Selecting the right power amplifier

swind0wn

Novice Member
I only have a little knowledge on amplifier specifications.

I would like to know what is of more importance when selecting an amplifier so for example:
- Amplifier 1 has a S/N ratio of -110 dB, 0.5% THD and -86 dB cross-talk
- Amplifier 2 has a S/N ratio of -100 dB, 0.1% THD and -70 dB cross-talk
- Amplifier 3 has a S/N ratio of -90 dB, 0.01% THD and -60 dB cross-talk

What amplifier would you pick? As in what of the different specifications is, in practice, of most significance - S/N ratio, THD or Cross-Over?

Recently I was reading guidance on what measurements are considered to be acceptable:
  • *Frequency response <20Hz and >20kHz
  • *SNR and/or Dynamic range >= 100db
  • *THD+N as close to 0% as possible
  • *IMD+N as close to 0% as possible
  • *Crosstalk <= -90db (Source: Click)
At the same time I read that anything under -70 dB is considered (so -80, -90) as that it can be heard very hardly which is considered unheard in practice (correct if this is wrong).

Another thing - is 90 dB S/N ratio noticeably worse than 100 dB?


Lastly, I have speakers Xarus 5000 and many people believe their frequency range is 30 Hz - 24 kHz (even though in the manuals it says it goes up to 20 kHz - click for my other thread). Accepting they go to 24 kHz, if I purchase an amp that delivers 20 Hz - 20 kHz, would I be missing out on tweets or is it more theoretical than practical?

I appreciate all of your spared time for all your comments.
 

Gaspode_TWD

Active Member
I'd say listen and decide. There is a quote, "There are three kinds of lies: lies, damned lies, and statistics."

Specifications for any item of audio gear should be looked at in these terms. Some manufactures will deliberately try to flatter their kit by taking measurements in the most flattering conditions. Others are deliberately conservative in what they claim. Human hearing is normally assumed to cope with the range 20Hz to 20kHz. This upper limit declines with age.

Don't buy on spec, check out the sound. For example, the amp may measure differently when used with different speaker loads.
 

Glen B

Active Member
What amplifier would you pick? As in what of the different specifications is, in practice, of most significance - S/N ratio, THD or Cross-Over?
Today's amplifiers in general all have excellent noise and distortion specifications. No manufacturer today worth their salt will get away with producing gear that measures poorly. I own several amps and could not tell you what their noise and distortion figures are. I just haven't paid close attention to those figures. As said above, just let your ears be the judge.
 

tfboy

Well-known Member
Also, the distortion figure on its own is almost meaningless if it's not accompanied by frequency, power and resistive load (speaker impedence). Maybe you have the figures and didn't post them, but THD by itself doesn't really indicate much. Normally, the distortion should be that listed at the power the amp is rated at. So for example at 300W of power into an 8 ohn load, it produces a distortion of 1%. If, however, you were to take the THD at, say, 250W, it might only be 0.5%...

Getting the opportunity to listen is really golden. Who cares about statistics if you really like the sound :)
 
I'd say listen and decide. There is a quote, "There are three kinds of lies: lies, damned lies, and statistics."

Specifications for any item of audio gear should be looked at in these terms. Some manufactures will deliberately try to flatter their kit by taking measurements in the most flattering conditions. Others are deliberately conservative in what they claim. Human hearing is normally assumed to cope with the range 20Hz to 20kHz. This upper limit declines with age.

Don't buy on spec, check out the sound. For example, the amp may measure differently when used with different speaker loads.
Always been told that you should listen before you buy,ask for a home demo if they refuse go somwhere else
Dont forget the balls in your court not theirs
They want your business,your money,haggle and keep on haggling till its right for No1......YOU
 

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