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Pass ACA Class A Power Amplifier Review
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HornJunkie
Member
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- Jan 11, 2021
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APx500. But the dongle is expensive.
HornJunkie
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- Jan 11, 2021
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MakeMineVinyl
Major Contributor
I just started using ARTA. Its a good program that I find useful. However the 5.2 versions of REW I find are better still for measuring electronic components. The reason for this is that the vertical scale now has % for distortion and dB scales for measuring frequency response which can be zoomed way in to see small response errors. I also like the ability to add detailed information about each measurement and overlay them to compare responses. I know its focus is on acoustic measurements, but its becoming more useful for purely electronic measurements.I see. 3000$ is not cheap.
Maybe I should try Arta.
ARTA and REW are both good programs. If you can stretch a few more bucks and have the patience to learn a more complex system, Virtins Multi Instrument is ridiculously versatile.
MakeMineVinyl
Major Contributor
I've used Multi-Instrument for years, and always find myself cursing at it for its bugginess and general unfriendly nature. It tries to be a 'poor man's Audio Precision', especially with its DPP functions. Lately for some cosmic reason it causes the Blue Screen of Death whenever I end a measurement. Then - like a miracle - it started to work normally again. As useful as it can be, I don't need that shit!
FWIW, I haven’t had any lockup or crash. Which version are you using?
MakeMineVinyl
Major Contributor
The latest version which I downloaded probably a month ago. This is on Windows 10. I usually had no problems with the basic spectrum analyzer. I unstalled/reinstalled it and it still caused the computer to crash. Then all of a sudden it didn't. I initially chalked it up to routine Windows updates causing things to break, but I don't think that was the case this time. At any rate, this episode prompted me to buy ARTA, which has essentially the same (or better) spectrum analyzer / THD capability. ARTA has worked solidly. I also don't like the overly restrictive licensing model of Multi-Instrument; I wanted to buy a 2nd hard key so I could use it in both of my labs without transporting the key. No dice, they would only let me have the one I had. The 'soft keys' have a habit of suddenly not working after awhile and I have to go through the hassle of getting another soft key for the same computer. Don't need that crap.....
Thanks for the detailed response! I’m using it on two different computers with zero problems. I particularly am impressed with the generator, but having auto and cross correlation might be my favorite feature.
I dread the day when the key goes missing...
That is a highly condescending statement just to prove a point. I don't want to hoot around my acquired skills, but I had been a professional tuner of active setups for some years and many in the profession including manufacturers will agree that measurement is only a tool, but ultimately voicing is always by listening.
Just because your measurement of certain gadgets bring out technical flaws does not mean that the persons who use them and find them to sound good are audiofools.
It is a simple fact of audio that it is a mystical experience that varies from one audiophile to another, the very reason the search for that perfect system goes on unhindered.
While I highly appreciate and salute your time and effort with your in-depth reviews, accept the comments there-in gracefully if an user finds his experience to be otherwise.
I haven't read or even flipped through the prior 41 pages.
Just an innocent, maybe stupid, but still well intentioned and innocent question:
As it's a DIY, could it be that it has been badly mounted, implemented, some faulty component or else ?
It's your worst tested amp and still has a prestigious name behind.
That raises questions, no ?
Just an innocent, maybe stupid, but still well intentioned and innocent question:
As it's a DIY, could it be that it has been badly mounted, implemented, some faulty component or else ?
It's your worst tested amp and still has a prestigious name behind.
That raises questions, no ?
AnalogSteph
Major Contributor
Not really. The ACA was only ever intended as a low-complexity, beginner-friendly DIY power amp. There's only so much you can do with 4 transistors per channel on an unregulated power supply, even in Class A. The original JLH 10 W Class A design was intended to be used with capacitance multipliers for supply regulation at least, increasing transistor count by 50%. That one was supposed to post generally <=0.1% THD figures at 9 W across the audio band, which wasn't bad for a DIY amplifier in the late '60s.
Its low output noise and gain do make the ACA a good candidate for driving high-sensitivity horns, like @mitchco does. You could probably achieve the same with a more standard amplifier and an L-pad though, so whatever.
Its low output noise and gain do make the ACA a good candidate for driving high-sensitivity horns, like @mitchco does. You could probably achieve the same with a more standard amplifier and an L-pad though, so whatever.
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This. I've even heard Nelson himself say this is a bad amp that isn't meant to sound good. It's meant to be easy to make and easy to understand at the fundamental level. It's meant to give newbies a build that can help them understand the fundamentals of amp design so that they have something to build on. It's like teaching kids Geometry first before teaching them Calculus, even though Calculus can better calculate the area under the curve. The Geometry will help them understand Calculus better and make them more proficient at it then had they started with Calculus.
And yet we have most reviews singing the praises of this amp, and people trying to defend it as a wonderful amp, simply because Nelson's name is attached. Really shows how significant of a factor expectation bias is when it comes to assessing the "sound quality" of audio electronics. IMO, it's the most important factor.
OP
- Thread Starter
- #815
There is no "voicing" in this simple amplifier.
I didn't use that term. I did however explain why audiophiles as a group do not have sensitive hearing when it comes to non-linear distortions. This is why many would fail a test of high-bitrate lossy codec to CD even though there is massive transformation of the source file.
The art is mystical. The equipment, anything but. This is a simple amplifier that is under powered and has a lot of distortion. If you can't hear those weaknesses, then fine but that doesn't make the equipment good. It just shows that some have much lower bar for performance. That is the difference between people. Otherwise we all like clean sound.
I was not talking about this particular amplifier. I was only stating that all audio companies voice their equipment, so tools are only tools, can never replace the organic ears.
Sorry, generalised statements. On the contrary, I have found n number of engineers struggle to make out without their tools. Ears can be trained to do that.
You are just going on repeating and grand standing. Please mature and look beyond your tools. AmpCamp is a sweet sounding amplifier irrespective of your criticisms. I have also read some other reviews of yours like the ATCs. Sorry mate the world thinks otherwise and so do I. I am highly critical of your listening skills which I presume are extremely poor as compared to your measuring skills.
But I don't wish to push this any further ahead and ofcourse I won't be replying to your repartee.
The world goes on in spite of your many a wrong assessment of products. I do find you highly biased though many others may see that the other way.
That said I recently purchased a pair of Revel Concerto M18 which are good value for money and has always found favor from your side. I also own AmpCamp and a Teac DAC/pre and have also gone though with an Audio GD and a Topping DAC.
In my opinion Toppings do not deserve the credit you reap on them, Audio GD is quite a good DAC and your reviews are off track therein...Teac sits at the top of the pile for me.
Have a great day.
restorer-john
Grand Contributor
@kannan is correct (partially) in one area. Manufacturers did often "voice" their amplifiers in the 1970s and 1980s, but it was done for commercial reasons, not for the benefit of the audiophiles.
The "voicing" was often done through the lifecycle of a product and most often involved adjusting the rolloffs at each end of the spectrum in order to better demonstrate the relative benefits of upper range models or differentiate them from the bargain basement models. Certain brands "voiced" their low end amplifiers/receivers to sound warm and fat, whereas further up the range, they became ruler flat. This was a choice to sell on the sales floor against competing brands who did the same.
Pioneer for instance appeared to "adjust" the power stage input RC filter values on receivers that were best sellers if they cannibilized sales of the upper range products. Or they tweaked the RCs in the NFB loop for less overall gain too early and into the audible low end. Basically, they rolled LF off deliberately- a great way to make an otherwise good sounding amp appear bass light or "dry" sounding. I've often seen running changes where the first models and the original schematic show better performance than the same model made a few years later. These were not changes to improve, they were the opposite. I think the reasons were, the engineers designed them all to be excellent performers, but the product sales teams wanted a range where there was incremental "audible" incentive to step up to better (more expensive) models in that range.
The "voicing" was often done through the lifecycle of a product and most often involved adjusting the rolloffs at each end of the spectrum in order to better demonstrate the relative benefits of upper range models or differentiate them from the bargain basement models. Certain brands "voiced" their low end amplifiers/receivers to sound warm and fat, whereas further up the range, they became ruler flat. This was a choice to sell on the sales floor against competing brands who did the same.
Pioneer for instance appeared to "adjust" the power stage input RC filter values on receivers that were best sellers if they cannibilized sales of the upper range products. Or they tweaked the RCs in the NFB loop for less overall gain too early and into the audible low end. Basically, they rolled LF off deliberately- a great way to make an otherwise good sounding amp appear bass light or "dry" sounding. I've often seen running changes where the first models and the original schematic show better performance than the same model made a few years later. These were not changes to improve, they were the opposite. I think the reasons were, the engineers designed them all to be excellent performers, but the product sales teams wanted a range where there was incremental "audible" incentive to step up to better (more expensive) models in that range.
I remember I had a Kenwood, Pioneer and a Sansui from the mid-late 70's and they where maybe 30-40 W/ch and they sounded weak and did not have much thump in them. I always thought they where simply weak. But the more powerful units of the same brands did have more thump. I don't know if they where voiced but they certainly did sound different.
I think this might be the reason why I almost always have not liked the commercial amplifiers. Together with undersized heatsinks and corresponding low idle current and savings on number of pairs of output devices.
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