers
Gary

[DYohn]

All ratings are meaningless to the user who does not know how to interpret them...

Power efficiency has nothing to do with "how it sounds." And unless it is very noisy and poorly designed, neither does using a switching power supply, really. A regulated power supply, as Keith mentions, is always a superior and more efficient system than an unregulated one. And more expensive to build. Class H multiple-voltage bus power supplies are quite good - perhaps the best overall efficiency VS output available.

The only thing a power efficiency rating would mean to a user is if they are very concerned about being "green" or if they have limited power budget in their home. This is one reason why Class D amps became so huge in car audio, by the way: power budget. Most vehicles have limited current capacity so better amplifier efficiency means lower current utilization for the same power output. This is important in car audio. It's really not all that important to the average home user. But if it is to you, then I suggest asking Emotiva technical support if they have data they can share with you.

[hemster]

Oct 2, 2017 18:35:58 GMT -5 DYohn said:

All ratings are meaningless to the user who does not know how to interpret them...
...

Amen! 

[leonski]

I've been saying how marginally meaningful specs are for YEARS and playing to deaf ears, largely.

And some specs or measurements which might mean more, are either not done or ignored. Like an amps real performance into a reactive load.

MOST Audiophiles / HT folks are ill-equipped to deal with detailed specs so rely on 'efficiency' of a speaker (wrong word, AGAIN) and power along with a bunch of
blather about crosstalk and a dozen other measurables which individually don't mean squat. Speakers don't have watts.

[Gary Cook]

A quick reminder, this thread came about because of another thread posing a question about power outlets/circuit and amplifier selection. I proposed that a 600 watt amp running at 250 watts didn't draw/need any more power than a 600 watt amplifier running at 250 watts and some debate ensued. If we had the data on the efficiency of an amplifier then the question could have easily been answered. But it wasn't/isn't easy to answer because amplifier manufacturers don't supply the data even though it's ever so simple to test and publish.

Choosing power amplifiers based on their power demands is a subject that comes up quite often, I'm pretty sure that if I tried a search on this forum that I'd come up with hundreds of threads/posts asking exactly that question. This is not at all like other amplifiers measurements/data, it's not supposed to tell us what it sounds like. It's for making a pretty simple decision, yes I have capacity to power this amp, or no I don't.

If the data isn't published what's the solution? Buy an amplifier then buy a watt meter and test it. If it draws too much power send it back? Or if there is power capacity to spare in your house/outlet/circuit then send it back and buy a higher wattage amplifier?


Cheers
Gary

[leonski]

Actually, Gary, I suspect that a 600 watt amp running at 250 watts DOES use more juice than a 250 @ 250.
Why?
Iron losses and Copper losses in the transformer, for one. Other PS and output stage losses are higher, even in proportion, for the higher output amp.
Such losses are 'fixed', to a large degree.
This is assumeing (VERY dangerous, I know) that the bias condition of the amps is similar and they have similar respons to the same reactive load, being the speaker.

Buying a amp by PS capacity and what 'the wall' will supply, is of course, silly, and you know it. Mention must be made of several things, not the least of which are the speakers and intended use.
My little 7x2 'T' amp is perfect in the garage. And powered by a 1 amp or whatever, Wall-Wart. Do I need to get a pair of Pass XS-150 mono blocks? At nearly 500lb, the 4-piece 'pair', They'll really
put a ding in anyones electric bill. 150/300 of pure 'A' power.

Manufacturers will 'rate' their product for a 15 amp circuit, usually. I got in Big Trouble for suggesting the 20amp recommendation from EMO was actually Serious, but others, like Outlaw make a 7 channel amp with
a requirement for 2x @15amp circuits. (same side of box, but completely seperate wire runs)

My answer relys on general design principles of linear PS. The higher voltages and currents required by th 600 watt 'capacity' amp will put a floor under it's power use which is higher than a similar 250 watt amp.

[Gary Cook]

Oct 2, 2017 23:57:18 GMT -5 leonski said:

Actually, Gary, I suspect that a 600 watt amp running at 250 watts DOES use more juice than a 250 @ 250.
Why?Iron losses and Copper losses in the transformer, for one. Other PS and output stage losses are higher, even in proportion, for the higher output amp.
Such losses are 'fixed', to a large degree. This is assumeing (VERY dangerous, I know) that the bias condition of the amps is similar and they have similar respons to the same reactive load, being the speaker. Buying a amp by PS capacity and what 'the wall' will supply, is of course, silly, and you know it. Mention must be made of several things, not the least of which are the speakers and intended use. My little 7x2 'T' amp is perfect in the garage. And powered by a 1 amp or whatever, Wall-Wart. Do I need to get a pair of Pass XS-150 mono blocks? At nearly 500lb, the 4-piece 'pair', They'll really put a ding in anyones electric bill. 150/300 of pure 'A' power.
Manufacturers will 'rate' their product for a 15 amp circuit, usually. I got in Big Trouble for suggesting the 20amp recommendation from EMO was actually Serious, but others, like Outlaw make a 7 channel amp with a requirement for 2x @15amp circuits. (same side of box, but completely seperate wire runs)
My answer relys on general design principles of linear PS. The higher voltages and currents required by th 600 watt 'capacity' amp will put a floor under it's power use which is higher than a similar 250 watt amp.

Although I may agree, what you saying is let's just guess how much power it needs. When the simple fact is we don't have to, the actual data is easily provided, takes no extra time and costs nothing.

As per signature below, my set up has the Samsung 4K TV, XPA-100 and 2 x XPA-1L's on one 240 volts x 15 amps = 3,600 watts circuit. On another 3,600 watt circuit for HT use I have the XPA-5 (3 channels), UMC-200, Apple TV4K, XSP-1 in HT bypass mode and the Oppo 203. On that same circuit when used for 2.1 music I have an ERC-3 or the Denon DD TT plus the XSP-1.

It would be very convenient to know exactly how much of the power outlet/circuit capacity I am using. Do I have enough capacity to swap the XPA-100 for an XPA-1 Gen1 or 2 or should I go for an XPA-1 Gen3 because of its better efficiency? When I kick the 5.1.2 Atmos/DTSX off with say an XMC-1 will I have enough capacity to run the other 2 channels of the XPA-5?

Common questions that I am sure plenty of people ask every other day. Expecting me (or them) to buy the equipment and then measure the power usage is simply ridiculous.

Cheers
Gary

[leonski]

Different question gets a different answer.

I'll agree that in principle it is EASY to measure an amps power draw. For steady state conditions my Kill-A-Watt which is 20$ US on Amazon will do a good job for steady state conditions. Test tones, maybe?
And it'll spit out a reasonable value for Power Factor, which will give an indication of PS reactance. Some amp manufacturers make a 'big deal' out of PFC, Power Factor Correction. I'm undecided, but will
just 'report' what I see.

An overachiever might use 2 meters. One, for measureing line voltage and the other, an 'amp clamp', maybe, for current. Power is a multiplication away.

In the Lab? I'd control for line voltage with a variac so every amp would be tested under the same conditions. This would be for published data. You'll have access to some real good metrology stuff, too,
with up-to-date calibrations and 6 digits or MORE resolution. We had such a meter MANY years ago for measuring 8mv which was the 'standard' voltage for thermocouple calibration in our furnaces. This was an
8 or 9 digit meter which was used ONLY for that one purpose. Later we worked with Jon Goldman on his FIRST data acquistion system for our type of furnace. Oh Boy! DATA.

For YOU at home? Get the Kill-A-Watt and be done with it. No standards currently exist. Or are likely in the near future. Any claim by any manufacturer without specifying conditions of measure (like 'speaker watts') I would
interpret as advertising nonsense.

I wish I could be more helpful.

[Gary Cook]

Oct 3, 2017 1:38:30 GMT -5 leonski said:

Different question gets a different answer.
I'll agree that in principle it is EASY to measure an amps power draw. For steady state conditions my Kill-A-Watt which is 20$ US on Amazon will do a good job for steady state conditions. Test tones, maybe?
And it'll spit out a reasonable value for Power Factor, which will give an indication of PS reactance. Some amp manufacturers make a 'big deal' out of PFC, Power Factor Correction. I'm undecided, but will
just 'report' what I see.
An overachiever might use 2 meters. One, for measureing line voltage and the other, an 'amp clamp', maybe, for current. Power is a multiplication away.
In the Lab? I'd control for line voltage with a variac so every amp would be tested under the same conditions. This would be for published data. You'll have access to some real good metrology stuff, too,
with up-to-date calibrations and 6 digits or MORE resolution. We had such a meter MANY years ago for measuring 8mv which was the 'standard' voltage for thermocouple calibration in our furnaces. This was an
8 or 9 digit meter which was used ONLY for that one purpose. Later we worked with Jon Goldman on his FIRST data acquistion system for our type of furnace. Oh Boy! DATA.
For YOU at home? Get the Kill-A-Watt and be done with it. No standards currently exist. Or are likely in the near future. Any claim by any manufacturer without specifying conditions of measure (like 'speaker watts') I would
interpret as advertising nonsense.
I wish I could be more helpful.

A kill-a-watt metre is of no use to me if I need to know what amps to buy, not what the current amps draw. To do that they need to produce the data.


Cheers
Gary

[KeithL]

The reality is that there is no single answer to your question.... because it depends on what music you listen to, how loudly, and even the impedance of your speakers.

We generally rate the power draw of our amps "all channels driven - with an 8 Ohm load".
This assumes you're connecting a test signal to each input of the amp, connecting each output to an 8 Ohm load resistor, and turning it up to maximum output.
While this is a nice "standard" way to measure things, and easy to compare between different amps, it's also nothing at all like the requirements for playing music.
(Think of it like rating the MPG of a bunch of cars, by testing them all at a steady 55 mpH, with no acceleration or braking, and no air resistance, on a dynamometer.)

However, playing music is more like city driving.
Depending on the music you actually play, for most people, the average power level you listen at is going to end up being between 1/10 and 1/20 of the loudest peak.
So, if you have an XPA-2 Gen3, which will put out somewhere over 300 watts into 8 Ohms, per channel.....
And you play "normal music" just about as loud as you can before it clips.....
Your average output level will probably be somewhere between 10 and 30 watts per channel.....
Of course, that's an average, and it will be a lot different if you play Bach toccatas than if you play Charlie Mingus.
And most people really don't play their music nearly that loud most of the time.

The only way to actually compare amps directly would be to make up a standardized set of samples, to be played at standardized levels, and measure all the results for each.
(Equivalent to making up a test course that approximates typical driving, driving a bunch of cars over the same course, under the same conditions, and tabulating the results.)

There are two major problems with doing this:
1) Nobody has made up such a standard test for amplifiers and, unless everybody agrees to run the same test on their amps, the numbers won't be at all comparable.
        (Well, to be honest, lots of people have made up just such a test, but they're all different, which sort of defeats the whole idea.)
2) Even beyond that, since different tests will favor different amps, each vendor is going to pick tests that make their particular amp look good, and everyone else's amp look bad.
        (And, if I made up the test, I would make sure it "showed off" - err.... "properly demonstrated"..... the benefits of Class H.)

Unfortunately, since the particulars do vary so much, all we can do is to make generalizations.

- The efficiency of a Class A/B amp is basically limited to around 70% (that's based on the circuit topology, and the nature of analog waveforms, and isn't negotiable).
- Any Class A/B amp is going to be most efficient at its maximum output power (so, yes, a 250 watt Class A/B amp running at 250 watts will be more efficient than a 600 watt Class A/B amp running at 250 watts).
- This limitation is based on the relationship between the peak and average voltages of the output waveform and their relationship to the supply rails.
- A "simple" Class A/B amp (with one set of rails that never move) will be most efficient at maximum power, and MUCH less efficient at most lower power levels... generally decreasing in efficiency as the output power goes down.
- By adding another set of power rails, the Class H topology "cheats" on this formula by adding a second point in the power graph where the efficiency is also almost as high as at full power.
    (The efficiency is highest "when the peak of the output waveform is close to the rail voltage"; since we've added another rail voltage, we've added another point on the power graph where this condition is true.)
- This means that, with typical music, our Class H amps spend more of their time operating at a more efficient place on their power curve (so, on average, they are most efficient).

NOTE, though, that the actual improvement in efficiency will depend on the music you're listening to, the average loudness you play it at, and the impedance of your speakers.

I should also note that the benefit is going to be cooler operation, less significant cooling requirements, and longer life.
If you're hoping for a major noticeable difference in your electric bill, then you'll probably be disappointed.

Oct 3, 2017 0:56:51 GMT -5 Gary Cook said:

Oct 2, 2017 23:57:18 GMT -5 leonski said:

Actually, Gary, I suspect that a 600 watt amp running at 250 watts DOES use more juice than a 250 @ 250.
Why?Iron losses and Copper losses in the transformer, for one. Other PS and output stage losses are higher, even in proportion, for the higher output amp.
Such losses are 'fixed', to a large degree. This is assumeing (VERY dangerous, I know) that the bias condition of the amps is similar and they have similar respons to the same reactive load, being the speaker. Buying a amp by PS capacity and what 'the wall' will supply, is of course, silly, and you know it. Mention must be made of several things, not the least of which are the speakers and intended use. My little 7x2 'T' amp is perfect in the garage. And powered by a 1 amp or whatever, Wall-Wart. Do I need to get a pair of Pass XS-150 mono blocks? At nearly 500lb, the 4-piece 'pair', They'll really put a ding in anyones electric bill. 150/300 of pure 'A' power.
Manufacturers will 'rate' their product for a 15 amp circuit, usually. I got in Big Trouble for suggesting the 20amp recommendation from EMO was actually Serious, but others, like Outlaw make a 7 channel amp with a requirement for 2x @15amp circuits. (same side of box, but completely seperate wire runs)
My answer relys on general design principles of linear PS. The higher voltages and currents required by th 600 watt 'capacity' amp will put a floor under it's power use which is higher than a similar 250 watt amp.

Although I may agree, what you saying is let's just guess how much power it needs. When the simple fact is we don't have to, the actual data is easily provided, takes no extra time and costs nothing.

As per signature below, my set up has the Samsung 4K TV, XPA-100 and 2 x XPA-1L's on one 240 volts x 15 amps = 3,600 watts circuit. On another 3,600 watt circuit for HT use I have the XPA-5 (3 channels), UMC-200, Apple TV4K, XSP-1 in HT bypass mode and the Oppo 203. On that same circuit when used for 2.1 music I have an ERC-3 or the Denon DD TT plus the XSP-1.

It would be very convenient to know exactly how much of the power outlet/circuit capacity I am using. Do I have enough capacity to swap the XPA-100 for an XPA-1 Gen1 or 2 or should I go for an XPA-1 Gen3 because of its better efficiency? When I kick the 5.1.2 Atmos/DTSX off with say an XMC-1 will I have enough capacity to run the other 2 channels of the XPA-5?

Common questions that I am sure plenty of people ask every other day. Expecting me (or them) to buy the equipment and then measure the power usage is simply ridiculous.

Cheers
Gary

[KeithL]

I would strongly advise against deciding what audio equipment to buy based on the electric bill.

Almost all simple Class A/B amps of similar power operate at similar efficiency.
Our Class H amps operate somewhat more efficiently than a simple Class A/B amp at certain power levels, and so operate more efficiently overall average when playing music.
However, the main benefits are cooler operation and longer component life.... while still delivering the same sound quality as a regular Class A/B amp.

If reducing the power bill is your main concern, or your only concern, then your only obvious choice is to go with Class D.
(Class D amps are very efficient, and most of them maintain that efficiency over a wide range of power levels.)

If you REALLY want to go the other way - then you need to start by measuring the wattage you actually use over time, with your particular speakers, under your particular listening conditions.
Then you could do some calculations, and run a few simulations, and decide which characteristics would enable an amplifier to be the most efficient and still meet your particular needs.
In a Class H amp, you need the high supply rails to be sufficient to deliver highest peak output you need - to avoid clipping peaks.
And you want the low rails to be just above the peak voltage that corresponds to the power level you use the most - for best efficiency most of the time.
We've picked numbers there that seem to work pretty well for most of our customers.
Unless you do that, then you wouldn't have much use for that detailed information even if we provided it.

Oct 3, 2017 4:27:04 GMT -5 Gary Cook said:

Oct 3, 2017 1:38:30 GMT -5 leonski said:

Different question gets a different answer.
I'll agree that in principle it is EASY to measure an amps power draw. For steady state conditions my Kill-A-Watt which is 20$ US on Amazon will do a good job for steady state conditions. Test tones, maybe?
And it'll spit out a reasonable value for Power Factor, which will give an indication of PS reactance. Some amp manufacturers make a 'big deal' out of PFC, Power Factor Correction. I'm undecided, but will
just 'report' what I see.
An overachiever might use 2 meters. One, for measureing line voltage and the other, an 'amp clamp', maybe, for current. Power is a multiplication away.
In the Lab? I'd control for line voltage with a variac so every amp would be tested under the same conditions. This would be for published data. You'll have access to some real good metrology stuff, too,
with up-to-date calibrations and 6 digits or MORE resolution. We had such a meter MANY years ago for measuring 8mv which was the 'standard' voltage for thermocouple calibration in our furnaces. This was an
8 or 9 digit meter which was used ONLY for that one purpose. Later we worked with Jon Goldman on his FIRST data acquistion system for our type of furnace. Oh Boy! DATA.
For YOU at home? Get the Kill-A-Watt and be done with it. No standards currently exist. Or are likely in the near future. Any claim by any manufacturer without specifying conditions of measure (like 'speaker watts') I would
interpret as advertising nonsense.
I wish I could be more helpful.

A kill-a-watt metre is of no use to me if I need to know what amps to buy, not what the current amps draw. To do that they need to produce the data.


Cheers
Gary

[rbk123]

Oct 2, 2017 19:05:26 GMT -5 leonski said:

I've been saying how marginally meaningful specs are for YEARS and playing to deaf ears, largely.

Agree 100%. And yet you go over to the big freak-out in the Gen 3 Stereophile review thread and a couple of prospective buyers are now terrified and, even if they buy the Emo, will always have doubts. Until the light bulb comes on inside their heads that is, but that takes years of learning how much snake-oil, marketing hype, gimmicks, and worst of all - pride - are present in this hobby.

[leonski]

I don't think I flipped out. When stereophile has a weird measured result, the best action is to read the comments in the listening portion of the review and see if any 'correlation' exists between what reviewers hear
and what the lab guy measures. The identification of some unrevealed issue with the test sample is both good and bad news. People won't get an exact copy is probably good, but also, how did stereophile GET the unit they did?
Sometimes stereophile will do a 'retest' which in this case should 'fix' the problems disclosed in the original measures.

Specs are one thing. Measured data quite another. And Meeting Spec is fairly important, if only from a credibility standpoint.


This is from a post I made early in the Stereophile Test Data thread::     Is this flipping out?     
What did the TEXT portion of the sterophile test reveal? Any notes there which could be associated with the measured data? If not, I'm not certain I'd worry about it.