Power comparison

[ifsixwasnin9]

In general, does a low power amp (~60wpc) and high power amp (~100wpc) put out the same amount of power if you're comparing them at the same low listening level (moderate/high conversation level)? And I was wondering at what point the higher rated amp will exceed the lower rated amp in ouput (at moderate or high listening levels, etc.)? (which might be tied in to the first question.)

I see here that an ideal power amp is linear in theory but reaches a point where the signal becomes saturated and cannot produce any more output: (Which I was curious about: I suppose the high power amp will saturate at a higher output than a low power amp will saturate.)
http://en.wikipedia.org/wiki/Amplifier#Linearity

 

[WaynePflughaupt]

Yes, with a particular set of speakers, both amps will produce the same output at low-to-moderate levels.

As to “at what point” the higher powered amp will exceed the lower powered amp’s output, that would be at the point where the latter runs out of steam.

Actually, a 100-watt amp isn’t tremendously more powerful than a 60-watt amp. The 100-watt amp will only put out about 2 dB more SPL than the 60-watt – if that.

Regards,
Wayne A. Pflughaupt

 

[Seth=L]

The amplifier rating system from manufacturer to manufacturer keeps things off keel making it difficult to differentiate which amplifier would have more power for a given application. For example. The amplifier rated at 100 watts may have been rated on a 1khz basis and the 60 watt rated from 20hz to 20khz. This means if the 100 watt amplifier were to be tested from 20hz to 20khz that it would likely achieve a closer wattage rating to the 60 watt amplifier. Another factor is impedance. The 100 watt amp might be rated at 6 ohms, and the 60 watt amplifier rated at 8 ohms. Amps are designed to be ideally operated in a certain impedance range. This is why you might see two similarly rated amplifiers have startlingly different power achievements at 4 ohms.

Another difference between ratings is constant output vs. peak. Both are relevant, though they are uncommonly both used when rating products. NAD is one manufacturer that tries to do both, by using the FTC rating system for RMS or constant output and IHF for it's peak power. Sometimes these peak power figures can be unrealistic and reflect output for near shut down, or shut down output levels (meaning the receiver or amplifier would open its relays to protect the amplifier from hard clipping).

I had a Rotel amplifier that was rated 60 watts per channel that I would put up against my Sony 150 watt per channel amplifier any day. The reason? The Rotel had greater headroom. The Sony has two liberally rated 15,000uF capacitors for reserve power from the power supply. The Rotel has four 10,000uF capacitors of very high quality for reserve power. The quality of the heatsink was higher, as were the output devices on the Rotel. The transistors (output devices) could cleanly produce higher output than the ones inside the Sony, and the reserves gave it the headroom to achieve higher output for moments when it's needed far exceeding its 60 watt rating. The Sony does have a bigger power transformer, so power can keep on coming through, but the power is wasted on cheap transistors and a mediocre capacitance keeps the amp from having the power on tap when it's needed quickly.

That's the difference between quality and quantity.

 

[ifsixwasnin9]

This is good information to know. I was wondering about a Sansui AU-517 60wpc and maybe upgrading to a newer Denon or Onkyo 100wpc. Have the way power ratings are presented changed much between 1980 to 2000? Or does each manufacturer print them the way they want to print them and not really pay attention to what the others are doing? The specs can be confusing to read and to quantitatively compare between manufacturers.
So the power is used up as you turn the volume (gain?) up and to what degree the tone control levels are turned up (or down)? Everyone should learn these things when you're an adolescent so you don't struggle with these concepts for years all the while going through many $ of audio equipment.
Thanks for the explanations.

 

[Seth=L]

This is good information to know. I was wondering about a Sansui AU-517 60wpc and maybe upgrading to a newer Denon or Onkyo 100wpc. Have the way power ratings are presented changed much between 1980 to 2000? Or does each manufacturer print them the way they want to print them and not really pay attention to what the others are doing? The specs can be confusing to read and to quantitatively compare between manufacturers.
So the power is used up as you turn the volume (gain?) up and to what degree the tone control levels are turned up (or down)? Everyone should learn these things when you're an adolescent so you don't struggle with these concepts for years all the while going through many $ of audio equipment.
Thanks for the explanations.

The AU-517 is rated 65 watts per channel RMS into 8 ohms 20hz-20khz. That amp is an excellent statement piece of the period. If you purchased a Denon or Onkyo 100 watt per channel receiver you would find them to be a disappointment in comparison. If you've never had a peek inside your amp here are some pictures to illustrate.

http://www.sansui.us/PGMP_AU517.htm

You notice the amp is packed full. Lifting this amp quickly reveals it's no cheap piece of equipment either. The design is a true dual mono amplifier with a stereo preamp built in. Each output channel has it's own dedicated power transformer and two large 12,000uF custom capacitors, that's 48,000uF total for all the reserve power you'll need for the majority of speakers out there. Most receivers use a pair of 10,000uF caps, hurting their headroom capability by a significant amount. Ample heatsinking and a hefty output stage make this amp a truly underrated jewel.

Assuming this amplifier is fully functional, it should be a beast.

 

[3db]

In general, does a low power amp (~60wpc) and high power amp (~100wpc) put out the same amount of power if you're comparing them at the same low listening level (moderate/high conversation level)? And I was wondering at what point the higher rated amp will exceed the lower rated amp in ouput (at moderate or high listening levels, etc.)? (which might be tied in to the first question.)

I see here that an ideal power amp is linear in theory but reaches a point where the signal becomes saturated and cannot produce any more output: (Which I was curious about: I suppose the high power amp will saturate at a higher output than a low power amp will saturate.)
http://en.wikipedia.org/wiki/Amplifier#Linearity

Ignoring what Seth just said for brevity sakes ( but what he says is true) , regardless of the specs, if two different amps are fed the same level input and are using the same speakers and are level matched at the output, they are putting out the same power.

To answer your 2nd question..yes.. the lower level power amp will saturate sooner than the higher powered one given both amps are of equal build quality.

 

[ifsixwasnin9]

Yes, I have seen the inside of my Sansui and I took some foolish advice from another popular forum to recap and it was a much bigger job than I thought it would be and I ended up losing one channel. So I had to get it repaired for $150. It worked just fine before I tried to recap it. I should have let it be but I thought that I was going to unearth some greater sound with a recap. I spent an extra $225 on an amp that I bought on Ebay for $164. But you've saved me some money investing in something else. And thanks for Electricity 101. I had a hell of a time with it in engineering school.

 

[Seth=L]

Yes, I have seen the inside of my Sansui and I took some foolish advice from another popular forum to recap and it was a much bigger job than I thought it would be and I ended up losing one channel. So I had to get it repaired for $150. It worked just fine before I tried to recap it. I should have let it be but I thought that I was going to unearth some greater sound with a recap. I spent an extra $225 on an amp that I bought on Ebay for $164. But you've saved me some money investing in something else. And thanks for Electricity 101. I had a hell of a time with it in engineering school.

The good news is, if your amp is in decent to excellent condition, then it's worth more than $225. The Sansui AU-717 is the most common of the AU series integrated amplifiers, and even though the AU-717 is a higher model the AU-517 often sells for about the same price. They aren't terribly different from one another, but they are very robust for the going rate.

Sansui is overlooked by pretty much all but avid collectors. I think they had more refined looking equipment for their day than Pioneer, Kenwood, or most other manufacturers in that period competing in entry level markets.

 

[mtrycrafts]

Yes, I have seen the inside of my Sansui and I took some foolish advice from another popular forum to recap and it was a much bigger job than I thought it would be and I ended up losing one channel. So I had to get it repaired for $150. It worked just fine before I tried to recap it. I should have let it be but I thought that I was going to unearth some greater sound with a recap. I spent an extra $225 on an amp that I bought on Ebay for $164. But you've saved me some money investing in something else. And thanks for Electricity 101. I had a hell of a time with it in engineering school.

Well, you learned an expensive lesson, don't fix something that is not broken especially when you hear it from who knows what sources.