Thanks Skeptic and RGA

[jbangelfish]

I had lost track of the Arsenal site and forgotten the name of it so thanks for the info.
With the AR9's being rated for 400 watts, I'm sure they like more than 100 watts and I'll give it to them. I don't think I've ever seen a 400wpc class A amp although one may exist. I don't know if I'll ever understand the ratings especially when Skeptic says watts are watts, end of story.
How a Class A rated at 30wpc is equal to 150wpc AB, makes no sense to me. I was OK with it until Skep said the watts is watts comment.
As far as not being able to get more power than what is available from the outlet, I agree. This said, the Parasound amp can draw 1000 watts of power which would only be around 10 amps (if my basic understanding of electricity is correct). On a 20 amp circuit, there should be no problem with this draw. It may never actually pull the full 1000 watts but the power should be there for it if needed.
When I ran two Parasound amps, the lights would dim with certain passages. Last evening, all lights were off for listening which is the way I prefer to listen. I have read of the distraction that lights can cause to a listening experience and have always been a believer in this concept anyway. The results were better than ever. I'm still in amazement.
Bill

[skeptic]

How a Class A rated at 30wpc is equal to 150wpc AB, makes no sense to me. I was OK with it until Skep said the watts is watts comment.

A watt is a watt is a watt. It is a scientifically defined rate of doing work. There is no such thing as class A watts, class B watts, solid state watts, tube watts, DC watts, AC watts, period. That's not an opinion, it's a fact. It is one amp (one coulomb per second) delivered by one volt through one ohm of resistance. It is the equivalent of 1/745 th of a horsepower. If some people feel that an amplifier rated for a given wattage can produce louder undistorted sound than another rated for the same wattage, that may be because wattage ratings may be more conservative by some manufacturers and their amplifiers actually are able to produce more wattage than stated or the ratings may be qualified by say frequency bandwidth or distortion and can actually produce more undistorted watts at some frequencies than stated. But with the same frequency(s) the same loudspeakers will produce the same sound pressure level (loudness) with the same amount of electrical power no matter what kind of amplfier is in use.

I use an amplifer rated at 60 wpc to drive my AR9s. They are at one end of a room that is nominally 14 x 30 x 9 1/2 feet high. Acoustics are on the live side. The amplifier may actually be able to deliver more power and is rated to deliver 250 in mono if reconfigured. The amplifier can power the AR9s to deafening levels without distortion anywhere in that room. I see no reason to exchange it for a larger unit unless the acoustics or the room I use them in changes and warrants more power.

[RGA]

Watts are indeed watts...and will SORT OF tell you how loud the sound is going to be. It is also a fact that a 200 watt amp will give you a 3db gain over a 100 watt amp which is barely audible.

Or think of it this way. The gains in volume will ONLY ever be achieved when you are pushing the speakers to the maximum levels before they start to distort. In other words UNLESS you are absolutely cranking your system, which is bad for your hearing, a 400 watt amp can only play twice as loud, as a perception to your ear, that a 40 Watt amp can offer. And this is a fact.

Most of us listen at normal to loud levels. My speaker is rated at 93db at 1 watt. 90db is considered LOUD. One watt is all it takes to play LOUD. Now there is losses because you sit further back, dispersion of the speakers, crescendo in music that make instantaneous demands but for my speaker 20 watts will play plenty loud. 20 watts with my Wharfedales will and has rattled a walls with deep poweful tight bass. Where as my 125 watt RMS Pioneer Receiver sounded distorted flabby and unfocused. Despite the glowing numbers. And it was just as good as the comparable Denons and Yammies of the day.

The preamp is going to determine clarity. A clean lower powered amp will give you the perception that you are playing louder because it will play a given level clearer. Whereas an amp with 5 times the power that sounds muddy may in fact be "LOUDER" but because you are fighting to hear what a singer is actually articulating, it will "seem" or give the "perception" of not being as loud.

Our brain takes information and picks and chooses what it chooses to focus on. When you're in a crowded bar and there are say five table around your table. Everyone is speaking at the same loud level say. If you want to hear the two good looking women's conversation have you ever noticed that you can kind of zero in on them and virtually shut out everyone else? You can...it's not about what your ear hears it's the filter in you brain. One problem with double blind tests is the very fact that they take out other sensory inputs - which on the one hand makes logical sense but on the other hand is invalid.

In the late 70s early 80s a lot of high end amps were considered powerful at 30 watts. Especially in Britain.

High watt amps are generally noisier(except good ones), separates have the same problems which is why people spend a lot of money on Integrateds.

But if your speakers are heavily damped and have power sucking crossovers and difficult impedences a high watt amp is recommended. After all you NEED to properly be able to control the drivers.

100+ watts however won't necessarily drive an electrostat better than a 50 watt amp. There is more to an amp than watts. The preamp is far more important to the actual sound "quality" than is a power amp. Most power amps from Rotel up are pretty much similar in quality...so why spend more than a Rotel? Unecessary IMO.

Which is why you see a lot of people with solid state amps buying a tube preamp. McIntosh has released a $10,000.00 Tube preamp for their solid state amplifiers with success.The preamp sends the sound to the power amp which merely takes that small signal and makes it louder hopefully without making a mess. SS amps can offer much higher power in this regard for far less cost - but you still get the sound of the tube pre without the artificial etching of most preamps.

The Bryston B60 is basically a Bryston 2BLP and a Bryston preamp. If you ever get the chance to compare the Bryston B60 with a 2B LP power amp and a dedicated Tube preamp you will be amazed at how much cleaner and tighter the sound is from top to bottom. This set-up was actually $300.00 less than the B60. Though you lose the remote function.

[jbangelfish]

Yes, I can't argue that point. Class A may have a different way of rating the amplifier, I don't know. I know that a friend uses an 80wpc amp to drive his AR9's, which I have mentioned before. His is a Great American Sound (GAS) Son of Ampzilla and is supposed to be Class A. When he told me that it weighs less than 20lbs, I was surprised. We plan to compare his amp to mine and will also try the old Crown. I don't expect any of them to outperform what the Parasound amp did for me but who knows.
My room is very similar to yours, 15 X 25 X 12, walls are wood, ceiling drywall and floor carpeted. I would not want the room to be much smaller with these speakers and the power being given to them. I listened to vinyl with the preamp volume at about 2 o'clock and was completely amazed by what I heard. Positively the best that I have ever had in my home and I've never heard better in anyone else's home. The volume was fairly loud but not overly so, I used to listen to the 901's at a higher level but got less from them and sometimes suffered ear fatigue. Not so anymore and I don't need the extra volume to find what I was looking for. This is what I've been looking for all along. Beautiful, clear music with no distortion (at least none that I can discern). Next big test is to see how they respond to CD's, maybe some of the faults that I previously experienced will go away.
Bill

[skeptic]

Amplifiers whether class A or AB or B are all measured and tested the same way. There is no magic to it. Here's how it's done. The speaker outputs are each connected to a load resistor of say 8 ohms and capable of dissipating enough heat so that they won't be destroyed in the test. An ammeter and a volt meter measure the voltage across and the current through the resistor. A distortion analyzer and possibly an oscilloscope is also connected to monitor at what point the amplifier begins to clip and produce high distortion. The input is connected to a siganal generator which generates a sine wave of one frequency at a time. The input signal strength is increased until the distortion analyzer shows distortion is increasing quickly and the oscilloscope shows the top of the sine wave flattening (clipping.) The current and voltage are noted. Multiplying the voltage by the current gives the wattage at clipping, the maximum undistorted signal the amplifier can deliver with that load at that frequency. To meet FTC requirements, all channels must be driven simultaneously and the amplifier must have been run at 1/3 power continuously for at least 20 minutes of "preconditioning." The experiment is repeated for many frequencies across the full spectrum of the audible band. When the frequency at which the maximum undistorted power drops by 50%, these frequencies are noted and this becomes the minus 3db power bandwidth of the amplifier. The test is repeated at 4 ohms, assuming the amplifier is rated to deliver power to a 4 ohm load. The test doesn't care what's in the amplifier box to get the job done whether it's transistors, tubes, class A, class B, cobwebs and fairy wings, so long as it gets it done. There Bill. Now you are an expert. Don't let anyone tell you any more rubbish about different amplfiers having different magical powers.

BTW, to determine the frequency response of the amplifier, the test is repeated but with a fixed input signal voltage at different frequencies where the output is in the vacinity of one watt. Deviations from dead flat response of the output are noted and that's how the specification is developed. Transistor amplifiers generally test just about dead flat across the audio band. Tube amplifiers do not usually measure so flat. That could be another reason why some of them sound louder. And in case you were wondering, no they don't test the frequency response at higher power levels, another possible source of differences in the way amplifiers sound. Rather sly and sneaky don't you think?

Bill, when you are ready for a DIY project to "kick it up a notch" , let me know. I'll tell you what I did with mine.

[jbangelfish]

And it is a good part of what I like about big power. It doesn't play that much louder, it just does it better in my experience. I too have had receivers and integrated amps but none ever compared to what I have found with separates.
I fully understand the 3db increase requiring twice the power. Seems to me that I read somewhere that 1db is what human perception can discern as an increase in volume. I don't know if that's true but it seems plausible. With that in mind, I'm not playing a whole lot louder, just more full and much more dynamic as the crescendos call for more power. How one of these high powered amps compares to Class A with less power, I have no idea but I have always been pleased with what big power does.
I have an old Accuphase integrated amp with about 115wpc which sounds much better than any receiver that I ever had but compared to the Crown or Parasound separates, it gets left in the dust. If it were paired with the right speakers, it would probably be a fine choice. I have just always had speaker systems that could handle lots of power and when I give it to them, I am rewarded with better sound.
Rotel, Perreaux, Bryston, Parasound, Adcom and others were all amps that I had considered from reading independent reviews. It seems that they are all in about the same league for price and sound quality. I found the two Parasound amps at a reasonable price while looking and settled on them. I'm somewhat surprised to see Bryston 4b's need for repairs. I also read that some people consider them to be alittle bright. Some say the Parasound can be bright also and it may be true to some extent. At present, I have the treble and mid's cut 3db on my speakers with excellent results at least in my last listening session.
I also use a Parsound PLD2000 preamp and am very pleased with it as well. The combination of this with my Cary tube phono stage and Fidelity Research low output MC cartridge feeding the AR9's made for the best listening session that I've ever had in anyones' home. Many factors made this possible but the combination made for an unbelievable performance in home stereo. Absolutely phenomenal.
Bill

[Geoffcin]

Well, I'm finally back on!

Regarding the differences between class A, A/B, B, ect. It was covered quite well a few weeks back. Skeptic posted a very good primer on amp design in the old forum, I would recommend that you go back and read some of those posts.

One of the reasons you dont see a lot of ultra high power "class A" amps is the heat. Class A runs hot, and usually put out as much energy in heat as watts it's rated for. A 400 wpc class A amp would be a toaster!

While it may be true that a 200 watt amp is only theoretically 3db louder than a 100 watt amp, in practice it's much more noticeable, especially with demanding passages. The gain in volume is really not what's it's about, the real story is to be able to push the speakers without clipping the transient louder passages. I was surprised to find out how easy it was to drive my 100 watt per channel receiver into clipping. With my higher powered audio gear this is not a problem. Speakers, especially woofers have to be controlled too. A lot of lower powered amps can get very muddy in the bass even before clipping sets in. To qualify this, I am using speakers that are not very efficient, so I need that extra headroom.

In the end though it comes down to personal preference. What I find good might not be Skeptic's, or RGA's cup of tea. Hey, if we all liked the same stuff there wouldn't be much need for the diversity in audio equipment!

[skeptic]

When Bill comes down from cloud 9, I'm going to show him how to make those AR 9s sing like he never heard them sing before.

[WmAx]

I don't know how the 2x power = 3db came up, but this erroneous.

2x power = 6db increase. 1.5x power = 3db increase.

According to my memory statsitcally derived tests on human hearing..... a 1db increment is the average min. level detectable on steady test tones. 0.2-0.25 db is the min. level detectable on a test signal containing broad band information WHERE you have a reference and only a narrow band is changed. EXAMPLE: Adjusting treble amplitude, while leaving mid/bass levels stabile.

6db is true 2x power/spl increase. Howver, humans on average, tend to percieve 6db as a 50% incrase in loudness, where as 10db is typically required to be percieved as a 2x increase.

-Chris

[skeptic]

Sorry to have to correct you but, you are wrong. +3db is twice the power, -3db is half the power. To understand it, go back to the definition of a decibel and go back to the theory of logarithms.

In the meantime, check out http://www.phys.unsw.edu.au/~jw/dB.html

[skeptic]

some clarification is necessary. The +/- 3db double/half power relationship refers strictly to electrical power. Read the entire page to understand different db measurements and what they signify.

[WmAx]

Sorry to have to correct you but, you are wrong. +3db is twice the power, -3db is half the power. To understand it, go back to the definition of a decibel and go back to the theory of logarithms.

In the meantime, check out http://www.phys.unsw.edu.au/~jw/dB.html

Thank you for the reply. I am in error. I was thinking of amplitude, not power. As your page specifies, comparing relative amplitude of voltage, current or sound pressure, thus 2x amplitude would equal 6db increase.

-Chris

[WmAx]

some clarification is necessary. The +/- 3db double/half power relationship refers strictly to electrical power. Read the entire page to understand different db measurements and what they signify.

Ok. I already replied to your first post before this.

-Chris

[jbangelfish]

At least that's one concept that I have understood for a long time and in part, leads me to my preference for lots of power. The difference in going from 100wpc class AB to 200wpc class AB is quite profound and whether it comes down to the simple matter of +3db, I don't know but it could be just that. It certainly sounds and feels as if there is more to it as I have described in the past, bringing speakers to life.
I am still on cloud nine, listening to the AR9's but I guess I'm also learning what the term "revealing" means in stereo. This seems especially true with my LP playback. Bad recordings sound worse than ever. I'll live with that as good ones sound better than ever. As for mods to the speakers, I may ask Skep in the future. I seem to remember 3 Audax tweeters per cabinet and some adjustment to crossover frequencies. No need to explain it all now, I'll wait awhile.
I read quite thoroughly through the class A and AB discussion and have a basic understanding. The part that baffles me is the claim that a 30 watt A is equal to 150 watt class AB. No need to explain this further either, I will be comparing an 80wpc class A against my 385wpc AB. This should tell me all that I need to know.
I also remember some amps which were rated rather low in power (65wpc to 100wpc) but had 4.5 to 9db of headroom. NAD and Naim were the ones that I remember. To me, this sounded like a way of fudging numbers when in reality, these amps could just have been given a higher power rating with less headroom. It is also possible that they would not have had the continuous power rating and were only capable of very short bursts of big power. Either way, they don't really interest me. They sounded fine to me in a store setting but being a power nut, I'd rather have the assurance of continuous power.
Bill