Crown vs Rotel

[Keith raufer]

Hi Everyone, I need some further information on different types of amplifiers. Looking at comparing a Rotel RB1090 2x340 watt at 8ohm class A/B hifi amp vs a Crown XLS2002 375 watt at 8ohm class D pro amp with .775 volt input sensitivity. Both fed unbalanced signal from my Yamaha receiver. Size is a huge deal given the massive difference between the 2 and cost but how would they compare in sound? My speakers like/need power (Svs ultra towers)


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[Verdinut]

The recommended amplifier power for those speakers is between 20 and 300 watts/ch.
A good alternative would be a QSC RMX1450a (260 w/ch) or the RMX2450 (450 w/ch at 8 ohms. They are reasonably priced and operate as Class A/B amps which are preferable to a Class D amp.
These are also built like tanks and will outlast a Crown.

I am inclined to think that the 1450a Model would be sufficient. Beforehand, I need answers to the following questions:
1. What is the size of your listening room?
2. At what sound level do you listen to music and films?
3. What will be your listening distance from your speakers?

 

[Keith raufer]

1. What is the size of your listening room?
Large open plan room

2. At what sound level do you listen to music and films? Mostly movies between -5&-10db

3. What will be your listening distance from your speakers
4.5 meters




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[panteragstk]

If they sound different then something isn't right. The input voltage can play a role in that, but I have the first gen drivecore and have never had an issue with them.

I would be very surprised if the crown didn't sound every bit as good as the rotel.

 

[Keith raufer]

If they sound different then something isn't right. The input voltage can play a role in that, but I have the first gen drivecore and have never had an issue with them.

I would be very surprised if the crown didn't sound every bit as good as the rotel.

So no real difference going between a hifi amp to pro style??


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[Verdinut]

There should not be an appreciable difference between a Class A/B Pro Audio amp and the Rotel.
IMO, either the RMX1450a or the RMX2450a would be a good choice. They have excellent honest specs.
In some pro audio gear stores, it's possible to rent one and you could see for yourself.

 

[panteragstk]

So no real difference going between a hifi amp to pro style??


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Some may argue to the contrary, but a good amp is a good amp. Hi-fi and pro labels need not apply.

Basically, if it sounds good and you are happy, why worry?

 

[panteragstk]

There should not be an appreciable difference between a Class A/B Pro Audio amp and the Rotel.
IMO, either the RMX1450a or the RMX2450a would be a good choice. They have excellent honest specs.
In some pro audio gear stores, it's possible to rent one and you could see for yourself.

Depending on the store (and whether or not you feel like putting in the effort) you could take your speakers and hook them up.

Also, QSC and Crown have been making great amps for a lot of years. They are among the most trusted names in the business. Can't go wrong with either.

 

[PENG]

Unless you listen to only classical music, for pops, rocks, even jazz amplifier music in live venues or recording studios, pro amps would be involved in one way/form or another. So in theory it depends while in practice, there will most likely be no to very minute audible difference when bias is removed and the amps are well below their clipping point. I would go with the Crown's proven class Ds. I am a little, just a little concerned that the QSCs maybe bias closer to class B at higher output.

 

[Verdinut]

Unless you listen to only classical music, for pops, rocks, even jazz amplifier music in live venues or recording studios, pro amps would be involved in one way/form or another. So in theory it depends while in practice, there will most likely be no to very minute audible difference when bias is removed and the amps are well below their clipping point. I would go with the Crown's proven class Ds. I am a little, just a little concerned that the QSCs maybe bias closer to class B at higher output.

ALL Class A/B amplifiers work in Class B at higher outputs.

 

[lovinthehd]

No, I read about that too, but that is not always true, I guess we both know not everything said online is correct.

Can you expand on this? You're saying what about an A/B amp at higher output levels, it stays in A rather than transitioning to B? I've always understood an A/B amp operates in A for the lower end of the output range, transitioning to B after that. In these examples of not always true when do they transition to B?

 

[ski2xblack]

So no real difference going between a hifi amp to pro style?

No, although there are many pro amps whose s/n specs are inferior to consumer gear (low noise is not a priority in live reinforcement, for example, but it is very important in the home environment). The Crown in question sports specifications that are on par with consumer amps.

Verdinut, class A/B amps, by definition, conduct slightly more than 180 degrees. They still do that, even at high power levels (they don't somehow switch to class B operation). Class B is inappropriate for audio purposes.

http://sound.whsites.net/articles/amp-classes.htm

 

[PENG]

ALL Class A/B amplifiers work in Class B at higher outputs.

Not really, I read about that too, but that is not always the case. I guess we both know not everything said online is correct. It depends on the bias control circuitry. IMO, a real class AB should be biased so there is always an overlap at the crossover point even at rated output, to minimize crossover distortions.

 

[PENG]

For example, in this article: http://www.audioholics.com/audio-amplifier/amplifier-classes, it explains class AB in very simple terms:

"Class A/B
Class A/B, as one might deduce, combines the best of Class A and Class B in order to create an amplifier without the drawbacks of either. Thanks to this combination of strengths, Class A/B amplifiers largely dominate the consumer market. So how did they do it? The solution is actually fairly simple in concept: where Class B utilizes a push/pull arrangement with each half of the output stage conducting for 180 degrees, Class A/B amplifiers bump that up to ~181-200 degrees. By doing this, there is far less potential for a “gap” in the cycle to occur, and consequently, crossover distortion is pushed down to the point where it’s of no consequence."

So even if the bias is there for the output stage to conduct for 181 degrees, it can qualify as class AB. Conducting for 181 degrees would indicate the design is almost class B, or barely class AB. It is part of the balancing act in trying to optimize distortions vs efficiency.

I will not knowingly buy class AB amps that runs almost like class B amps at higher output.

 

[PENG]

Can you expand on this? You're saying what about an A/B amp at higher output levels, it stays in A rather than transitioning to B? I've always understood an A/B amp operates in A for the lower end of the output range, transitioning to B after that. In these examples of not always true when do they transition to B?

I know, it's the internet thing, please see post#12 and #14 and best follow the link to the AH article.
One reason why I don't always mind amps that runs warmer is that as long as the extra heat is from being bias for a larger conducting angle and not due to poor heat dissipation. I prefer the theoretical lower crossover distortions than overall amp efficiency.

 

[Verdinut]

I know, it's the internet thing, please see post#12 and #14 and best follow the link to the AH article.
One reason why I don't always mind amps that runs warmer is that as long as the extra heat is from being bias for a larger conducting angle and not due to poor heat dissipation. I prefer the theoretical lower crossover distortions than overall amp efficiency.

Crossover distortion is a harmonic distortion of the 3rd and 5th order. But if an amplifier is producing a THD of only 0.1% at rated power, please explain how you could hear it. I understand that distortion under 2% is undetected by the human hear.
Also, why wouldn't a solidly established company like QSC adjust the bias to the proper level, in order to reduce that crossover distortion to its minimum?
Here another article on x-over distortion: http://www.electronics-tutorials.ws/amplifier/amp_7.html

 

[ski2xblack]

But if an amplifier is producing a THD of only 0.1% at rated power, please explain how you could hear it.

You wouldn't. As for crossover distortion, specifically, it's a problem that has been solved long ago, and you won't hear any in a competently designed class a/b amp.

For that matter, you most likely wouldn't be able to tell an amp biased hard into class a operation from one that isn't.

Marketers really hit the "class a" thing hard, but the actual supporting evidence of audible superiority is severely lacking, while there is considerable evidence that amps that meet certain basic criteria, regardless of circuit topology, cannot be distinguished by ear in bias controlled listening tests.

 

[Verdinut]

Here is article from QSC: It explains how Classes B and A/B amplifiers operate. Since crossover distortion which is an annoying buzzing like sound only develops at very low output levels, while the Class A amplification is supposed to occur, it would be most likely heard and it would have to do with an improperly set bias:
https://www.qsc.com/resource-files/articles/q_ar_sys_amp_anatomyofanamplifier.pdf

 

[ski2xblack]

I would posit that an amp that exhibited buzzing noises, at any output level, is damaged.

Also, why wouldn't a solidly established company like QSC adjust the bias to the proper level, in order to reduce that crossover distortion to its minimum?

What leads you to believe they haven't done so? QSC has a decent rep, and amp design is not exactly rocket surgery.

 

[PENG]

Crossover distortion is a harmonic distortion of the 3rd and 5th order.

Again, not really, crossover distortion involves not just 3rd and 5th harmonics, but "non harmonic" ones too such as IMD.

But if an amplifier is producing a THD of only 0.1% at rated power, please explain how you could hear it. I understand that distortion under 2% is undetected by the human hear.

At rated power output it should not be a problem. I would agree 0.1% is good, but 2% seems a little much. I typically listen at less than 0.5W average with peaks to 50W or 100W absolute max, but I prefer less than 0.1% from 0.25W to rated output, whether I can detect it or not but that's just me. Many amps have more than 0.1% THD at below 0.5W output level, exactly where mine's spend most of the time doing.

Also, why wouldn't a solidly established company like QSC adjust the bias to the proper level, in order to reduce that crossover distortion to its minimum?

I never said they wouldn't, I said I was just a little concerned, seeing that their class AB amps offer very high power output to weight and price ratio. Having browsed through their website quickly, I can see that base on bang/watt for the money and specs available on their website, they are excellent values. If I were to consider one of their class AB amp I would certainly read through the fine print of their specs and google for any bench test information, and probably email them for more information too. At the moment, I guess I just feel more comfortable with Crown's class D design that they have been doing forever, that's all, but yes, QSC's maybe even better.