More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.
Not every SS amp made does this trick. Some very expensive ones don’t quite get to twice their 8 ohm rated power when impedance halves to four ohms. BAT, darTZeel, Wells, and Ypsalon to name just a few.
An amps ‘‘soul’’ or it’s ‘voice’ is the main reason why I would opt in on choosing an amp initially and keeping it. Simultaneously , I’d consider its power and the demands of what ever speakers may be intended to be run with it or them.
I’ve heard, 80% of the music we are listening to is made in the first 20wpc! I’m sure there’s some wisdom in there somewhere as many SS amps running AB, are biased to class A Only for a small portion of the total output EX. 10 – 60 wpc of 150 or 250 wpc.
After all, any amps true output levels are a complete mystery when anyone is listening to music anyhow.
I suspect, not being able to actually measure true power consumption, the vast majority of listening sessions revolve around 60wpc or so being at hand with traditional modern reasonably efficient speakers.
Sure, there are those speakers which don’t fit into the traditional loudspeaker power needs mold such as panels or electrostats, and this ain’t about them.
The possibility of clipping a driver is about the only facet in amp to speaker matching which gives a person pause while pondering this or that amplifier.
I feel there is more to how good an amp is than its ability tou double output power with 50% drops in speaker impedance.
However, speakers are demanding more power lately. Many are coming out of the gates with 4 ohm ‘nominal’ IMPs which lower with fluctuations in frequency. Add in larger motors on larger drivers, multiple driver arrays, and on paper these SOTA speakers appear to need more power.
IMHO It is this note which introduces great concern.
I’ve read every article I can find on Vienna Acoustics Music. Each one says give them lots of watts for them to excel.
Many times good sounding speakers I’ve owned sounded better with more power, albeit from arguably a better amp.
I tend to believe having more than an adequate amount of cap power is indeed integral. … naturally the size and type of transformers in play possess a strong vote for an amps ability to successfully mate with speakers.
Controlling a driver’s ability to stop and restart is as well a key to great sound and only strong amplifiers can manage this feat. Usually this gets attributed to ‘damping’ factor, but damping as I read it is more a shadow than a tangible real world figure as it depends on numerous factors. Speaker cable length alone can alter damping factors.
A very good argument exists about those mega watt amps voices. Each 500 or 600 wpc amp or amps, I’ve heard have had stellar voices too, not merely more watts.
So is it predominately these mega watt power house amps souls or their capacities that fuels the speakers presentation?
Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?
Choosing this latter option also saves one money as the more powerful amps do cost more than their lower outputting siblings.
More than a few people over the years on these pages have said only those SS amps which double down in output power as impedance drops are truly special or worthy amps. Eg., 200 @ 8ohms; 400 @ 4 ohms; 800 @ 2 ohms; etc.
To put it more simply:
No amp will exactly double all the way, anyone who advertises this is stretching the truth. Ones that can come close to doubling (usually good bi-polar output amps) all the way to 2ohms, can push good current into hard to drive speaker EG: most Wilsons especially Alexia ( .9ohm epdr in the bass) and many other brands.
This is however not an indication of good sound quality, but your half the way there with a "very" important part of the equation to get it, but your half the way there with a very important part of the equation to get it. It's up to you then to sort these out with best one sound wise, as you taken care of the drive (current) factor.
It's not a matter of the first few watts. It is a matter of how the electrical frequency response changes based on the speaker.
A perfect amplifier has a flat electrical FR, regardless of the speaker. A weak amp may have it's FR adulterated by the speaker crossover, and that happens even before 1 watt.
Here is a measurements page from a Prima Luna design, to see what I mean:
You don't need an ideal amplifier to have good sound. Goodness knows
most tube amplifiers barely meet this requirement, but it is a good
indicator of the current drive, and guts of the amp.
Nelson Pass does make a related, but not the same, point about the first watt being most important. But he's talking about noise and distortion. He, rightfully, states that Signal to Noise at 1 watt is a far more important gauge of sound quality than Signal to Noise at full power (which we never spend time listening to).
Picking up on Erik Squires’ reference to Nelson Pass....
I recently purchased a First Watt F7 amp. It generates 20 watts into 8 ohms and 30 watts into 4 ohms, so it doesn’t "double down". On a couple different levels it seems to embody "the less is more principle". I also think it shows not all watts are equally "capable". I’m mainly using it with moderately efficient Silverline Prelude Plus speakers (nominal 92 db sensitivity). Sound quality is extraordinary with the Preludes and was absolutely astonishing when the F7 was used for a short time with 87 db sens. Totem Forests. It won’t peel paint but the sound produced is "to die for".
At the risk of being accused of exaggeration, listening with it is like going from B&W TV to color, if you will pardon the non-audio(phile) analogy. And this by comparison to many different higher power amps including tube mono blocks and, more recently, Hegel H200 and Merrill Audio Taranis (both still part of "the fleet").
In the interest of full-disclosure, while the sound with the Forests was absolutely magical (the best they’ve ever sounded) concerns about yielding to temptation and pushing the volume into clipping territory and damaging a tweeter led me to discontinue that experiment. SPL readings of upper 70s db at 10 feet diagonal from the speaker (C weighting; Slow response) were easily achieved beforehand with no sign of strain - very satisfying levels for late night listening. With the more sensitive Preludes, low to mid 80 db peak SPL are regularly registered at the same 10 foot listening position. Completely satisfying levels for the kind of listening I do.
So, in reply to Blindjim’s question, "Would you buy an ‘uber expensive’ amp based more on its voice or soul, than on its ability to output loads of watts, even if you feel the amp may be somewhat under powered for the application?" The answer is "yes"...except for the uber expensive part. The F7 lists for $3000.
(FWIW - I believe NP credits Dick Olsher with "the first watt is the most important watt" comment).
absolutely astonishing when the F7 was used for a short time with 87 db sens. Totem Forests. It won’t peel paint but the sound produced is "to die for".
Here is a classic example of a good amp that doesn't need too much current to drive this easy Totem Forest load, but the same amp on a hard load that dips down much further in impedance and negative phase angle would be very handicapped.
I agree the Forests are an "easy" load (as has been noted in the reviews) and attempts to mate the F7 with a low efficiency/low impedance speaker would NOT be a happy pairing. I suppose there’s no surprise that 20-30 watts are enough to get some sound out of the Forests. The bigger surprise for me was the quality of that sound and that the F7 experience turned on its head prevailing wisdom about Forests needing a lot of horsepower to sound their best. Many comments here on A’gon to that effect (I still believe this to be generally true, by the way). Not only was the F7 able to drive them but it did so in a manner producing the best sound I’ve heard from them to date, even when compared to that with a 200 wpc Hegel or 400 wpc Taranis. Imaging, sound stage, detail and musicality add up to a magical experience: sheer, seductive listenability. In my O-pinion, the F7 is not just a "good" amp but a great one (paired with the right speakers, of course!) and an even greater value. Make the F7 exhibit one for Blindjim’s contention, "...there is more to how good an amp is than its ability to double output power with 50% drops in speaker impedance."
And here’s what Stereophile measured test concluded: "(fig.1) revealed it to be a very easy load for the partnering amplifier to drive. —will hardly stress even the most current-challenged tube amplifier."
A flat frequency response is crucial for a natural representation of the music. You don’t want the system to artificially boost or depress certain frequencies, and hence change the sound from what it was. As has been remarked, there are two sides to this. First there is the speaker. It should have a relatively flat impedance curve without deep dips. There are plenty of speakers that present an easy load (Harbeth are good, but there are enough others), but there are also speakers with a devilish load. Second there is the load dependency of the amplifier. A good amplifier should not be too troubled by impedance swings. Tube amps have a harder time here, given their design with output transformers. The Prima Luna that Eric referred to, with its absolutely massive frequency swings, is an extreme example of how not to design an amplifier. Compare this to an affrodable Yamaha AS 500, tested here: http://www.avhub.com.au/product-reviews/hi-fi/yamaha-a-s500-amplifier-review-test-395710 Even under realistic speaker loads it maintained a flat frequency response within 0.05 dB, an amazing performance not matched by many amps costing ten times more. Taken together, I think speakers that are not easy to drive and amplifiers that are load dependent are just bad engineering, and are to be avoided. If you succumb, you will suffer the dreaded synergy problem and all the audiophile Angst that comes with it.
The second problem is power output. Most good speakers are not very efficient, so you will need lots of power to drive them. If you don’t have enough power, you will suffer clipping distortion on dynamic peaks, with a ’dirty’ distorted and compressed sound as a result. Again, some people like this, but it does not meet the criterion of neutral and life like representation. So how much do you need, not for average levels, but for dynamic peaks? A few years ago, having moved to a larger house and having upgraded from the Quad els 57 speakers to the less efficient Quad 2805 I decided to replace the 2x45 watt Quad 303 by a 2x140 watt Quad 606-2. There was no diference on small scale music, but it sounded much more realistic on the large and dynamic repertoire. I began to realize that I now also played my music rather louder, because the sound remained so clean. Since then, I have concluded that even more power may well further improve the sound. As another anecdote, Harbeth's Alan Shaw recently demonstrated his big M40.1 speakers in the Netherlands. Even he was surprised that on dynamic music the big amplifier that was used was putting out more than 500 watt per channel. Fortunately these days watts are no longer particularly expensive.
Years ago Harry Pearson (TAS) tested a pair of 1000 watt Bryston monoblocs. He was impressed by the clarity of the sound - especially at low listening levels! He concluded having all that power available was certainly beneficial, regardless of listening level!
George - I agree. 20 wpc being adequate to drive the Forests to moderate volume levels might not be particularly remarkable. I’ve read all the available on-line reviews about the Forests and am familiar with their reported specifications. In light of statements from various A’gon participants however, I still found that adequacy unexpected given they are 87 if not 86 db sensitive speakers. Regardless, no one seeking speakers to pair with an SET or SEP amp is going to choose Totem Forests. BUT, more to my point, it is the quality of sound those 20 F7 watts produce with the Forests and with Silverline Prelude Pluses (more sensitive and also a nominally easy load) that I’m finding very remarkable. I’m not sure nature of the load provides the complete explanation for what the F7 does. In support of this statement, see the lengthy Six Moons F7 review where it was coupled with a range of very different speaker types. Link here:
A flat frequency response is crucial for a natural representation of the music. You don’t want the system to artificially boost or depress certain frequencies, and hence change the sound from what it was.
I think you should buy what you like, and whether it is perfectly realistic or not is not among my first purchasing priorities. I spend money to make myself happy, not reviewers and not any of the 4 measuring microphones I own. :)
Having said this, I think discussions about technology, pros/cons are always fun and interesting, but honestly, some of the best sounding amps I've ever heard were seductive liars.
Dynamic range overrides frequency response any day of the week. Besides unless you’re prepared to pony up lots of cash on room acoustics you will never get flat frequency response on any room.
Well, it is a free world, fortunately. However, for me it is not the job of my gear to change the sound of the music - I am not the artist. What I want is simply what Quad once called ’the closest approximation to the original sound’. I accept that that is a very modest brief, and at least for the electronics part of the chain easily achieved (witness the Yamaha that I linked to). With speakers and room interaction it is a different story, unfortunately. Shaping the sound to your liking can be done much more cheaply than by buying exotic gear and expensive cables - just use a graphic equalizer, or if you want to get fancy, use one of the modern plugins for recording studios: vinyl, a Studer tape machine or tubes on the cheap and without the hassle.
My power amp has a sliding bias so it stays pure class A up to 2/3 power...that is what ATC chose to do with their active speaker electronics.
I dont recall what Bryston does but big poweful class AB amps that dont have specific solutions to this problem need to be serviced often to ensure zero crossing distortion remsins as low as possble.
Both of willemj’s favorite speakers - LS3 5a and Quad electrostatics - both of which I’ve owned and am very familiar with, sound much, much better with tube amps than with solid state. I thought everyone knew that. Geez, Louise! Just say NO to solid state.
Hmmm. Looks like the orig version of this thread was shifted from amplifiers to Tech talk. I debated myself on which one choosing amps instead.
A number of posts were made to that one with many good thoughts. All were and are certainly appreciated.
To put a point onto this exercise I’ve found myself lusting after several amps, and several brands of speakerage. Few were measured by Stereophile. Some are quite new and or newer versions of previous iterations so that might explain why. However, it leaves me pondering not so much which would be optimum, but which amp should be omitted from the collection of possible marriages.
Atop my never heard speaker list are Vienna Acoustic Music and Listz. TAD E one floor standers are next. The rest of the list contains speakers I will likely be able to hear soon enough…. KEF Blades I & II Wilson Sabrinas, Sashas Magico S5 latest ver. Eggelston Ivy, andreas II or III.
Amps on close approach radar are … Ypsalon Alieus Gryphon Coloseum Bermister 911 Master Sound Classic BAT VK 655se PSA BHK monos Pass labs XA has a shot.
Gryphon has a different approach to amp power than you see normally. Their base amp shoves out 150w @ 8, doubling up as IMP halves all the way into 0.5 ohm!!
BAT, Bermester and Ypsalon differ from the doubling up and down crowd relying on caps as reserve power albeit, Gryphon uses this ploy too.
I’m opting into SS land once again as I don’t feel the tube power needed to properly conduct any of the speakers on my list will be a cost effective outcome. I feel most of these speakers will devour low power. Tube amps under 200wpc. Once more, I speculate.
Dunno if this input is needed here, as it was asked for in the Amplifier topic corral. Its here now anyhow.
Has anyone here seen third party measurements on these pieces?
I’ve felt since being a member here and relearning most everything I once knew about electricity, electronics and sound for that matter, that I buy with my ears mainly. My wallet next, and then good judgement or what I can find of it if any remains.
If the sound doesn’t thrill, or no perception of enormous potential is unearthed, I gotta move along. Especially at these prices..
So in my book, science often does not have the last word in my life. Everything it seems requires accommodations, compromise, and tolerance in this world regardless what it is called. .
The anxiety here is choosing an amp which does not have quite the legs it needs for these loudspeakers.
I’m sure all will work with whomever. Yet some great dark concern prevails around picking the power plant which has fascinating sonics, but does not have earth moving power.
PS AUDIO 200C 200 to 8 ohms, 400 to 4 ohms, 800 to 2 ohms,
I call BS on this, just advertising, there are always losses, independent non affiliated bench test would impress me if it did. As that’s like "perpetual motion"
Show me one (any) Stereophile tested amps that can do this as they nearly always give those 8-4-2ohm wattage figures when they test amps.
Madrigal Audio Labratories states: The 300-series power amplifiers operate as perfect textbook cases of a "voltage source". This is to say that they will maintain whatever the appropriate voltage might be at any given moment (given the demands of the music, and within the rated voltage output of the amplifier) without any particular regard for the currenf demand of the loudspeaker.
Because of this "voltage source" characteristic, the 300- series amplifiers double their power demands every time a loudspeaker impedance is cut by half. For example, the no. 336’s continuous rated output is 350 watts per channel at 8ohms; 700 watts at 4ohm; 1400 watts per channel at 2ohms. A "continuous" test of the no.336 at maximum power requires about 50 Ampere s at 120V. The laws of physics refuse to be cheated. Long-term, you cannot deliver more power into the speaker than you can pull from the wall.
Stereophile also reported that the ML no.33H mono’s have a 1200 watts per channel at a 1ohm rating.
Geoff did not read my earlier posts carefully enough, for my other speakers are no longer the LS3/5a (lent those to my son while he is saving for a pair of Harbeth M30.1’s) but the much better Harbeth P3ESRs. As it so happens I once attended one of Peter Walker’s blind comparisons between his three amplifier designs. Those were the days when people began to claim that tubes sounded better, and he thought they were nuts. I subjected myself to the test rig, and did indeed think that I could hear differences. Peter was pleased no end when he could show me that I had been no better than completely random. And I learned a valuable lesson. The stricture is, of course, that amplifiers have to be designed properly. If you read the Stereophile test of his valve amplifier, you can see that Peter Walker’s own valve design does indeed perform quite well under a varyring speaker load (flat within 1dB): https://www.stereophile.com/content/quad-ii-classic-monoblock-power-amplifier-measurements That is much better than many other valve amplifiers. It is indeed a legendary design, just like his later 303 and the more powerful 405 current dumping model that still lives on in the again more powerful 606, 909, QSP and current Artera models. As Peter told me, the only practical difference is that of more power. Since at the time I was using the ELS57’s that could not handle more than my 303’s 45 watt per channel, he assured me there was no point in upgrading to the 405. A true gentleman.
It's generally assumed by speaker designers that the amp will be a voltage source as opposed to a current source. Consequently, speakers are designed to behave flatly according to voltage.
All that said, I'm driving a pair of Focal 936's with a muscled up First Watt F5. The nice thing about a push-pull amp is you can get a bit more head room without hard clipping. As it sits it has a potential class A envelope of about 80 watts. But, at 8 ohm that envelope drops to 52. My Focals have a low point of 2.8 ohm. That means the class A envelope collapses to a whopping 18 watts. Sure, it will drive more power up into class AB, especially since I deleted the current limiting transistors. It's pretty easy to tell if you're pushing a class A amp out of it's envelope because they get quite a bit hotter. I've been listening to Tool's 10,000 Days here loud enough to feel it in my chair for a cool half an hour at least. The amps is still at idle temperature. It's probably not belting out 18 watts much, if at all. And if it does at that impedance low point it just transitions to class AB.
This thing is about all the amp I need and these aren't the easiest speakers in the world to drive. I have no idea why people need 500 watt amps in a normal sized room with decently sensitive speakers. I'm not sure why people get so worked up about an amp's ability to double it's current into half the load. 6moons reviewed the F5 and noted that if your speakers need more that the F5's 25 watts they're probably poorly designed and I tend to agree with that based on what I'm hearing right now. I seriously think people should listen to a simple, well designed, low power amp before they form opinions about the importance of current delivery ability and kilowatts of power potential. It sounds like @ghosthouse discovered that. I think Fist Watt amps represent exceptional, perhaps unmatched, value in terms of quality for the dollar, and I doubt much of anybody really needs more power.
@willemj, thanks for illustrating that tube amplifiers are not graphic equalizers after all. Whew! That was a close one! Also, be advised that it’s an Old Wive’s Tale those iconic speakers cannot be driven with a high power amplifier. There are lots of Old Wive’s Tales in audio.
The primary trouble with Peter Walker’s Quads is the ridiculous heavy metal screens which really must be removed if one is to have a chance at high end sound. Otherwise, the Quads constrain and suffocate the sound and rattle. And that’s aside from their requirement for tube power, that is if one is determined to enter Audio Nirvana.
Regarding the disagreement about whether or not some solid state amps can "double down": As I see it both sides are correct, but are focusing on different things. One side appears to be focusing on **measurable** maximum power capability, and the other side appears to be focusing on **rated** maximum power capability.
Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability. A reputable manufacturer will, or at least should, choose a margin that is large enough to be comfortable relative to anticipated sample-to-sample variations, reasonable variations in line voltage, etc., but at the same time is not a margin that is so large as to be misleading. And likewise when it comes to choosing the distortion percentages upon which the power ratings are based, and in defining whether the power that is being referred to can be delivered continuously or just on a short-term basis.
@willemj, once the argument turns to name-calling I win by default. Better luck next time. 🍀 by the way, I think I see your problem. You think you’re the smartest guy in every room you walk into.
@georgehifi Thanks for the insights. I sincerely am grateful for them.
RE – compatibility From what you are saying it remains a dicey prospect to try considering an amp & speaker combo without knowing some of the measurements of the loud speakers. In particular the phase angle…. What ever that is.
georgehifi > Don’t just talk watts, talk about the watts be able to double for each halving of impedance as well.
Blindjim > Hopefully, I’m beginning to get the gist of an amps characteristic to double down in fact, with IMP halving, as it speaks to an amps ability to remain consistent or cohesive when powering the entire bandwidth as the speaker makes its demands for more power here on that freq or less on this freq for whatever SPL is being requested.
Isn’t this ability to instantly supply intricate and exacting speaker demands aided or even supplanted by having on board an enormous cap storage power reserve from which to draw upon?
Installing enormous banks of caps for reserve or auxiliary power does appear a philosophy some makers prefer to employ in their amps topologies wherein the doubling facet is not its inherent trait.
It seems too this is a tact utilized by amp makers that do not use negative feedback designs, and limited gain stages.
As I’m seeing on youtube, and many are seeing in person at shows loads of amps are providing very capable competent performances with a very wide assortment of loudspeakers. Albeit, many amps on display are larger outputting amps. Mostly. Though not all.
Gryphon KODO speaker system for example being driven by their Mephisto 175wpc amp has I believe 32 drivers and overall, weighs a ton. Appears a formidable load for any amp, let alone one rated under 200w @ 8. = = = = = = = =
@kosst_amojan > It's kind of assumed that the amp will deliver whatever current the load demands for the voltage. Higher impedance, less reactive speakers do better with current sources though.
Blindjim > huge thanks for the considerate reply.
since I was introduced to Ohm’sLaw decades back I’ve always had to think the proportionate relationship between voltage and current remains constant respective to the load.
Consequently, the mention of each article, voltage and then current being now, somehow unrelated confuses me.
This thing needs voltage… that one neds current… Hmmm. WTH?
Regardless, if a thing needs current or voltage those needs should be met depending on purely the voltage exciting the potential or here, the amp feeding whatever load.
The only question in my mind then is how large to make the supply or categorizing amps as to their outputs, how many watts can this one or that one feed to the load in general? = = = = = = =
And, yes. We’re back to looking at watts… not current or voltages for comparison’s sake. This is not necessarily my desire, but what other more appropriate baseline is there for choosing amplifiers?
My EXP says arguably, when it comes to amps, money often dictates not just the amount of power, but how well it is served and the quality with which it is provided to prospective loads.
Its easy to see as well, there’s no slide rule that solves the riddle of which amp fits which speaker, adequately, very well, or perfectly, and as with most equipment arrangements in audio, it’s a best guess scenario that obliges one to lean on the EXP of the amp and or speaker makerand or that of your own practical real world experience.
… and that is too bad.
And a bit of scary excitement at the same time.
I feel going on the rated or claimed power is the best one can do when finding their way thru the forrest of amplifiers.
Be it an advertising ploy, or hidden because of advertising gratuity, the proof is always on the pudding. Pairing whomever up to whatever will undeniably unfold the truth.
As for the obsessive desire for humongous watt outputting amps, I agree, it is mostly senseless. A belt and suspenders approach for sure. Too many watts is a non issue. Too few is a sincere worry.
Perhaps that notion alone says why many hold to mega watt amps as their default system amp.
Decades back, it was me too.
I’ve seen first hand a pr of EL34 monos putting out reputedly 120wpc, but IMO more like 60wpc as they were but four in each amp… were able to drive to quite satisfying listenting levels a pair of 3 way towers that were rated at 87db 4 ohms. The maker said to me the IMP on these units could drop as low as 1.9 ohms.
Using the 4 ohm taps, things were pretty good. They were here so I had to find out more about this watts vs watts argument first hand. Rated vs measured. Tube vs SS.
At this point all I know is 4 EL 34 tubes wired as ultralinear do quite well with moderately sensitive speakers whose IMP aren’t supposed to be considered tube friendly.
Further eXP from buying used speakers showed me what happens with speakers when someone feels they should use them as PA speakers but only have a 60wpc INT to push them with. Two tweeters needed to be replaced of the four on board as clipping burnt them out..
It took a while for me to figure this out but that is or was indeed the facts. I had the BAT VK 500 at that time and I;’mn sure the Big BAT had enough juice to keep them from clipping..
As for the quality of da watts…. Invariably, I will always have one, and likely two or more amplifiers available at any given time. None are monster amps. All at rated power of < 200wpc. All are SS. Multi ch, 2 ch, and multi ch receivers. The lowest rated output of nay amp is 110wpc. I regularly now use one of these if not more, to run in what ever speaker before even thinking of putting it into a main system. Low to moderate levels for a month.
In the interim, it’s a learning experience to see how few watts it takes to achieve very good results with many various and varied loudspeakers..
The obvious diffs in amp to amp is not volume but Quality of the presentation. Every time.
Many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling. It's only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling.
Here's what I mean, both taken from Stereophile on one of the latest 60 .8 series.
Manufacture: Specified as putting out 60W into 8 ohms and 120W into 4 ohms (both 17.8dBW),
Stereophile measured: The XA60.8 considerably exceeded that power, delivering, at 1% total harmonic distortion (THD), 150W into 8 ohms (21.8dBW, fig.4), 240W into 4 ohms
So you see 150w into 8ohms but only 240w (not 300w) into 4ohms, where's the other 60w gone????
Because of this "voltage source" characteristic, the 300- series amplifiers double their power demands every time a loudspeaker impedance is cut by half. For example, the no. 336’s continuous rated output is 350 watts per channel at 8ohms; 700 watts at 4ohm; 1400 watts per channel at 2ohms.
Again, many manufacturers understate in their literature the 8ohm wattage so the 4ohm and 2ohm wattage looks to be doubling. It’s only on independent tests this shows up the 8ohm to be higher and the 4ohm or 2ohm not doubling.
The no.334 manual does not give a rated output for a 1ohm output load. 8 ohm- 125; 4 ohm- 250; 2 ohm- 500 watts. However John Atkinson found his test sample to measure quite closely to the ML literature:
"..John Atkinson also measured the No.334’s maximum output power using the Miller Audio Research Amplifier Profiler and a low-duty-cycle 1kHz toneburst to avoid loading down the AC line and the amplifier’s power supply. The result is graphically shown in fig.8. Though with this signal and one channel driven, the amplifier did meet its specification into 4 ohms, there was still a very slight shortfall into the demanding 2 ohm and 1 ohm loads. Into these impedances, 492W and 829W were available, these powers equivalent to output currents of 15.7A and 28.8A, respectively..."
So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response.
But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead.
EG: Like the blackish grey trace shows in this graph of a tube amp that can't stay flat into a easy simulated speaker load. Which is plus and minus 6db!!! very far from sounding flat, and very mush a tone control.
Saying this the ML's are a fine amp and have enough current to drive probably everything, just that they don't double their wattage for each halving of impedance, they come as close as I would expect, no amp can double all the way down to 2ohms.
@georgehifi So the upshot is, if you have speakers that are a kind load to the amp, then the amp is not called for to deliver current, and will stay reasonably flat in frequency response.
But if the speakers are a load that asks the amp to deliver current at certain frequencies, and the amp can't, then what happens at those frequencies is the amp "sags" in power at those frequencies and therefore cannot stay flat in frequency response, and becomes a tone control instead.
Blindjim > now this particular note, I feel I understand pretty readily. Thanks.
= = = = = == =
@nutty > The laws of physics refuse to be cheated. Long-term, you cannot deliver more power into the speaker than you can pull from the wall.
Blindjim > makes sense. Tanks much.
= = = = = = = @almarg
Regarding the disagreement about whether or not some solid state amps can "double down": As I see it both sides are correct, but are focusing on different things. One side appears to be focusing on **measurable** maximum power capability, and the other side appears to be focusing on **rated** maximum power capability.
Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability. A reputable manufacturer will, or at least should, choose a margin that is large enough to be comfortable relative to anticipated sample-to-sample variations, reasonable variations in line voltage, etc., but at the same time is not a margin that is so large as to be misleading. And likewise when it comes to choosing the distortion percentages upon which the power ratings are based, and in defining whether the power that is being referred to can be delivered continuously or just on a short-term basis.
Blindjim > Mucho gras Al. Would you mind clearing up this thought of your’s? Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability
Margin? Section? Area? Range? Who picks them or it? The amp maker, Yes? No>?
I’m so confused.
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Perhaps the slant I see is not as much an argument as it is which side of the coin should one stand upon when deciding to throw IMHO a ton of frog skins at any amplifier whose job it will then be, to drive some unknown, unmeasured loudspeaker!
Be steadfast on the side of measurements alone for both speaker and amp, or capriciously dash ahead towards claimed HP and the amps audible attraction?
Dunno. But I’m begining to.
The ongoing thread here however continues to be IMO about pulling the trigger on what ever amp based solely on its ability to ‘reputedly’ double HP as IMP halves, OR choose one based on a likely ‘best guess’ notion with what appears to be enough watt/HP as you adore the influence the amp presents in music playback.
And the winner is?
Only a very small portion of all amps are being measured by third party outlets, and from what can be gleaned just on this thread, some amp makers aren’t too concerned with providing verifiable data to begin with… or so it seems.
For anyone seeking an imperical or metered method for picking out the next amp, good luck.
The technical side of the coin simply can not deliver a suitable or even just verdict as to how best to choose which watt for what speaker. Especially when taste or user preffs are batteling with the bank account for the priviledge of steering the selection committee.
This whole past time should be called Audio ambiguity.
If at all possible, as monos and run them on the same phase but different ckts. To restrict them less electrically.
The only sensible thing to do, If both are the same or quite similar topology, is to weigh the two final amp choices, and buy the heavier one.
That is one measurement which can’t be hidden or misrepresented.
Mucho gras Al. Would you mind clearing up this thought of your’s? Any amplifier having low output impedance can be rated to deliver twice as much power into 4 ohms as into 8 ohms, if the 8 ohm rating provides a large enough margin relative to actual capability
Margin? Section? Area? Range? Who picks them or it? The amp maker, Yes? No>?
Hi Jim,
Yes, I’m referring to ratings that are claimed by the designer/manufacturer.
I’ll explain further with a hypothetical example: During the design process the designer targets a capability of 120 watts into 8 ohms and 180 watts into 4 ohms, based in part on a belief that he can accomplish that with a design that will fall into a price range he wants to compete in. When he tests his initial prototype of the design he finds that it can meet but not significantly exceed those numbers, on a continuous basis (as opposed to just being able to meet them for say a few minutes without self-protection mechanisms being triggered), with reasonably low distortion, when supplied with an AC input of 120.0 volts.
He will then presumably want to allow some margin in his published numbers, relative to those numbers, to account for sample-to-sample differences that may occur in production, and to take into account reasonable differences that can be expected in line voltage, ambient temperature, and other variables. So let’s say that he decides to introduce a margin of approximately 16% (about one sixth) into each of the published specs, resulting in published ratings of 100 watts into 8 ohms and 150 watts into 4 ohms.
However **some** designers in that situation may instead choose to publish ratings of 75 watts into 8 ohms and 150 watts into 4 ohms, which as George has pointed out may help sell amplifiers because it can lead potential customers to consider the amp as being able to "double down." While from a marketing standpoint the downside of that kind of "specmanship" would be mitigated in the minds of many potential customers by the fact that 75 watts is only 1.25 db less than 100 watts!
The only sensible thing to do, If both are the same or quite similar topology, is to weigh the two final amp choices, and buy the heavier one.
Weight is actually a criterion that can indeed be helpful to take into account in choosing an amplifier, IMO, as there does tend to be a correlation between weight and quality (albeit a loose correlation of course), among amplifiers having similar topologies and that provide roughly similar power capabilities. Unfortunately, though, weight also tends to be significantly correlated with price, given those similarities.
However **some** designers in that situation may instead choose to publish ratings of 75 watts into 8 ohms and 150 watts into 4 ohms, which as George has pointed out may help sell amplifiers because it can lead potential customers to consider the amp as being able to "double down."
Al, the big boys nearly all do it, just look at their own spec sheet proper-gander, and then compare it to actual test performed by independent testers.
I’ve PM’ed you a really good audio test sight, far more in-depth testing than Stereophile’s testing. You'll be able to view 2003/4 testing but have to join to view later ones
Hey... Can I point out that what a designer decides to call his "rated output" is little more than the number he feels like advertising? So the amp will drive 100 watts into 2 ohm. It'll probably have no trouble driving 50 into 4 ohm and 25 into 8. And it will do 4 and 8 quite well because it can probably do better than that 50 and 25 watts. I know for a fact Nelson Pass does stuff like this. It's not like there's some law that stipulates an amp can ONLY do what it's rated for. It makes sense to understate the ratings and show excellent measurements.
The Gryphon Kodo has active bass cabinets with a dedicated 2000 watt amplifier inside each. The high/mid panels are very effecient and requires very little power.
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