Darren Posted December 1, 2003 Share Posted December 1, 2003 I posted this on a different topic the other day, so excuse me for repeating myself (wasn't sure if it got lost down the list). I've always looked for power in the "watts" rating, but I'm hearing more and more about the benefits of "high-current" power. Some of the amps I've researched don't even list that measure (probably a bad sign). Harmon Kardon, on the other hand, seem to boast about it. Is this important (and why)? If it is important, what makers should I be looking into? Thanks! Quote Link to comment Share on other sites More sharing options...
skonopa Posted December 2, 2003 Share Posted December 2, 2003 Here is a good article about the basics of amplifiers on the Secrets of Home Theater and Hi-Fi website. Also, look at this article from the same website about speakers, especially the "impedence" section. Having more current, given the same wattage, will allow the amp to deliver a better, cleaner signal to the speaker. A high-current amp will not have to work as hard to drive the speaker at a given wattage as a low-current amp. The low current amp will more likely distort when cranked up than the high-current amp. Kinda like in cars. People often quote horsepower when talking about how much power they have under the hood. That would be like wattage in an amplifier. However, there is also torque, which would be like current in an amp. Two cars given the same horsepower, the one with a better torque rating would have an easier time getting up hills, acclerate faster, etc. For example, rock-climbers may not have as much horsepower as an indy-car, but they have an incredible amount of torque delivered to the wheels. Do you think a rock-climber would have an easier time getting up those steep slopes than an indy-car racer? An amp with a higher wattage, but low current may still be able to play louder than an amp with low wattage but higher current, if driving the same pair of speakers. But, the higher-current but lower wattage amplifier will be able to deliver a cleaner, more detailed sound with less distortion. Yeah, the higher wattage may play louder, but how good do you think the sound would be? Fortunatly, in our case with the Klipsch, these are very sensitive speakers, so a low-wattage, but high-current amp will produce an incredible sound with plenty of volume through these speakers. Again, using the rock-climber and indy-car analogy. A rock-climber usually has around 400hp, but incredible amount of torque, were as an Indy-car may have 1500hp, but not as much torque. The rock-climber would probably be able to acclerate much more quickly, but the indy-car racer will be able to top-end at a higher speed (240+ mph) vs a rock-climber (if I am not mistaken, I hear they can do a good 150+ mph). Thus do you think an amp given the same wattage, but higher current would have an easier time driving your speaker, thus producing a better, cleaner, more detailed sound, then an amp with lower current? I know my B&K Reference 200.7 amp is rated at 200 watts of 75 amp current on each channel. That is most likely why I hear a difference between driving my speakers through the B&K vs through my Denon AVR3802 reciever (unfortunatly, there is no amperage rating for the Denon listed in the manual). Hey, look at that, even I learned something new by doing a little research to answer this question Quote Link to comment Share on other sites More sharing options...
MrMcGoo Posted December 2, 2003 Share Posted December 2, 2003 Darren, "High current" amps are as much myth as fact. Most manufacturers ratings in multi-channel receivers in particular are misleading. What you want is the all channels driven test reports for a receiver. Many receivers produce less than half of their rated power with all channels driven at the same time. A few make rated power with all channels driven. Separate amplifiers (not part of a receiver) usually make rated power with ease. Separate amps usually drive 4 ohm speakers well; receivers usually do not drive 4 ohm speakers well. With Klipsch speakers, high current amps are not really needed IMO. Good amplification is a bit different with Klipsch due to the very high sensitivity rating of most Klipsch speakers. The quality of the first watt is of critical importance if your speakers put out more than 100 db with one watt. Low noise is key with the first watt, if you own Klipsch speakers. Bill Quote Link to comment Share on other sites More sharing options...
FirebirdTN Posted December 2, 2003 Share Posted December 2, 2003 IMHO, I think "High Current" amps are just another marketing "gimic". Basic electronics will tell you that P=IE or P=I^2R. In other words, Power is equal to the voltage accross a given resistance, multiplied by the current flowing thru that resistance. Or, as in the second formula, Power is equal to the current flowing thru the resistance squared, then multiplied by that resistance. So basically, the resistance in question here is the speaker resistance (well, impedance, but lets keep it simple instead of dragging varying impedance vs frequency in). Since, in essence, the resistance is never going to change, the only way to make a given power is by the amount of current flowing thru that resistance. Higher Current will yield a higher power. If we have 3.15Amps of current flowing thru an 8 ohm speaker, then the power consumed by the speaker is 80 Watts. You could have an amplifier capable of delivering 5 amps to the same speaker, but then guess what, if that is the case, then the amp should be rated at 200Watts (5^2=25; 25*8=200). Its the current capability that gives an amplifier its ratings, so I don't see how "High Current" has any significant meaning in this case. Now, THAT SAID, there is one advantage I CAN see with "High Current" amplifiers. That is the ability to drive low impedance speakers, such as 4 ohm or even less. Using my examples above, that same 3.15 amps flowing thru a 4 ohm resistance, shows the speaker is only consuming 40 Watts. So, in order to get the 80 Watts out of that 4 ohm speaker, we now have to increase the current to almost 4.5 amps. (4.5^2*4ohms= close to 80 Watts). Keep in mind, my example shows less power from a given current for lower resistance speakers. That is slightly misleading, because actually, the less resistance you have for speakers, the harder your amp has to work. Good receivers will handle lower impedance speakers with no problem. So, the way I see it "High Current" amplifers (even though I think is still a marketing slogan), should ALL be able to drive low impedance speakers. A not so good design, is my very own newly purchased Sony 1000ES receiver. Oh, it does have a 4/8 ohm switch setting, but basically all that does is reduce the amplifiers output so they don't get fried when using speakers less than 8 ohm. I intend on running 8ohm speakers, so I didn't really mind about that, but the truth is, only a "High Current" amp should be considered if you plan on driving speakers with less than 8 ohms. Hope this helps in some small way... My Nickel. -Alan Quote Link to comment Share on other sites More sharing options...
Strabo Posted December 2, 2003 Share Posted December 2, 2003 ---------------- On 12/2/2003 12:04:42 PM FirebirdTN wrote: High Current" amp should be considered if you plan on driving speakers with less than 8 ohms. -Alan ---------------- Therein lies the rub. If speakers were a constant 8 ohm load that wouldn't be a problem. But if I remember correctly my Forte's can dip down to 4 ohms with peaks going the opposite direction all in a short frequency range around the cabinets resonant frequency. So yes, high current amps will help control the sound of your speakers and it explains why when people move from an integrated amp to separates they find all the bass their speakers were supposed to have but were missing. You can check that out on a few of the threads here recently. Quote Link to comment Share on other sites More sharing options...
FirebirdTN Posted December 2, 2003 Share Posted December 2, 2003 Just a quick note: EVERY speaker's impedance varies with frequency. Every single one. The impedance rating of a speaker is a "nominal" rating, usually rated at 1 Kilohertz. Being speakers are inductive in nature, all speaker impedances will be lower at frequencies below the nominal rating, and higher at frequencies above it (except maybe some exotic design that I may not be aware of). Its just the nature of the beast. -Alan Quote Link to comment Share on other sites More sharing options...
dougdrake Posted December 2, 2003 Share Posted December 2, 2003 "So yes, high current amps will help control the sound of your speakers and it explains why when people move from an integrated amp to separates they find all the bass their speakers were supposed to have but were missing." I'll vouch for that. When I added a dedicated 3-channel 200wpc Acurus amp to my mix, the bass in my Forte's leapt to life, and it wasn't really slouching before that being driven directly by my Denon AVR. Quote Link to comment Share on other sites More sharing options...
Colin Posted December 2, 2003 Share Posted December 2, 2003 A couple of points: One of the confusing arguments in the classic tube versus solid-state debate is the amount of voltage versus wattage the two types of amplifier produce. As Peter van Willenswaard graphically demonstrates in his Stereophile magazine articles of 2000 and 2001 (http://www.stereophile.com/features/357/index5.html), Tubes Do Something Special." His figures show a vintage Nikko 25W solid-state amplifier generating 7.6V peak to peak (p-p) at the mike amp output. A 10W 300B tube amplifier easily beats it with 11.3V p-p (fig.5). Even a flea-powered 4W amplifier with EL84 tubes excites the microphone to just beyond the level produced with the 25W solid-state amp, at 8.1V p-p (fig.6). The he does another test: The closest I could do was to place my Tandy (RadioShack) sound-level meter next to the measuring microphone. I played the fff part again and noted 100dB SPL (C-weighted, fast response) for the 300B, and 97-98dB SPL for the 25W solid-state and the 4W EL84. This seemed to correspond reasonably well with the peak-type measurements. Perhaps an expert in perception could comment as to which of the two measurements, peak-peak or averaged, is the closer approach to what the ear registers as loudness.The evidence is somewhat less obvious than in the former case, perhaps, but still quite convincing. Tubes are louder. (One reader says Is all this discussion another way of saying that tubes have euphonious distortion? Louder is not always better. More dynamic is not always more accurate. Another says One difference between a tube and solid-state amplifier that was not discussed is that tube amps have audio output transformers and solid-state amps do not. Transformers do have some characteristics that can influence voltage and current outputs to the load.) All loudspeaker manufacturers should make their frequency response and impedance curves easily available. Regardless of the nominal rating (my dollar bill is rated at a nominal 100 cents, but that is not what it is worth), loudspeakers that change impedance quickly or have very low impedance are difficult loads for both solid-state and tube amplifiers. There is little that is nominal about a speaker load that bounces from 2-ohms to 30. Both solid-state and tube amplifier makers should publish THD power charts showing noise levels at micro and mini-watts. They should all rate their amplifier power for 16, 8 and 4-ohm loads. In my opinion, an amplifier that doesnt double its power into a lower impedance load is not fully capable of truly controlling the load, high current design or not. Bottom line: it is only how it sounds and only what it costs that matter. Quote Link to comment Share on other sites More sharing options...
Jef Posted December 2, 2003 Share Posted December 2, 2003 Hi Darren I had written the reply below a few months ago. It is an electro-mechanical explanation to avoid all jargon associated with electronics, in this case inductive-, capacitive loads and complex impedances. ------------------- Power output of amplifiers is given in Watts and when used on a resitive load this covers 'all' as it can be interpreted as heat generation. But a loudspeaker is not a resistor at all. Imagine your 50 Watt amplifier accelerating the woofer outwards then have to stop the moving mass and bring it in again. At the moment the woofer has to be stopped and has to move inwards again a large current is needed to generate a forcefull magnetic field that counteracts the inertia. If your 50 Watt amplifier is 'just' capable of generating the currents associated with the specified resistance - lets say 4 ohm - that would be something like 3.5 Amps (on a resistor). That will bring the woofer back ... eventualy ... Compare this with the 35 Amps capacity of a H/K (or other decent amp), you can immediatly see that the H/K has 10 times more current (read magnetic force) to stop and restart the woofer. So the more current an amplifier can genenerate the more 'control' it has on the moving mass of the woofer cones = a tighter and better controlled bass. The explanation does not take the interaction with the air in the enclosure into account, but the basic idea remains. Hope this helps ... Jef 1 Quote Link to comment Share on other sites More sharing options...
FirebirdTN Posted December 2, 2003 Share Posted December 2, 2003 After my post, I started wondering why speaker manufacturers don't publish impedance curves for speakers, but then again, I think we are getting to the point of being to nit picky? Maybe not if your really serious about your audio. I will agree though, that differing impedance curves is just one more paramter that sets the sound of speaker "A" apart from speaker "B". Interesting read on tubes vs. solid state. Although I have no tube amp experience, it was my understanding that the voltages/currents output by a tube amp are identical with the voltages/currents ouput by a solid state amp. It seems logical to me that the output transformers job in a tube amp was to transform the voltage/current ratio to match the impedance of the speaker. Tubes are high resistance devices; solid states are low resistance devices, making solid state amplifiers more suited to directly match a low load impedance (speaker), whereas tube amps need some type of matching device (such as, but not limited to an output transformer). NOTE-All, I am saying is, technically, SS amps are better matched to low-impedance loads (like speakers)-I am not saying that means they sound better! Two completely different things! Also, as far as needing much current to pull a woofer back after being pushed-That isn't really a good explanation-1) If you pull a woofer out of its center "rest" position, and let it go, it will return by itself back to the rest position with no additional force needed. Granted, its not a "controlled" movement, but the point was you don't need an abnormal amount of power to accomplish it. 2) Being that the speaker wants to return to its natural position anyway, it won't take any additional power to accomplish returning the speaker to an inward movement. Since the natural position at rest for the speaker is "centered", then actually, it would take less power to bring it back in. 3) and lastly, when a current pushes a speaker outward, hopefully, it doesn't push it out, then suddenly and immediately stop and expect the speaker to immediately change direction! If so, then your amp is clipping! Since audio waveforms are sinusoidal, the transition from outward to inward movement should be smooth and gradual, not immediate and jerky! The only analogy I can think of at the moment, is a swing. Your speaker movement should be similar to a swing, in that you want to travel in one direction, slow down, and smoothly come to a stop for an instant, change direction, and accellerate, in the opposite direction, then smoothly slow down again, etc. You wouldn't want your speaker to go full bore in one direction, and IMMEDIATELY stop. If so, then you are definately clipping the amp! Sorry if I get long winded...just like to help when I can. -Alan Quote Link to comment Share on other sites More sharing options...
Jef Posted December 2, 2003 Share Posted December 2, 2003 Hello Alan, sorry but the analogy is correct. Music is not sinusoidal signals only, the complex waveforms can be broken down into sinus signals and inversely if you add multiple sinuses you can get any shape you want, depending on amplitude and phase of the individual atributing signals - as proven by Fourier - but this definitely not mean that all signals are sinuses. Below is an example of a real signal, allthough not really complex. Asuming it is a low frequency, the woofer must accuratly follow the outline to reproduce the sound, as you can see the signal is not symmetrical and the woofer has to manipulated heavily. It takes alot of current if you want to track the outline precisely. You can also see the woofer does not just swing back and forth but has to go out twice at places. The following link leads to a series of excellent articles on sound, signals etc http://eamusic.dartmouth.edu/~book/MATCpages/chap.4/4.9.phys.mod.html Clipping is what happens when the signal flattens at the tops and bottoms because the source cannot provide enough amplitude, this happens most frequently with amplifiers but can also happen with speakers that are pushed beyond their design limits. If the signal contains a flattening, like with a square wave signal, than this is not called 'clipping'. Best regards ... jef 1 Quote Link to comment Share on other sites More sharing options...
TheEAR Posted December 2, 2003 Share Posted December 2, 2003 Darren, As was pointed before no speakers present the same load over the range they operate,even speakers rated at 8Ohms nominal will drop below and climb above depending on frequency. And many high quality speakers are rated at 4Ohms and some even 3.2Ohms(Thiel),at times these drop to 2 Ohms and less!Making them complex loads for the run of the mill POS amp that fills most receivers chassis. Often receivers have a poor power supply and the output stage cannot deliver the claimed power,only on peaks does it come close(and at 1KHz),too many receivers have phony numbers given.H/K is one of the very few to back their claims,and yes these receivers will drive most speakers better than even more costly gizmo packed "top of the line" jokes populating the receiver world. And as far as serious amps go H/K receivers have nothing on serious separate power amps. Just take my little ATI 1505 and 2505,these power amps can deliver the claimed power in RMS full bandwith ALL CHANNELS DRIVEN. Not some 1KHz bozo rating,for a microsecond at 10% THD. And when I take a real heavyweight like the Krell FPB600 I use with my Dynes,it can deliver to any load,to any speaker in the world would present with total ease,and it doubles its output each time you half the magic number(down to 2Ohms,over 2500W per channel if the current is in abundance at the outlet).Plus the FPB series will best the superman ratings(as measured by a few known publications Stereophile and others)! This has to tell you the power supply is overbuilt and the whole amp is a serious piece. Me I will not settle for any receiver amp,they are all quite limited.High current label or not.Even with my Klipsch I use amps capable of driving Thiel speakers to whiplash levels. But if you do go with a receiver H/K and B&K have the best built power amps with some top of the line Pioneer Elite the Integra 9.1DTR and Denon 4803. If you have some extra $$$$ the receiver with the most powerful and best sounding power amp is the Sunfire Ultimate receiver,with 200W RMS times 7 its amps could be packaged as a stand alone power amd and still whip many multichannel power amps! Quote Link to comment Share on other sites More sharing options...
FirebirdTN Posted December 2, 2003 Share Posted December 2, 2003 Jef- Real quick-Yes, I agree that music is a series of very complex waveforms; however, NONE of the content should have any type of abrupt polarity change, or flattening, as the poster above indicated in his example of having a speaker still traveling in one direction, to be asked to stop and instantaneously change direction. -Alan Quote Link to comment Share on other sites More sharing options...
Piranha Posted December 2, 2003 Share Posted December 2, 2003 ---------------- On 12/2/2003 12:15:06 AM skonopa wrote: Here is a good article about the basics of amplifiers on the Secrets of Home Theater and Hi-Fi website. Also, look at this article from the same website about speakers, especially the "impedence" section. Having more current, given the same wattage, will allow the amp to deliver a better, cleaner signal to the speaker. A high-current amp will not have to work as hard to drive the speaker at a given wattage as a low-current amp. The low current amp will more likely distort when cranked up than the high-current amp. Kinda like in cars. People often quote horsepower when talking about how much power they have under the hood. That would be like wattage in an amplifier. However, there is also torque, which would be like current in an amp. Two cars given the same horsepower, the one with a better torque rating would have an easier time getting up hills, acclerate faster, etc. For example, rock-climbers may not have as much horsepower as an indy-car, but they have an incredible amount of torque delivered to the wheels. Do you think a rock-climber would have an easier time getting up those steep slopes than an indy-car racer? An amp with a higher wattage, but low current may still be able to play louder than an amp with low wattage but higher current, if driving the same pair of speakers. But, the higher-current but lower wattage amplifier will be able to deliver a cleaner, more detailed sound with less distortion. Yeah, the higher wattage may play louder, but how good do you think the sound would be? Fortunatly, in our case with the Klipsch, these are very sensitive speakers, so a low-wattage, but high-current amp will produce an incredible sound with plenty of volume through these speakers. Again, using the rock-climber and indy-car analogy. A rock-climber usually has around 400hp, but incredible amount of torque, were as an Indy-car may have 1500hp, but not as much torque. The rock-climber would probably be able to acclerate much more quickly, but the indy-car racer will be able to top-end at a higher speed (240+ mph) vs a rock-climber (if I am not mistaken, I hear they can do a good 150+ mph). Thus do you think an amp given the same wattage, but higher current would have an easier time driving your speaker, thus producing a better, cleaner, more detailed sound, then an amp with lower current? I know my B&K Reference 200.7 amp is rated at 200 watts of 75 amp current on each channel. That is most likely why I hear a difference between driving my speakers through the B&K vs through my Denon AVR3802 reciever (unfortunatly, there is no amperage rating for the Denon listed in the manual). Hey, look at that, even I learned something new by doing a little research to answer this question ---------------- Can you provide me the names of any push pull tube amps that have at least 100 WPC output? Quote Link to comment Share on other sites More sharing options...
skonopa Posted December 3, 2003 Share Posted December 3, 2003 ---------------- On 12/2/2003 11:40:18 PM Piranha wrote: Can you provide me the names of any push pull tube amps that have at least 100 WPC output? ---------------- Sorry, can't help you there, at least I don't know of any that don't cost several 10s of thousands of dollars. This one (Decware Zen TORII) is around $1600, and it only has 12 watts. I cannot imagne how much something like that that would be capable of putting out 100 watts would cost, though. Quote Link to comment Share on other sites More sharing options...
Darren Posted December 3, 2003 Author Share Posted December 3, 2003 Man - that's a lot of info...my head hurts! Thanks everyone - really appreciate you all taking the time. I have to let some of this sink in a bit. Quote Link to comment Share on other sites More sharing options...
Piranha Posted December 3, 2003 Share Posted December 3, 2003 ---------------- On 12/3/2003 12:21:22 AM skonopa wrote: ---------------- On 12/2/2003 11:40:18 PM Piranha wrote: Can you provide me the names of any push pull tube amps that have at least 100 WPC output? ---------------- Sorry, can't help you there, at least I don't know of any that don't cost several 10s of thousands of dollars. This one (Decware Zen TORII) is around $1600, and it only has 12 watts. I cannot imagne how much something like that that would be capable of putting out 100 watts would cost, though. ---------------- Personally speaking I think I'd rather have any one of the following amps in or below that $1600 price range. MC 240, Jolida JD-202A, Any Scott 233, 272, 296, 299 series integrated. Plus, they all have more output. Quote Link to comment Share on other sites More sharing options...
space_cowboy Posted December 3, 2003 Share Posted December 3, 2003 "Can you provide me the names of any push pull tube amps that have at least 100 WPC output?" I still don't understand the tube talk, but what about this? http://www.divertech.com/hurricane200dt.html Quote Link to comment Share on other sites More sharing options...
space_cowboy Posted December 4, 2003 Share Posted December 4, 2003 Or this.......... http://www.manleylabs.com/containerpages/250_Y2K.html Quote Link to comment Share on other sites More sharing options...
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