So what DOES make for a good amplifier?

[Swerd]

For those who are interested, Bob Cordell has a website http://www.cordellaudio.com./. In it he mentions that he will be at the Home Entertainment 2007 show in New York, May 11-13, where he will be presenting a series of 6 workshops on:

* Amplifier Measurement Clinic
* Amplifier Listening Comparison
* Speaker Auditioning Clinic
* Speaker Measurement Clinic
* The Peak Power Demands of Well-recorded Music
* Active Loudspeakers - An Example

The Peak Power Demands of Well-recorded Music is apparently a more developed presentation of the demonstration I saw about a year ago that convinced me that powerful big-iron amps had a demonstrable benefit.

See more details here http://www.cordellaudio.com./he2007/. If anyone will be going to HE2007, I think Bob Cordell and his associates would be worth hearing.

 

[Bassman2]

That article was written to debunk a bogus spec that some receiver manufacturers boast about instantaneous current. It does NOT negate the importance of a solid power supply or an amp with REAL world headroom.

I plan on doing some more articles on this topic when time permits.

Yes I misspoke a little. I meant over designed power supplies which is a relative term I guess. But so many manufacturers "boasts" are false or misleading so I wanted to get the low down.....the straight dope, as it were.

It's funny that in guitar amps we often want small power supplies that saturate, "sag" and compress. So you usually find fairly small output transformers with small caps.

I look forward to reading your next articles.

 

[tbewick]

I don't think anyone's mentioned this site:

http://www.dself.dsl.pipex.com/ampins/ampins.htm

It's run by Doug Self and is referenced at Rane Audio and Audioholics. It has lots on the engineering aspects of amplifiers. I tried reading it some time ago but couldn't understand most of it.

http://cas.ee.ic.ac.uk/people/dario/courses/2e_analog/

The above site is a very hardcore link to a site on amplifier design at the electrical engineering department of Imperial College London. The biographies of famous engineers (eg. Alan Blumlein, an Imperial graduate) are probably also worth looking at.

 

[Ampdog]

From another amp designer of some experience (does >50 years qualify?):

1. Distortion: Touched on by Gene; absence of high order harmonic distortion, as in below audible/noise level. This is of prime importance in avoiding listener fatigue, and I fear not absent in some pretty "high-end" amplifiers. In this sense THD has become meaningless. It mostly leads to the adage that "specs are no good" because some amps with low distortion (thd) sounds bad and vice versa. About 0,1% should be in order, provided there is nothing beyond 3rd harmonics.

2. Good open loop response - unfortunately there is little that the client can do to check this. All too often excessive NFB is used to cover up mediocre design, with stability problems, thus the loop frequency response has to be severely curtailed. In its turn it leads to reactive operation in the audio band (h.f.), TIM effects and the like. Tests can reveal this state of affairs.

3. Damping factor: To put a figure to "enough": As is currently defined, over 10 is OK in most cases, over 20, no audible effect. [That is because of the wrong current definiton of d.f. The total resistance available over the loudspeaker to damp it includes the voice coil resistance; about >5 ohm for 8 ohm systems. Thus the real damping factor can never be more than 1,5! (Not including motional feedback.)]

4. "Juicy" power supply: If the voltage do not drop enough to have an audible effect at severe signals, that should be sufficient. For me that often translates into having a large enough power supply output capacitor to be able to supply the peak needs. This is alleviated by the low ratio of peak/average signal energy in most music. But high current power supplies (e.g. switching) are becoming more practical; it is the designer's choice.

I am not repeating matters already mentioned.

 

[mtrycrafts]

... absence of high order harmonic distortion, as in below audible/noise level. This is of prime importance in avoiding listener fatigue, and I fear not absent in some pretty "high-end" amplifiers. .

Well, they got to give you something for your money, right? LOL

 

[Ampdog]

Especially since those often advocate "shortest possible signal routes", thus doing you out of copper as well.

 

[Tony3d]

Have you thought about a Pro Amp?

Well, I'll tell you compared to my Onkyo M504 power amp my new Crown XTI-2000 amp simply reproduces music with the kind of muscle one associates with a live performance. I get much tighter, deep, dry bass. To be honest the top end seems a little more sterile, but hardly what I would call harsh. Maybe a better word would be analytical. All in all I see no reason to look at a very expensive consumer amp again. I was very skeptical before I bought this amp myself, and I posted on many boards before buying. I have listened to live music for many years. My brother was a jazz guitarist for 35 years. His very good friend Gene Palumbo went on to arrange, and conduct for Judy Garland for a couple years before her death. I believe I have a well trained ear, and what it hears is very neutral reproduction. I'm sure a lot of these $5000.00 amps are excellent and produce better specs, but to tell you the truth after hearing Krell, Threshold, and some H/K Citations over the years, this Crown stacks right up there with the best of them. Even the fan which I thought was going to be the big issue has not come on once that I can tell. I'm sure under laboratory listening conditions, these high end consumer amps may reveal more detail, but I listen in my living-room. So far I feel like I stole this amp for $699.00. I'll never run out of headroom at 475 watts per channel, and it will probably outlast most consumer amps. In the past I personally owned a Phase Linear 400 series 2, H/K Citation 16, and an Onkyo M504. Each amp failed for one reason or another within a 8 years span. I know non of these where ultra high end, but they represented a good buy in their day, and were not exactly cheap. The only component I have from the very early 70's that has continued to perform with no maintenance at all is my Crown IC-150 pre-amp. If I get half the life out of this amp I should be in an old folks home by then. I'm not trying to sway anyone here, just presenting the facts as I see them. Pro amps are every bit as good as the high end consumer amps. The only difference is there priced right! One more thing this amp's signal to noise ratio is excellent. Dead quite between tracks.

 

[wire]

Well, I'll tell you compared to my Onkyo M504 power amp my new Crown XTI-2000 amp simply reproduces music with the kind of muscle one associates with a live performance. I get much tighter, deep, dry bass. To be honest the top end seems a little more sterile, but hardly what I would call harsh. Maybe a better word would be analytical. All in all I see no reason to look at a very expensive consumer amp again. I was very skeptical before I bought this amp myself, and I posted on many boards before buying. I have listened to live music for many years. My brother was a jazz guitarist for 35 years. His very good friend Gene Palumbo went on to arrange, and conduct for Judy Garland for a couple years before her death. I believe I have a well trained ear, and what it hears is very neutral reproduction. I'm sure a lot of these $5000.00 amps are excellent and produce better specs, but to tell you the truth after hearing Krell, Threshold, and some H/K Citations over the years, this Crown stacks right up there with the best of them. Even the fan which I thought was going to be the big issue has not come on once that I can tell. I'm sure under laboratory listening conditions, these high end consumer amps may reveal more detail, but I listen in my living-room. So far I feel like I stole this amp for $699.00. I'll never run out of headroom at 475 watts per channel, and it will probably outlast most consumer amps. In the past I personally owned a Phase Linear 400 series 2, H/K Citation 16, and an Onkyo M504. Each amp failed for one reason or another within a 8 years span. I know non of these where ultra high end, but they represented a good buy in their day, and were not exactly cheap. The only component I have from the very early 70's that has continued to perform with no maintenance at all is my Crown IC-150 pre-amp. If I get half the life out of this amp I should be in an old folks home by then. I'm not trying to sway anyone here, just presenting the facts as I see them. Pro amps are every bit as good as the high end consumer amps. The only difference is there priced right! One more thing this amp's signal to noise ratio is excellent. Dead quite between tracks.

My Bryston is a Pro amp . No difference than the home amp and is over 20 years old and still as good as new .

 

[dave1490]

My Bryston is a Pro amp . No difference than the home amp and is over 20 years old and still as good as new .

i get nothin but pro amp,s had a bose 1801 now 2 bryston,s all with .01 thd.wouldn,t mind a crown MA-5002VZ macro-teck.@1300watts per channel 8ohm,s.should make thing,s interesting.


http://www.crownaudio.com/amp_htm/maspec_2.htm

 

[Tony3d]

i get nothin but pro amp,s had a bose 1801 now 2 bryston,s all with .01 thd.wouldn,t mind a crown MA-5002VZ macro-teck.@1300watts per channel 8ohm,s.should make thing,s interesting.


http://www.crownaudio.com/amp_htm/maspec_2.htm

You got it. I really don't understand what these people have against pro amps. If it's the price that puts them off one must remember the list is $1139.00. Crown and other pro amps are able to sell at this price because of the quantity they make. I am very impressed with this amp! So much so I sold my Mint Onkyo M504. The amp is rated at 475 watts per channel at 1000hz, but still puts out 412 watts from 20 to 20,000! I asked Crown about The THD, and The maximum THD is .5 into 4 or 8 ohms, and 1% into 2 ohms. That is worst case, according to Crown it typically runs .1 under clipping into 8. The signal to noise is very impressive real world. This is one powerful amp. It seems to never run dry, and the low end is glorious! With built in DSP, and Crown reliablity this amp is just a steel. I'll never look back!

 

[Bassman2]

Well, I'll tell you compared to my Onkyo M504 power amp my new Crown XTI-2000 amp simply reproduces music with the kind of muscle one associates with a live performance. I get much tighter, deep, dry bass. To be honest the top end seems a little more sterile, but hardly what I would call harsh. Maybe a better word would be analytical. All in all I see no reason to look at a very expensive consumer amp again. I was very skeptical before I bought this amp myself, and I posted on many boards before buying. I have listened to live music for many years. My brother was a jazz guitarist for 35 years. His very good friend Gene Palumbo went on to arrange, and conduct for Judy Garland for a couple years before her death. I believe I have a well trained ear, and what it hears is very neutral reproduction. I'm sure a lot of these $5000.00 amps are excellent and produce better specs, but to tell you the truth after hearing Krell, Threshold, and some H/K Citations over the years, this Crown stacks right up there with the best of them. Even the fan which I thought was going to be the big issue has not come on once that I can tell. I'm sure under laboratory listening conditions, these high end consumer amps may reveal more detail, but I listen in my living-room. So far I feel like I stole this amp for $699.00. I'll never run out of headroom at 475 watts per channel, and it will probably outlast most consumer amps. In the past I personally owned a Phase Linear 400 series 2, H/K Citation 16, and an Onkyo M504. Each amp failed for one reason or another within a 8 years span. I know non of these where ultra high end, but they represented a good buy in their day, and were not exactly cheap. The only component I have from the very early 70's that has continued to perform with no maintenance at all is my Crown IC-150 pre-amp. If I get half the life out of this amp I should be in an old folks home by then. I'm not trying to sway anyone here, just presenting the facts as I see them. Pro amps are every bit as good as the high end consumer amps. The only difference is there priced right! One more thing this amp's signal to noise ratio is excellent. Dead quite between tracks.

I also grew up around a lot of musicians in high school who also being audio enthusiasts always said why buy a "stereo" when you can buy the real thing? Meaning the same amplification used for live music. While it made sense for loud rock music at parties, I always thought that there were problems with this idea.

Over the intervening 30+ years I've always thought about this idea as I played gigs or sat in the audience listening to the usually awful sound blaring out of the PA system. So I've held off on buying one of these amps, while I know a lot had to do with the PA monitors and the overall setup.

I am very intrigued by what you are saying here and in fact just spent the last half hour price shopping the whole Crown line of amps to see what falls into my future budget. The XTi-1000 looks like a contender especially since I think 200 watts would be plenty and is all my speakers can handle.

But what about the clean power aspect of these beasts? judging by the specs and my ears at most gigs they don't seem to be smooth and undistorted enough, but I realize that this could be the application and not the amp.

 

[mcBaby]

A good amplifier has a crystal clear sound quality.


__________________
Lito
McIntosh MC252 - Get the MC252 Power Amplifier Catalog by McIntosh Laboratory, Inc.

 

[Seth=L]

A good amplifier has a crystal clear sound quality.


__________________
Lito
McIntosh MC252 - Get the MC252 Power Amplifier Catalog by McIntosh Laboratory, Inc.

Any well designed and built amp should do this, respectively
(all dependant on the loads imposed on said amp)

 

[Nuglets]

I've never regretted purchasing my pro amp. It can drive my speaker's quite loud and when compared to my RX-V1400's internal amplifier it sounds very similar until I begin to reach the RX-V's limitations and the PV keeps pumping more and more power.

 

[gene]

I also grew up around a lot of musicians in high school who also being audio enthusiasts always said why buy a "stereo" when you can buy the real thing? Meaning the same amplification used for live music. While it made sense for loud rock music at parties, I always thought that there were problems with this idea.

Over the intervening 30+ years I've always thought about this idea as I played gigs or sat in the audience listening to the usually awful sound blaring out of the PA system. So I've held off on buying one of these amps, while I know a lot had to do with the PA monitors and the overall setup.

I am very intrigued by what you are saying here and in fact just spent the last half hour price shopping the whole Crown line of amps to see what falls into my future budget. The XTi-1000 looks like a contender especially since I think 200 watts would be plenty and is all my speakers can handle.

Its usually NOT a good idea to use pro gear for home theater. Pro gear is designed mostly for sound reinforcement - very high powerful amplifiers whose sole purpose is to produce a alot of sound at the expense of a high noise floor and overall fidelity. In a concert venue this is appropriate. In a home theater, where the listener is much closer to the speakers and in an acoustically controlled enviroment, this is usually NOT an appropriate choice when fidelity is concerned.

If you look at the URL to the Crown amp that was posted eariler in this thread, you will note the amp has an SNR of 105dB at rated power. In this case, the amps rated power is 1300 watts into 8 ohms. To scale that back to 1 watt (where the amp spends most of its time in a typical home theater), you get a very mediocre SNR of 73dB. A typically good home theater amp will run between 80-90dB at 1 watt.

The same applies for speakers. Most pro speakers are designed for very narrow dispersion, hence long throw horns are utilized - again appropriate for a large concert venue but NOT a home theater.

 

[Bassman2]

Its usually NOT a good idea to use pro gear for home theater. Pro gear is designed mostly for sound reinforcement - very high powerful amplifiers whose sole purpose is to produce a alot of sound at the expense of a high noise floor and overall fidelity. In a concert venue this is appropriate. In a home theater, where the listener is much closer to the speakers and in an acoustically controlled enviroment, this is usually NOT an appropriate choice when fidelity is concerned.

If you look at the URL to the Crown amp that was posted eariler in this thread, you will note the amp has an SNR of 105dB at rated power. In this case, the amps rated power is 1300 watts into 8 ohms. To scale that back to 1 watt (where the amp spends most of its time in a typical home theater), you get a very mediocre SNR of 73dB. A typically good home theater amp will run between 80-90dB at 1 watt.

The same applies for speakers. Most pro speakers are designed for very narrow dispersion, hence long throw horns are utilized - again appropriate for a large concert venue but NOT a home theater.

Thanks Gene, that's what I thought. I've made quite a few friends AND enemy's with other peoples sound-men because I cant stand to see a great band have their sound destroyed by an awful mix at the board and poor speaker placement. Along the way I've realized the limitations of the gear, it's loud, but that's about it most of the time. I do know one guy who has worked with the likes of Pete Townsend, Graham Parsons, John Entwistle, Jack Bruce, Peter Frampton and the Who, as well as some other names, and this guy really makes you think you're listening to a studio recording for the most part so it can be done at least to a great extent. But it's STILL not as clean as home hi fi. I thought maybe the newer crown amps were better for home use but probably not.

 

[Tony3d]

Its usually NOT a good idea to use pro gear for home theater. Pro gear is designed mostly for sound reinforcement - very high powerful amplifiers whose sole purpose is to produce a alot of sound at the expense of a high noise floor and overall fidelity. In a concert venue this is appropriate. In a home theater, where the listener is much closer to the speakers and in an acoustically controlled enviroment, this is usually NOT an appropriate choice when fidelity is concerned.

If you look at the URL to the Crown amp that was posted eariler in this thread, you will note the amp has an SNR of 105dB at rated power. In this case, the amps rated power is 1300 watts into 8 ohms. To scale that back to 1 watt (where the amp spends most of its time in a typical home theater), you get a very mediocre SNR of 73dB. A typically good home theater amp will run between 80-90dB at 1 watt.

The same applies for speakers. Most pro speakers are designed for very narrow dispersion, hence long throw horns are utilized - again appropriate for a large concert venue but NOT a home theater.

I can tell you this much my XTI-2000 is at least as quite as my Onkyo m504. If I turn the gains all the way up on the 2000 I have to get within 3 feet of my B/W 802's to here even the slightest amount of hiss. There is absolutely no hum or buzz either. If you read my post you would have seen that this amp's S/N is dead quite at any volume level. Sorry guys I just don't buy the fallacy that consumer amps out perform pro amps. Years ago that may have been true, but not today. Say what you want, but until you hear one of these amps I wouldn't knock them. Their simply excellent sounding beasts. Period! There was a day I would have never bought a pro amp. Today I'll never look back.I don't know about other pro amps, but these Crowns are very impressive!

 

[finalcut82]

Ditto for the latest version of the Crown XLS 602 amp. Sound is outstanding driving Polk SDA SRS 1.2 TL speakers. Paid 360.00 for the amp after rebate and included 14 gauge, 25 ft speaker wire with speakon connectors.

 

[fmw]

Good question. In the small world of DIY speaker building, I once met an electrical engineer named Bob Cordell who had past experience in audio amplifier design. There is a brief interview of him on the internet http://members.aol.com/_ht_a/pjay99/guruscordell.htm where he describes what he thinks makes a good amp. Take the time to read it, and tell us whether it answers any of your questions.

I had previously believed that "big iron" amps were overkill, but in a series of demonstrations, Bob convinced me that amps, in the 150+ watt per channel range, were needed to play most music at moderate or higher levels through speakers that are moderately or more efficient without any clipping. Despite the common use of the term "amplifier clippping" most of us (myself included) do not recognize what clipping sounds like.

He is probably not a home theater guy. Home theaters are meant to have powered subwoofers and the amps in the powered subwoofers supply the great majority of power needed to reproduce movie soundtracks. The mids and highs require very little power in comparison. That's why you rarely see receivers over 100 wpc. 100 wpc is overkill for the typical home theater system. My own home theater would be just fine with 10 wpc for the mids and highs.

 

[Seth=L]

Pro amps have lots of headroom typically. If you have hard to drive speakers (low impedance, inefficient) that can handle large amounts of power a Pro amp can be a good cost effective alternative to typical home gear. On average we don't use more than 10 watts, often less, but transients may require more power than a receiver can deliver.