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Is there a noticeably audible difference between two level matched solid state amps under controlled

  • Yes... I believe a notable difference can be heard.

    Votes: 136 48.6%
  • No... I do not believe there is any audibly significant difference.

    Votes: 144 51.4%

  • Total voters
    280
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The automotive analogies are stretched, but what you are proposing is that we race, say, a Ferrari Italia 458 and a Porsche 911S, but limit the top speed to 150 mph. Which one is the faster car?
Very true, but are we asking "which amp is 'better'" or are we asking "which amp better reproduces music X"? They are very different questions.

Even then: our question is more narrow than that. In a car we might discuss fuel efficiency, as in an amp we might discuss efficiency. A car might have comfort where an amp has attractiveness. Both have interfaces. Where a car has acceleration and top speed, an amp has THD and max power.

But the question is about the ability to deliver music... so which one can better transport a briefcase down the highway at 70MPH? A Ferrari Italia 458 or a Porshe 911S?

They are the same when it comes to how long it takes the package to arrive.

I contend that overload performance is what separates the good power amps from the bad, and most people have no idea what levels they are listening to. Witness the repeated, controlled tests, where every amp is kept in its linear range, that is to say derate the Porshe by 3 dB, from its top speed of 209 MPH to 150 MPH, and we find out that every amp sounds the same, i.e. the Ferrari can do 150 MPH too. These are not real world conditions. Power amps get driven into overload every day in normal use. The way they respond to this colors the sound, and that's what people are hearing.
It may happen every day... and there may be people that "normally" drive amps into overload.

I don't. No one I'm familiar with from audio circles does in "normal use". The audio shops I've been to do not (at least not on their SS units). I've got at home and used at shops amps with level meters, and amps with clipping indicators.

*All* amps color sound at overload. So which option is better? Getting an amp that colors it less, or getting one you don't overload?!?
 

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Discussion Starter #102
I think most people are very sensible when it comes to amps and their limits and I do not see the evidence to support people driving their amps into overload "every day in normal use". You have a few folks who will crank their system up close to or perhaps even exceeding its limits on occasion to maybe show off their system... but in every day normal use... amps are not driven near their limits. The typical home theater enthusiast is much different than your typical car audio teen driving his car around town trying to blow the windows out of his car. Sure people will test their systems on occasion, but normal use is not consistently overloading their amps on an everyday basis... it just ain't happening.
 

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I don't believe the question is speed at all..., its the ride. Just as can you tell the diff between An Audio Note Monoblock pair and a Sound Design receiver. All wiring and other conditions being equal. The question is not can you tell the diff when they blow up the Q. is "can you tell the diff when each is set up to show what it can do".
 

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However, if you would like to create your own challenge. If you offer $10,000 to see which amp handles overload best..., I will..., let me be the first to say "my amp will beat your amp" I am ready willing and able.

Gregr:boxer:
 

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Alright, you have everybody dancing a pretty good jig. I think I get your point. I have a few extreme questions myself.

Why do we do the amp test on your turf Sonnie. I might accept your challenge if you brought your amp anywhere else though I would prefer it if you were to set up here in my home but you cannot touch my equipment or treat the room in any way. Just set up your equipment next to mine. Then the A/B switch is handled by anybody that has no idea which is which and the person who sets up the the equipment cannot see which switch is open or closed. A true double blind study without placebo control. Although it might make things interesting..., no that would only increase your odds and decrease mine. a third amp is literally "out of the question". The original research question is "can I tell the difference between my amp and yours with all being equal.
 

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Discussion Starter #107
If I were the one offering the challenge, I would have to offer it on the same terms as Richard Clark and request it be brought to me... after all... I am the one paying out the $10,000. That is part of the challenge.

Actually it appears some of his challenge is more like a bet... and I would not gamble for a penny, so his challenge is not appealing to me. Would it prove a point? Sounds like it would. I would however, want a non-bias third party to set up the testing conditions.
 

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One more question..., since we are all in such a testy mood. Did I meet, exceed or did I fail your your real research question. Hope I didn't fail too badly in providing entertainment at least for smollion(i can't read the small type excuse the spelling please).

Some of the answers are interesting. I have to say I believe I have learned a little about most of the contributors to this thread "can we hear a difference between amps". This is a good question and I do not believe the discussion is complete. Because I do believe Sonnie can set up the experiment so that nobody could possibly hear a difference. I believe in my environment I will pick out the peculiar resonant frequency of my amp in my environment. That would be different in any other environment and I am sure I will not know the difference if there were no resonant frequency. Unless maybe if we use my wires: power cables interconnect, speaker cable, fuses..., not part of the original research question.
I am not going to challenge anybody. I have too many questions.

Room Tx
crossovers
All the best of course but inexpensive Ha! Ha!?

Gregr
 

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Where did Sonnie ever suggest that he was trying to set up an experiment at all, much less set it up so that such a result was achieved? There are differing perspectives here. No surprise in that. I agree that there is more to the question, but no one will be allowed to be testy here and no one is attempting to judge your success nor failure at any task. The topic was raised to engage discussion on a matter that has very different perspectives. Just because people have strong opinions does not mean that we cannot discuss it in a civil manner nor that anyone is going to be set up for a particular result.
 

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My mistake I assume too much, excuse me, please. However, I am enjoying watching all of you. I had hoped I wasn't alone. But you know what I am not having fun anymore.
Good By
 

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Because I do believe Sonnie can set up the experiment so that nobody could possibly hear a difference. I believe in my environment I will pick out the peculiar resonant frequency of my amp in my environment. That would be different in any other environment and I am sure I will not know the difference if there were no resonant frequency. Unless maybe if we use my wires: power cables interconnect, speaker cable, fuses..., not part of the original research question.
So you're saying that you might be able to tell the difference between your amp and Sonnie's amp because your amp has a fault that causes a 'resonant frequency.'
 

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The test would need to be done in an Anechoic chamber if we are really talking about doing the test properly. That said, any room influence should be the same across all amps, and shouldnt be a factor, but removing it as a possibility would be the ideal.
 

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I think this thread is moving along pretty well. Over at the "Science" forum, the discussion would have fragmented into personal attacks long ago. We're a level-headed group over here, and stick to the issues while staying civil. And in the vein of sticking to the issues...

No more car analogies. As I said, they are stretched.

I haven't used the word "clip" in this discussion, but rather "overload". There is a distinction. "Clipping" is a particular overload that occurs when the output transistors enter the saturation region (base forward biased, collector forward biased), which happens quickly, within a volt or two, at the peak of the waveform. In the saturation region, collector current will not be controlled by base current. In the linear region of operation, with the base forward biased and the collector reverse-biased, the collector current will (largely) follow changes in the base current.

My definition of overload is more general, with clipping being a special case. In real world operation, the load is rather dynamic, and especially the speaker's crossover can provide pathological loads. More than one 3-way crossover presents a series-resonance to the amplifier at the crossover frequency that can cause the impedance of an 8-Ohm speaker to dive to <3 Ohms, i. e. 2.8 ohms in one highly regarded speaker. If the amplifier has the drive reserves to maintain a low distortion output in the face of a 3 Ohm resonant load at (say) 400 Hz, then there will be no coloration of the sound. If it doesn't, then there will be a coloration. The output drive capabilities are dependent on output level, because the amp is inherently very non-linear, and depends on a lot of feedback to correct its response. At high drive levels, and low-value load impedance, an amplifier can run out of drive and begin to distort, well before onset of clipping.

I had one such amplifier, a brand-name AVR with an 8-Ohm rating, and a switch to set it to 6-Ohm. I never liked the sound of this amplifier, but didn't know why, until one day it actually tripped-off on a sound transient in a movie. I could re-create the event over and over. The sound level at this time was not especially high, and not at the amplifiers limit, in terms of clipping. After discovering the <3 Ohm speaker impedance at 400 Hz, I set this amp to 6-Ohm operation. After that, it wouldn't trip off, but I liked the sound even less. So I replaced the amp, and picked out a better specified amplifier with generous 4-Ohm ratings. You can spot that on a spec sheet because the power at 4 Ohm is double the power at 8 Ohms. Since replacing that amp, I now like the sound of my HT, and also use it for music.

Because I lived this event, it has made a lasting impression on me, and forms part of the basis of my opinions of these items. I would agree that two amplifiers, operating well inside their spec envelopes, will sound virtually indistinguishable. However, I will also add that this happy situation happens less often in the real world than we would like, and that is the reason threads like this one are perpetually, heavily subscribed.
 

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Discussion Starter #114
I had one such amplifier, a brand-name AVR with an 8-Ohm rating, and a switch to set it to 6-Ohm. I never liked the sound of this amplifier, but didn't know why, until one day it actually tripped-off on a sound transient in a movie. I could re-create the event over and over. The sound level at this time was not especially high, and not at the amplifiers limit, in terms of clipping. After discovering the <3 Ohm speaker impedance at 400 Hz, I set this amp to 6-Ohm operation. After that, it wouldn't trip off, but I liked the sound even less. So I replaced the amp, and picked out a better specified amplifier with generous 4-Ohm ratings. You can spot that on a spec sheet because the power at 4 Ohm is double the power at 8 Ohms. Since replacing that amp, I now like the sound of my HT, and also use it for music.
I know my Onkyo receiver has a 6 ohm setting... and I might understand a lower powered receiver that is "over-rated" in power having a difficult time driving low impedance speakers... such as my MartinLogan Prodigy's... and a few others... if played at or near reference levels continuously... especially if it is all five channels driven. I use Emotiva XPA-1's on my Prodigy's and my 906 runs the center and rear. I hopefully plan to upgrade to a UMC-1 and XPA-3 sooner or later.

Take the Onkyo 876 receiver rated at 170 watts minimum continuous power per channel, 6 ohm loads, 2 channels driven at 1 kHz, with a maximum THD of 0.1%. But what is it with all channels driven at 6 ohms... and the receiver is NOT rated at 2 or 4 ohms... in reality it is not designed to power 3 ohm speakers. So in this case you are not comparing apples to apples. You even said you picked up an amp with a generous 4 ohm power rating. Had you been running Klipschhorns, do you think you would have noticed that same difference?

You can probably find an exception with several lower powered receivers vs higher powered amps (or even amps designed to run 2 ohm loads) if you are using speakers that are not really designed to be used with those kinds of lower powered amps.

Where I think most people are claiming there is no audible difference in is between say an $18,500 Krell 402e at 400/800 watts per channel 8/4 ohms respectively... a $2995 Bryston 4B-SST at 300/500 watts... a $1,350 Parasound 2250 at 250/400 watts and maybe a $709 Emotiva XPA-2 at 300/500 watts.... and maybe we do throw a few receivers in the mix... say a Rotel RSX-1560 A/V Receiver and a NAD T-785. I think you might have a hard time even with difficult to drive speakers determining a difference in these under equal testing conditions.
 

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The car analogy was simply to point out the absurdity of testing amps for listening difference at clipping and get back to the initial question of whether a person can hear the difference between two amps under identical listening environments.

I have been in studio recording and live sound off and on for 25 years. I am an electrical engineer and have been on jobs where all these subtle parameters are tested and documented. In all my experience we have never designed nor used any system anywhere near clipping. That is just poor system design. It is also terrible for speakers. In any given situation we design plenty of headroom into the system so that we never approach clipping. We never come close to clipping and if it were to happen we would back it down and fix it as soon as possible.

Design the system correctly, use it within its design limitations, and enjoy pure clean sound. If you need more power buy more power. Nobody designs amps to be run at clipping and nobody designs systems to clip at top volume.
 

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... and the receiver is NOT rated at 2 or 4 ohms... in reality it is not designed to power 3 ohm speakers. So in this case you are not comparing apples to apples. You even said you picked up an amp with a generous 4 ohm power rating. Had you been running Klipschhorns, do you think you would have noticed that same difference?

You can probably find an exception with several lower powered receivers vs higher powered amps (or even amps designed to run 2 ohm loads) if you are using speakers that are not really designed to be used with those kinds of lower powered amps.

Where I think most people are claiming there is no audible difference in is between say an $18,500 Krell 402e at 400/800 watts per channel 8/4 ohms respectively... a $2995 Bryston 4B-SST at 300/500 watts... a $1,350 Parasound 2250 at 250/400 watts and maybe a $709 Emotiva XPA-2 at 300/500 watts.... and maybe we do throw a few receivers in the mix... say a Rotel RSX-1560 A/V Receiver and a NAD T-785. I think you might have a hard time even with difficult to drive speakers determining a difference in these under equal testing conditions.
I have to point out that all my speakers are rated at 8 Ohms. They have been connected to amplifiers rated to drive 8 Ohm speakers. The problems are in what is not in the ratings. The issue with 3-way crossovers has come up in speakers costing hundreds at Best Buy, and speakers costing thousands, and sold only at authorized dealers. I don't know what kind of load the Klipschorn presents to the amp. I do know that you should have plenty of headroom in a small room with these monsters, since you are sitting in the mouth of the bass horn. I expect my old amp would have done well with them, because of all the headroom.

I'm not dropping names about what brands of amplifiers will sound better or worse, that has never been my point, or the amount of money you spent. I hope that spending 6 figures on an amp will give satisfaction, but I'm not so naive that I really expect it. In the experiment quoted above, Zipper couldn't tell the difference between an old Yamaha and some boutique monoblock.
 

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The car analogy was simply to point out the absurdity of testing amps for listening difference at clipping and get back to the initial question of whether a person can hear the difference between two amps under identical listening environments.

I have been in studio recording and live sound off and on for 25 years. I am an electrical engineer and have been on jobs where all these subtle parameters are tested and documented. In all my experience we have never designed nor used any system anywhere near clipping. That is just poor system design. It is also terrible for speakers. In any given situation we design plenty of headroom into the system so that we never approach clipping. We never come close to clipping and if it were to happen we would back it down and fix it as soon as possible.

Design the system correctly, use it within its design limitations, and enjoy pure clean sound. If you need more power buy more power. Nobody designs amps to be run at clipping and nobody designs systems to clip at top volume.
Well I'll agree that the car analogy was absurd.

Since we're sharing resumes, I hold an MSEE and had a pro sound career many years ago. After that I went into aerospace and most recently work in the energy industry. In all my experience we never designed or used a system outside its specifications: Clipping, gain compression, third order intercept, and pages of other requirements were analyzed, inspected or tested. That's engineering.

This forum is about home theater. People buy some equipment, plug it together, and start showing movies. There is no design engineer, no spec, no testing, no nothing, and a lot of equipment that ought to play well together doesn't. So people hear problems. I know I did. They aren't sure what it is, and it may be room acoustics as well as anything else. Amplifiers frequently get blamed, and maybe some a culpable, and probably most aren't. Maybe they are clipping the amp by overdriving it, or maybe it's some other fault. We will never find out.

What I have contended over and over, and will repeat myself yet one more time, is that when people are hearing a difference between two amplifiers they are hearing some kind of problem with the system. Changing the amp may fix the problem, but there was some departure from normal operation that they heard.
 

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Discussion Starter #118
I have to point out that all my speakers are rated at 8 Ohms. They have been connected to amplifiers rated to drive 8 Ohm speakers. The problems are in what is not in the ratings. The issue with 3-way crossovers has come up in speakers costing hundreds at Best Buy, and speakers costing thousands, and sold only at authorized dealers. I don't know what kind of load the Klipschorn presents to the amp. I do know that you should have plenty of headroom in a small room with these monsters, since you are sitting in the mouth of the bass horn. I expect my old amp would have done well with them, because of all the headroom.

I'm not dropping names about what brands of amplifiers will sound better or worse, that has never been my point, or the amount of money you spent. I hope that spending 6 figures on an amp will give satisfaction, but I'm not so naive that I really expect it. In the experiment quoted above, Zipper couldn't tell the difference between an old Yamaha and some boutique monoblock.
Granted... not all speakers are created equal regardless of their ratings. MartinLogan's are typically rated at 4 ohms, but an amp is going to see a 1-2 ohm load from those speakers at certain frequencies.

I know where you are coming from with your previous situation of swapping out a receiver for a more powerful amp and your speakers coming alive, so to speak. I had a Denon 2807 on full MartinLogan setup (Ascent i's for mains) and when we were cranking it on up pretty well on David Gilmour in Concert, we felt like the receiver was running out of gas... and it really did not sound like what I was expecting it to... it certainly did not have that clarity that I was hearing at the lower volumes. It sounded like the instruments were bleeding together... distorting. We contributed it to the receiver (which I believe was tested at about 70-80wpc true power) not being able to handle the demanding ML's at higher volumes. Don't get me wrong... I fell in love with the ML's on that Denon receiver at moderate-medium listening levels... it was astounding, but we were really cranking it on up there on a few occasions. Later I connected an Anthem setup (AVM-50/MCA-50)... did not notice any difference until we cranked it on up really high. We certainly perceived it was cleaner at those higher volumes. Later I place a NAD T-785 in the system... no difference from the Anthem setup whatsoever at any volume. So I firmly believe there are certain speakers that simply will not perform to their full capabilities on a lower end lower powered receiver.
 

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Discussion Starter #119
In the experiment quoted above, Zipper couldn't tell the difference between an old Yamaha and some boutique monoblock.
It does not say what volume levels they were listening to... and the Duntech Marquis speakers may not have been that difficult to drive.

I will say that it is not in my plans to buy any expensive amps (such as Pass Labs) for my ML's.
 

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The test would need to be done in an Anechoic chamber if we are really talking about doing the test properly. That said, any room influence should be the same across all amps, and shouldnt be a factor, but removing it as a possibility would be the ideal.
Actually no it wouldn't at all. You can use almost any system or room you want provided that: #1. It stays exactly the same other than the change of amps. #2 The speakers and level used do not present a load that drives the amplifier into a range of non linear operation. ( No using electrostats at high volume with a cheap receiver guys.:nono:) #3 The amps are perfectly level matched. #4 The listener attempting to discern the differences cannot see or otherwise know which amp they are listening to at any time. #5 the amps shouldn't be intentionally color'd to begin with. Some amps are (tube amps, older rockford fosgate car amps, etc.)
 
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