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Topic: Multichannel amplifiers (Read 7836 times) previous topic - next topic
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Multichannel amplifiers

Since I bought my new speakers, I've been looking around for a more powerful amplifier. Unfortunately it seems that those bloody surround amplifiers have taken over the market completely. My local hi-fi store only sells one brand of stereo amplifier, with that one being an insanely expensive high-end model.

So very briefly I considered whether I should go with the flow and buy a surround amplifier, also known as a movie toy. I have certain prejudices and bad experiences against them, so I would like to hear your opinion about those things.

Can surround (6-ch Dolby Digital) amplifiers honestly compete with stereo amplifiers for normal stereo music listening? A rather lot of people are using a Dolby amp for stereo music and have seemingly no problems with that.

One time I went to audition a pretty heavy-duty H/K surround amplifier at my local hi-fi store. The store had exactly the same speakers as I do available for testing. We hooked the amplifier to stereo mode for CD listening. Almost immediately after pressing the play button I asked the salesman whether that thing had Loudness on. He replied no. Then I asked whether someone has turned the bass and treble knobs way up, or was it using an equalizer preset. He said no. I walked around the room to see whether it was room interference, but no. That damned thing sounded frighteningly like a cheap boombox with Loudness (or MegaBass or whatever) on. Another, a much lower-end surround amplifier sounded even worse, this time listened in a different room. My friend has also experienced this "megabass" problem with a few surround amplifiers. Is this effect common amongst multichannel amplifiers or was that just bad luck?

Even if all that had been a placebo effect or bad luck, there are still some theoretical issues I wonder about surround amplifiers. What kind of compromises usually have to be made in a multichannel amplifier? They have to fit six or more power terminals to the same space that previously contained two. And what about power distribution and capacity? My current amplifier gives about 2 x 30 W @ 8 Ohms with high distortion levels. I could use about 80 W @ 8 ohms per channel of relatively clean power with high current yield, meaning ~160 W @ 4 ohm, ~300 W @ 2 ohm and so on.

Could a low-end surround amplifier possibly be able to deliver that load in stereo mode? Naturally almost all of them are rated 5 x 100 W or more, but I consider that as a very unamusing joke..

Multichannel amplifiers

Reply #1 –
Surround sound starts with the basic two channels of stereo and goes from there.  If you are playing a two channel stereo source through the amp, and have turned off all the surround channels and speakers you will be listening to "old-fashioned" stereo.      B)
Nov schmoz kapop.

Multichannel amplifiers

Reply #2 –
In my (limited) experience with multichannel amps I have had the same experience. I combat the problem by using an arcam 8 power amp to drive the front l/r speakers, bypassing the amps in my yamaha 5.1 reciever.

Movie and music both sound great, tho music is my main concern.

I don't think it's a hard and fast rule that multichannel amps can't perform as well with stereo music as a stereo amp.

Multichannel amplifiers

Reply #3 –
There's still a great selection of oldy-but-goody amplifiers
available on eBay, if your not opposed to going that route.

Dex

Multichannel amplifiers

Reply #4 –
Quote
There's still a great selection of oldy-but-goody amplifiers
available on eBay, if your not opposed to going that route.

Yes, I'm currently browsing for second-hand stereo amplifiers on my local finnish eBay-lookalike. Too bad that these folks seem to know the value of their equipment, no good used amplifier is on sale under 200 €.

Probably my best bet would indeed be buying a good, powerful, second-hand amplifier. I can keep my current one should I ever want an amplifier for some rear speakers

Multichannel amplifiers

Reply #5 –
Quote
Can surround (6-ch Dolby Digital) amplifiers honestly compete with stereo amplifiers for normal stereo music listening? A rather lot of people are using a Dolby amp for stereo music and have seemingly no problems with that.

According to German Hifi-magazines: NOPE. I took a short look in the top1000 of stereoplay and here's what my conclusion of it. Stereoplay rated the soundquality of both: multichannel and stereo of surround receivers. The stereo-soundquality rating of multichannel amps is comparable to the stereo sound-qualtiy of stereo amps. That means that e.g. 50points represent the same quality for both amps.

A 1000€ multichannel-amp sounds as good as a 500€stereo-only amp. But please don't take this rating too serious. It differs from brand to brand and model to model. You should draw the conclusion that if you only want stereo a multichannel amp is a waste of money.
I love the moderators.

Multichannel amplifiers

Reply #6 –
From my experience, multichannel amps were specificaly designed with the the low-end commercial speakers in mind. They seem to be made heavey on the bass and treble, neglecting the mids. I use NAD stereo amps for music and the multichannel only for movies. The multichannel seriously seems to be equalizing the sound coming from the CD player, I don't think its because of bad design. I think it is intentional. Therefore, if you have good speakers, maybe using a multichannel amp is not the best way to go. Just my experience. 

Of course, if you are willing to spend enough money, I am sure there are great multichannels out there too.

Multichannel amplifiers

Reply #7 –
Quite a few companies still make stereo equipment. You may need to look to "higher-end" companies though. A company to which I'm a satisfied customer is NAD. They make very nice amps and offer excellent performance for the price. (NAD is effectively a Canadian brand although it started elsewhere).

NAD Electronics

Multichannel amplifiers

Reply #8 –
Well, it depends on what you mean by "multi-channel amplifier". If you mean just an amplifier, then yes, they are just as good as a good dedicated 2-channel amp. When you're trying to compare 2-channel A/V receivers to surround sound ones though, then you really have to look at the much more expensive receivers to get something that is "equal" simply because of the larger amount of electronics that they have to put into a similar-sized box while keeping a competitive price. Really, what you get should depend very much on what your speakers can handle/deserve. If you've got very efficient speakers, then often times a decent receiver will do you fine, but if you've got electrostats or something awfully fancy, then you better get the amp(s) to match.

Considering the fact that a receiver is essentially a pre-amp and amp in the same box with, often times video components sharing space as well, I don't think you'll ever get the "best that you can get" from a receiver. A good pre-amp/amp system though, costs a heck of a lot more.

Multichannel amplifiers

Reply #9 –
A little tale about amplifier sound & quality:

At some of the rec.audio newsgroups, an audiophile equipment salesman and an ABX hobbyist agreed to do a test: the salesman would try to tell his powerful monoblock amplifiers from a cheap yamaha integrated amplifier from the ABX hobbyist, just by listening, by means of a hardware ABX box. The salesman said he would do in a breeze.

The test day arrived, and the test was carried out. Result? The audiophile *coulnd't* tell each one from another. This didn't surprise the ABX hobbyist, since he had performed many similar tests before and nobody had had success in similar tests. Some time after that, the salesman left the audio newsgroups, but the ABX hobbyist is still around.

...

Well, the thing is that this is a true story  , and it suggests it's not difficult or expensive at all to build audibly transparent amplifiers.

Multichannel amplifiers

Reply #10 –
As to niktheblak experinece, it is very possible that the shop acoustics had a definitive influence in the perceived differences, even when he listened at several positions.

Multichannel amplifiers

Reply #11 –
Quote
As to niktheblak experinece, it is very possible that the shop acoustics had a definitive influence in the perceived differences, even when he listened at several positions.

Yes, I never excluded that option and I still consider it very possible since the amplifier I listened was pretty high-grade.

Agreed, pretty much everything an amplifier can do is to deliver enough current. But if the consumer-grade 6ch amplifiers have an intentional built-in "MegaBass", like it seems they do, that's definetely a reason to avoid them.

@RiskyP

Those NAD amplifiers look really good. I was pretty impressed by their concise specification system, they aren't the kind of company that says "this amplifier delivers 2 x 500 W. [span style='font-size:8pt;line-height:100%']*cough* during a nanosecond period with THD of 95% *cough*.[/span]"

Edit:

How that FONT tag got in there...

Multichannel amplifiers

Reply #12 –
Hmm... in theory, both a stereo amp and a more-than-stereo amp should sound the same. This is because a stereo amp is just a two-channel amp, while a home theater amp is 5 channels. DD and DTS both have full-bandwidth surrounds (afaik) so any good home theater amp will just be 5 amps in one box. You don't really get anything going with a monoblock since all you are doing is placing the amp boards in different boxes. The only difference might be in the power supply, but again, it all depends on how it's built.

I just don't believe that you listened to a "good" home theater amp/receiver. Maybe it was bad acoustics, or maybe the store has a hidden equalizer somewhere. Remember that the normal consumer loves the "happy face" EQ setting. You don't have to get anything super fancy like Krell or McIntosh. Hell, just a good Pioneer or Yamaha or Denon will do the trick. Of course, be sure to turn off any DSP tricks they might have if you just want plain-vanilla stereo. I don't know of any amplifier that actually EQs the sound, well maybe except Bose.

Just buy one, take it home, play with it, and if you don't like it just take it back!

Multichannel amplifiers

Reply #13 –
Quote
Well, the thing is that this is a true story, and it suggests it's not difficult or expensive at all to build audibly transparent amplifiers.

The story interested me as I have often thought that an amplifier doesn't really have to "do" much.

Why are there many different amplifiers available that sound different to each other?

* edit: can't spell today

Multichannel amplifiers

Reply #14 –
Let's have some common sense here. If built to the same price, the piece of equipment that contains 2 amp channels will be higher quality than the piece that contains 6 amp channels and an AV switching system! Either that, or the 2 channel amp manufacturer is making a larger profit!

I don't buy the "all amps sound the same" argument. Certainly a lot sound very very similar. But there are some real dogs out there, and some real gems. Some lack (or have) the sound of having lots of instantaneous power, and this doesn't seem to be related to the quoted power figures, which are usually RMS (when they're not in fake units!).

Though it's theoretically easy to make an excellent amp, there are still some wide (measurable) performance variations out there. Bizarre but measurable things like RF immunity really do matter - you never see this measured in Hi-Fi mags though.


I've had to use a 6-channel amp that was a dog, and a 2-channel amp that was a gem, but that may be coincidence.


Cheers,
David.

Multichannel amplifiers

Reply #15 –
Another thing to consider possibly is that most recievers have their own DAC inside. Many will be tempted to use the digital out of their CD player and let the DAC in in the amp do the converting instead of the DAC in the CD player. If you have a good CD player, I swear to you, this makes a world of a difference.

When I bought my CD player, the Burr-Brown DAC inside was so much more superior to that in my DVD player/reciever, that I could hardly believe the results. From my experience, the 3 most important factors regarding the performance of a sound system (this is assuming transistor amplifiers) is the loudspeaker, the DAC and the room acoustics.

If you have a good CD player make sure to use the analog out and let that reciever do the amplification part only.

@niktheblak:

If you go with NAD, I promise you (this is not a dealer talking) you won't regret it. I have one of their amps from 1985 as well, and even that is (seemingly) much-much better than the Onkyo receiver that I own.

@KikeG:

You are right, well designed transistor amps don't really color sounds very much (perhaps at low AC voltages) but many designers, I feel, intentionally make non-linear amps. These days, most people are more impressed by non-linear home theater equipment, of course this does not go for the audiophile crowd. From my experience, Yamaha actually makes well-designed receivers, maybe that is part of it?

I've never seen curves for my Onkyo receiver, but it was constantly in the home theater magazines in the US for months, it was rated as Stereophile's class A and was among very expensive units. Yet, when I play a classical concert on it, and compare it to the same performance on the NAD from 1985, the NAD makes it sound more realistic.

I can't prove anything, but I wouldn't be surprised if this difference (if it really exists) would be due to intentional design.

Multichannel amplifiers

Reply #16 –
@2B

I am finishing my bachelors in Electrical Engineering Technology, and I can tell you that designing an audio amp is not difficult at all. With the level of integration we have now, it basically boils down to a few ICs and a power supply. In reality, the only difficult part is building a beefy enough power supply to handle all the current, and that only really affects the bass. Tweeters don't take much power to move air.

And yes, almost all "audiophile" eq out there is way overpriced. You are paying from a brand name. It is very likely that a $5k receiver is using the exact same electronics inside as a prosumer $500 is. Do you really think a BWM Z8 costs $100k to manufacture? Yes, board design is different, but designing a 20kHz system is trivial nowadays.

The differences come when dealing with digital circuits. Those have a lot of high-speed components inside, but again they are not THAT complicated. I mean, if you want complicated look at RF design. Maybe the $50 Aiwa boombox/hometheater receiver will sound like crap, but I am sure that any of the "higher-end" prosumer devices will be just fine. And again, I stress that people do not use the special DSP effects that most of these devices have. DD and DTS have a standard chipset situation, so that a DD or DTS stream will decode the same across all brands. Ideally, the decoder would then send the analog signal to a bank of capable amplifier to be sent out to your speakers.

Multichannel amplifiers

Reply #17 –
Quote
From my experience, the 3 most important factors regarding the performance of a sound system (this is assuming transistor amplifiers) is the loudspeaker, the DAC and the room acoustics.

Well, speakers and room acoustics have much more influence than the DAC, by far. Also, good DACs can be very cheap nowadays.

Multichannel amplifiers

Reply #18 –
@ KikeG

I won't refute that observation, but the new DAC made a very significant impact in my system.

Even though a DAC might be cheap to make (I don't know), most manufacturers don't use good DACs. I think this is obvious if you compare CD players.

EDIT: Btw, if there were some cheap way to properly ABX my equipment, I would be willing to take part in such a thing.

Multichannel amplifiers

Reply #19 –
Quote
I am finishing my bachelors in Electrical Engineering Technology, and I can tell you that designing an audio amp is not difficult at all. With the level of integration we have now, it basically boils down to a few ICs and a power supply. In reality, the only difficult part is building a beefy enough power supply to handle all the current, and that only really affects the bass. Tweeters don't take much power to move air.

And yes, almost all "audiophile" eq out there is way overpriced. You are paying from a brand name. It is very likely that a $5k receiver is using the exact same electronics inside as a prosumer $500 is. Do you really think a BWM Z8 costs $100k to manufacture? Yes, board design is different, but designing a 20kHz system is trivial nowadays.

I'm sorry, but you've over-simplified this to the point of being meaningless.  Lets consider this from the point of just one resistor.  Two identical amplifier circuits but one uses a larger negative-feedback (NFB) resistor than the other.  The one with the smaller resistor, (more NFB), will have a much lower THD on paper at the cost of a lower dynamic range in listening.  I can't tell you how many people I sold audio to, who would select the .001 THD amp over the .1 THD amp, all else be damned.  There was just no telling them that THD wasn't the end-all spec with which to make their decision on.

And IC output stages are to discrete components, what Xing encoders are to Lame.

There's a helluva lot more to amp design than schematics and theory. The amplifier design in my clock radio is very similiar to the design in any Mark Levinson amp, but, power supply considerations not-withstanding, they are not the same animal.

Dex

Multichannel amplifiers

Reply #20 –
I agree.

Multichannel amplifiers

Reply #21 –
It seems to me that a 6 channel amplifier is the same thing as 3 stereo amplifiers, a DAC, a DSP and some plugs (digital connections being quite expensive). Thus there should be a difference in price for the same stereo content.

Multichannel amplifiers

Reply #22 –
@Dex

Yeah, I guess I simplified too much, but this is what I was trying to get across:

1. It is not "extremely difficult" to design a good audio amplifier. There is no reason why one should pay a premium for a brand name. And like lossy audio codecs, it is an issue of diminishing returns. You can keep increasing the bitrate, but once you are past the point of transparency, or once you are getting a higher bitrate with lossy than you would get with lossless, then you stop throwing bits at the problem. Same thing with the whole audio chain. If you can't hear 1% distortion, then there is no point for spending 3x the amount in an amp with 0.1% distortion.

2. There is no intrinsic deficiency in a multi-channel amplifier, since it is just a "stereo" amplifier with more channels. For example, a 6-channel amp can be just 3 "stereo" amps in one box.

Multichannel amplifiers

Reply #23 –
Hey LoKi;  Your point is well taken.  Sometimes, talking about "good" audio is
like talking about "beautiful" women.  To each his/her own!

I'll be back!    Dex

Multichannel amplifiers

Reply #24 –
Check www.parasound.com for good amps: www.parasound.com

Off-topic:

Let's assume that I have some large floorstander speakers, 86dB/V, 4 Ohm nominal impedance and dipping to 1.6 Ohm on heavy bass passages. As you can see, they're pretty insensitive & demanding.

I tried a SONY stereo integrated amp on them: 2x'100' power rating, IC output stage. I won't get into stuff like dynamics, but I'll just say that the damn thing went into protection mode whenever I tried to play my speakers at a decent volume. Luckily for it, it had protection for overload or it would have fried.

So I think that a good amp should have:
- flat frequency response;
-stability into driving difficult impedance loads;
-instant current capability - you'd be surprised to hear what 2x200W instead of 2x90W did in my case (both ReVox amps)...