my personal opinion -- get a modern pass, coda or krell, you won't need to worry about the speakers being well driven, the parasound and musical fidelity are (slightly) lesser units
Amplifier current vrs watts; why is current more important?
Lately when talking to knowledgeable people in the audio industry I’ve been hearing how current delivery is more important than watts in determining weather an amplifier will drive a speaker.
So what exactly is current and how does it effect speaker performance? How can a amplifier rated at 150 watts into 8 ohms vs one rated at 400 watts into 8 ohms be a better match for a hard to drive speaker?
hiendmmoe
So what exactly is current and how does it effect speaker performance? How can a amplifier rated at 150 watts into 8 ohms vs one rated at 400 watts into 8 ohms be a better match for a hard to drive speaker?
hiendmmoe
67 responses Add your response
Thank you for the detailed response, I'm still learning about all the ins and outs of this topic but think I've gotten a decent grasp on it now. And I totally agree with your point on sound, I've never been a 'spec buyer' but like to balance good objective performance and subjective performance.
While my Arcam PA240 is ok at higher volumes, it lacks low-mid volume punch particularly in the bass department. And I want to get a better quality amp anyway as my system is at a much higher level than when I first got the Arcam.
For what it's worth, the amps I've shortlisted are Pass Labs x250.8, Parasound JC5, Coda 8, and Musical Fidelity M8 series. Also have Krell on the radar. |
@christianb5s4 What is important is whether your amp can behave as a voltage source on your speaker. This does not mean it has to double power into 2 Ohms from 4 Ohms at full power even if your speaker does dip to 2 Ohms. It will have to double power from 4 Ohms to 2 Ohms at less than full power. Do you see the distinction? The only time there might be a problem is when you are pushing the amplifier hard, like really at full power as loud as the amp will play. All that will happen is if the amp isn't able to do the job at full power it will overload. So just make sure that the amp makes enough power to satisfy your requirements in your room. IMO/IME its more important to get an amp that sounds like music, rather than to get one simply on its ability to double power as you cut impedance in half. That's a bit more challenging, since to get an amp to double power as impedance is halved will require (most of the time) that the amp also use feedback. To use feedback properly without the feedback causing brightness and harshness, you really have to jump through some hoops on the design side and frankly, 99% of amps out there simply don't. What good does it do you to have an amp that can double power into 4 or 2 Ohms if it simply sounds harsh and no-one wants to hear it??
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+1 … nailed it In other words… Q.” …. I just don’t know how to read amplifier specs to identify whether an amp is high current. …” A. Don’t look only at the headline power figure - see what happens when the impedance drops to four ohms. If the number nearly doubles, then your amplifier has good current delivery and will be capable of driving more demanding speakers. E,g, My integrated amp A no compromise, super high performance, 162 W into 8 Ω (250 W, 4 Ω), dual mono amplifier. |
i think you are on the right track, nothing substantive to add, good luck! |
I'm currently planning an amplifier upgrade (current one is an Arcam PA240), and read through this thread with a lot of interest as my speakers (Focal Kanta 3) have some pretty large impedence dips in lower frequencies which has led me to look for an amp that has strong current capabilities. I'm far from an electrical expert but I'm starting to understand the above. So far the criteria I've gathered from research is to look for:
Is there anything I'm missing in terms of specs to look for that indicate good current output? Amp manufacturers don't make this easy as many list out spec sheets with varying degrees of information.
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those 1, 2, 15 W watt amps are useless.Really,... have a list to these 20w only into 80hm amps, and say that again. https://img.canuckaudiomart.com/uploads/large/2097160-65b80b07-mark-levinson-ml2-class-a-mono-block-... |
The sound level of reproduced music is proportional to the voltage. Hence, voltage is most important.; A sagging voltage would ruin the experience. How much current you need, depends on your speaker’s resistance to AC (a.k.a. impedance) in the audible range. Well-engineered cone loudspeakers like Tannoy, Lowther, Wilson, etc. have a high resistance to AC and require hardly any current to prevent the voltage from sagging. Electrostatic speakers, which have a low resistance to AC require a lot of current to prevent the voltage from sagging. |
Yes, keep simple! those 1, 2, 15 W watt amps are useless. Get a good amp w minimum 250-300W at 8ohm. Don’t look back, all this nonsense of if 1 watt is great, why have more......?? Really? jackalope! Power works, these flea watt, moth,bunny, butterfly fart amps w 1, to 15 watts amps are a joke. done mess around. get a good amp, and don’t look back. silly stuff. 1 watt, HAHAHAHAH |
Wow, what a rabbit hole you guys took this poor guy. His question was a simple one, one I try to answer from time to time, but within a couple of responses you guys were into slew rate, and it went down from there, with different people flexing their knowledge muscles. And I know you were trying but like a lot of forum questions it takes very little to take your eye off the ball. I thank you, for you enhanced my general knowledge but I'm not sure anyone answered his question. |
Even though the OP’s title is "Amplifier current vs watts; why is current more important?" Just to take it off topic as oddio did, with his (excuse me) even grosser misinformation. To show why output impedance (damping factor) is not the only cause for "tone control" behaviour, but also "available current" is just as if not more important. Here is a typical case where "current" ability is the factor to making a flatter frequency response, more so than output impedance (damping factor) Here are two very similar (save for their current ability) amps solid state linear each 60w into 8ohms, but their output impedance (damping factor) is more that 10 x different from each other, these are frequency response measurements (black trace) into exactly the same Kantor simulated speaker loads. NB: Make sure you see what the graph graduation scale is for both. 1: This Budget Schiit is the one with lowish current , but the "best" lowest output impedance ( best highest Damping Factor) of DF=226 Output impedance=0.03ohm It’s FR is +- 2db https://www.stereophile.com/images/416Schiitfig01.jpg 2: This Pass Labs one with high current but, worse 10 x higher output impedance and worse 10 x lower damping factor especially in the bass, and yet has far better control over the same simulated speaker load. It’s FR is only +- 0.025db!!!! https://www.stereophile.com/images/1116Pint60fig01.jpg As you can see the one, 1: with the "best" lowest output impedance (highest damping factor) is the one behaving like a "tone control" more that the other!!!!!!. This is because the Schiit is current is limited into the low impedance loads of the simulated Kantor speaker load compared to the Pass labs. Now back on topic, sorry hiendmmoe Cheers George |
The " tone control" effect you speak of is due to output impedance of the amp. Yes, this also as well on top of current starvation we’re talking about. Any amp that has low damping factor, (output impedance is that high) should not be considered as well if one wants an amp that will not sound "coloured" and stays flat in frequency response. Cheers George |
I have the so called "easy to drive" Legacy Focus speakers because of their high 98 db efficiency. But their low impedance (subsequent 20/20s were more difficult to drive) and 4 ohm preference make them difficult to drive. Maybe it's their 3 12" woofers. Anyway, an EAR 890 amp has great difficulty in driving them, lacking in bass and dynamics and just sounding pushed. It's a Class A 70 watt design. It sounds excellent on the Legacy Signature IIIs which have 3 10" woofers and slightly easier impedance curve. I can drive the Focus speakers with a highly modified 35 watt Dynaco 70 which has an electrolytic cap the size of the chassis underneath as opposed to the original. Lots of power stored in that cap. They're plenty the Sig. IIIs. For the Focus speakers, I use a pair of 130 watt tube monoblocks, custom made, with 2 3" X 7" storage caps, huge compared to the tiny row of caps found in the EAR 890. I bet my big amps could drive most any speaker despite the limited wattage (although tube watts are 2 to 2.5 times more than SS watts generally, not including Pass amps or other high current ones). |
As a Magnepan owner I will tell you I went through a couple amps trying to get the best out of them. Maggie's are notorious for chewing up lesser quality amps and spitting them out. They literally put one amp of high wattage into protection mode within 5 minutes and cooked the power supply. I had a couple of monos built with about 220 watts but monster current and I finally heard all that the Maggie's had to offer. Too much emphasis on watts. |
In a simple DC circuit, Amps = Volts/Resistance. Watts = Volts X AmpsUsing the water analogy, Voltage is the pressure pushing the water thru the pipe, Amperes,(current) is the volume of water & Resistance is the size of the pipe restricting flow. When you introduce AC current with coils, capacitors & such things get much more mathematically complicated, as the previous posts outline. Thank Heaven for the brilliant engineers who design our great gear. |
With digital room control you can do whatever you want as long as you have enough power, volts and current to support the corrections. Power is everything in a SOTA system. The problem with low power high efficiency solutions is that power requirements are geometric. They go up dramatically with peaks. Low power systems can't support this unless you just listen to string quartets. The other problem, and this is my ears talking, is that horns always sound like PA systems to me. An amplifier is a voltage source. It's job is to pump electrons stored in the power supply into the speaker. If the speaker is high impedance fewer electrons (current) are required to do the job. Lower impedance than more electrons. If the power supply runs out of electrons all the pumping power (voltage) in the world will not do any good. None of this says anything about efficiency. |
it could be done more specifically and more consistently with an equalizer than with the chance So true, why have an amp that can't maintain a flat frequency response, into a speakers wavering impedance load, you may as well have a graphic equalizer, at least with it you can pick where the boost and cuts of the frequencies are going to be. Look below at the black wavy line, that is the frequency response you will hear!!, and that's into an easy simulated speaker load, a hard load will be even worse This is the well known Prima Luna Prologue Premium 25w tube amp with very questionable current. Cheers George |
It would seem to me that if one wanted to tailor the frequency response; it could be done more specifically and more consistently with an equalizer than with the chance of amplifiers not lining up with impedances of loudspeakers in just the right manner towards that end. In that loudspeakers have mechanical considerations that amplifiers do not; it seems quite understandable that it would be much more difficult to build loudspeakers with truly flat impedances, than to build amplifiers that can linearly adapt to fluctuating loudspeaker impedances. Having a linear base line is an important consideration towards the goal of "high fidelity". Even if one wanted to deviate from that goal, amplifiers that can better adjust to loudspeaker impedance fluctuations would be easier to use with the afore mentioned equalizers. |
Unless you have a very benign flat impedance speaker (rare) that doesn't wander to much from being a flat impedance between 20hz to 20khz, only then is an amp with watts but little current OK.This statement is false. The impedance *curve* is not so important. The *overall* impedance is, and more importantly than that the intention of the designer of the loudspeaker. As an example, many ESLs have a fairly low impedance at high frequencies and yet amps with a fairly high output impedance (aka 'low current') can do quite well on them. This has to do with the simple fact that an ESL is fundamentally different from box speakers in that its impedance curve is not also a map of its efficiency. In a box speaker the impedance peak in the bass is due to the resonance of the driver in the box; its much more efficient at this point. ESLs don't behave this way at all and as a result many solid state amps have troubles making enough power into the bass region of the electrostatic. This is only one example and there are many more, but the bottom line is that you don't need a flat impedance curve, just an impedance that is high enough. Of course: ... SETs. They would not exist if the above quote were true. Of course no speaker has flat frequency response! Trying to get flat response is a Sisyphean task. |
Get over it. Bit rude! that response for being shown the truth. After all it’s what the subject of this thread is all about. Educating is a form of telling, and if you don’t want to learn why current is needed from an amp, and what happens when they don’t have enough for the load they’re seeing and become tone controls because of it, then don’t listen or partake in the discussion Cheers George |
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And for me, that’s OK and perfectly fine. A little response tailoring often suits me. It’s not your place to decide what’s OK for folks. No need to get your knickers in a knot. That fine, if you're willing to take the chance, as the "response tailoring" as you so quaintly call it, will be different for every speaker you put it on. So you never know if your going to like the "tailoring" it's doing until you bought it. BTW: It's still a tone control that doing EQ, which ever way you look at it, which will be a different EQ for every different speaker. Cheers George |
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Unless you have a very benign flat impedance speaker (rare) that doesn't wander to much from being a flat impedance between 20hz to 20khz, only then is an amp with watts but little current OK. You need an amp with both "watts" to suit the dB efficiency to get the loudness you want, and "good current" to keep the "loudness" you want during the "low impedance" dips (that nearly all speakers have). This stops the amp becoming a tone control, and modifying the flat frequency response. Just as in the graphs I put up. https://forum.audiogon.com/posts/1730185 Cheers George |
I am not sure I understand your last statement. Are you saying that zero feedback amps can supply more current and would do better driving low impedance loudspeakers?No. I am saying that some loudspeakers (like Sound Labs) don't need a very low output impedance in order for the amp to sound right on them. Other examples are most horns, most full-range-driver loudspeakers (like Lowthers) and other speakers where the designer found that he preferred the smoother sound of tubes. |
Hi atmasphere. I love your amps by the way. If I had reasonably normal loudspeakers I'd have a pair for sure. I have my eye on a pair of Soundlabs which I understand do wonderfully with your MA 2s. I am not sure I understand your last statement. Are you saying that zero feedback amps can supply more current and would do better driving low impedance loudspeakers? |
Doesn't matter what "spin" is put on it, when you have good current, the amp stays flatter in frequency response, instead of looking like a tone control. An amp needs current along with the watts, as these frequency response graphs show, of the same "wattage" amps with and without good current ability into the same easy speaker load. https://forum.audiogon.com/posts/1730185 Cheers George |
But a monoblock amp like the "Legendary" old Mark Levinson ML2 monoblocks that are only 25w!! into 8ohms, will sound better into them, because it’s said they double their wattage for each halving of impedance all the way down to 1ohm with the current it can generate, so they will stay flat in frequency response, where the 500w’ers will sound like a tone control.What is important is that the amp behave as a voltage source, not whether it can double full power as the load is cut in half. The latter is a subset of the former. Of course, a good number of loudspeakers in high end audio don't even expect the amp to behave as a voltage source. That is why there are so many successful zero feedback tube designs, which behave more like a power source. |
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The issue is a little complex when discussing audio frequency modulated currents. Voice coil speakers use alternating electric current in copper coils in close proximity to the speaker magnets to create the mechanical motion of the speaker cone. Audio modulated AC current in any coil produces frequency dependent reactance and impedance not simple 8 ohm DC resistance that might be inferred by the speaker specification. The accuracy of overall sound reproduction is the ability of the amplifier to overcome the reactance and impedance across the audio spectrum otherwise sound distortion is introduced. There is also the issue of electrical resonance and the amplifier needs to be able to dampen such. In general all modern amplifier designs effectively deal with these issues unless you’re an electronics hobbyist building your own amp. |
A speaker is an INDUCTIVE load. What that means is that it proportionally resists the rise of voltage across it. In Calculus, the voltage across an inductor is given as: V = L x di / dt L: inductance in henries and di / dt is the rate of change of current thru it. When transients occur, the amp has to overcome the resistance of the speaker to increasing the voltage across it. That is why it is difficult to drive inductive loads. To be able to do that, amp has to be able to deliver loads of current. Electronics 101: inductive loads. PS: Music is not a straight sinusoid signal. It is a MESS of transient signals. A piano for example is almost like a steep 90 degree rise in signal. To faithfully reproduce it, an amp must be able to supply LOTS of transient current, hence the need for an ENORMOUS power supply. Having said that electrostatic speakers a different ball game. They are capacitive loads. Combine different frequencies and it is a miracle that modern amps actually work :-) |
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viridianThat’s fine, so long as the speaker then chosen doesn’t cause that amp to become a "tone control" To me I would think in that easy "Kantor Simulated Speaker Load" graphs I posted above, that Stereophile uses, that +- 1 or 2db deviation from flat would be acceptable. That means easier loads than the "Kantor" horns, JBL ect the amp would be almost flat and on harder to drive than the "Kator load" the deviation would still be just acceptable at +-3db deviation from flat. . Cheers George |
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Here is proof to what I posted above, and the speaker load in both instances, is a very easy to drive Kantor simulated speaker load, a bad load will look far worse. Look at the black wavy line. This is the well known Prima Luna Prologue Premium 25w tube amp with very questionable current. 8ohm tap + - 7db!! frequency response, "a tone control" https://www.stereophile.com/images/1116PLPPfig01.jpg 4ohm tap+ - 5db!! frequency response "still a tone control" https://www.stereophile.com/images/612PPPfig01.jpg Here is the Pass XA25 25watter with far more current that the PL above, it’s +- 0.1db frequency response. Virtually flat as it should be!!! https://www.stereophile.com/images/218PXA25fig1.jpg Cheers George |
Amplifier current vrs watts; why is current more important? KEEPING IT SIMPLE. Amps with big watts and little current alone don’t drive speakers with low impedances and stay flat in frequency response, amps with big current do. EG: One of the worst low impedance speakers ever made, the Wilson Alexia v1, they go down to 0.9ohm in the bass. A 500w stereo P.A. amp or a 500w Class-D will work into them to a point only, but will sound like a tone control. But a monoblock amp like the "Legendary" old Mark Levinson ML2 monoblocks that are only 25w!! into 8ohms, will sound better into them, because it’s said they double their wattage for each halving of impedance all the way down to 1ohm with the current it can generate, so they will stay flat in frequency response, where the 500w’ers will sound like a tone control. Cheers George |
Andy2-you were a little off on your car comparison. Wattage/current is kind of like a car horsepower/torque. Torque is your bottom end power. Torque will get you off the line much faster or when you want to pull away. Some cars could have decent horsepower with low torque and that means its gets off the line slower, no power to pass, and all the horsepower is at a higher rpm. Your Sony/pioneer amps might have a decent wattage rating but no current to drive the lower end or react instantly to high peaks |
Similarly, extra current (if it were somehow to exist) does not affect bandwidth. What **does** affect bandwidth is output transformers; generally speaking the bigger you make them the less bandwidth you get.This seems to be limited to tube amp which requires an output transformer. Interestingly, atmasphere specializes in OTL tube amp which does not need an output transformer. But this seems to be getting away from the OP original question. |
As someone who imports and sells a line focused on current vs. wattage, I have a POV. Art Audio amps are biased toward current. That is, our amps are high current and deliver lower wattage vs. many of our competitors. This means that with any given tube, we could deliver a much higher wattage number but opt against it. Most of this is false. Current does not exist without voltage; further, wattage does not exist without voltage and current. IOW you can't make one (current) without the others (voltage and wattage). Similarly, extra current (if it were somehow to exist) does not affect bandwidth. What **does** affect bandwidth is output transformers; generally speaking the bigger you make them the less bandwidth you get. In voltage amplifiers if you can't put enough current through the tube you might lose some high frequency bandwidth; that is why 12AX7s are not a good input tube to use in a power amplifier unless bandwidth isn't important. |
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As someone who imports and sells a line focused on current vs. wattage, I have a POV. Art Audio amps are biased toward current. That is, our amps are high current and deliver lower wattage vs. many of our competitors. This means that with any given tube, we could deliver a much higher wattage number but opt against it. This absolutely does allow for better handling of lower impedance speakers. But that is not the only reason and it is not just marketing. The extra current delivers better frequency extremes. You get lighter & airier treble with better nuance and detail. Bass response is tighter and more refined. Maximize wattage in SET or Push Pull triode and treble gets rolled off and bass gets flabby. You can find 35w SETs with 845 tubes. Why would Art Audio choose to produce an 18w amp when we could produce a 35w amp? The 35w amp will have flabby bass and rolled off treble while the 18w Carissa will deliver frequency extremes you woudn’t think are possible from a tube amp. But it certainly won’t drive every speaker. That being said, the comment above where a kosst_amojan says ’it depends" really is true. It comes down to your speakers. I have seen a speaker with a high SPL of 98dB but has a minimum impedance of 3.2 ohms. Way harder to drive than you would think and even though 5w of power is enough to drive them in normal circumstances. You need 5 really good, current heavy watts. Alternatively, I will be introducing a speaker (Verdant Blackthorn 1) with an 84dB SPL and a minimum impedance of 7.2 ohms. Not a difficult speaker to drive at all and current is of minimal concern. You just need enough power into 8 ohms to hit the volume you are looking for. 5w would deliver a whisper, 30w a bare minimum to have 10dB in headroom above 85dB. I can say that my 18w Carissa could drive Focal Sopra Floor Standers mentioned by kosst_amojan with 15dB of headroom above 85dB. That same amp can’t drive my Blackthorn 1. Alternatively, I have a 140w SS Class A/B amp that would do a wonderful job with my Blackthorn 1 but would blow a fuse if I tried to drive Sopras with it because it is barely stable at 4 ohms. |
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