Practical Amplifier Basics

[Seth=L]

From what I have read and heard about Emotiva amplifiers I would have to say "pass". A lot of reliability issues and they don't perform to fantastic either. They are heavy, there expensive to ship if there is a problem with it. They are inefficient (hence the weight). If you want strictly home audio amplifiers Adcom is often suggested. I would personally go with a pro amplifier from Behringer or Yamaha if I needed lots of power.

 

[TLS Guy]

Interesting thread and it has really helped me a lot. So an Emotiva XPA-5 (200Wx5 @ 8ohm and 350Wx5 @ 4ohm) seems like what I am looking for. A price I can live with what seems to be enough power to drive most speakers.

More of a theoretical question but assuming I had very inefficient mains (or some other reason to need more power) can you have multiple amps? Could you have the XPA-5 do the center and surrounds and then have a separate XPA-2 for the mains? Other than taking up more space are there any issues with this kind of setup?

If you think you need the power, that would be a good way to go.

 

[TLS Guy]

From what I have read and heard about Emotiva amplifiers I would have to say "pass". A lot of reliability issues and they don't perform to fantastic either. They are heavy, there expensive to ship if there is a problem with it. They are inefficient (hence the weight). If you want strictly home audio amplifiers Adcom is often suggested. I would personally go with a pro amplifier from Behringer or Yamaha if I needed lots of power.

At SOTU I found them to be well built amps. The failure rate is 1% which is pretty typical. I don't think there would be a problem with those over most other amps.

Unless you go class D a good amplifier will be relatively inefficient. The only way too make it more efficient is to bias the amp more heavily to class B bias, which is not a good thing.

I really do feel that class D design is going to replace all other classes for audio work.

 

[TLS Guy]

BTW- CuSO4 isn't from bad battery cable terminal design, although I agree that what they use is hardly adequate, it's because of exposure to H2SO4, often from the stud being tightened too much and cracking the rear of the lead insert by bottoming out. The leak may not be more than a tiny trickle, but that's all it needs to kill the cable and terminal(s). GM went to that version because it saved money and padded their profits. Just another example of bean counters making things worse, just so they could pray at the alter of the almighty bottom line.

It is from bad design, because the terminal is soft, and the screw and head small, so that as the terminal is tightened it becomes conical and cracks the battery terminal. Mechanics keep over tightening them to make contact. You practically always find the fixating nut already rounded off and have to take vice grips to it.

I take the screw out and repalce it with a bolt. I place a nut and large washer on the bolt and then tighten the connector down with the nut. The washer pushes against the entire surface area of the terminal. This saves a ton of grief. It should not be this way. It should have been attended to a long time ago.

The three stooges will be back for the second act next week. If they give them any public money, I will resent every cent.

We are ready for innovation. In 1900 there were about 2000 tractor companies in the US. We need about three thousand car companies and let the fittest survive.

 

[TLS Guy]

Hold on now TLS, there is NO need to be insulting. I think that both of our explainations were quite good and covered all the bases.

Nor is my education lacking, I learned all of the basics that most kids that I hear today obviously paid no attention to if their speech is anything to go by.

I didn't ask you to dumb down anything, but you should also realize that people can be educated without taking a physics course. And if it is not used in whatever you do for a living are you really going to remember it?

The idea should be to spread knowledge one way or another so that everyone can understand.

And if it is required to have a physics degree in order to understand something like a stereo system then this world is in trouble!

You do it your way & I'll do it mine.

I'm sorry if you felt I was insulting.

The fact is I'm very concerned that we heading to disaster. People are not coming close to being taught the skills necessary for the modern world. I had a particularly egregious example today, were an individual was incapable of performing a pretty straight forward service task for me because of significant knowledge deficits.

What I posted in no way requires a degree in physics to comprehend. It should be easily understandable by every high school graduate.

In Korea slightly over 50% of graduates go into scientific based further education. They are producing skilled engineers and physicists etc. On the school exam day, the South Korean air space is closed so as not to disturb the students with aircraft noise.

They are preparing for this complicated world, which is going to get exponentially more complicated as we move away from fossil fuel. A particle physicist in every car dealership is not far fetched.

All we seem to be able to produce is people to ring cash registers, and pitch sales.

I'm very concerned we will be the third world and pretty fast.

In the twin cities they have found that not quite 50% of high school students can pass the required math test. As things now stand only about 50% of students will get their high school diploma. The cry is that common sense require that the test be made simple. The Koreans would laugh until they fall off their chairs if they knew!

 

[fmw]

Interesting thread and it has really helped me a lot. So an Emotiva XPA-5 (200Wx5 @ 8ohm and 350Wx5 @ 4ohm) seems like what I am looking for. A price I can live with what seems to be enough power to drive most speakers.

More of a theoretical question but assuming I had very inefficient mains (or some other reason to need more power) can you have multiple amps? Could you have the XPA-5 do the center and surrounds and then have a separate XPA-2 for the mains? Other than taking up more space are there any issues with this kind of setup?

You can but it doesn't help. The problem is that tweeters don't need much power at all so powering them with a separate amplifier won't accomplish much. Here's some information I wrote on the subject.
http://www.foodieforums.com/otherimages/biamplification.htm

 

[TLS Guy]

You can but it doesn't help. The problem is that tweeters don't need much power at all so powering them with a separate amplifier won't accomplish much. Here's some information I wrote on the subject.
http://www.foodieforums.com/otherimages/biamplification.htm

I didn't get the sense the OP was suggesting biamping. I thought he wanted to use a five channel amp for five speakers of his 7.1 system, and use a two channel amp for his mains.

If that was a biamping question, then yes, that would be a waste of time.

 

[highfigh]

It is from bad design, because the terminal is soft, and the screw and head small, so that as the terminal is tightened it becomes conical and cracks the battery terminal. Mechanics keep over tightening them to make contact. You practically always find the fixating nut already rounded off and have to take vice grips to it.

I take the screw out and repalce it with a bolt. I place a nut and large washer on the bolt and then tighten the connector down with the nut. The washer pushes against the entire surface area of the terminal. This saves a ton of grief. It should not be this way. It should have been attended to a long time ago.

The three stooges will be back for the second act next week. If they give them any public money, I will resent every cent.

We are ready for innovation. In 1900 there were about 2000 tractor companies in the US. We need about three thousand car companies and let the fittest survive.

I did car audio for a long time and dealt with literally thousands of GM battery cables, many of which had a replacement bolt that wasn't sourced from the same place as the OEM and they were generally too long, some by a significant amount. Why, I don't know- it's not very hard to measure something of this size. Squashing soft plastic when tightening a bolt is a pretty good way to get something to go farther than it was designed for and I would bet that if the designer of this "system" were asked, they would advise against shortening the threaded end because it would reduce the holding power. Even the brass replacement bolts that had a threaded stud and nut, for making it easy to connect power cables at the battery were often too long.

My last battery needed to be replaced because the lead insert on the battery detached and not long after that, the same thing happened to the car owned by someone I know. These were the only two I have seen.

The 5/16" bolt head is A) too soft in the first place, B) about the right size for someone with the mental abilities of a clam to know that it shouldn't be over-tightened and C) too close to the metric equivalent that the wrong socket or open-end wrench is guaranteed to be used, resulting in the rounding off of the lobes. Snap-On, Craftsman and most other larger tool makes sell a specific wrench for these and it works well.

GM is the only company stupid enough to use this system. ALL other automakers and even the marine industry uses either the traditional lead or steel clamp or a large, sometimes heavy, ring terminal that goes over a stud and it secured with a large nut. I have also done marine service work and have never seen one of these on a single boat.

 

[zhimbo]

Regardless, not everyone is a math/science wiz and there are many reasons for this.

While TLS certainly earns no diplomacy points, his underlying point is that you don't need to be a 'wiz' to understand the basic concepts of electricity. The level of physics in his post would be considered trivial middle-school busy work in many countries.

 

[highfigh]

I'm sorry if you felt I was insulting.

The fact is I'm very concerned that we heading to disaster. People are not coming close to being taught the skills necessary for the modern world. I had a particularly egregious example today, were an individual was incapable of performing a pretty straight forward service task for me because of significant knowledge deficits.

What I posted in no way requires a degree in physics to comprehend. It should be easily understandable by every high school graduate.

In Korea slightly over 50% of graduates go into scientific based further education. They are producing skilled engineers and physicists etc. On the school exam day, the South Korean air space is closed so as not to disturb the students with aircraft noise.

They are preparing for this complicated world, which is going to get exponentially more complicated as we move away from fossil fuel. A particle physicist in every car dealership is not far fetched.

All we seem to be able to produce is people to ring cash registers, and pitch sales.

I'm very concerned we will be the third world and pretty fast.

In the twin cities they have found that not quite 50% of high school students can pass the required math test. As things now stand only about 50% of students will get their high school diploma. The cry is that common sense require that the test be made simple. The Koreans would laugh until they fall off their chairs if they knew!

We could spend the rest of our lives discussing the faults of the education system but IMO, too many generations of American kids have had almost no discipline. They have been allowed to do what they want, when they want and not worry about consequences. The kids don't go to school and if they do, they don't pay attention. Teachers can't discipline them or "get through to the little darlings", and when faces with dropping test scores and graduation percentages, the decision is made to make it easier to pass the class, which leads to more graduates. The drop out rate in the city of Milwaukee is over 50%. The school system budgeted for tens (if not hundreds) of millions to upgrade some of the buildings and now, only about 5 years later, these very buildings are dormant. The MKE school system budget is now in the neighborhood of $1.7B and the school board recently requested (and always receives) a 14.7% increase in funding.

As I said, not all kids are a wiz when it comes to math and science. Some are pretty good with scientific concepts and general analysis but not necessarily at math. Some go to schools that cater to the best and brightest, with the rest falling through every available crack.

Government doesn't want to tell parents that they're doing a terrible job raising their kids and most people are far to engrossed in the TV wasteland to lift a finger. "Reality TV", video games, MySpace and anything other than reading or actually thinking is much more FUN than doing something constructive.

 

[highfigh]

While TLS certainly earns no diplomacy points, his underlying point is that you don't need to be a 'wiz' to understand the basic concepts of electricity. The level of physics in his post would be considered trivial middle-school busy work in many countries.

In my HS freshman Algebra class, I sat next to a kid whose family came to the US in '69, when the USSR invaded Prague. He saw his first test score and just shook his head in disappointment at his B. I asked why, since it was only our first test and he said that he was very bored and that what we were covering was what he had done in their version of 3rd grade.

He was soon taking advanced math and science courses at Marquette University and now works for NASA.

 

[PENG]

It took me the better part of the afternoon to reset up my system once I moved to my new place.

New place? I wonder how difference your system would sound then. Would you let us know please?

 

[PENG]

Some of the speaker lines I am interested in have an impedance of 4 ohms. The TX-SR605 does not support 4 ohm speakers and it does not have pre-outs for anything but the subwoofer.

Some receivers can handle 4 ohm speakers but they still won't rate them for 4 ohms. Denon does talk about it in their FAQ. If you want to be sure, at least add a 2 or 3 channel amp using the receiver's preouts.

So if I were to purchase 4 ohm speakers I would need at least a new receiver if not an external amplifier. My question is at what level of speakers do you actually _need_ an external amplifier. From reading these and other forums it seems like certain brands of speakers are always paired with stand-alone amplifiers. If I were to purchase a receiver that is in the $1500 range such as an Onkyo TX-SR876 (140wx7 @ 8ohm) or a Denon AVR-2809CI (115wx7 @ 8ohm) can those actually power good mid-range speakers? This would be for a small room now (11x13x10) but the system would eventually be placed in a slightly larger room.

It depends a lot on the sensitivity of your speakers and the room acoustic conditions. For a 11X13X10 room, I would say the 876 is better equipped to deal with 4 ohm speakers but the 2809 should be fine too as long as the sensitivity of the speakers are not too low. Anything better than say 90 dB per watt @ 1 meter would be good.

Do Paradigm Studio 100's or Rocket floorstanders need standalone amplification? Those are 8 ohm but the Studio 100's list their max power as 210 watts. Even for a large room or if you wanted an extremely high volume can a good $1500 receiver do the job well?

The Studio 100 can play quite loud in a room much larger than yours so they could use a lot of power for sure. Your room isn't that big so a $1,500 receiver such as the Onkyo 875/6, 905/6 or Denon 3808 can do a decent job on them.

For 4 ohm speakers like Triad Gold LCR's or Thiel speakers or PSB Synchrony One's can you effectively drive those with a $1500 receiver in a 5.1 setup?

For that setup, I would go the separate route, or receiver + a 5X200W (minimum) power amp. It is just too much to expect from a $1,500 receiver.

I think part of my confusion is that you can get a $1500 receiver that can push 140wx7 that also handles all kind of processing and connectivity but a stand-alone amplifier that does 140wx8 and nothing else is $2400. Are stand-alone amplifiers like $50/foot speaker cable or are they actually so much better than the all in one AVR's?

Receivers are mass produced, separate systems are not and are therefore inherently much less cost effective to manufacture. Unlike $50/ft cables, separates can improve sound quality if you need the extra power that receivers cannot provide. If you don't need the power then you may not benefit from them because no matter how powerful the amp is, it will only produce what is needed.

 

[cfrizz]

Well Peng it does sound different since I'm went from 400sf to 670sf. I went from carpeting to hardwood floors. So needless to say, I have more room to spread out & I'm sitting much farther from my speakers.

I had to recalibrate them to accomodate the larger space. There is perhaps a little bit of brightness/echo (its hard to describe) that didn't exist in my old apt, but it isn't anything that makes me want to dump them .

At some point I will get a couple of area rugs for the place, but that is far down on the things to get list.

What is even more amazing is how different my brother's LSI 7's sound in his new house. Now that he has the space to crank them, and they are up on stands where they belong they sound like a whole different speaker! We now are really hearing what they can do, but one thing is definite in that he really now needs a sub!

New place? I wonder how difference your system would sound then. Would you let us know please?

 

[highfigh]

Well Peng it does sound different since I'm went from 400sf to 670sf. I went from carpeting to hardwood floors. So needless to say, I have more room to spread out & I'm sitting much farther from my speakers.

I had to recalibrate them to accomodate the larger space. There is perhaps a little bit of brightness/echo (its hard to describe) that didn't exist in my old apt, but it isn't anything that makes me want to dump them .

At some point I will get a couple of area rugs for the place, but that is far down on the things to get list.

What is even more amazing is how different my brother's LSI 7's sound in his new house. Now that he has the space to crank them, and they are up on stands where they belong they sound like a whole different speaker! We now are really hearing what they can do, but one thing is definite in that he really now needs a sub!

The brightness should be a major difference, not just a little bit. Carpet absorbs a huge amount, compared to hardwood floors and if you turn the system down, clap your hands, you'll hear the sound bounce for quite a while. If you can, put one speaker in a room with carpet, turn it on and listen to it. Then, cover one ear. That will be basically how a single microphone picks up the sound and the difference from room to room will be drastic.

If you have ever played racketball, think about the effect on the balls motion if the floor in the court was carpeted.

 

[PENG]

Well Peng it does sound different since I'm went from 400sf to 670sf. I went from carpeting to hardwood floors. So needless to say, I have more room to spread out & I'm sitting much farther from my speakers.

That's an increase of 67.5%. Good thing you have that Sunfire power. So all you have to do is to tame that little brightness, hopefully not too hard to do. Good excuse to buy some nice looking rugs!

Thanks for the quick response.