Amplifier Audio Characteristics

pds · Jul 12, 2003

I keep seeing postings listings some amps as bright, mellow, or sounding better with certain speakers etc. How can this be???

Some time ago the Hirsch/Houck labs did a double blind test on many high end and garden variety receivers. They came to the conclusion that all amps sound the same. The golden ears people couldn't accurately tell the difference between any of the receivers tested and, actually, why should they? An amp is only supposed to amplify an audio signal without adding, deleting, or changing the signal in any way other than to make it louder. Virtually all decent amps (both medium and high end) amplify sound without audible distortion. Therefore when I see amps listed as bright sounding I can't help but wonder why.

The conclusion that the Hirsch/Houck labs came to was simply that a receiver should be bought for the amount of power required, build quality (i.e. heavy duty etc.), and also bells and whistles that the buyer might want. As mentioned above, no one could reliably tell the difference in sound between the amps themselves.

I would be curious to see some responses to the above.

Yamahaluver · Jul 12, 2003

You are absolutely correct about the neutrality of the amplifier in the chain. I too have that issue of Stereo Review where they did the null test. However, in the real world, it isn?t that straight. Most good manufacturers try and make an amplifier with ruler flat response curve and come pretty close to it. The biggest culprit in this equation is speakers, majority of them have a tendency to impart their own sonic characteristics and some so-called big name speakers are equally guilty of this aberration. They even have the gall to claim it as a part of their character and soul. This is real skullduggery as a speaker should try and be as transparent as possible.

Years ago when Yamaha launched their beryllium midrange/tweeter with pure carbon fiber woofer NS-1000, it was tested by many magazines to have the flattest response, many studios, musicians and famous broadcasting corporations started using these speakers for their work. Funnily, the public response and the audio magazine response were really mixed. Many hated it and called it too harsh. Being transparent had its price, with poorly recorded digital material and a noisy amp, the speakers sounded real badly and as we all know that truth is always a bitter pill to swallow. So in my opinion, even though the receivers do have their own sonic characteristics, it is the speakers which either exaggerate or suppress this distinctiveness.

gene · Jul 12, 2003

PDS;

Your concerns are valid and argument interesting.  I agree partially.  If two different amplifiers are well designed, low noise, ample power supply and output devices to source large amounts of current for low impedance loads, flat frequency response within the audio range, they should sound very similar.  However, this isn't always the case.  A lesser designed amp may have a harder time coping with difficult loads and thus may also run out of gas when pushed too hard to drive these loads at loud SPL levels which can lead to excessive distortion, brightness, etc.  Noise is another issue many people, including amp companies, often overlook.  Most amp companies rate SNR at full power.  When you translate that down to 1 watt, which is the usual average power consumed at low listening levels, the noise figures can be quite high.  Believe me I have heard significant differences when evaluating poorly designed amplifiers.   The sad truth is some of these poorly designed amplifiers are being touted as high end, yet the amp section in a well designed receiver are usually superior.  

Back to your original question, again if two different amps are well designed, and can drive the loads they are asked to with ease, there should be little audible difference between them.

Alternatively, some people prefer amps with high output impedances that roll off the high end when connected to high capacitance cables, thus giving a "warmer" sound characteristic.  Other prefer the added distortion of tubes.  I suppose one mans meat is another mans poison

Yamahaluver · Jul 12, 2003

Just wanted to add that slew rate and damping factors differ from amp to amp. Also reactive load and impedance are different for each and every amp. All this does add to the amp/speaker interaction equation and therefore the 'sonic signature' syndrome is pretty much unavoidable.

Another reason to ponder is that most high end amps weigh a ton due to their massive transformers, use huge capacitance value and use higher number of output stages unlike their cheaper counterparts. Why go through all the trouble when one can simply put a class D amplifier which weighs less and generates more power. One reason is stability, the other reason is the 'SOUND'. One can do with two capacitors and four output stages transistors instead of 22 per channel used by high end amplifiers.

Guest · Jul 12, 2003

gene : Other prefer the added distortion of tubes. I suppose one mans meat is another mans poison

A brave man indeed !!

I could not agree with you more myself.

However, there is a army of zelots who will whole heartedly disagree.  They also do it with a flair and style that puts most extreme religions to shame.    

Not that tubes are bad thing, each to his own.  If they are better or not is a totally subjective topic (usually loaded with crappy poetry).  What I hate is that tubes are constantly pimped as "Better" or "more detailed", but that "added little bit" they are "unlocking" is not there in the first place.

Especialy if your using a CD-player (aka a _digital_ source), which I do see quite often in Hi-Fi reviews.  What amazes me is there are no "tube" DSPs, I'm sure you could simulate many popular tube amps and bulbs on a single DSP.

Rob

Yamahaluver · Jul 13, 2003

Now I am going to get slaughtered for this:

Tubes generate second order harmonic distortion and to the tube swearing human ears that sounds nice because all humans like tubes are imperfect and therefore some of us are intimidated by the precise sound of a properly designed amplifier. Perfection, like truth is always a bitter pill to swallow. Whats funny is that the NS-1000 is a hot favorite among tube amp crowd even today because of its accurate sound. Since the tube amps are inherently warmer sounding than the equivalent SS amps, they find this combo complimentary.

Vinly versus CD is another issue as good turntable/cartridge combo does sound rather excellent over poorly recorded digital matter played on a cheap crappy CD player. Good quality CD player with properly recorded CDs do come pretty close to vinyl sound.

To make a DSP tube amplifier, it would be a logistical and economic nightmare.

Gene has put it very nicely, 'One man's meat is indeed another man's poison.'

Guest · Jul 13, 2003

Yamahaluver : To make a DSP tube amplifier, it would be a logistical and economic nightmare.

no no,  I think you mis-understood me (it's ok, I'm amazed anyone can even understand my posts).

I mean put a 300b mode into a DSP for use with todays latest and greatest sound processors.  I'm guessing it's not been done because most consummers don't really care and tube guys will find it "insulting".

Rob

Guest · Jul 13, 2003

The Designer/Inventor of Dolby Pro Logic II, Jim Fosgate, which was later sold/licensed to Dolby, also designed an all tube DPL-II 5.1 processor/preamp, the FAP-V1. It also has a 7.1 pass-thru.

If you want a tube preamp for surround this is it.

Audioholics · Jul 13, 2003

For an easy DIY test, go into a "mid/hi-fi" audio store and see if you can compare a $300-$400 Yamaha (RX-VXXX) vs. a $300-$400 Sony (non-ES) receiver... then compare the ~$300 Sony receiver to a ~$1500 Sony ES or Yamaha receiver.

You should hear a considerable difference, assuming you can use the same speakers (most of these places let you switch just the receiver.) Doing this is what originally got me onto Yamaha as I couldn't afford Sony ES at the time.

pds · Jul 13, 2003

Sorry Hawke, as mentioned in my original posting, there was no one able to distinguish the difference between high end and standard garden variety receivers in the Hirsh/Houch lab double blind tests.

There are many reasons to buy an expensive receiver as I mentioned in my original post and they are valid reasons. As an example, take a capacitor. You can make a very large, heavy duty capacitor and it will last a very long time. However, that same heavy duty capacitor shouldn't sound any different than the smaller standard duty capacitor as long as it is of the same electrical value and operating within the specifications it was designed for. There would certainly be a difference in the quality and longevity of the capacitor but that shouldn't affect the audio as long as both capicators are operating properly.

I found Gene's posting above to be most refreshing and unbiased.

Please keep in mind that I am not suggesting to anyone that their equipment is either better or worse than anyone elses or what to buy. If buying expensive equipment gives anyone piece of mind or makes them feel better then that alone is enough to justify the cost. Everyone has their favorite equipment and that it as it should be. Otherwise there would only be one brand.

Guest · Jul 13, 2003

PDS (free Intergraph advertising?)

As the devils advocate here, in a way you could compare this review to saying all cars drive the same on fresh straight pavement at 20 miles (or 30K) an hour. Well ya, your not going to see too much of a difference there.

I would like to see that review myself, it does sound interesting. By the definition of their purpose all amps should "sound" the same. What's wrong with using pro-amps, some people have a real issue with this, I don't (you can run into some fan noise issues).

I can see how a person would (and should) not be able to tell squat if it was just a basic stereo test being fed into the analog inputs (if it was some time ago, I'll bet it was). At a low volume driving reasonable speakers, you should not notice anything.

A few things to consider about this test
What units did they test?
What is the amps REAL wattage rating?
What was the volume of the listening test?
What is the source material and media being used?
What about the speakers they used?

What it comes down to is how an amp handles things when it's being really driven, or using greedy speakers (when and where will I clip today). Also a stereo receiver is not the same beast as multi-channel HT/audio processor.

For myself, as far as I'm concerned their are no "golden ears" (the cost for health insurance would be too great)

It's a known fact that there are many "golden marketers", well paid too, work with magazines a lot.

If I wanted to buy based on wattage and power I guess I could go for that Wall-Mart "110 WATT PER CHANNEL" special. I think that logic is just as flawed as going for seven of those Bryston mono blocks.

Rob

Audioholics · Jul 14, 2003

pds : Sorry Hawke, as mentioned in my original posting, there was no one able to distinguish the difference between high end and standard garden variety receivers in the Hirsh/Houch lab double blind tests.

For such a generalized statement as this is, I'm surprised you dismiss me so quickly. Perhaps you need more details?

Take a non-ES Sony receiver and crank it up. Listen on 4-ohm speakers.  Next, take an equivalent Yamaha receiver and crank it up - same speakers, of course. You will hear the difference unless you are deaf. Compare the original Sony to  an even higher-priced Yamaha (or insert other good quality amp here, inlcuding Sony's ES line) receiver and you will really hear a difference.

I wonder if the Hirsch/Houck tests were done at low to moderate listening levels. Distortion and damping factor are more easily perceived once the volume knobs are turned up.

I'd be curious to see what receivers Hirsch/Houck compared as well as their parameters. Perhaps the comparisons were all between fairly well-constructed units. I could not find anything online about this particular test you cite.

pds · Jul 14, 2003

Thanks for your reply Hawke. I would be curious to know what your expensive or special receivers are doing to the amplified signal that the others are not. If any of the receivers you mentioned are modifying the signal in any way other than amplifying it, I would consider this highly undesirable. Just about any receiver, Denon, Harmon-Kardon, Marantz, Yamaha etc. should be able to amplify just about any signal without distortion or changing the wave other than amplification. If you overdrive any amp you will, of course, get distortion. The answer to that is simple, just get a more powerful amp. Just a personal opinion but I believe you will get far more variations in audio with different speaker brands and types then you would with different amplifier types. This is only my opinion and I really don't wish to start an argument. I am certainly not recommending any type of gear to anyone.

gene · Jul 14, 2003

Using pro amps in home audio is usually not a good idea since the SNR of these monster power amps is usually considerably higher.  Most of the time the average power consumption in a home audio system is only a few watts or so, and this is why you want an amp with a high SNR.  Note, most amps list their  SNR at full power.  This is very misleading.  IF you want to figure out the amps true SNR at 1 watt use this simple expression:

SNR @ 1 watt:

SNR(full power) - 20*log( sqrt(watts*load)) / 2.83

One should compare SNR between amps at a common reference such as one watt so its a true apples to apples comparison.  

As for sonic differences, I agree, the most significant sonic differences in audio equipment are usually attributed to loudspeakers, followed by preamp/power amps and CD/DVD players.  Let's also not forget the importance of room treatment which could make or break a high performance system.

Guest · Jul 14, 2003

gene : Using pro amps in home audio is usually not a good idea since the SNR of these monster power amps is usually considerably higher.

True, pro-amps are designed for well "Pro" use.  However, lots of the new amps are now fanless and have excellent build quality.  

I don't know if it's possible, but I'd love to see you technically review a few of them that look suitable for possible home use.

You might be surprised, or just reaffirm what you already know.  I don't know, but a lot of people toy with this idea and would probably be interested in reading something about it.

Rob

Guest · Jul 16, 2003

In one sentence you guys are using the term "amps" and then in the next "receivers". A receiver is more than just an amp, as you well know, and has a pre-amp stage in the loop. Also, unless you are listening in 'direct' mode you are also most likely getting an additional A/D and D/A conversion. The preamp and the A/D and D/A converters can also influence the sound greatly, hence the reason not all receivers sound the same. Granted, well designed amps shouldn't sound discernably different, all other things being equal. I have auditioned many brands of receivers and they often sound noticibly different.

bturk667 · Jul 17, 2003

All I have to say is that in my personel experience I have heard differences between amps. Sometimes it's not so much in sound but in the way a particular speaker performs. I will tell you can definitly hear the difference between a S.E.T. and a high power amp, say like a Krell!

petermwilson · Jul 18, 2003

Hi
The part of amplification that I don't understand is "amplification". I understand the "all channels dviven part,  "I think".  what I don't get is how a 70w tube amp can give a better result or power than a 120w transistored amp.

My A/V reciever is an upgraded Denon 5800 THX ULTRA II. It has 7 separate 170w amplifiers.  I presently use Totem Model 1 4ohm speakers all around and rarely get below -20 in the volume range for my room and everything sounds great.

I was thinking of upgrading to the Mani-2's from the same manufacturer, which are also 4ohm, but with double woofers in isobaric configuration.  To my amazement both my Denon dealer and Totem Acoustics tell me I don't have enough power at 170w of separate amplification per channel.

Unless something happened while I was sleeping (I know there are more powerful amps) of the flagship "all-in-one-box" products the Denon has the most juice and is bench tested by "Home Theatre Choice" magazine in the UK as putting out 308.9w into 4ohms.  What in audiophile's world do i have to add to drive those Mani's?

Peter m.

Audioholics · Jul 18, 2003

petermwilson : The part of amplification that I don't understand is "amplification". I understand the "all channels dviven part, "I think". what I don't get is how a 70w tube amp can give a better result or power than a 120w transistored amp.

I don't get into tubes vs. solid state, but one of the sub-topics going on here had to with amplifier audio characteristics.

Two different amps may have the same amplification specs (say, 200W/ch, all channels driven) but if one uses cheap components and the other uses high-quality components the differences will be noticeable in the areas of distortion and especially noise floor.

I hate analogies, so I won't provide one here. The facts and science are pretty easy to understand.

Great topic, by the way.

gene · Jul 18, 2003

Peter;

Sounds like the dealer is trying to sell you another amp.  I am using the Denon AVR 5803 to power all of my 4ohm reference speakers to ear bleeding levels in a 20' x 18' room.

The truth is, for low efficient, low impedance speakers, you may need an amp that has the ability to provide continuous high power for loud listening levels.  The AVR 5803 should be able to easily drive just about any reasonably efficient well designed speaker on the market.  IF you are choosing low impedance ESL's (such as the old Quad that dips down to an ohm at certain frequencies) you may wish to preamp out and get a big power amp that can handle the load.

The truth is most of the time under normal listening (say 80dB or so) conditions, your amp is only dissipating a few watts of average power.  I keep saying this, but I need to write an article explaining this when I have the time.

One more thing, don't judge how much power you have available, or using by position of volume control.  Each product have their own volume sensitivity, half up on brand A may actually be less overall gain then 1/4 up on brand B.  This is also a topic I will need to touch when time permits.

My advice to you is try the new speakers with your existing amp.  If you are not satisfied, buy a nice amp with a good return policy, bring it home and see if you hear an improvement.  Also if you are only doing 5.1 and not using multi room as an amp, you can reroute the unused amps in your Denon to the front to biamp you main speakers and add 3dB of more headroom.  Think about that!

Amplifier Audio Characteristics

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