Jan,
OK, nice quoting Voltaire, but beside the point.
With all due respect no-one's trying to shoot the guy.
The topic of the discussion here is building the Amp, no?
AFAIK amirmaj has not built the ACA, has no intention to build the ACA, only thing he wants is discuss his review.
I think there's a conflict here.
And I know he did not start it, I mentioned that in one of my previous posts.
But I get your drift, I am also not discussing ACA, although I built 3 of them (1 stereo, 2 parallel monos) and am following the thread with interest.
Stan
OK, nice quoting Voltaire, but beside the point.
With all due respect no-one's trying to shoot the guy.
The topic of the discussion here is building the Amp, no?
AFAIK amirmaj has not built the ACA, has no intention to build the ACA, only thing he wants is discuss his review.
I think there's a conflict here.
And I know he did not start it, I mentioned that in one of my previous posts.
But I get your drift, I am also not discussing ACA, although I built 3 of them (1 stereo, 2 parallel monos) and am following the thread with interest.
Stan
No. All he does is defend his measurements against attacks, many personal. That at least is reasonable. Look at your own previous post. Clearly you try to damage him personally by putting things like 'reviews' between quotes. But we all know that his reviews are factually better than anything we see here. Because that's his business. The business here is enjoying your own building and listening. Two different things.
Cut out the personal attacks. If that is all you have instead of rational arguments, perhaps it is better to move on. Because it is against the forum rules and subject to mod intervention. You don't want that.
Not that you are the only one.
Jan
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It is very much to the point. You try to damage and shut up someone and ask to throw him out only because you don't like what he says and you have no counter arguments.
Jan
Why there is circa half a Volt compression on the negative going sine's peak? Maybe you pushed it at 4Ω? Was it already losing CCS steam?
I think the graph shown by Salas above shows a basic limitation of the circuit. It is not symmetrical, the pos gain is a bit higher than the neg gain. That is reflected in the spectrum.
Using premium (whatever than means) parts will not change that. What you would need is more gain in the amp that can be used to linearize it. But again, the point of this design is not to build the worlds best amp. It is to enjoy building a nice amplifier and enjoy listening to it
Nelson's motto is: 'It's all entertainment'. That is the point.
Jan
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Jan, I disagree.
His (amirmaj's) arguments—the measurements—seem to be accurate and aren't disputed.
But then he gets very subjective (and nasty). And—his opinion seems quite contrary to probably everyone's opinion here.
It's not about the joy of diy, it's about conclusions that don't correlate at all. It insulting by implication. I'll stop here.
His (amirmaj's) arguments—the measurements—seem to be accurate and aren't disputed.
But then he gets very subjective (and nasty). And—his opinion seems quite contrary to probably everyone's opinion here.
It's not about the joy of diy, it's about conclusions that don't correlate at all. It insulting by implication. I'll stop here.
Not sure who these ALL are.
Are you trying to speak for me?
Me trying to damage someone, are you serious?
Too much hot air has been produced here lately and I do not want to contribute more to that.
I'll let you have the last word.
Stan
A while back I did a basic distortion measurement on one of my original modified ACAs to see how it performed. The amp was in standard stereo mode, using the original 24V kit SMPS. Using my HP339A analyzer, I turned up the input signal until the THD reached 1%, and observed 6.493 Vrms, which happens to correspond to 5.27 Watts into the 8.0 Ohm resistive load that I used. The residual distortion signal shows primarily 2nd order harmonic, with some 3rd present as well. Nothing to indicate the excessive amount of distortion present in the sample that produced the controversial SINAD measurements.
The modifications changed the feedback network and the output current sensing resistors, in addition to using some higher quality components. Quiescent current was measured at about 1.54 Amps. Details are in the "ACA With Premium Parts" thread.
Attachments
Nelson's original plots showed this amp's technical profile not much differently at all than the recent test. So no surprise. This amp needs careful application to load and system gain structure.
Surely a more representative result for the usual application of an ACA. Even though most people with easy speakers would use it at an even lower output voltage most of the time. For 86dBSPL at 2M distance a 90dB 8Ω speaker pair would ask for 2.83V. Not to go about horns now.
*85dBSPL is the maximum long term safe exposure limit. 90dB is lawn mower not recommended for more than 8 hours use.
What would it take to improve the circuit ?
Better than heavily modify make another bigger Nelson's amp.
Mate it with an efficient speaker. Preferable 8ohm
Well said. Sums my post above.
I've no beef with the measurements made on the ACA. They are what they are.
It does annoy me, though, that it was proclaimed terrible based on measurements. There are several amps in my place and it's likely all of them measure better than the ACA. Yet the ACA is such a great sounding amp.
Course my system is using very sensitive speakers with a very easy impedance curve. There are several speakers in the house that wouldn't work well with the ACA but those aren't the speakers mated to it. One set of speakers requires too much power and the other set has a fairly difficult impedance curve so they remain mated to more suitable amplifiers.
Mating the ACA, or any piece of audio gear, to a completely unsuitable match would be silly. Sillier yet, to then proclaim something wrong with the amp based on that mismatch. It'd be just as silly to proclaim the speakers bad, too, when hooked to the wrong amp.
The really unfortunate thing is that after the posted review of the ACA it appears the regulars of that forum all jumped in to comment about how terrible the amp is. The only ones that defended the amp were a couple of folks who had actually heard it.
Funny, that.
It does annoy me, though, that it was proclaimed terrible based on measurements. There are several amps in my place and it's likely all of them measure better than the ACA. Yet the ACA is such a great sounding amp.
Course my system is using very sensitive speakers with a very easy impedance curve. There are several speakers in the house that wouldn't work well with the ACA but those aren't the speakers mated to it. One set of speakers requires too much power and the other set has a fairly difficult impedance curve so they remain mated to more suitable amplifiers.
Mating the ACA, or any piece of audio gear, to a completely unsuitable match would be silly. Sillier yet, to then proclaim something wrong with the amp based on that mismatch. It'd be just as silly to proclaim the speakers bad, too, when hooked to the wrong amp.
The really unfortunate thing is that after the posted review of the ACA it appears the regulars of that forum all jumped in to comment about how terrible the amp is. The only ones that defended the amp were a couple of folks who had actually heard it.
Funny, that.