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 Post subject: Who are they kidding?
PostPosted: Jul Sun 04, 2021 8:03 pm 
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Picked up this RCA model VFT 62 claims it can produce 150 watts peak... measured the output at the amp and at half volume makes 9.5 to 10 volts... looking at the size of the power amp... would say it would be lucky to make 25 watts...


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Sun 04, 2021 8:21 pm 
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There was a lot of that sort of thing; odd ways of reporting the output so that the numbers were larger. I think the King of Misrepresentations was Instantaneous Peak Power (IPP).


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Sun 04, 2021 8:29 pm 
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hwhall wrote:
There was a lot of that sort of thing; odd ways of reporting the output so that the numbers were larger. I think the King of Misrepresentations was Instantaneous Peak Power (IPP).


Sorry to disagree: there's also the subjective power, a term oten used by Audiophools. The only problem is that there's no know test equipment or procedure to measure it.


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Sun 04, 2021 8:35 pm 
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Tubologic wrote:
hwhall wrote:
There was a lot of that sort of thing; odd ways of reporting the output so that the numbers were larger. I think the King of Misrepresentations was Instantaneous Peak Power (IPP).


Sorry to disagree: there's also the subjective power, a term oten used by Audiophools. The only problem is that there's no know test equipment or procedure to measure it.


Re. the RCA, if the exact test conditions are not specified any published value is just meaningless (and/or deliberatly misleading). "150 watts peak" in which load, at which frequency, waveform, which duration, etc... ? A radar could send pulses of magawatt(s) power but for a very short duration only...


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Sun 04, 2021 9:28 pm 
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http://rocketroberts.com/techart/powerart_a.htm

Often times Peak Power only really means the square of the peak voltage that can be delivered to a speaker divided by the speaker impedance usder saturated conditions (i.e. distorted). So working backwards Square root of (150 X 4)= 24.5 V.

So if you had +/- 25 volt supplies for the output transistors (one PNP and one NPN) you could claim 150 Watts peak power up to saturation of the output stage during a peak excursion.

There was also once "music power" which was even more meaningless. Then there are the ones who specifiy the power drawn from the supply rather than the power delivered to the speakers!

It's all meaningless because the signal is distorted before this point is achieved, but it's specmanship (my amp is bigger than yours).

Curtis Eickerman

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 12:58 am 
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The mass-market manufacturers like RCA used to rate amplifier output in terms of EIA Music Power, which was 5% distortion at 1kHz into whatever impedance the amplifier was intended to drive, but using an external regulated power supply rather than the amplifier's own power supply. Then they would double it and call it Peak Music Power. So 150 Watts Peak would be equivalent to 75 Watts EIA Music Power, which was probably around 50 Watts RMS, or 25 Watts per Channel. Looking at that hefty power transformer, I think that's clearly within the realm of possibility.

-David


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 11:07 am 
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ahhhh.....the 'horsepower' wars. Peak Music Power... my favorite. What's the maximum instantaneous peak power an amplifier can produce for a fraction of a millisecond into a 1,200 ohm load ;-) Yes, I made that up. Just like the manufacturer advertising departments did before RMS became the only sane reference. And even then, you had to watch out for the load the amp could drive and at what distortion level. Basically, if you had a power amplifier that could do double duty as a welder, you were probably all set (Phase Linear Dual 500 comes to mind)

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 1:32 pm 
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I have(not currently used) a modern amplifier that is rated for a certain RMS power but also has a peak rating, as they want to claim that they can produce more transient peak power than comparable powered amps. That may be legitimate. Higher peaks for a few milliseconds, might reduce transient distortions or give more perceived impact or something. And tube amps clip nicer than alot of solid state so they are often claimed to "sound louder than their rating". That could be legit too, an amp that makes hash or harsh sounds when it clips would have you turning down volume I suppose.

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 4:06 pm 
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I'm not trying to start a "Which is better, tube or solid state?" debate, but solid state watts never sounded as loud as tube watts. Even at 25 wpc and efficient speakers, it would be easy to run into clipping and distortion before you got the desired volume output you wanted.

I had an RCA ss console---didn't like it.

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 5:31 pm 
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Huh? Watts is watts. Yes, if you are near clipping tubes vs solid state will absolutely sound different. But at, say, the 50% point, I’d challenge anyone to note a difference.

Distortion doesn’t even come into play at those levels

Of course, this will only hold for same spec amps

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 6:32 pm 
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You would lose that challenge. A 25 watt tube amp will sound far louder at 50% than a 25 watt solid state one will. A big part of this reason is due to second-order harmonic distortion--the tube amp sounds louder because it has more midrange.

I had a very nice Fisher integrated transistor amp from the late 60's that put out 30 wpc. I also had a console-pull RCA amp with P-P EL84's making around 12 wpc---the RCA was far louder, and with less audible distortion

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 7:13 pm 
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mental note.....never debate with someone that fancies themself as an audiophile ;-)

Subjective analysis, to say the least.

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 9:02 pm 
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Barry H Bennett wrote:
mental note.....never debate with someone that fancies themself as an audiophile ;-)

Subjective analysis, to say the least.

:wink:

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:18 pm 
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Barry H Bennett wrote:
mental note.....never debate with someone that fancies themself as an audiophile ;-)

Subjective analysis, to say the least.



Who said I was an audiophile? Not me. The difference is profound, anyone would notice it.

Take two 25 watt amplifiers, one tube and one SS, and turn both up to 50% volume. Then record the spl with test equipment at the speakers---let's see which one sounds louder.

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:32 pm 
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You are comparing OUTPUT .... so a tube amp sounds louder than a solid state amp? I seem to have again used imprecise language.... when I mentioned 50%, I was trying to convey that the sound would be just as pure from one amp as the other, not that they would necessarily be at the same absolute amplitude as each other.

Here try it this way .... take both of your amps, into identical speakers, driven with the purest sine wave you've got, and set them both so at the speakers they are both putting out 15V P-P, or 15 Watts RMS, or whatever you want to measure.....at whatever level you want within the center of their operating ranges.... They'll both sound identical. That's all I was trying to say ;-)

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:32 pm 
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What is 50% volume? Do you mean 50% of maximum RMS power? Then it is true -- Watts is Watts, and the two will sound the same.

Are the amplifiers being driven beyond the linear region? Then tube-type will sound louder, since the hard clipping of the SS amplifier will be unlistenable, never mind hazardous to tweeters.

Or do you just mean 50% rotation of the volume control? In that case the comparison is completely irrelevant since what is being compared is gain, not power.

-David


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:37 pm 
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Barry H Bennett wrote:
You are comparing OUTPUT .... so a tube amp sounds louder than a solid state amp? I seem to have again used imprecise language.... when I mentioned 50%, I was trying to convey that the sound would be just as pure from one amp as the other, not that they would necessarily be at the same absolute amplitude as each other.

Here try it this way .... take both of your amps, into identical speakers, driven with the purest sine wave you've got, and set them both so at the speakers they are both putting out 15V P-P, or 15 Watts RMS, or whatever you want to measure.....at whatever level you want within the center of their operating ranges.... They'll both sound identical. That's all I was trying to say ;-)


Yes, I was referring to output---an amp that sounds louder by nature doesn't need to be turned up as loud, hence avoiding things like clipping and distortion

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:40 pm 
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"...sounds louder by nature" is due to difference in clipping behavior.

-David


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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:41 pm 
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Well, there is also the "loudness" control which is a preset bass/treble setting that gives the system a "kick" so it sounds better (to the designers anyway) when you are listening at lower volume levels. It's a compensation for the non-linear nature of the human ear, preselected in the factory for the "average" listener I suppose.

I'm not sure, at this point, what we're even comparing anymore :) Wheeeeeeeee

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 Post subject: Re: Who are they kidding?
PostPosted: Jul Mon 05, 2021 10:42 pm 
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dberman51 wrote:
What is 50% volume? Do you mean 50% of maximum RMS power? Then it is true -- Watts is Watts, and the two will sound the same.

Are the amplifiers being driven beyond the linear region? Then tube-type will sound louder, since the hard clipping of the SS amplifier will be unlistenable, never mind hazardous to tweeters.

Or do you just mean 50% rotation of the volume control? In that case the comparison is completely irrelevant since what is being compared is gain, not power.

-David


But it IS relevant though, because the perceived loudness you hear with your ear is what matters. If you have to turn the SS amp up to 3/4 volume (or more) to match the 50% volume setting of the tube amp, third-order harmonic distortion will rear it's head. This is what I encountered with my old RCA SS console---anything even approaching a semi-loud listening level would cause distortion

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