Back before I could justify buying a signal generator I didn’t even do that. I’d use a 6.3 volt power transformer and a pot as a signal source. You can get by without a scope, too. Use a peak detector (diode and cap) on your DMM and measure DC. Drive the amp *into* audible clipping with the 60 Hz sine wave from the transformer, and calculate equivalent sine wave “RMS” power - Vpeak^2/(2*RL). Don’t forget that pesky factor of two to get “real” watts.
150 watts would measure 34.6 volts RMS. Or 49 volts measured with that peak detector. If your amp can’t do a test like this for at least 5 seconds without exploding or having the power supply go into hiccup mode it needs to be *junked* IMO.
IMO clipping behaviour is very important when comparing tubes to SS.
Tubes produce mostly 2nd order and remain listenable much further into clipping than SS.
SS amps must be generously proportioned so they will never get anywhere near clipping.
With tube amps you can sail much closer to the wind as it were before they become dangerous or unpleasant to listen to.
YMMV
Tubes produce mostly 2nd order and remain listenable much further into clipping than SS.
SS amps must be generously proportioned so they will never get anywhere near clipping.
With tube amps you can sail much closer to the wind as it were before they become dangerous or unpleasant to listen to.
YMMV
Well it s a *tube* amp, is it not? Mine will do 210 watts. Haven’t left it on all day like that, but one of them did run for an hour or so, with nothing overheating or any nasty looking glow inside the tubes. I call it good enough.
I did leave my “CS800 clone” on at full power into dummy loads for two days back when I developed it.
Low frequency output below 120 Hz tends to be limited by the main filter caps. The pole frequency between the cap and the load resistance needs to be about 2Hz in order to approach full power at 20 Hz. It’s easier to do this with tube amps because the load impedance is high and it doesn’t take a ridiculous number of microfarads.
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I was under the impression current thinking was moving toward 6 dB as double perceived loudness. Two speakers are 6dB louder than one for example. Are two perceived as twice as loud?
In theory. Two sets of the same speakers powered by two of the same amp should result in a 6db SPL increase.
Where do you get that figure?
My (typo) mistake, I should have said that 24.5 VAC RMS into 8 ohms is about 150 watts.
And I'm going by the "old school" measuring method of wattage calculation which back then was the standard of the industry and documented and offered by McIntosh products.
It's 75 watts.
And there are no "old" and "new" schools of calculating that. It's just one formula.
Unless you're talking about the total power output of the stereo amp.
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Charles Darwin,
Generalizations are just that . . . Generalizations.
The nature of different solid state amplifiers are not always similar.
Many have dominant 3rd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
Some solid stage amplifiers use totem pole output stages. Some use single ended output stages. Some use push pull outputs driving an output transformer, similar to a push pull tube amplifier.
The nature of different push pull tube amplifiers are not not aways similar.
Push pull amplifiers often have dominant 3rd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
The nature of different single ended tube amplifiers are not not aways similar.
Single ended amplifiers often have dominant 2nd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
What happens if the clipping occurs at the driver, or at the earlier stage, and not due to the output stage?
What happens if the clipping occurs at about the same level for both the driver and the output stage?
What happens to a single ended amplifier where the driver 2nd harmonic distortion is equal to the output stage 2nd harmonic distortion, and the two distortions cancel (serial cancellation)?
Before stating about the orders of harmonic distortion, and which is dominant, first consider the particular topology of the amplifier, and the implications thereof.
Or . . . just measure it, so you can be sure.
Generalizations are just that . . . Generalizations.
The nature of different solid state amplifiers are not always similar.
Many have dominant 3rd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
Some solid stage amplifiers use totem pole output stages. Some use single ended output stages. Some use push pull outputs driving an output transformer, similar to a push pull tube amplifier.
The nature of different push pull tube amplifiers are not not aways similar.
Push pull amplifiers often have dominant 3rd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
The nature of different single ended tube amplifiers are not not aways similar.
Single ended amplifiers often have dominant 2nd harmonic distortion, both before clipping, and at clipping.
But not all respond that way.
What happens if the clipping occurs at the driver, or at the earlier stage, and not due to the output stage?
What happens if the clipping occurs at about the same level for both the driver and the output stage?
What happens to a single ended amplifier where the driver 2nd harmonic distortion is equal to the output stage 2nd harmonic distortion, and the two distortions cancel (serial cancellation)?
Before stating about the orders of harmonic distortion, and which is dominant, first consider the particular topology of the amplifier, and the implications thereof.
Or . . . just measure it, so you can be sure.
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The ears have an automatic self adjusting sensitivity, versus the sound level.
Ear muscles adjust the ear's bone's position according to the sound level.
The varying bone's position changes the mechanical advantage as the bones transmit sound energy from the eardrum to the drum on the Cochlea.
In the literature (if I could find it again), 10dB more sound is perceived by the ear, as a doubling of sound level.
I do not see anything in the literature that talks about the percieved sound level, as related to feeling the sound on your body, legs, etc. There are no changes of mechanical advantage on those nerve sensors, so perhaps a 3 dB or 6dB increase of sound level might be perceived as a doubling or quadrupling of sound in terms of vibration.
Ear muscles adjust the ear's bone's position according to the sound level.
The varying bone's position changes the mechanical advantage as the bones transmit sound energy from the eardrum to the drum on the Cochlea.
In the literature (if I could find it again), 10dB more sound is perceived by the ear, as a doubling of sound level.
I do not see anything in the literature that talks about the percieved sound level, as related to feeling the sound on your body, legs, etc. There are no changes of mechanical advantage on those nerve sensors, so perhaps a 3 dB or 6dB increase of sound level might be perceived as a doubling or quadrupling of sound in terms of vibration.
V^2/R (Ohm's Law)
25.5^2/8 = about 80W.
24.5^2/8 = about 75W (not 150W)
So yeah 150W total power for a stereo amp
75W/channel, is a 75W amp, in my book
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Wait. It sounds like you are saying that any amp that can't output 150 watts for at least 5 seconds is junk?
If this is true, then all I can say is there are a lot of truly excellent sounding pieces of junk on planet earth.
I err on the side of caution and agree with the two companies who made my power amps and phone pre who put the onset of clipping at the point where THD exceeds 0.03%.
That is safely below the level I find audible which according to the Klippel test and my speakers is 0.5%.
Again YMMV
I never considered 0.03% to be anywhere within Miles of clipping . . .
unless there is an extremely unusual sharp transition from linear to non linear.
Your Mileage May Vary.
I have never owned an amplifier that was rated at 0.03% distortion (-70.5dBc total harmonic distortion), even at 1 Watt.
Neither 60 dB of negative feedback, Nor super-complex super-compensated circuitry that is somewhat similar to a really good chip OP amp, can ever be my cup of tea.
There may be other configurations that also give that kind of performance.
Performance aside, I do not want to spend that kind of money.
The original whiz-bang solid state amplifier from Audionics in Portland worked wonderfully into a power load resistor.
100% of them came back from the customers, they all blew up when loaded with a variety of models of loudspeakers.
Just my opinions.
unless there is an extremely unusual sharp transition from linear to non linear.
Your Mileage May Vary.
I have never owned an amplifier that was rated at 0.03% distortion (-70.5dBc total harmonic distortion), even at 1 Watt.
Neither 60 dB of negative feedback, Nor super-complex super-compensated circuitry that is somewhat similar to a really good chip OP amp, can ever be my cup of tea.
There may be other configurations that also give that kind of performance.
Performance aside, I do not want to spend that kind of money.
The original whiz-bang solid state amplifier from Audionics in Portland worked wonderfully into a power load resistor.
100% of them came back from the customers, they all blew up when loaded with a variety of models of loudspeakers.
Just my opinions.
No, an amp that can’t run at full signal sine wave for five seconds (at whatever power it clips at) is JUNK. Even home theater receivers can, usually. Some *really* cheap HT receivers don’t have enough SOA in the output transistors to run at full signal for even a couple seconds, and as such are walking time bombs. That makes them JUNK, since they will end up in a landfill because it’s only a matter of time till failure. A lot of cheap class D garbage will shut itself down, go into hiccup mode, cut waaaaay back on power, or otherwise misbehave when you ask for more than a few watts or tens of watts of average power even for a second. So-called “professional” units among them.
Charles, far too much of a generalization. Topology of the amp, and its execution are more imortant than tube vrs SS but the different transfer curves of the devices does tend to dictate the topologys most often used.
dave
With a lot of low end stuff the pressure is on to keep price down.
So corners can often be cut.
Its a tough market out there.
So corners can often be cut.
Its a tough market out there.
You guys have me confused, I have a 25w chip amp and the rails are +/- 25V AC. Firstwatt amps typiclly use the same rails an output <25w.
dave
Given that THD has been shown to be a meaningless piece of data to tell us what an amp says, it makes the rest of your narative meaningless.
dave