Axiom Home Page Forums General Discussion Advice from Axiom Owners Small, inexpensive 2-channel amps?

Agreed.

Speaking of small, inexpensive amps...........Radio Shack is now stocking a couple of low end Sherwood AV/receivers and, I thought I saw a 2-channel as well.

Also, if the distortion (THD) specs.on an "amp" are even close to 1%..........you're gonna hear it.

Did someone say crazy talk?...............play nice, now.

The crazy talk I was referring two was audibly detecting a difference between .05% and .07% THD.

Más ridículo.

Right; THD is a non-issue on any amplifying equipment which we would seriously consider. The blind listening tests on audibility of distortion vary with the type of music being employed, but a generally accurate statement would be that in real-world music listening it has to be over about 1.0% before it can be detected.

What would be a good THD+N number for 20Hz-20kHz?

Chris, as I indicated, in my view THD as a practical matter should be a non-issue for us. It appears that power delivered with less than about 1% THD is audibly clean in listening to music, so anything up to that number should be fine. It could also be noted that a unit with a relatively "high" rating of say 0.7%(possibly to make the "magic" 100 watt mark while still complying with mandatory FTC power rating regulations)would probably measure about 0.1% just a few watts lower. Measurements in thousandths of a percent, while a testament to engineering excellence, aren't of audible significance.

Of some interest is the Yamaha discussion in the power rating section of their faqs. Although they follow the typical practice by rating their receivers at a power level where distortion is a little under 0.1%(e.g. 0.07%), they acknowledge the lack of significance of such a number.

The problem with any discussion regarding measurement and audibility of harmonic distortion is that our sensitivity to harmonics varies with what order distortion we are hearing. Even order or low order harmonic distortion can be difficult to distinguish at high volumes and may even sound pleasant. For example, many people would be surprised if they knew how much second order harmonic distortion they listen to unknowingly with their favourite subs. Tube amps in particular have high levels of low order HD which is why many people find them appealing.

The offensive stuff is the high order or odd order harmonics. Very small amounts of odd order distortion can be detected at low volumes. While the 1% THD stat is frequently cited as a threshold amount for amplifiers, especally with car applications, what that stat ignores is the composition of THD and the fact that each of us has different sensitivity to HD. I often hear my tube amp friends talk of the "harshness" of solid state amps which I interepret to mean their sensitivity to odd order harmonic distortion. Listening test studies have shown odd order harmonics in the 2khz to 8khz range can be detected as low as .01% by some individuals.

I would strongly recommend not buying any solid state amp which is spec'd at 1% THD without knowing how much of that number is odd order harmonics (though not many manufacturers would dare cite that that number). Also try to determine what the THD curve looks like when graphed against frequency response. THD will also vary with frequency and manufacturers will often cite the most favourable looking stat.

Instead of creating a new thread, I just thought I'd add on to this one. I've seen the Behringer A500 Reference Amplifier mentioned in a couple of places, and it seems like a bargain. I think I'll have to try it out at some point. Is anyone here using one (or more) of these?