Ampifier's current output ratings

VPI Bronze Member Username: Hi_fi_guy Post Number: 15 Registered: Nov-06	Posted on Friday, December 29, 2006 - 12:24 GMT While brands like bryston, music fidelity, parasound, sunfire (i think) and such brands, put out the current in amps their amplifiers put out, this information is not available for most of the other "mainstream" (for lack of a better word) brands. any idea about the current output rating of these amps ? NAD C272 Rotel RB 1070 Rotel RB 1080 would really appreciate any inputs. thanks, VPI
Jan Vigne Gold Member Username: Jan_b_vigne Dallas, TX Post Number: 9539 Registered: May-04	Posted on Friday, December 29, 2006 - 23:07 GMT . Amperage is the same as watts since current is a portion of the equation for watts. Amperage can be constant or peak and the difference can be substantial as can the cost of one or the other. Much depends on the dynamic and changing speaker load rather than what the amplifier can produce into a static test bench load. Why do you ask? .
VPI Bronze Member Username: Hi_fi_guy Post Number: 16 Registered: Nov-06	Posted on Saturday, December 30, 2006 - 13:28 GMT I've read in a couple of places that different amps output varying amount of current for the same RMS rating. it was suggested that the speaker driving capability of an amp is not just dependent on the RMS p/c rating, but also on its current output. so i was curious to know how the above mentioned amps fared on that aspect, since its not mentioned on their websites along with the rest of their specs.
Nuck Gold Member Username: Nuck Post Number: 5075 Registered: Dec-04	Posted on Saturday, December 30, 2006 - 14:26 GMT Soft clipping: Go back to that square wave and look at its shape, all 90 degree corners. That is the shape that a signal takes on when it is "clipped". In other words the signal should represent the ideal of a curvaceous sine wave with a smooth transition from its upward movement to its downward path. When the signal is overdriven you are asking the electronics to produce a larger swing upward than they are capable of producing. They run out of juice (voltage). When you look at this overdriven signal on an oscilloscope you will see the signal stays clean and rounded up to a point that represents the maximum voltage the circuit can produce. As the signal has more voltage pushed into it at the front end (the volume control) the circuit cannot produce (swing) enough voltage to push beyond its limits. The signal then appears clipped at the top similar to what you see as a square wave. If the edges of the top of the waveform (sinewave) are clipped at very extreme angles (90 degrees) that is called hard clipping and almost always contains distortion products (odd order harmonics) that are unpleasasnt and will damage components (tweeters). When the sinewave is rounded at the top before it moves in another direction you will have soft clipping. This is different from the example of muddy bass where the signal takes its time getting to the top voltage level. In this case the signal can move in the required 90 degree upward movement but will simply round off the top of the waveform instead of a hard angle at the top. Soft cliping has the less objectionable components of even order harmonics as the majority of the distortion. In genreal tubes and FET transistors are likely to exhibit soft cliping while bipolar transistors are more likely to do hard time. That's an old JV quote from here https://www.ecoustics.com/electronics/forum/home-audio/56618.html High current amps IMHO refer to a heavy power supply, which can deliver enough amps into a load without stretch the voltage available. The amps you listed also use varying amounts of feedback (global or negative) to 'balance' out voltage spikes 'layman' terms here.
Jake Ryan Bronze Member Username: Thecrypt Post Number: 14 Registered: Dec-06	Posted on Saturday, December 30, 2006 - 15:11 GMT Wow Nuck, that is a great thread. I only got halfway through it and I'm dizzy from reading it. I'm inspired! Thanks man. All those definitions will help me expand my knowledge!
Nuck Gold Member Username: Nuck Post Number: 5076 Registered: Dec-04	Posted on Saturday, December 30, 2006 - 15:35 GMT Jake, I agree. That is a classic thread and I am re-reading it again now as well. I was getting a little sloppy in tossing around slew rate IM/THD and damping factor. The square wave reference changed the way I listen (and buy) stereo.
Jake Ryan Bronze Member Username: Thecrypt Post Number: 17 Registered: Dec-06	Posted on Saturday, December 30, 2006 - 15:41 GMT It'll help me in looking for a Car and Home audio system as well! In home theater and car audio I've posted about what I'm looking for in a system. Maybe a tube amp could be better than a transistor amp? We'll see. I've got a lot of learning to do.
Nuck Gold Member Username: Nuck Post Number: 5079 Registered: Dec-04	Posted on Saturday, December 30, 2006 - 15:44 GMT As do we all, Jake.
Jan Vigne Gold Member Username: Jan_b_vigne Dallas, TX Post Number: 9548 Registered: May-04	Posted on Saturday, December 30, 2006 - 20:31 GMT . Taken out of context, my comments regarding soft clipping don't always make sense and I'm not exactly certain how they relate to the topic of current delivery in an amplifier since clipping is measured only by the amount of volts an amplifier can deliver into a static load. Volts are fairly easy for an amplifier to swing since the power supply can be so loosely regulated that the output transistors are literally pulling voltage from the wall socket as needed for a short term blast of "power". Amperage is a bit more difficult to suck through the straw. When I was selling equipment I often made the distinction between volts and amps as being similar to horsepower and torque. One is the potential for work to be done while the other is the job getting done. With 500 horsepower and 10 Lb/feet of torque you can go 150 M.P.H. but it will take you all day to get to that speed. With lots of volts you can play loudly but you might not like what you hear if the amplifier cannot deliver sufficient amperage to deal with the load. The concept somewhat falls apart, however, when you consider the different jobs an engine and an amplifier perform. The engine will need lots of torque to pull a load, say a heavy trailer uphill. This would be the equivalent of an amplifier driving a loudspeaker with a very difficult load. Reduce the load on the amplifier and you will reduce the need for current from the amplifier. Not quite so in the automobile engine since it it always going to need some torque to effectively do its work. One reason you don't see some manufacturers giving specs for current delivery is the lack, to my knowledge, of any real world measurement that would give meaning to the numbers. Most manufacturers who quote amperage specs do so by the mathematics they use to construct a circuit, not by any particular measurement technique. As the load on an amplifier increases, either from lowered load impedance (4 Ohm rather than 16 Ohm) or a more negative going electrical phase angle introduced by the crossover elements of the speaker - or more importantly, both in combination, the amplifier will have to deliver more current to do its work. In other words the speaker system goes from being a voltage driven device to a current driven device. If the amplifier cannot rapidly follow this swing, it will fall on its face - at least temporarily. Since the amount of current needed will be a dynamic requirement, there is no really good way to establish just how much amperage the power supply can deliver on demand beyond the mathematics of the circuit. And merely delivering current on demand is still not the same as doing the job efficiently and well. Reread the parts about rise time and slewing rates in the quote Nuck supplied. Then consider what the dynamic requirements of the music you listen to might be. If the amplifier drains its power reserves to hit one big note, it is not in control of the speaker until it refills it capacitive reservoir which can only happen at a set rate. At that point the speakers's motor(s) begins to drive the amplifier's outputs by way of back electromotive force. Therefore the need for over built power supplies increases with the speakers' load and the demands of the user. All this really goes to the notion of specs being very meaningless to the consumer. If your speakers do not present a difficult load to your amplifier, the amplifier will not be delivering high current no matter what its spec might claim as potential amperage delivery. Even if your speaker presents a difficult load to the amplifier, if you do not stress the amplifier, it will not be delivering large amounts of current to your speakers. So, the lesson should be to not look at the on-paper numbers but rather to know what you are combining and to understand how the components work together. If you have a speaker load that demands high current, buy the best amplifier you can for that situation. How will you know what amplifier is best suited to that situation? By listening for one thing. As I said, if the amplifier is not stressed by your requirements, then small amounts of current will be sufficient. If you know your needs require stressing the amplifier, you should buy according to your needs and not expect a too puny amplifier to run your difficult to drive speakers just because you want it to. As Nuck suggested, the heavier the amplifier the more likely it is to have a higher amperage power supply. My general advice is to buy the heaviest amplifier you can afford as it will usually have the best chance of dealing with the broadest range of loads. That's pretty generic advice however, and doesn't take into account many other factors concerning which amplifier will best suit your system needs. If you know your speakers are a very dificult load, my very best advice is to deal with a retailer who is experienced in selling equipment to match such speakers. If you know your speakers are not a hard to drive load my best advice is to deal with a retailer who is capable of understanding the difference. A capacitive load (an electrostatic speaker) is different than driving a resistive load (a typical dynamic speaker) yet each require higher levels of current than many amplifiers can swing. "The amps you listed also use varying amounts of feedback (global or negative) to 'balance' out voltage spikes 'layman' terms here." I think this needs some clarification since all amplifiers use some amount of negative feedback or, in the case of a very small number of mavericks whose ideas haven't been well received by the populace, some amount of positive feedforward. Negative feedback has been discussed in yet another thread and isn't a subject I'm fond of rehashing since its implications feed into so many other aspects of how a system operates. But, "global" and "local" are two ways to use negative feedback. "Global" is not an alternative to "negative feedback". Negative feedback is negative feedback and its application is done either locally around a portion of a circuit (which is the preferred method for most high end applications), or it is applied globally and encompasses the entirity of the amplifier's circuitry (which is usually seen in less expensive amplifiers since it is less expensive to implement, but this method can be far more destructive to an amplifier's sound quality). Global negative feedback is not a totally poor way to operate an amplifier as long as the circuits are designed and built to be as stable as possible to begin with and the amount of feedback is kept to reasonable levels. Amplifiers that advertise no feedback are typically playing with words as they probably have some amount of local feedback applied. If they didn't have some form of feedback (or feedforward), they would be very unstable into any real world load. Single ended triode amplifiers often advertise they use no feedback but do not tell you triodes, by their nature, have a small amount of feedback in their design. (Don't ask me to explain how triodes manage this task, I'm not up to that much typing. Just accept it as a truism somewhat like knowing that when you throw a ball up in the air it will always come back to Earth landing in the softest pile of dog poo in the yard.) .
Nuck Gold Member Username: Nuck Post Number: 5087 Registered: Dec-04	Posted on Sunday, December 31, 2006 - 02:56 GMT Jake, you digging this man? I wonder what happens if I poke Jan with a stick? Jan, you mentioned that damping factor increase was enabled by the lowering of output impedence. Is the enabilization by coincedance or advertising?
Jake Ryan Bronze Member Username: Thecrypt Post Number: 22 Registered: Dec-06	Posted on Sunday, December 31, 2006 - 04:46 GMT lol POKE poke Yeah I was wondering how impedance affects the damping factor and sound quality etc. Hmm.
Nuck Gold Member Username: Nuck Post Number: 5093 Registered: Dec-04	Posted on Sunday, December 31, 2006 - 05:04 GMT Jake, notice that it was the output impedence of the amplifier I was referring to, in regard to the damping factor of an amp. Sound quality will not likely be found on this page of text.
Nuck Gold Member Username: Nuck Post Number: 5094 Registered: Dec-04	Posted on Sunday, December 31, 2006 - 05:07 GMT How the load impedence affects an amp, refer back.
Jan Vigne Gold Member Username: Jan_b_vigne Dallas, TX Post Number: 9555 Registered: May-04	Posted on Sunday, December 31, 2006 - 06:19 GMT . "Is the enabilization by coincedance or advertising?" Nuck, I think you created a word there. I assume you want to know whether damping factor is always related to an amplifier's output impedance or is it mostly advertising. It's all advertising, Nuck. Damping factor is once again a static number that has little real meaning when it comes to making the amplifier drive the speaker. As I have stated before, previous to the mid 1970's introduction of the Phase Linear 700 amplifier, most all amplifier manufacturers considered a DF of 50:1 or greater to be more than adequate. Carver introduced the PL gear with a DF of 1,000:1. This was at a time when specs were undergoing some radical changes in how they were stated and was also at the beginning of the horsepower race amongst the major receiver manufacturers of the day. Not surprisingly, the PL spec stated one of the highest wattage outputs/lowest T.H.D. specs of the day for the dollar spent (the PL 400), or, in the case of the 700, among the highest wattage amps available - period. DF, in and of itself, has little to do with how an amplifier reacts to a speaker. DF is affected by too many variables to make a blanket statement regarding its value in an amplifier. Not only is the impedance of the load relative to the output impedance of the amplifier at any one frequency/moment the largest consideration in determining DF, but the amount of negative feedback will alter the DF at various frequencies. And, in some cases, raising the DF can make the amplifier less stable into highly reactive loads. What can be counted on is the higher the output impedance of the amplifier, the more reactive it will be to the impedance swings of the loudspeaker. This is typically the excuse given for an SET's poor measurements. With the very high output impedance of a single ended triode amplifier, any variation in load will affect the frequency response of the amplifier in quite an obvious manner. When driving the amp into a load resistor, the amplifier measures poorly in most common tests. When connected to a properly matched loudspeaker, the amplifier will probably have some amount of sweetness added but typically sounds much better than it measures. One selling point of a common solid state amplifier will be its typically low output impedance. (A solid state, direct coupled amplifier will likely have an output impedance of 0.10 Ohm or lower while a transformer coupled amplifier will probably be in the range of 1.0 Ohm or higher.) The direct coupled transistor amplifier should be more immune to the vagaries of the load impedance compared to the higher output impedance, transformer coupled amplifier such as a common vacuum tube amp. The lesson here is to know what will happen to the amplifier's frequency response when you choose speakers with wide impedance swings and/or low impedance loads. Tube lovers argue that anyone who dislikes tube amplifiers has never heard a well matched combination of tube amplifier and loudspeaker. .
Andre Money Silver Member Username: Arande2 400dB could probably d..., 4000 isnt ev... 100,000dB FU... Post Number: 528 Registered: Dec-06	Posted on Sunday, December 31, 2006 - 07:12 GMT Hi guys, I see that Jan has been writing a storm as usual. Well one of my favorites system combinations I've heard so far is this two channel 60w/rms amp with the combination of these two 4311 JBL control monitors. It also has much better response than my main system.
Nuck Gold Member Username: Nuck Post Number: 5109 Registered: Dec-04	Posted on Monday, January 01, 2007 - 04:47 GMT If I made it a word, could I make it a rule? Andre, stay WITH THE FERKIN TOUR!
Andre Money Silver Member Username: Arande2 400dB could probably d..., 4000 isnt ev... 100,000dB FU... Post Number: 537 Registered: Dec-06	Posted on Monday, January 01, 2007 - 09:13 GMT Ok Nuck, sorry. I don't like arguing so I'll just next time pay more attention before I make a response.
VPI Bronze Member Username: Hi_fi_guy Post Number: 17 Registered: Nov-06	Posted on Tuesday, January 02, 2007 - 19:37 GMT thank you all and especially Jan for your detailed inputs. I won't pretend to have understod all of the technical points, but I do have a better idea now. but I still wonder about one thing. why does my 60 WPC amp sound much better than my 95 WPC amp ? soundstage is bigger, theres clearly much more power available, music is more alive and has better punch. so what design consideration or flaw (?) could be the cause of this ?? thanks in advance for your replies.

« Previous Thread Next Thread »

Main Forums

Forum Help

Follow Us