Why Don't We See More High Current Electronics?

Tvad, I for one would hate to lose you, and your valued balanced contributions to this forum. This particular thread doesn't seem that contentious to me. I do hope you'll reconsider.

03-16-11: Unsound
Tvad, I for one would hate to lose you, and your valued balanced contributions to this forum. This particular thread doesn't seem that contentious to me. I do hope you'll reconsider.

I strongly second these thoughts. Grant, as I indicated earlier I have nothing but the highest respect for your innumerable contributions to this forum, from which I and countless others have benefited greatly. I too very much hope that you will reconsider.

Best regards,
-- Al

Yes- audio equipment does not care what kind of music you play on it.

An amp with a low output impedance does not have a frequency response that varies with a speaker's impedance.

That depends on how the speaker is designed. Take a look at
http://www.atma-sphere.com/papers/paradigm_paper2.html

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Yeah, we've had this discussion before. Same old same old. Lots of assertions, but no supporting data. Negative feedback is bad because it causes time-domain distortion, distortions we can measure aren't important, and high output impedance doesn't really affect frequency response linearity. Frankly Atmasphere, your assertions remind me of Audioquest's argument that skin-effect really does matter at audio frequencies, even though all of the measurements say it's inconsequential.

I think it has been well-said previously in this thread that we don't see more high-current amps because they're very expensive to build, and because most people don't need anywhere near as much power as they think they do at low impedance levels, so very high current amps are mostly for people that have more money than sense (like me).

Tube amps are for people even more skewed towards money than sense. ;-)

Isn't clipping an even worse consequence than unbalanced frequency response alone?

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Yes, absolutely. But unless you listen at *very* high levels (like averaging higher than 95db) most audiophile amps (100w+ per channel) with most speakers (89db sensitivity at 2.83v) probably won't clip. If you are clipping there are lots of 200w+ amps into 8ohms that will likely do you or your speakers harm before they clip.

Actually, my experience is that most audiophile speakers sound like crap at very loud levels. There are notable exceptions like Legacys, big Wilsons, and the top-of-the-line Revels, to list a few, but most don't, so I'm wondering what people think they need so much power for? I know people think they need 600w/channel into 4 ohms, and if they're willing to pay for it I say: go for it, but the math looks like you'd be producing 120db+ peaks, and I can't believe people are listening at those levels. Or am I naive? :-)

"Actually, my experience is that most audiophile speakers sound like crap at very loud levels. There are notable exceptions like Legacys, big Wilsons, and the top-of-the-line Revels, to list a few, but most don't, so I'm wondering what people think they need so much power for? "

Add OHM Walsh (omni) speakers to the list of exceptions.

These shine at lifelike levels but also require the power and juice to do it best. Part of this is the Walsh driver and teh omni design that fills the room with sound more like a live acoustic performance rather than directing all its energy at you and making you want to leave the room, like speakers at a rock concert.

Most people who have owned the over the years run them off more commonplace amplification and probably have never likely heard what they are capable of. That included myself as well until recently.

My Dynaudio monitors do not mind the power and current, but can also get by better without it, though they will never deliver the meat on the bones at higher levels like a pair of large, robust suitably powered full rangers.

I think some people, especially those running ss amps, are comforted by the idea that there is nice margin of available power away from clipping. Others claim that some distortion is audible from stressed amps before full clipping occurs. Some times the extra power is not that much more expensive. Some amp manufactures claim that their Class AB amps slide from Class A to Class B at a ratio of power, e.g. 20% of rated ouput. Some amp manufactures claim that their Class A amps are only capable of sustaining full Class A output at their 8 Ohm rating, as the impedance drops so does the ability to maintain Class A output, e.g. at 4 Ohms those amps are only capable of producing half their typically rated output into 8 Ohms in Class A. If that's the case, the higher powered amp(s) might sustain higher quality sound further into power demands, though not quite up to full available power output.

Tvad, your advice and experience would be missed if you refrain from posting in these forums. I hope you'll reconsider.

Well, Tvad, since I assume I'm the root of your urge to leave, I think you're over-reacting. For one thing, in the interest of full disclosure, I was multitasking when I typed in that response, and while (I think) everything I said was correct I actually *misread* your post in my haste! Yes, IMO, you still have a misunderstanding about ss amps work, but I'm actually feeling pretty stupid at the moment for explaining some behavior related to what you were talking about, not the specific effect you were actually describing! Sigh.

I also admit to enjoying banter like this entirely too much, and it was never intention to chase you (or anyone else) away. So how about you stay, and I'll try to cool my responses a bit, and I'll also try to improve my focus before I type!

Oh yeah, and a correction of my multitasking math, assuming a speaker with 89db sensitivity at 2.83v, and assuming a 4 ohm impedance, 600w/ch does not give you clip-free 120db+ peaks, you'd get about only 114db peaks or so.

Boy I'm stupid today.

Why would you want less power then?

Why would I want less power? I think the better question is why would I accept less. My reasons:

1. Even 110db peaks are really, really loud. I'd like to hear for a lifetime.
2. Most audiophile speakers will have significant distortion at these volume levels. Why listen to so much distortion?
3. Most stereo solid state amps will need well over 20amps at 120v from the wall power outlet to produce 600w/ch. What are you plugging the amp into? ;-)

Where's kirkus?

He knows more than anybody about this stuff.

Hope he jumps in.

Irv, thank you for offering the words of reconciliation to Grant.

03-16-11: Irvrobinson
For a good voltage-source amp with 100w into 8ohms, if the speaker has a peak impedance of 16 ohms into 4KHz the amp will clip at 50w, and if the lowest impedance occurs at 40Hz with 4ohms the amp will clip at 200w, but the frequency response at 50W will still be flat (within the amp's spec) across the entire spectrum up to 50w.

Trick question - what happens if the speaker is reproducing 4KHz and 40Hz *at the same time*?

Well, since one frequency is far higher than the other, there will be instants of time at which their peak amplitudes will simply sum together. If both frequency components have the same amplitude (which is highly unlikely with music), the amp could provide half of its maximum output voltage at each frequency, without clipping. Since for a given impedance power is proportional to volts squared, power delivery at each frequency at the clipping point would be 1/4 of the numbers you cited above: 12.5W at 4kHz, and 50W at 40Hz.

At least, I think so :-)

Regards,
-- Al

Not sure how this thread deteriorated into a philosophical argument. Typical example of the audiophile niche market.

"High current" has faded as marketing buzz word. That's all. Still continues as a design philosophy. Don't make me name names. Doubling down, well that requires, along with adequate power supplies, a specific kind of circuit and feedback, which happens to be the new buzz word.

There's one brand, to remain nameless but with unusual sincerity, that only tests the amp into 4 ohm power resistors, and only at 1 kHz. They divide that by 2 for the rating into 8 ohms. They also claim stability into 2 ohms. It's a good brand and an impressive amp so I'm not disputing. Just saying that advertised ratings are not real-life, reactive loads.

One can and sometimes does hear in excess of 110 dB. It's not just the volume, but the duration and the frequency that one hears these peaks that are of concern. When it's appropriate, it's nice to have the capability. Some speaker can handle it without significant distortion.

Yeah, we've had this discussion before. Same old same old. Lots of assertions, but no supporting data. Negative feedback is bad because it causes time-domain distortion, distortions we can measure aren't important

Of course there is plenty of supporting data, and the distortions we are talking about *can* be measured, as well as heard.

high output impedance doesn't really affect frequency response linearity.

I don't know where you got that but you did not hear that from me. In fact the whole point of that paper (which now I am guessing you did not read) is that you have to **pay attention** to these things to **prevent** errors in 'frequency response linearity'.

so very high current amps are mostly for people that have more money than sense (like me).

Tube amps are for people even more skewed towards money than sense. ;-)

So, are you saying here that you have a tube amp in your future?? :)

Yes, factor in the ability to handle transients as well as the more macro dynamic/loudness aspects and the case for making sure your amp does not break a sweat doing it's job one way or another goes way up.

I'm not an expert on amp design by any stretch, but what I do know based on experience and reading tells me in my gut that this is the right approach.

So, are you saying here that you have a tube amp in your future?? :)

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I can't imagine it. ;-) But after reading your website and reading so many of your posts I wish it wasn't such a PITA to listen to what your amps, which have a design I wouldn't normally consider, would sound like compared to my Levinson amps. Unlike properly designed speaker cables, power cords, and the like, I suspect there could be audible differences, though I more strongly suspect that these differences would be coloration, not greater accuracy. Nonetheless, even a curmudgeon like me occasionally succumbs to curiosity.

You can get the exact same current delivery for a given load without the expense of an amp that doubles its power when the impedance is halved. It's true that such an amp, depending on its power capabilities, could accomodate a wider range of speakers, but in general it's unnecessary.

Which would you prefer, a 250 watt amp into 8 ohms that doubles into 4 ohms or a 600 watt amp into 8 ohms that produces 900 watts into 4 ohms? -03-14-11: Bob_reynolds

Errr ...ahhhh.... Hmmm.. the one that doubles thank you ...

regards,

03-15-11: Atmasphere

Why not ask what the relationship is between doubling power and how your ear/brain system hears? The short answer is that you get flatter frequency response, but only with certain speakers. This comes with a price- distortions that the ear is extremely sensitive to. The ear hears these distortions as a variation (coloration) in frequency response! So in a way, you can't win with the explanation of flat frequency response.

- Atmasphere

LOL .. Deja vu Ralph ?

there are more manufacturers here in the US of vacuum tube audio products than there was in 1958! - Atmasphere

Yeah, but i wouldn't hold it against them, it's their use of carburetors that gets me... :)

regards,

Ooooo . . . I've been summoned, like Notorious B.I.G.!
http://www.southparkstudios.com/clips/155324/the-ghost-of-biggie
Actually Al, you're correct save a small arithmetic error. A "pure voltage source" amplifier that clips at 100W into 8 ohms of course puts out a maximum of approximately 40 volts peak-to-peak before clipping, regardless of the input waveform or load impedance. So for the combination of two equal-amplitude sine waves at 4KC and 40C, that's 20V peak-to-peak for each before clipping, or 14.14VRMS each . . . corresponding to about 12.5 watts RMS at 16 ohms, and 25 watts RMS at 8 ohms, or each at 1/4 the rated power like you said. To some, these numbers might seem like a large amount of "loss", but this waveform into even a low-sensitivity domestic loudspeaker would be absolutely ear-splitting (and probably tweeter-frying in short order).

interesting, but unfortunately, simplified theoretical scenarios are not very enlightening regarding what really matters playing real music.

Having a well made amp that is in no risk of breaking a sweat in practice is simply one of the best and simplest strategies to pursue in putting together a system. The actual benefits may vary, but it is an insurance policy at worst.

Few other decisions in audio can be made this easily, so doing it provides a firm playing field for mucking with all the rest as needed.

Thanks Kirk. But note that Irv specified a 40Hz impedance of 4 ohms, so I believe that my indication of 50W (rms of course) at 40Hz was correct.

Also, I think that when you referred to 40V and 20V "peak-to-peak," you meant to say "peak." The 100W figure, presumably rms, corresponds to 28.28Vrms into 8 ohms, which would be 40V peak, or 80V peak-to-peak.

Dividing by two, to reflect each of the two frequency components of equal amplitude, whose peaks will add in phase at some instants of time, we have 14.14Vrms (equivalent to 20Vpeak or 40Vpeak-to-peak), which equates to the 12.5Wrms into 16 ohms and 50W into 4 ohms that I stated.

Best regards, and thanks for spotting the "summons." :-)

-- Al

I was listening to a nuclear "expert" from a well recognized American University explain on CNN a few days ago early on in the Japan nuclear fiasco why theoretically there was nothing to really be worried about with the troubled reactors in Japan.

These reactors had containment structures, no problem!

So much for that theory.......

But to comment on the thread . . . this is some REALLY well-trodden ground. Please see:
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1258580057

I have two main points of contention with Atmasphere's "white paper" to which he frequently links. The first is simply the lack of citation of any historical or scholarly references, or measurement data. This need not be . . . I think that Atmasphere could actually support his design choices much better by a properly researched, documented, and peer-reviewed paper on the subject.

The second is the interchangability of pespectives on amplifier output power ratings, output impedance, and circuit design, specifically the use of negative feedback. Obviously, Atmasphere prefers Class A OTL designs with little loop feedback . . . and the consequences are very poor power efficiency and a high output impedance, both of which are key factors in the rated power outputs of Atmasphere amplifiers.

The wholly illogical part is the inherent value judgement against amplifiers that have clipping-power-versus-impedance characteristics that are different from Atmaspheres'. Because an examination of this data gives ZERO information about how much current an amplifier will produce, what its output impedance is, or the amplitude of any distortion products in its output.

So to answer the original poster's question . . . there are plenty of high-current amplifiers on the market. However, you can't tell which ones they are by examining the clipping-power ratings into various load impedances.

Ooops, Al, you're correct. Didn't see the 4-ohm bit . . . blasted eyes!

When I was looking at these kinds of amps for my rig, I looked at power ratings into various loads and specs indicating current delivery capability explicitly. In general, the higher current capable amps seemed to correlate pretty well though not exactly with the ability to at least mostly double down. I recall amps with higher current delivery capabilities almost always did this better at least than those indicating low current in general.

I also tending to look for higher damping factor to go along with this for my particular speakers.

This approach has worked out well for me.

I had a low current, high power 360 w/ch (to 8 ohm) carver m4.ot amp prior to a Musical Fidelity A3CR that delivered 120w/ch. The MF sounded more balanced with my "current hungry" speakers than the Carver, though the Carver could go usably louder.

The BC monoblocks I have currently raised the power level level to 500w/ch and also promised good current delivery, doubling down as well based on specs.

The results were exactly as expected. Good tonal balance plus ability to go louder and clearer. Mission accomplished!

The first is simply the lack of citation of any historical or scholarly references, or measurement data. This need not be . . . I think that Atmasphere could actually support his design choices much better by a properly researched, documented, and peer-reviewed paper on the subject.

Kirkus, thanks for your comments. I can produce a lot of data on this, but FWIW the paper I have often linked to is designed to be easy to read, and also easily understood by someone who does not want to go through mathematical proofs that they may well not care about. However I take your point so perhaps a second document that is a bit more in-depth?

The second is the interchangability of pespectives on amplifier output power ratings, output impedance, and circuit design, specifically the use of negative feedback. Obviously, Atmasphere prefers Class A OTL designs with little loop feedback . . . and the consequences are very poor power efficiency and a high output impedance, both of which are key factors in the rated power outputs of Atmasphere amplifiers.

I should clear something up here. Yes, this paper is on our site but it does not specifically point to our gear as the solution. I see this as a bigger issue! I have had a few people accuse me of making this stuff up- what I suggest to them is use Google to look for older Fisher amplifiers with the variable damping control (it has a spot on the dial labeled 'constant power').

I don't go for feedback simply because I've never seen it sound right (I use master recordings as a reference FWIW). Audiophiles are always looking for that 'difference' in gear that is responsible for it sounding like music rather than electronics. I have run into plenty of info on the subject, from such luminaries in the industry as Norman Crowhurst and Nelson Pass and it seems redundant on my part to restate that which has been part of the lexicon now for over 50 years.

The wholly illogical part is the inherent value judgement against amplifiers that have clipping-power-versus-impedance characteristics that are different from Atmaspheres'. Because an examination of this data gives ZERO information about how much current an amplifier will produce, what its output impedance is, or the amplitude of any distortion products in its output.

Again, this is not just about the amplifiers with which I am associated. You will find similar characteristics in SETs and P-P tube amps that feature little or no feedback. Contrast that against the Wolcott, a tube amplifier that behaves as a Voltage source, and the point is made in better contrast. But there are SS examples of zero feedback designs which I have often mentioned and admire.

With regards to why I eschew loop negative feedback, which I regard as a crucial issue, to restate myself: feedback adds odd-ordered harmonic distortion to nearly any (traditional) tube or transistor design and it is very easy to prove that our ears use odd orders to determine the volume of a sound (I can provide a simple test scenario that almost anyone with test equipment can perform to prove this). Essentially, a fundamental rule of human hearing is being violated in order to reduce (apparent) distortion on paper and to reduce output impedance. Its not coincidence that feedback affects distortion the way its does and we are able to hear its effects the way we do.

Regarding distortion, FWIW our gear makes primarily the 3rd harmonic and is absent of the even orders on account of cancellation throughout the circuit, due to its fully differential topology.

Now I think it is understood that I prefer tubes, but the truth of the matter is I would rather work with transistors. They are a lot less work to build than a good tube amp! So far I've not got transistors to sound right, and I have yet to hear a transistor amp that does. Being in the industry, I've had plenty of opportunity to hear a lot of amps- it comes with the territory. We can write that off to preferences, but there is enough standing evidence and literature to the contrary (IOW, that there is more to it than preferences) without *my* input.

Well, I suppose the original answer from my thread was answered. Can any of you electronics experts recommend a high current amp? That

doubles down
100 watts minimum (200 watts or more preferable)
input impedance- highish 50-100 ohms (for a tube preamp)
quality sonics (known for clarity, powerful bass, neutral, transparent, without leanness)
$2k or less on the used market

Caveat: I know nothing about the seller:
http://www.audiogon.com/cgi-bin/cls.pl?ampstran&1304255043&/Threshold-S500-Jon-Soderberg-U

Foster_9, I think there was a typo in your last question- the input impedance you are looking for is 50K ohms (50,000 ohms) or 100K ohms.

Most transistor amps, FWIW, seem to be closer to 10,000 ohms input.

Audio research has some SS amps that come up in that price range that meet the criteria as I recall.

I strongly considered these when looking in a similar price range because AR is primarily known for its tube gear and their SS amps are seemingly designed to match well with higher impedance tube pre-amps and were generally well received.

If I had not decided to splurge as I did on the BCs, one of the ARC SS amps was probably next in line for me especially in that I already owned an ARC tube pre-amp.

If you decide to go for an inegrated, the Krell 300i or 400i if you can squeeze it could be an interesting choice.

I have heard these and was quite impressed running both full range Martin Logan and Focal Profile speakers.

Krell is known for providing a nice full low end and having excellent clarity and resolution. That is what I recall hearing as well. Extremely transparent with holographic like imaging as well, at least in the big, open and airy display room that I heard it in.

Yes Atmasphere that was a typo. I meant an amplifier input impedance of 50k Ohms - 100k Ohms.

Fitting your criteria, I really liked the Moon W5 in sound, build quality, and bench performance when I had one on loan. The Bryston 3BSST is also a nice amp.

The McIntosh MC7200 might also work, but their input impedances are usually like 22k. BTW it's a high current amp with a low output impedance, which can't be inferred from it's specs that don't "double down". It's continuous power output into lower impedances is limited by the power supply . . . but that's not really a criticism, as there's still a ton of power available, and lots of dynamic headroom.

Here's my vote: a zero-feedback transistor amp that behaves as a voltage source, from Ayre.

http://www.ayre.com/mxr_details.htm

Input impedance is very high- any preamp will work with it.

Foster-9, if you're looking for used amps there's a lot of selection:

Any Krell amp. There are several Evolution 302s available, as the 302e just came out. The older FBPs are great too. Any higher power than a 300-series amp just seems like overkill to me.

Any Levinson 33x or 43x-series amp, or any later models. My one caveat with Levinson is that service can be complex and expensive. My 334s have been bullet-proof, but in current dollars remember that even the low-end 334s would likely be $10K each.

The Parasound JC-2. These have always tempted me, and they are occasionally available used. They were $3K each when they were introduced in 2003, but now they retail for $4500 each.

Bryston, Ayre, Pass Labs, Classe, Coda, Boulder... mostly North American stuff, since high current amps seem to be a largely western hemisphere thing. Of course, these are all very expensive amplifiers. For used equipment there's a good economic argument for Krell & Levinson, simply because there's an active market and these amps retain high resale values. Any of them will be costly to service.

New high-current amps that claim to double power with halved impedance seem to start in the $5K range and go up. Way up. Krell and Levinson seem to think $20K amps are mid-range nowadays. Mostly I think what we're paying for is fancy aluminum casing work and Swiss-watch-class build-quality in a North American factory. (Most of the components will be imported.)

IMHO, the most important spec for a properly design solid state amp these days (well, at least the one I look at first) is signal-to-noise ratio. Almost everyone has low distortion and high power, but noise is a different story. Most amps are rated at something like -100db below full power, and since they usually have 25-30db of gain we're talking in the range of -70db of noise, sometimes worse, below 1 watt of output, which can be audible with some speakers, especially if the frequency distribution of the noise amplitudes include a good bit of output below 20KHz. Maybe it's just me, but I find a dead-quiet background attractive. The latest Krells are very low noise, for example, the older Levinsons less so.

Accuphase, is often overlooked, very good amplifiers...

regards,

Irv, I guess you didn't see his $2K budget limit?

I can't for the life of me understand those that spend thousands on an amplifier that shows current limiting and power supply issues going from 8-4 ohms.

Ahhhh bwoy ...

Unsound, I did miss the $2K limit. That makes it difficult... and my previous post useless. ;-)

Atmasphere threw me off with that Ayre recommendation. :-)

Weseixas, If some have speakers that don't operate within those impedances, why would it matter to them?

Because it shows a deficiency in the power supply and hence topology being used IMO, nothing to do with speakers.

Why spend thousands on an amplfier that has a mediocre PSU and Amplifiers that do so always sound unmusical IMO, same with high bias Class-A ( SS) amplifiers, they give up life for smoothness and is usually preferred by those not familiar with recordings of live music and or poor speakers.

Regards,

Irvrobinson, he wants something that doubles power as you cut the load impedance in half. But I don't like feedback (human hearing perceptual rules meow meow...)...

Looking down the list for my interpretation of your electronic/price/weight criteria:

Sale pending: BAT VK500 (105 lbs), Threshold S500

Used: Belles 350A Reference

New: W4S ST-1000

Irvrobinson, he wants something that doubles power as you cut the load impedance in half. But I don't like feedback (human hearing perceptual rules meow meow...)

-03-18-11: Atmasphere

Atmasphere, technically there is no such thing as no feedback in an electrical circuit and hence a zero feedback amplifier, can you quantify your statement ?

regards,