Watts per channel

 

Bronze Member
Username: Tdub

Saskatoon, Sask. Canada

Post Number: 12
Registered: Nov-04
This is a simple question I hope. I have 20 plus year old Bryston 4-B power amp. It is rated a 250 watts per channel into an 8 ohm load 400 into 4 ohms. I use it on a equally as old Cerwin Vega AT-15's. This set up is quite loud when pushed. I resently aquired a Grant Fidelity A-88 integrated tube amp. It is a dual mono design rated at 65 watts Ultra linear to 32 watts in triode mode. Now my question. Why would this 65 watt amp deliver equal power (to my ears) as the Bryston? it sounds very clean at higher volumes as the Bryston was.
thanx
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13280
Registered: May-04
.

Tubes clip in a different manner than transistors which makes tube clipping less egregious.

Once you get beyond about 50-75 watts with most amplifiers, increasing power gains little in the way of SPL increases. On paper you have about 6dB of headroom with the Bryston for peak power delivery. If the material you listen to doesn't have very much dynamic range, then you probably won't notice the increased headroom since neither amp is running at maximum power output for anything more than an instant.

.
 

Gold Member
Username: Nickelbut10

Post Number: 2289
Registered: Jun-07
The fact that those Cerwin Vega's are arguably the easiest speaker to power, you probably are not even using on average 30-50 watts to get them at a insane loud volume.
 

Bronze Member
Username: Tdub

Saskatoon, Sask. Canada

Post Number: 13
Registered: Nov-04
thanx for the info. I have a Telarc disc by Papa Doo Run Run called California project that uses no compression and has a lot of dynamic range and compare the two.
Thanx
 

Platinum Member
Username: Nuck

Post Number: 11418
Registered: Dec-04
And Grant Fidelity makes a very good product.
 

Bronze Member
Username: Tdub

Saskatoon, Sask. Canada

Post Number: 14
Registered: Nov-04
I have to agree. Very well built and sounds great. I also have his P-307 which I am using as a phono stage for my Pro-Ject Xperience TT.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2943
Registered: Dec-06
You should totally find the resonant frequency of each driver chamber in the speaker, then the amplifier's max power at each frequency. Then you could play all three signals with power proportioned by each driver's power handling. After that you would find the signal voltage needed to get the max power out of those frequencies, and play it. Then you can find your system's limits in volume as well as annoy neighbors or lose your speakers or worse..

Oops - there I go again
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13290
Registered: May-04
.

Where ya'been, Andre?
 

Platinum Member
Username: Glasswolf

NW, MI USA

Post Number: 12307
Registered: Dec-03
a couple additional notes. as mentioned, tube amps produce odd ordered distortion, which is more pleasing to the ear than even ordered distortion produced by an SSA amp. This odd ordered distortion is what we preceive as the "warmth" of a tube amp.
Also, in regards to the power output, remember that it takes ten times the actual power to audibly double the volume of a speaker. That means to double the volume of your 65 watt amp, you'd need a 650 watt amp, at full output, or, since we don't typically run at full output for obvious reasons, the reality is that at typically moderate volumes, you're only using an average of about 50 watts of power total with a 7.1 channel AV receiver, so for 2 channel critical listening, you're using even less.. closer to the range of 20 watts RMS on a reactive load with a very dynamic source signal.

Short of it is, you're not using nearly what either amp can really do at it's limits, so increasing to bigger amps doesn't automatically mean much louder music. It takes a LOT of power to make speakers remarkably louder.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13292
Registered: May-04
.

"a couple additional notes. as mentioned, tube amps produce odd ordered distortion, which is more pleasing to the ear than even ordered distortion produced by an SSA amp. This odd ordered distortion is what we preceive as the "warmth" of a tube amp."

I don't believe anyone did mention the distortion components of tube amplifiers. I mentioned tubed power amplifiers clip the signal in a generally different manner than transistor outputs but that doesn't have anything to do with their distortion component at lower levels. When an amplifier clips, all distortion products generally go up and not just even or odd order components. Most of what happens when a well designed amplifier clips has to do with the load it works into and how well constructed the power supply is to handle such loads. This doesn't really vary between tubed or transistor outputs though a tube power amp generally has a bit of an edge here since it will probably have an output transformer between the output devices (tube[s]) and the load (speaker[s]). The transistor amp, on the other hand, is generally less sensitive to load.

However, in most cases tubes do have what is considered a "softer" clipping (rounding the edges of the waveform rather than squaring them as you would see from most transistor outputs) when they are just beginning to enter clipping. This will probably make the early onset of clipping less noticeable with a tube power amplifier and often contributes to the old idea that tube watts are twice as powerful as transistor watts. That's no longer a truism - actually it never was, watts is watts and clipping is clipping - when listening to modern amplifiers of either type. Broad statements such as "tube watts are twice as powerful" just doesn't take into account sufficient information to really be useful in most situations, particularly with the very reactive loads presented by far too many home audio speaker systems today.

Triodes operate differently than pentodes which work differently than beam power tubes and how the output transformers are coupled to the power supply/tubes and then to the load all make a large difference when you are discussing tubes. A single ended amplifier has advantages and disadvantages compared to a push/pull design when either is used as an output topology.




Speaking in very broad terms though you have the concept backwards. As a rule tubes and FET's (a solid state device, MOSFETs are often said to sound "tube-like") tend toward low order, and more even order harmonics (a good deal of second order and some amount of third in most good amps which is generally considered "musical" in nature) while transistors typically display higher order and more pronounced odd order harmonics along with the second and third order products (it's not uncommon to see some seventh order harmonics in a solid state amplifier though some tube amplifiers display this same behavior). This is the basis for J.G. Holt's admonition that it is not the amount of T.H.D. that matters but the distribution of the harmonic components that tells a more complete story.



Unfortunately, I think you're woking under older concepts of both solid state and tubed electronics. As transistors have improved through the decades and the two technologies have moved closer together in sound quality (at least in the very best components), the distortion products of both devices have become more similar with the designer's taste being more apparent in either design. Power supplies and better output devices have made for less annoying distortion products from solid state devices with today's best transistor amplifiers having distortion components that are far less load dependent and at all times far more benign than what was available when the "tubes do this and transistors do that" concept evolved. IMO other than some very cheap transistor amplifiers that rely on heavy doses of negative feedback (which will induce its own sound on the amplifier) for their on paper specs, the old thinking doesn't really hold water nowdays. Cheap transistors have no more to do with the sound of a high quality solid state amplifier than would a vintage Magnavox tubed console have to do with a modern McIntosh tube product.

In your brief assessment you ignore the effects of triode vs. pentode vacuum tubes and the audible effects of output transformers on the sound of a tubed amplifier. Neither of those considerations apply to your typical solid state amplifier. You also dispatch the biasing of the amplifier into the various classes of operation without comment. If one amplifier runs in, say, an "enriched" class A into higher wattages, then its sound will be more "musical" for most people.

What all this means is there are far too many considerations to account for when generalizing what gives any amplifier its "sound" than the old "odd/even order distortion" concepts. But, Glasswolf, you do, as a rule, have the concept backwards in your statement.


"That means to double the volume of your 65 watt amp, you'd need a 650 watt amp, at full output, or, since we don't typically run at full output for obvious reasons, the reality is that at typically moderate volumes, you're only using an average of about 50 watts of power total with a 7.1 channel AV receiver, so for 2 channel critical listening, you're using even less.. closer to the range of 20 watts RMS on a reactive load with a very dynamic source signal."


I have no idea how you arrived at that math. I'm not certain how you decided "50 watts ... total" for a 7.1 system and then how you reduced that to "20 watts RMS". And "on a reactive load"? So the 7.1 isn't working into a "reactive load" while the 2.0 system is? That makes no sense and doesn't appear to have anything to do with this thread.

The op is running CV's, about as "non-reactive" a load, or at least closer to a resistive load, as you'll find in a modern multi-way speaker system. I would tend toward giving the speaker load both amps see in the CV's a lot of credit toward the tube amp sounding "powerful" in this situation. They require little in the way of current from the amplifier and, as has been stated, they are sensitive enough to not require huge amounts of voltage before your ears give out.

It is to, put it plainly, the electrical sensitivity and the overall efficiency of the speaker system that determines how loudly a specific amount of "watts" will play. If the amplifier is up to the task of driving the speaker system and its demands for current delivery (this is why the more accurate input power of "2.83 volts" rather than "1 watt" is preferred when stating sensitivity specs), 5 "watts" will play equally loud no matter the amplifier type. If you add more speakers to the room, all receiving the same amount of power, then the "acoustic power" in the room goes up. If you reduce the number of speakers in the room, then you would require more electrical watts to reach the same acoustic SPL.

With that in mind, I am not understanding how you arrived at your numbers or what they actually mean.



.
 

Platinum Member
Username: Glasswolf

NW, MI USA

Post Number: 12310
Registered: Dec-03
yes I got odd and even backward. I was having a bad day and was distracted by a number of more important issues when I scribbled that note down on here.

If we're going to play the "pick appart the message" game, then fine. here:
"I have no idea how you arrived at that math. I'm not certain how you decided "50 watts ... total" for a 7.1 system and then how you reduced that to "20 watts RMS". And "on a reactive load"? So the 7.1 isn't working into a "reactive load" while the 2.0 system is? That makes no sense and doesn't appear to have anything to do with this thread."

50 watts AVERAGE for a 7.1 receiver was derived from numerous measurements of a myriad of systems at a moderate "watching a movie level" output.
A speaker, usually, is a reactive load. period. the change from 7.1 to 2.0 is derived by 5 less speakers being driven into the same volume level by the receiver. 2 speakers and two amplifier channels will use less power than 7 of the same will. Why is that so confusing?

"The op is running CV's, about as "non-reactive" a load, or at least closer to a resistive load, as you'll find in a modern multi-way speaker system."
Not really. My KEF 104/2s are a resistive load. The CVs I've experienced, though I grant you, it isn't anywhere near their entire line, haven't been such, and the ones Ive used were older models. I will agree that the CVs I used were extremely sensitive.

sensitivity and efficiency in a speaker are not the same thing. not even close.


and again, by wasting so much time picking apart every nuance of my reply, you missed the forest for the trees. My point was that he asked about one amp not seeming much louder than the other, and my point was that he isn't going to hear a drastic difference in the two, as to hear double the audible volume, he'd need about ten times the power put into the same speaker, regardless of where that power comes from.
The common misconception people seem to have is that a 110 watt amp won't be nearly as loud as a 140 watt amp.
 

Platinum Member
Username: Glasswolf

NW, MI USA

Post Number: 12313
Registered: Dec-03
my apologies for being snappish. I'm still not having a great day.. having some health issues with blood sugar and an organ transplant that have my nerves a bit frayed right now. I didn't mean to be rude.

Anyway, the power figures in relation to decibel output are fairly standard figures. you were correct on my mistake on the ordered harmonics, but really I was just trying to point out mainly that the difference in rated power may not make as large a difference as the OP may have expected.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 13294
Registered: May-04
.

OK, no problems here. Good luck with the BS and your other health related issues.

But let's clarify a few things to make this interesting to someone else.

I wasn't picking apart your post. Your post had what I saw as two halves and neither half was correct. I did separate "sensitivity" and "efficiency" when discussing speaker loads so, yes, there is a distinct difference between the two though many people continue to interchange the terms.



Now, as I remember them, the KEF 104.2 is not a "resistive" load in actuality. As you say, "A speaker, usually, is a reactive load. period." The KEF's, to my recollection, were designed to be a far less reactive load than most of the speakers of the day and since that time. That includes the numerous speakers that have amplifier mangling impedance curves and phase angles. I know of no speaker that is a purely resistive load - not even my single driver systems. If it has a crossover, it is reactive to some degree. If it has a voice coil, it is reactive to some degree. If it doesn't have a voice coil, I don't know of a modern speaker that doesn't present some other sort of inductive or capacative load to the amplifier.

As far as the CV's go, their fairly simple crossovers make them better than most when you consider what an amplifier must deal with.



"50 watts AVERAGE for a 7.1 receiver was derived from numerous measurements of a myriad of systems at a moderate "watching a movie level" output.
A speaker, usually, is a reactive load. period. the change from 7.1 to 2.0 is derived by 5 less speakers being driven into the same volume level by the receiver. 2 speakers and two amplifier channels will use less power than 7 of the same will. Why is that so confusing?"



Well, we're sort of wading into the weeds here, but its confusing for several reasons. First, because in your original post you swap from "average" to "RMS" power and, secondly, because you state numbers that aren't realistic. I think if we stay with "average" we'll do better here. That takes into account a few things that "RMS" doesn't when discussing music/movie material played into a speaker load. But you ingore the fact that most 7.1 or 5.1 systems are not ouptutting equal wattage to all channels at the same time on most situations. And, if you assume the system is putting 50 watts "average" into all seven speakers, their accumulated output will raise the SPL in the room by virtue of the additional speakers.


Possibly this will help clear up the issue;
http://myhometheater.homestead.com/splcalculator.html




"The common misconception people seem to have is that a 110 watt amp won't be nearly as loud as a 140 watt amp."

I don't have a clue as to whether the op knows enough to understand how little volume comes with a doubling of output power or not.

In case the op doesn't, it is generally assumed to be roughly +3dB.

That figure is suspect though since most of us who have been doing this for awhile understand that all things must be equal for that 3dB to be realisitic and we know things usually are not equal when you compare two amplifiers. Most of us have also heard 50 watt amplifiers that trounce 150 watt amplifiers when it comes to SPL - not to mention sound quality.

But, here's the thing about the op's post, on paper there should be about +6dB higher SPL capacity with the higher powered unit working into the same speakers. I would normally consider +6dB to be more than enough to notice a difference in volume level. (If you know how much output increases with each position on your volume control increase the level by +6dB and isn't that likely to be a noticeable difference in volume?)

So, in this case why isn't there a noticeable difference between the level both amps can achieve? I think that's what the op is asking.


.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2944
Registered: Dec-06
I was pretty busy with an online game
 

Platinum Member
Username: Nuck

Post Number: 11445
Registered: Dec-04
Andrew, we expect much more from you.
 

Gold Member
Username: Nickelbut10

Post Number: 2306
Registered: Jun-07
Dont tell me your one of those World of Warcraft kids?lol At least play GOW2 online.lol.
 

Silver Member
Username: Magfan

USA

Post Number: 412
Registered: Oct-07
I think it is fairly simple::
The CVs are hi sensitivity.
The lower powered tube amp can pretty much 'red line' them.
The Bryston is massively over the top, power wise, even for the 'too much is never enough' school of Hi-Perf audio.

So, what you are hearing is the limits of the speaker, not amplification.
OH! the Bryston may have more 'slap' and be more dynamic, but this will apply only to the point where you fuse the weakest link, be that x-over component, woofer, tweeter, or your EAR.
 

Gold Member
Username: Arande2

Rattle your ... Missouri

Post Number: 2946
Registered: Dec-06
Well.. I was playing RS.. These days I've reached a point on it where a lot of the stuff I can still advance in isn't as fun. Once you're level 126 with multiple maxed skills it gets a little boring I guess..

There's more to do than just play games these days.

Powerful amps + sensitive speakers + Volume MAX = severe Tinnitus
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