Large receivers' power comparisons, how reliable are they?

[steveUK]

A common topic is a comparison of the SX-1250 and the SX-1280. One of the answers that inevitably comes up is the power ratings of these units, that the 1280 is a tad more powerful, ie 185W/ch vs the 160W/ch of the 1250. But is that true? Certainly, when the monster receivers wars first started, manufacturers were still pretty conservative about their ratings. But as the war quickly hotted up, did manufacturers try to quote every last watt that they reckoned could be had from their receivers in order to 'win the war' ?

In his review (lab test report) of the Pioneer SX-1250 in the UK's 'Hifi Choice Receivers' book, the legendary and well respected Angus McKenzie recorded that the receiver's average power, both channels driven, was 210W into 8 ohms at 1% distortion. Out of interest, the average power, single channel driven into 4 ohms was 333W. Unfortunately, Hifi Choice did not go on to lab test the SX-1280, so we don't know what 'actual readings' would have been obtained for it. Of course, that 1% distortion figure kinda screws up a comparison of actual and claimed power figures, but nonetheless it's still impressive.

It's just left me wondering if later machines' manufacturers' quoted power levels were less conservative than when the wars first began, for the reasons that I say above. Interesting. What's your view? Are you aware of any reliable, third party tests on - particularly Pioneer - receivers that show higher power ratings to the ones stated by the manufacturers? and did the quoted figures and the actual figures get closer as time went on?

 

[SaturationPt]

You ask a question with a lot of answers.

The first comparison of the 1250 vs 1280 is interesting: The 1250 used a heavier transformer and 4 22,000mfd capacitors in the power supply for example (same caps used in the 1980) to the higher v lower e torroid in the 1280 and IIRC 4 16,000mfd caps. The 1250 was rated at 160 (8ohms) and 200wpc (4ohms) where the 1280 was rated 185wpc (8ohms) and 185wpc (4ohms). 8ohm speakers are typically 8ohm nominal, not always, and will dip considerably at crossover frequencies etc. which can require more current. This doesn't mean that the 1280 can't hand out more power in real use, but I certainly would lean toward the 1250 for hard-to-drive speakers.

I'll throw in another comparison. The Marantz 2285 and 2285B. IIRC the 2285 was rated 85wpc, 10Hz-60kHz at .08%THD. The 2285B OTOH was rated 94wpc, but at a reduced 10hz-50kHz and higher .1%THD.

Not that this is what Marantz did, but when you are rating power (ex: 85wpc) under the standards available you can rate it either way, provided the specs are accurate. Or in other words, the 2285 might also produce 94wpc at the higher distortion and lower frequency response where the 2285B is rated. Marantz from what I have read though rated after 1hour of music/program played at rated output both channels driven, which was more than what was required at the time.

McIntosh also was known for under-rating their equipment, and you would find this out when you took your equipment to a clinic and had it tested.

I feel that the overbuilt and under-rated pretty much ground to a halt for high-production brands in the late '70s for consumer gear.

Another thing that you can look at is pro-gear vs consumer gear. Consumers read specs (sometimes), buy it and take it home. Pro gear (studio etc.) actually gets set up with instruments and measured, if it isn't meeting spec it gets sent back. Further, a lot of pro gear you will find rated at +/- 1db etc., where consumer gear is more +/- much more.

 

[steveUK]

Great answers, thanks Jeff.

 

[savatage1973]

The issue has been hit upon above--it all depends on how the power rating is done. A bench test with a 1Kz sine wave into an 8 ohm standardized load is a lot different than a musical program into a speaker with an 8 ohm rating. The first is a static measurement, the second is a dynamic situation with multiple variables.

Based on the specs quoted above, the 1250 IMO is more powerful (or at least more robust) than the 1280--for several reasons.The larger transformer and capacitors tend to indicate a greater "reserve power", and the fact that the 4 ohm rating is substantially higher than the 8 ohm rating. The 1280 has a smaller transformer and capacitors, and the 4 ohm rating is almost the same as the 8 ohm rating--indicating that it is pretty much "maxed out" at the 8 ohm rating, with no room for more.

I have 4 Krell KMA 160 monoblocks--each is rated at 160w/8 ohm, 320w/4 ohm, 640w/2 ohm and 1280w/1 ohm, which is (to me) a very powerful/robust amplifier--but each one weighs just shy of 100lbs, has a toroid the size of a coffee can and PS caps the size of beer cans, so the 160w rating at a standard 8 ohms is pretty much worthless.

 

[whoaru99]

Numbers games, for the most part.

 

[quaddriver]

rhetorical question/observation....but when sitting in a mancave and you dial past 3 watts output, the total number becomes mute as your hearing drops off, the bigger question then becomes, "which is more likely to start a fire when it blows"

 

[SaturationPt]

Above is an example of an early '90s Pro amplifier. Rated at 165wpc - 8ohms (first column) it is processing two channels of pink noise. Slide across the columns and you will see how it can be rated with different inputs, such as with only a 1khz input (still both channels driven). You can "rate" it even higher if you go to testing it with only one channel driven (if the power supply were not up to the task of max. output on both channels simultaneously).

Next look at the available output at lower impedance, and even in bridged mode. This is a high-current amp, not a high-gain amp. The difference is obvious when you turn an amp up and can't get past the 12:00 point without the music quality starting to suffer, or even just by noticing how fast the volume increases which is NOT A MEASURE OF HOW MUCH POWER AN AMP HAS, only how much gain (voltage). A high-current amp like this one (or another example is an Integra amp I should have kept) will have less volume gain as you turn it up, ... but it'll drive a block of steel a full volume. High-gain amps are popular because volts (gain) squared divided by resistance (pretending the 8ohms is straight resistance) is calculated power (watts). If you don't build a high-current amp you can build a high-voltage one, ... and rate it with high wattage output (but no headroom). Real speakers have a reactive load that changes impedance and need headroom. This amp also has a damping factor >400 at 8ohms (max, speaker wiring will substantially reduce this) which is designed for large speakers and a minimum speaker load of 2ohms (2-channel mode), both stout specs.

Much like sav's explanation and Krell example above, high-dollar amps are usually also high-current, and perform better than their simple 8ohm watt ratings. I think that there are amps today that have published ratings that are conservative just as they did in the '70s, ... but you probably won't find them on the shelves at a box store. Quality gear is still quality gear, even though some of the (brand) names have changed.

 

[whoaru99]

Gain is simply multiplication (or I suppose attenuation in the case of negative). Gain has nothing directly to do with current or power. Trying to make some tie in there will only cause confusion and further msunderstanding.

 

[zebulon1]

A real world view of the 1250:
A friend of mine who has a taste for audio and can hear a pin drop. Can discern speakers like nobody's business and who has tried, listened and owned tons of equipment from the 70's, took my SX-1250 for a tryout.
He texted back a few hours later and said he had never heard a receiver continue to pound out the music like the 1250. "It keeps driving no matter what was thrown at it". "Continuous power in spades" I think he said.

 

[SaturationPt]

Gain is simply multiplication (or I suppose attenuation in the case of negative). Gain has nothing directly to do with current or power. Trying to make some tie in there will only cause confusion and further msunderstanding.

Gain (voltage gain) does directly affect power, but isn't an indicator of available power. Voltage gain without current capacity will create clipping.

The amplifier specs I referenced above (just somewhat random from my archives, a Crown PS-400) has reasonable current reserves indicated by the chart. Further, that amplifier design (being designed to be bridgeable) has lower voltage gain (IIRC 27v rails) than its output might suggest because you will be doubling them when bridged. The amplifier has voltage amplifier stages which are succeeded by the current amplifier stages to create a stable high-current design.

My point is much like yours: volume increase (voltage amplification) doesn't mean that you have a more powerful amp. The reason that I mention it is because of how many times people have told me that their system has so much power because they can't turn the volume past half-way without it being too loud and therefore there is so much more power than they can use. As many people seem to expect that when they buy a nicer higher-power amp that it will be louder, and in most cases it is not (or barely).

In reality, these people have more voltage or voltage gain than they can use, and in many cases their amplifier simply can't produce the current necessary to use the entire rated power output, ... it simply amplifies (gain) more than it can sustain. Thus the gain can contribute to the rated power output. Gain (voltage) is measured, load/resistance is measured, power (watts) is calculated from these two not measured directly *(yes you can read directly from a display on some measurement equipment, but it is being calculated internally from the RMS voltage across a shunt for current measurement).

I look at these components much like adrenaline: deceptively high speed / strength but unsustainable. Therefore regarding the OP, reliability of the manufacturers' power ratings and comparing high-power receivers needs to address how power ratings are determined, and how applicable the rated power is to real-world use. Power ratings that have no "headroom", no reserve current capacity, will look better on paper than they will sound.

 

[rcs16]

Hi Jeff, the answer to your ?'s is in the actual test measurements. if you ? the mfg or 3rd party measurements, do your own measurements. if you do the exact same measurements on any gear you will get the answers that you need to compare the gear.
yes voltage gain has nothing to do with 'the current necessary to provide the rated power output" into a specific load. The gain in a audio amp stage is distributed amongst all the gain stages, from the low level i/p's to the final o/p being the speakers. You need enough gain in order to drive the amp into clipping.
They dynamic headroom spec is also an important spec that is left off many mfg and 3rd party specs. All these spec are important and determine the differences between amps performances. Most importantly it is the transformer, big ecaps and o/p bjts that make the biggest difference in a PA's ability to drive loads with lots of current. I am not talking about class "D" amps which are a different kettle of fish.
Suggest to read a book like Bob Cordell's audio power amp design to find out the details if you are interested in knowing the real in's and out's of PA design.

Zeb, I'd be interested to have your friend compare the SX-1250 vs the Accuphase P300 that you have

 

[SaturationPt]

Thanks, but I didn't have questions.

 

[rcs16]

It's just left me wondering if later machines' manufacturers' quoted power levels were less conservative than when the wars first began,

Sounded like you were unsure of how these measurements are made.

 

[whoaru99]

Gain (voltage gain) does directly affect power, but isn't an indicator of available power. Voltage gain without current capacity will create clipping.

The amplifier specs I referenced above (just somewhat random from my archives, a Crown PS-400) has reasonable current reserves indicated by the chart. Further, that amplifier design (being designed to be bridgeable) has lower voltage gain (IIRC 27v rails) than its output might suggest because you will be doubling them when bridged. The amplifier has voltage amplifier stages which are succeeded by the current amplifier stages to create a stable high-current design.

My point is much like yours: volume increase (voltage amplification) doesn't mean that you have a more powerful amp. The reason that I mention it is because of how many times people have told me that their system has so much power because they can't turn the volume past half-way without it being too loud and therefore there is so much more power than they can use. As many people seem to expect that when they buy a nicer higher-power amp that it will be louder, and in most cases it is not (or barely).

In reality, these people have more voltage or voltage gain than they can use, and in many cases their amplifier simply can't produce the current necessary to use the entire rated power output, ... it simply amplifies (gain) more than it can sustain. Thus the gain can contribute to the rated power output. Gain (voltage) is measured, load/resistance is measured, power (watts) is calculated from these two not measured directly *(yes you can read directly from a display on some measurement equipment, but it is being calculated internally from the RMS voltage across a shunt for current measurement).

I look at these components much like adrenaline: deceptively high speed / strength but unsustainable. Therefore regarding the OP, reliability of the manufacturers' power ratings and comparing high-power receivers needs to address how power ratings are determined, and how applicable the rated power is to real-world use. Power ratings that have no "headroom", no reserve current capacity, will look better on paper than they will sound.

Gain does not define anything about power. Gain is gain, power is power. Two different things.

I have some other comments too, but presently considering if I'll take the time to parse and respond.

I only hold fast on the gain definition because in many threads I observe misunderstanding of gain vs. power.

 

[SaturationPt]

We agree 99, gain is not power. I simply stated (in your quote above) that gain does directly affect power.

 

[whoaru99]

We agree 99, gain is not power. I simply stated (in your quote above) that gain does directly affect power.

Gain does not directly affect power.

There can be high gain, but zero, low, or high power.
There can be low gain, but zero, low, or high power.

If gain directly affected power then we could say a system with 40dB gain would always produce more power than 20dB gain system but that is not the case.

The notion they go together in any particular way is why it is often misunderstood.

 

[steveUK]

Sounded like you were unsure of how these measurements are made.

Your point being...? Not sure what you're getting at. My first post is what this threads about, and the third para in that is the 'poser'. I'm a qualified electronics engineer, the many and various ways that manufacturers can make and quote their equipment power levels are known to me.

 

[SaturationPt]

Re-read post #7 99. I thought that I was making it very clear that gain is not power, that it is not a measure of how much power an amp will have, and that it deceives many into thinking that an amp has power. That was my point.

In simple EE terms however (if it is simply about the debate), if the load is constant or the current is constant, increasing voltage (gain) will increase power using P=IxE or P=ExE/R. This is irrefutable but it was not my original point and I don't know why you persist in making it so. Dissecting and paraphrasing that post will however help you to increase your post count, ...

 

[whoaru99]

Re-read post #7 99. I thought that I was making it very clear that gain is not power, that it is not a measure of how much power an amp will have, and that it deceives many into thinking that an amp has power. That was my point.

In simple EE terms however (if it is simply about the debate), if the load is constant or the current is constant, increasing voltage (gain) will increase power using P=IxE or P=ExE/R. This is irrefutable but it was not my original point and I don't know why you persist in making it so. Dissecting and paraphrasing that post will however help you to increase your post count, ...

Sorry, but trying to shoot the messenger doesn't redefine gain.

Gain has nothing to do with power.

What you are doing is defining a system to support your position about gain, but the constrained system is not the basic definition of gain.

This not about you, per se, it's about a clear definition of what gain is and is not.

 

[SaturationPt]

You seem to like debating semantics, enjoy.

When you turn up the volume, you are increasing gain. Gain (as a specification in audio equipment) is voltage delta from input to output. Increase voltage into a constant load and you are increasing power/wattage. If you don't, then the volume will not increase.

Ohms law has worked for centuries, is referenced in post #18, and it applies (as does this post) to post #7. If you want to continue to muddy the water, go for it as I am finished.

You are free to mis-interpret or paraphrase and add obscure references to **prove your point** and misdirect this discussion as it seems you are doing, I have made valid points and am finished here.