In my never ending quest to improve my sound I was wondering if adding a two channel amplifier (the Halo A23) to my HK AVR 645 be worth it. I don't know a whole lot about an amp added to an AVR. will it be a noticable improvement to my 2 channel listening? Does it work for home theater too, or will the fronts overwhelm the rest of the system? Any advice would be appreciated. Thanks.

To your second two questions, yes, and no. It would work fine for HT (same thing, really, when you get down to it), and if you calibrate the system properly, they'll put out the same volume as if you didn't have the amp.

I wish i knew the answer to your other question.

I beleive the general consensus is at lower volume listening, there is little to be gained by adding an amp, slight improvement in low end slightly better treble etc. but for louder listening you should find a noticeable improvement.

Ken, would you order the UPA 2 already so you can have a definitive answer for these types of questions!!!

The Halo would be 125 watts into the m22's compared to the HK's 75 conservative rating, you might gain 1-2 dB's at reference, thats it.

Alex; Ken, you have the board.

Ken; Alex, I think I'll take "Emotiva Amps" for $269 inc shipping.

Alex; Damn right you'll take it for $269 inc shipping!!

:DJust having fun Ken!

Who started this thread anyway? ...uhhh, oh yeah.

actually in my owners manual it says the 2 channel is rated at 90 watts, so it might be even less noticable. For the price of some of the better amps I've researched one would hope for a marked difference in sound quality.

To be fair, even those subjective improvements (at moderate volumes) are a topic of hot debate around here.

Gary, in actuality there's no good reason to "hope" for any difference in sound quality, much less a "marked" one. Your present 645 is conservatively rated, as is the HK practice, and if any difference in the maximum sound level exists with the A23(125 watts)it wouldn't be more than about 1dB. For example, if a brief split-second peak could be played at 105dB with your 645, the A23 might be able to play it at about 106dB, not an appreciable difference. Furthermore, discussion of maximum level capability on brief peaks shouldn't overlook the fact that most of the time the speakers will be using about 1 watt for a comfortably loud listening level, even if a 1000 watt amplifier is connected. You control the amount of power used(with the volume control, of course), not the amplifier.

Your 645 powers the entire 20-20KHz spectrum with level response and inaudibly low noise and distortion. Within its designed power limits you can't do any better than this; there's no mysterious factor that somehow results in better than audibly flawless amplification. This is the case regardless of how expensive the separate amplifier is or how high its maximum power rating is. Don't waste your money.

Noted. thanks for the advice. You guys are a big help.

Hi Gary

It is my understanding that adding a stereo amp to a home theater system to drive the front L&R speakers has 2 objectives:
1. relieve power reuirements on the other channels, and/or
2. produce a "better" sound for stereo playback of music sources (CD,FM, TT,MP3)by using a "better sounding" stereo amp and/or a more powerful amp.

IMHO, with your system, not much benefit would be derived unless you added something like a 200w x 2 Bryston or Parasound Halo.

Mike19

Mike, in a true blind A/B tests, those theories go right out the window.

Or you could add an Emotiva XPA-2 for the fronts...

Mike, welcome to the forum!

<rant>
There seem to be two camps on this forum - those who say that basically all amps sound the same, and those who say that "Amps ain't amps". I'm in the second camp. I suspect that companies like Bryston would also be, along with thousands of testers in thousands of magazines.

I think it's an oversimplification to say that any amp with a flat frequency respone and low THD sounds that same as another other amp. I'm sure some amps do sound the same, but there are a lot of them out there. I don't want to get into an argument about it but I shake my head every time I hear it.
</rant>

I still love this forum though - and I don't even own any Axioms

Shane, amps don't "sound" they amplify the signal.

What has more impact on separation in a 2 channel system--the processer or the amp? I say the processor but many say the amp has as much or more impact. When I say many, many of those many are the manufacturers themselves.

Don't do it Shane, just accept that all amps sound the same from $98 to $98,000. No such thing as higher quality components, or DACs, or DSPs making a cleaner signal path unless it can be measured in THD. Just accept it.

Charles, if by "separation" you mean the degree to which signals in one channel of a 2-channel amplifier or receiver are attenuated with respect to the other channel, then this hasn't been a problem for many years and there's no need to consider what has an "impact" on it. Generally, 40dB of inter-channel separation is sufficient for full stereo effect with no audible leakage. Some of the test labs(e.g., HomeTheater Magazine)still include the crosstalk measurement in their tests. I don't recall any unit in recent years that had less than about 70dB of separation and typically a receiver would measure in the 80s(the very inexpensive receiver that I have on at the moment measured about 90dB). Some units have 100dB or a bit more of separation and this is an indication of excellent design but isn't of any added significance to the listener.

JohnK,
Thanks. Didn't realize this but it makes sense that this concept is basic to the design of a receiver or processer. I hear and read so much on the subject that it makes you think that it is still being perfected. That's what sells. Separation to me is being able to hear where instruments and vocals are-left to right and even front to back on good recordings and equipment.

But isn't an amp that adds zero sound over the original signal impossible? Every capacitor, every circuit, does something to the sound. If so, the question is audible change. The sound of an amp, as the uninformed like me use the term, is the noise added to the original signal. But does THD tell that tale in absolute terms in terms of audible change. It may. I'm not saying it doesn’t, I'm just surprised that a cheap amp with .05 THD sounds the same as a high quality amp with .05 THD.

I'm happy if it is true. My use of 12v amps for years just tells me the spec sheets don't tell the whole story. I have not tried near as many home amps, so I, again, am not saying the position is wrong. Just don't understand it I guess. I know, books are available - but I want it spoon fed for free. I am American...

A common term for that is soundstage.

Ok. I'll go back to my corner now

I just replaced my old Denon PMA 860 integrated amp with a new Denon AVR 1909, and I can affirm that the older Denon provided far superior transients. This quality was, and is missed.
The 860 was 80 w/ch and the 1909 is 90 w/ch, which are essentially the same however, the 860 had what probably was a better power supply to run two channels than the 1909 has to run seven channels, this makes a big difference in sound quality, particularly when the music gets to live listening levels.

I was told that the 2809 and up has better power supplies (or maybe that was the 3000 series and up but I think it was the 2809) Got that from Denon Tech Support a while ago. Give them a call if you need to know. I remember that I had wished I had the extra money for the 2809 and I think that was one of the reasons besides the pre-outs.

I believe the 28XX and up are using the same P/S. Although my old 1804 apparently was an overachiever according to this review, so who really knows what manufacturers are putting in these things these days.

That's what I find so frustrating. I don't think all amps/AVR sound the same just b/c they have the same specs. The science background crowd says they are all the same as a matter of physics. But if that is true, then there must a be a measure - current , THD, Widgetifaction - I don't know. Maybe I'll go dig into Byrston v. Sony or something to look for variation. I did note the other day that Integra lists the current capacity of its AVRs, and you can see a change from 36A to 70+A even when the watts moves only a bit. I checked Denon and they don't give the same kind of data. maybe that is a key spec for comparison.

Charles, the current actually used is determined by Dr. Ohm, not manufacturer hype. At an average listening level using about 1 watt, the current is less than 1 ampere(square root[power/impedance])while if a split-second peak hit over 100 watts, the current would be on the order of 5 amperes.

Well yes, there are measureable differences and marketing hype will tell you that Mr. customer will hear a difference, but...

Look at it this way. If you could measure the difference between 70db and 70.0001db, could you hear it? We can take pictures of stuff with electron microscopes you could not ever hope to see with the naked eye.

This is a very good thing for us consumers, but a pain for companies that would like to sell us things at very high margin.