[Inertia]

OK gang.

I'm in the market for an amp. I've read a lot in this forum, plus others across the web about different amps that I'm considering buying. My question is to you, the avsforum members:


How do amps influence the "sound" of music?


I'm not interested in the whole "oh this is what 'bright' means, this is what 'warm' means,or the 'opposite of bright is dark argument' etc" I want to know how *you* personally think amps can 'colorize' sound (and for the love of God, don't discuss what I mean by 'colorize.'). If one of you has strong feelings about a particular element of sound, then good - I want to understand what you are saying.


I am interested in both the technical, as well as the esoteric. If you have a personal idea on how an amp can influence sound (if at all), then tell me. I hope that no one will criticize another, because that is not the intent of the question.


I am not interested in arguments in this thread - this is more of a "tell me what you think and I'll keep quite" thread, that is all. As far as I'm concerned, there is no "wrong" answer.


I do not understand how an amp can influence sound. How do they do it?


Cheers,

Nert

 

[tvtech1]

An amp that doesn't have a true linear response will influence the sound.

 

[Inertia]

But how can I tell if an amp has a linear response?

 

[tvtech1]

Frequency response graphs, listening to it. etc.

 

[Inertia]

How can listening to it tell me if it is linear or not? I don't have a reference to start from?


Where do I get the graphs?


Also, if someone wants to PM me (because you think people will think you are silly) instead of posting to this thread instead then go for it, I will respond to each statment.


(edited to add some additional comfort )

 

[Dave W]

In my view, a hi-fi amp should be as transparent as possible, merely amplifying the input signal. There are three major ways an amp can screw this up, and hence "color" the sound:


Power - the input signal has a sharp spike in it, and the amp simply doesn't have the reserves to amplify the spike completely, and "clips" the top off. We normally think of this in regards to very loud playback, where the amp is clipping off fairly substantial peaks. However, in these days of digital content, the spikes in the signal can be VERY tall, and so even moderate volume playback can result in the clipping of the peak, if only for an instant, resulting in slightly less dynamic sound, or less "alive".


Frequency Response - if an amp doesn't have a flat frequency response, it will alter the sound substantially in any variety of ways, leading to a "bright" sound, a "flat" sound, a "tubby" sound, or a variety of other adjectives.


Speed - an amp must be able keep up with the input signal. Obviously the amp doesn't know what's coming, so all it can do is react to what it's given. If the input signal has a sharp spike that rises in 10 microseconds, but the amp requires 20 microseconds for the same rise, it will "slur" the edge, leading to a less detailed sound. I think the adjectives "veiled" and "muddy" may apply here.


Just my two cents.


Dave

 

[tvtech1]

All of those are examples of non-linear response.

A power amplifier is supposed to increase the power of an input signal, in order to drive a load (speaker), the only thing that must change is the amplitude, not it's bandwidth (frequency response), nor should other signals be added (distortion). Unfortunately, no-one has been able to design an amp that does nothing but increase amplitude. They've come close though, but then reality rears its head.

 

[Inertia]

Another query, why are there people spending $10K to $15K for amps (REF the +20K home theater forum) of avsforums.com. Are they getting flatter responses over thier frequency range?


Does it all boil down to the $$ that one spends?!?!?


BTW, thank you tvtech1 and Dave W for your comments. I really appreciate them.

 

[M NEWMAN]

Very, very nice summation Dave, to which I'll only add that the output load can have an effect on the amp's performance too. Some speakers (electrostatics come to mind) are exceedingly difficult loads to drive - very reactive. Consequently, if an amp doesn't have extremely robust outputs (many don't), then certain loads will affect an otherwise decent performing amp. Measurements are typically done with purely resistive loads for publication - very few manufacturers will test on highly reactive loads and publish that. More 2 cents...now you're up to nearly a nickel...

 

[AcuraCL]

Quote:

Originally posted by Inertia Another query, why are there people spending $10K to $15K for amps (REF the +20K home theater forum) of avsforums.com. Are they getting flatter responses over thier frequency range? Does it all boil down to the $$ that one spends?!?!? BTW, thank you tvtech1 and Dave W for your comments. I really appreciate them.

I'd say, trying to maintain system parity ... or eliminating the weak link.


Let's say they have a HTIB. Put a $10k amp in there, and you won't hear much difference between IT and the HTIB amp.


Now put the $10 amp in there with a Theta Casablanca III and Wilson or Revel speakers. Such a system can reveal the subtlest of differences in components. So the amp that was okay in the HTIB system, and was ok when paired up with a Outlaw pre/pro and some Paradigms, it's weaknesses (non linearity) will be heard in the upgraded system.

 

[Inertia]

AcuraCL,


Thank you for your input.


Let me ask you something, though. I recently attended a Dianna Krall concert (please don't judge me LOL). I notice that in fact that she was singing in a microphone, and that was being pumped through a set of speakers mounted in the theater. I could swear, that (per my sig below), that my system sounded better/as good as the live performance. Would you suggest that I don't need to upgrade my system to an amp because of my experience in the concert?

 

[Bigus]

An amp can color the sound by:


- Having a non-flat frequency response

- Distortion components

- Output devices not able to handle reactive loading

- Output impedance too high (related to non-flat frequency response hooked to most real speakers)

- Power output


That's about it, really. Most decent amplifiers (including those in the majority of mid-fi receivers) have the frequency response covered pretty well, at least into a purely resistive load. You won't know the difference if your amp is -3dB at 25kHz or 125kHz... all else being equal.


Look for reasonably low distortion and nosie figures, though the simplistic numbers of THD and SNR are extremely vague and crude ways of telling you about an amps distortion components. About the best you can do is rest assured that most amps with pretty low THD and pretty high SNR will perform well enough when measured with a more detailed test regimen that the distortion will be inaudible. If you're looking at an esoteric Class A design with 10% harmonic distortion, rest assured that this absolutely will have an effect on the sound. If you like it, that's your own business...


As for the ruggedness of output devices, output impedance, and power capability, these are all somewhat related (though output impedance might be designed high even for a very rugged amplifier). Look for a reasonably high damping factor, say 100 or greater for the entire bandwidth (hard to find out, since many specs are published at only one frequency). In multichannel amps sustaining power with all channels driven is a good indication of a rugged power supply. The ability to drive low impedance loads (like 2 ohm) is an indication of output supply ruggedness. IMO, this is one of the most difficult aspects to determine by looking at or listening to an amplifier, and the one most likely to cause whatever audible differences may occasionally pop up.



My personal advice on buying amplifiers is to get something with a good reputation that is solidly built and of adequate power for your needs. Don't spend a lot of money - amplifying low bandwidth audio signals is relatively easy in the electronics field, and despite the existance of a gazillion different designs out there a solid amp will likely be completely indistinguishable from another solid amp. And if there are small audible differences, they will be orders (emphasize the plural there) of magnitude smaller than those caused by your room, and your speakers. Amplifiers are waaaay down the list on priority, falling behind behind source equipment and processing as well as the room and speakers. Crown or Krell... doesn't really matter in the grand scheme, though I tend to pay a bit more than I could get by with to have amps that look nice together with other equipment, and perform to a level that I never have to concern myself with.

 

[Artisn]

I was thinking of just getting a Marantz SR5400 and running a separate power amp through the pre outs for the mains. Something like a Behringer or Crest.
http://www.zzounds.com/cat--Power-Amps--2747


I was hoping for a lot of power in a small area with a minimal cost (less than $400).


My thinking has been that power is power, and the receiver creates the sonic signature. Are there other factors I should be considering?

 

[M NEWMAN]

Nert,


Something to clarify.....out of all the components in yours or any given system, probably the least "colored" of all the components is the amplifier. Your speakers are the most influential in your system (with the room acoustics even MORE of an influence), followed by your pre/pro & source. Consequently, I'd say don't worry much about the amp.

 

[Inertia]

Bigus,


What a great post! Thank you for taking the time to post your opinions. I understand completely the concept of buying an amp that physically "looks good" with my other components (i.e. why get a silver faceplate when all my other components are black." My question to you is:


If I have speakers that I consider "bright/detailed/etc", should I look for an amp that accentuates the lower freq spectrum, if that is what I "think" I am missing? In other words, per your *own* opinion (per understanding caveats listed below in my sig), do you think I should focus on "warm" sounding amps? I can easly spend a lot less money buying an *outlaw* amp than I can a gemstone, sunfire, Anthem...

 

[M NEWMAN]

Quote:

Originally posted by Inertia Bigus, What a great post! Thank you for taking the time to post your opinions. I understand completely the concept of buying an amp that physically "looks good" with my other components (i.e. why get a silver faceplate when all my other components are black." My question to you is: If I have speakers that I consider "bright/detailed/etc", should I look for an amp that accentuates the lower freq spectrum, if that is what I "think" I am missing? In other words, per your *own* opinion (per understanding caveats listed below in my sig), do you think I should focus on "warm" sounding amps? I can easly spend a lot less money buying an *outlaw* amp than I can a gemstone, sunfire, Anthem...

If I might interject..... I would suggest NO! Frankly, the amp can't really "darken" the sound without a lot of manipulation to the high end of the frequency response. If your speakers are "bright" then I'd suggest replacing them or room treatment to deaden the highs. This will have faaaaarrrrrrrrrrr more effect on the sound than an amp ever will.

 

[Inertia]

Newman,


Well, you can pretty much guarantee that I will not be replacing my speakers or any audio treatments that I have in my room *cough cough wife cough*. So, I take it that per your own opinion (per caveats listed in my sig heh) that there will not be much of a difference. That is very good input, In my opinion, thank you!

 

[AcuraCL]

Quote:

Originally posted by Inertia ...If I have speakers that I consider "bright/detailed/etc", should I look for an amp that accentuates the lower freq spectrum, if that is what I "think" I am missing? In other words, per your *own* opinion (per understanding caveats listed below in my sig), do you think I should focus on "warm" sounding amps? I can easly spend a lot less money buying an *outlaw* amp than I can a gemstone, sunfire, Anthem...

I'd like to pipe in here. The way I do things may not be good for the next person ... but really my first step (several years ago) was to start with a plan. What do I want in a system? How much do I want to spend on it? What components do I want? Then I made a roadmap to get there. I'll upgrade these items (for me it was pretty much everything) in this order ... as I can afford it and as it will have an impact on my overall plan. It took me really about 3-4 years of research, planning, auditioning components (by far the longest of those was speakers), then finding the best deals and buying.


So ... the ultimate goal was the best music system I could put together for my budget and room. The secondary goal was good movie (audio/video) performance.


I tried not to select components based on overcoming an existing system weakness, but with the absolute goal of neutrality and accuracy. So maybe my then-current speakers were in the "bright" range (Polk LS70s, nice floorstanding speakers, but yes, a tad bright). I didn't select my amps (Acurus) to tame them, but to be as neutral as I could find for the dollar. Now plenty of people call Acurus bright, but I did not find them so, and the best most trustworthy reviews I could find classified them as excellent value with just the slightest tendency to be bright. And the response curves showed very flat performance. Same criteria for the preamp, the speakers, etc. Not to balance current shortcomings, but to attain the ultimate goal ... neutrality ... no color added, none subtracted.


I was willing to be patient and live through the weaknesses knowing that ultimately, I could have a great system that would satisfy me for a long long time.


On the "do I not upgrade my amps bec. they sounded better than the concert" ... tough question. But maybe not the right approach. Bigger question: when you sit down to listen to music/movies, do you sit there and say "Ouch, that sounded nasty ... hmmm, that just doesn't sound real ... dam, I'm disappointed in this or that" or is it what you want to hear/experience in the moments just before you fire it all up and you're thinking, "I'd like to listen to/watch such and so"?


What's wrong with Diana Krall anyway? I have about 4 of her CDs and one DVD. I think she rocks !!! What a voice ....

 

[Artisn]

Diana Krall is my favorite new artist in the last 5 years. Sweet, sultry and yes, she does rock!

 

[MikeTz]

I've got an amp that's fast, has flat frequency response, power reserves, and can handle tough loads. My source components are also very accurate. Trouble is none of that was realized until I corrected for my room.


Many people I know, myself included, are seduced by the marketing, word of mouth, technical specs and listening tests (in corrected rooms) of great audio equipment. We go out and buy wonderful components and can't understand why they don't sound spectacular at home. It's the room. Amps and source components with ruler flat frequency response in a room with a response curve like shark's teeth (my room) won't produce that magic sound.


Before you consider buying more components it is probably worth some time to characterize your room's response. Some well placed treatments and/or an equalizer can make a modestly priced system outshine very expensive systems. This will also let you get the maximum benefit out of any future components you purchase.


MT