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bonsai171 21st February 2004 09:42 PM

pro amplifiers vs. home audio amplifiers
This might seem like a strange question, but why do people seem to prefer to buy a home audio amplifier to use for their stereo as opposed to a pro audio amplifier, such as a Crown or Behringer? It seems that pro amplifiers are much better at playing low impedances, and are less expensive considering how much wattage they put out (i.e. The Behringer EP1500 puts out 260W X 2 into 8 ohms, whereas something in home audio with similar wattage, like the Parasound Halo A21 costs tremendously more money??) Is there any real difference in sound quality?? tia

millwood 21st February 2004 10:13 PM

Re: pro amplifiers vs. home audio amplifiers
one of the reasons people buy home audio gears vs. pro gears is that home audio gears tend to be more expensive, :)


Originally posted by bonsai171
Is there any real difference in sound quality?? tia
probably not. I have heard very very good pro amps (dynacord for example).

Bink 21st February 2004 10:25 PM

Amp Shootout March 27-28 in Emeryville, California
Pro touring, install and cinema amplifiers are equipped with more protection mechanisms such as thermal, undervoltage, overcurrent, short circuit, too-low output impedance etc. Many people consider these circuits to be less than ideal for fidelity. Less is more, in other words. Straight wire with gain and all that.

I intend to measure the differences in late March when I perform an Amp Shootout. I'll compare 600wpc-into-4-ohm road-worthy amps with the Bryston 14B-SST dual monoblock amp, if Bryston is willing. The only protection I know of in the Bryston is thermal.

By the way, your Behringer amplifier example is a total 100% design rip-off of the QSC RMX line. Might as well spend the extra money and get an amp that is supported by the manufacturer. Behringer will let you twist in the wind if anything goes wrong. It's your choice...


Amp Shootout details:

sek 21st February 2004 10:35 PM



Crown or Behringer
Ouch :smash: those two names just one word apart ;)


It seems that pro amplifiers are much better at playing low impedances
That's not true in general. But in particular there are more amps that are designed (and testet) to be used with lower load impedances. I assume we are speaking of class AB amplifiers here.

The problem is this: the power that an amplifier has to deliver is determined by the (complex) load impedance of the speaker and the output voltage of the amp only.

If the amp can deliver enough current into a connected load at it's nominal output voltage in order not to violate Ohm's law I=U/R and thus P=U*U*I, it is capable of powering a speaker with this impedance. And if it's not capable of delivering enough current, well, then it's just not. Actually it all depends on the power supply and the current capability of the used output transistors.

There are two well known "cheats" in (so called) professional amplifiers:

1. Exaggerating the output stage for much more current than is needed under normal load conditions (so that temperature rises not too much under heavy overcurrent).

2. Compensating the amplifier for high frequency stability in case the damping factor gets too low (e.g. so that the amp does not start to oscillate even when negative feedback is greatly reduced).

Both these steps will leave the whole issue to the power supply. As standard BJT or MOSFET transistors are relatively cheap, it's not very difficult to build many of them into the amp (e.g. twice as much as needed for just a couple of bucks).

The "cheat" is in the fact that a power supply will drop it's voltage under load. Just calculate for yourself: A significant drop of the maximum output voltage under heavy load will lead to an inherent reduction of the maximum output power.

This phenomenon is marketed by many (so called) pro manufacturers under the term "2 Ohm Stability" and does only mean that the amplifier won't break under a 2Ohm load. But it does not mean that the amp is usable with a 2Ohm load, as this power compression does sound absolutely awful and is what lets you recognise an amp as "overdriven" or "underpowered"...


and are less expensive considering how much wattage they put out
Mass production, expected price range in the pro audio community, saving on certain design criteria, etc.

In the (so called) high end audio scene, over-dimensioning is sometimes considered a must. Whatever one might think of that phenomenon, there are arguments pro and con.

But in pro audio gear manufacturing, as in every industry, every dollar counts! If a smaller toroid is sufficient to achieve design specifications, it is likely to be used. Same applies for supply capacitors, heatsinks, connector hardware etc.

It's not that all pro gear manufacturers do so, as you'll know, there's a wide price range, from ridiculously cheap to seriously expensive...


Is there any real difference in sound quality??
Sure. Actually any PA amp with the above considerations will need active cooling with fans, and for safety and reliability reasons they are usually kept running all the time. That's one thing that doesn't sound good!

OTOH, there are amps on the pro market that just don't sound very good, and only the designers know (or even don't) why there were neccessary things left out or flaws built in...

Despite that (e.g. let's imagine you've found an amp that has good sound up to good specs and that leaves it's fans off below a certain temperature), a PA amp can sound absolutely great with any kind of speakers. Building (very good) amplifiers is said to be an art, but that applies to all amps, independent of their intended use.

I've read of people who use PA amps at home where they just installed a temperature control unit for the fans. They are kept off until they are really needed. A very good approach, as it is very likely that one will be happy with those amps for a couple of decades :D


millwood 21st February 2004 10:52 PM

a lot of the problems Sebastian highlighted also exist for the home audio market, high-end or not. so I wouldn't say that they are unique to pro audio.

as to undersized transformers, i would say that it is more of a problem for home audio market as the pro audio gear buyers tend to be a little bit more sophisticated and the applications more demanding. in the home audio market, few will push the amp / avr to their rated capacity so an undersized transformer will do far less damage.

Having seen some pro audio gears, I wouldn't say that their transformers are undersized.

sek 21st February 2004 11:06 PM


Having seen some pro audio gears, I wouldn't say that their transformers are undersized.
Great, You've seen some of the good pro audio gear :D

And in no way would I :cool:, I mean I, say that pro audio gear is worse than hifi stuff. Everytime I need some reference for a good implementation of a design concept, I search for schematics and applications on pro audio manufacturers' websites first, then on DIY hifi sources...

sam9 21st February 2004 11:31 PM

I think the principal advantages of (good) pro gear for home use are cost/watt, physical toughness (they are relativly resiliant to abuse by dumb humans) and flexability.

The disavantages tend to stem from the same considerations. They oftem achieve weight and cost reduction through the use fans and hum-drum appeareance, they often include protective circuitry (against those dumb and clumbsy humans) that unavoidably compromises noise and distortion to some degree, and they sometimes include features of little benefit for home use or which can result i home misuse.

Nonetheless, I would not dismiss them out of hand as there is a wide range of performance in home audio and there may be circumstances or work arounds offset the disadvantages of pro gear.

usekgb 22nd February 2004 01:04 AM

I think the Crown K1 and K2 work excellently in the home environment. They provide high output power, low power consumption, and no fan. my company has provided many of these amps to everyone from the Utah Symphony to high-end home theater enthusiasts to recording studios. Some other good pro amps that work in the home are the Hafler P series. They don't deliver as much power, but they sound very good. As for the lower end amps, i.e. Behringer, rate, Peavey etc., they don't belong in the home environment. They are designed for bands and D.J.'s that just can't afford a higher quality amp. The lower end amps tend to deliver less current, have more distortion, and are less reliable.

Now, the real question.......Would I use a pro amp for my citical listening? Sure I would, if it were a quality amp. Will it sound as good as a high powered Pass Labs amp? probably not. They are just different beasts. Keep in mind also, that many people consider Bryston to be pro gear. I've seen many Bryston amps in top-notch recording studios. Just my 2 cents (pence?)


bonsai171 22nd February 2004 09:23 PM

information overload!
Hi everyone, thanks for the information about the amps. It sounds like in general there are circuits inside some of these amps which are unnecessary, and could create a difference in sound. The Crown K1 and K2 look very nice, but WAY too expensive! Part of the reason that pro amps seemed attractive was their relatively low cost for the wattage. Has anybody heard of a company called Inter-m? In particular, they have an Amp called the M2000 which looks really nice (you can find it on the site). Power output into 8 ohms is 710W X 2. I would like to run the following speaker system (passive):

Morel Mdt-30 Tweeters (200W power rating)
Morel MDM-55 Dome Mids (200W power rating)
Selenium WPU1207QCF 12" woofer (500W power rating)

This system would be used for home audio. Will this amp blow the tweeters and mids since they have a much lower power rating? Also, the amp costs about $699 U.S. dollars.. Is there a better amp out there in this price range? Tia


Bink 22nd February 2004 09:54 PM

amp ratings vs. speaker ratings
Dave, you can get any amp for any speaker as long as you don't clip the amp or give the speaker too much voltage, heat or mechanical shock.

More speakers are blown from a too-weak amp than a too-strong amp. Strange, eh? Many, many more people have undersized amps and push them too hard which results in square waves being fed to the tweet. Ask any home stereo speaker repair shop which drivers are replaced more often for electrical failure and the answer will be HF drivers.

The professional sound reinforcement rule of thumb for buying amplifiers is to double the rms watt rating of the speaker. If your speaker can take 500w rms then you are shopping for a 1000w per channel amp. There's a bit of slop in this guide; you could settle for an 800w amp or splurge on a 1250w amp and still be safe. Call it 2x rms plus or minus 20%.

At home you are likely benefiting from a good deal of 'room gain' and are not listening to sustained loud music for hours. If you are primarily watchng DVDs and casually playing CDs for ambience, simply matching speaker rms to amplifier rms has made plenty of home listening rooms quite enjoyable.

If you get the bigger amp your music will sound cleaner -- the transients aren't being clipped. You will have more headroom. Typically in listening rooms there is (shhhhh) an acceptable percentage of very brief signal peaks that get clipped, limited or flattened. Going the budget route pretty much guarantees this occuring.

I say save up some extra money for the 2x rms solution. A side benefit is that your amplifier will last longer due to its not working as hard.

Regarding the Inter-M amplifiers, I have never heard one. I will be testing at least one and maybe three of the biggest models at my Amp Shootout March 27-28.

If you can wait until April 5 for your purchase, I'll have the test results for the Inter-M amplifiers available online and you can judge for yourself.

Good Luck -


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