Pass ACA Class A Power Amplifier Review

[Xulonn]

Might be interesting to compare the ACA performance with something like this:
Kinter K3118 Texas Instruments TI Digital Hi-Fi Audio Mini Class D Home Auto DIY Arcade Stereo Amplifier with 12V 3A Power Supply Black https://www.amazon.com/dp/B0787BRQ2F/

$23. '15w' Has ASR already done a similar one and I missed it in the Index of Tests?

Seriously. Such a test could set a floor on what should be minimum performance from any amp today..

The Kinter is a TI clone of the identical looking Kinter and Lepy (Lepai) Tripath 2020 amplifier and many other brands with different chip amps. Apparently, someone is selling lots of those cases.

I own the Lepy amp and use it outdoors at the weekly market where I sell arts & crafts. The bass pot is going bad and is terribly scratchy. It cuts off the right channel sound unless you twiddle it a bit.

So, my Lepy is a $25 piece of junk, but it actually has worked for some time - somewhat - and continues to function, unlike the two $105 Topping PA3 mini amplifiers that died on me.

If you look at Amazon reviews for any of these amplifiers, they mostly have 10% or more 1-star ratings and lots of dead units - new or after a short life. So, apparently I'm not the only one to experience problems. But what do should one expect for such cheap electronics?

OTOH, my $180 Trends TA10 a 12wpc "T-amp" with a Tripath chip is over 10 years old and lots of use still works. Unfortunately, I dropped it and broke off the shaft of the Alps volume control. I should probabaly open it up, ID the part, and order a replacement.

 

[BDWoody]

I read fast.
.

Ahhh...well by all means then, speak as an expert on the group. Or, at least denegrate it... That's a good start.

 

[Azookey]

I would greatly appreciate it if you'd test the bridged configuration.

Tom

Same here... True Balanced input is supposed to cancel distortion.. be curious if true and how much.

 

[direstraitsfan98]

great review!

 

[JaapDeventer]

I've built my own ACA 1.6 amp. I use the ACA in a small (6x12 feet) study with Khadas ToneBoard and KEF Q300. It goes louder than I can stand. In my main system in my living room with 86dB 4Ohm monitors the ACA plays just loud enough. I do like the sound of the ACA. Especially in my study system. The sound is nice and sweet. No audible distortion. No sharpness to the music. It's a beautifull amp. Fun to build and very useable in a small room.
Not meaning to dispute amirm's measurements.

 

[Xulonn]

So it's an 'assembly experience'? That's a new one on me. But if it makes someone happy hanging with their audio-guru, building substandard electrics, t....

building substandard electrics ? No, just learning to solder and make something very simple that functions. Otherwise, if one preceeds to supposedly "better" components, one might end up like jkeny and his Ciúnas Audio ISO DAC with it's "artistic" approach to soldering.

 

[anmpr1]

building substandard electrics ? No, just learning to solder and make something very simple that functions. Otherwise, if one preceeds to supposedly "better" components, one might end up like jkeny and his Ciúnas Audio ISO DAC with it's "artistic" approach to soldering.

If Nelson subsidizes the 'experience' at his amp-camp (which is what some say), I'd have no problem showing up in order to solder a circuit board with him and some pals. And maybe a few beers over bar-b-q later.

I just can't take a three hundred dollar kit like this seriously. Unless...of course, the kit that is reviewed here is defective. That is always a possibility, however remote it might be. If other examples are shown to be typically much better in the electric department, then I'd at least give it the benefit of the doubt--A) for a learning experience and B) for very limited and specific applications--applications that I can't think of off the top of my head, but could be out there.

 

[Azookey]

I've built my own ACA 1.6. I use the ACA in a small study with Khadas ToneBoard and KEF Q300. It goes louder than I can stand. In my main system in my living room with 86dB 4Ohm monitors the ACA plays just loud enough. All without audible distortion. I do like the sound of the ACA. Especially in my study system. Just my feeling. Not meaning to dispute amirm's measurements.

I agree, i have run my ACA with Kef LS50's and its plenty loud, and those speakers are known to be very ineffecient. Amir not being able to hear his speakers using the ACA doesn't seem correct.

 

[amirm]

As requested, here is the bridged performance:

Dashboard at 5 watt again into 4 ohm:

Second harmonic is knocked down quite a bit with third harmonic now dominating. Since THD+N/SINAD are sum of all harmonics, they improve substantially. We can see this much better in power versus THD+N:

Lack of extra power into 4 ohm is likely due to insufficient current.

This of course does away with "distortions are mostly 2nd harmonic" and any kind of cost equation.

 

[amirm]

Note that the above sweeps took upwards of 4 volts so you need more than your typical RCA to XLR adapter to get more power.

 

[amirm]

So, my Lepy is a $25 piece of junk, but it actually has worked for some time - somewhat - and continues to function, unlike the two $105 Topping PA3 mini amplifiers that died on me.

I have had the Lepy sitting to be tested for months. I can put it on the bench now if there is interest.

 

[Xulonn]

I just can't take a three hundred dollar kit like this seriously.

Nelson Pass neither sells nor endorses a $300+ kit. But he did allow others to use his kit circuit, and they grossly abused the privilege based on unethical levels of greed.

Why don't you attack instead, those who sell the $300+ kit? They are the charlatans who should be castigated.

 

[peng]

2) As @restorer-john shows, the parts set you back about 15 dollars.

I highly doubt you can get the parts including the output transistors at today's price in small quantities. Also you still need the PCB, connectors, chassis/heatsinks and power supply for a complete kit.

 

[Azookey]

As requested, here is the bridged performance:
Lack of extra power into 4 ohm is likely due to insufficient current.

Would using this amp in a speaker with an imedance in the 12-16 range change the distortion?

 

[amirm]

I read fast.
Like the post where someone said amirm should do the listening test before the measuring so that the listening results wouldn't be affected by the bias of knowing the measurements and they got torn a new one because how dare they say he couldn't be objective.

I gave the answer why that criticism was without merit. More than once I think. Here it is again. When a test is blind, nothing helps you identify which gear is which so prior knowledge does not bias the results. After all, if it did, then it would not be blind and of no value!

What knowledge of measurements enable you is to focus on the right content, right segments in that content, right conditions, etc. For example, if the output impedance of a headphone amplifier is high, you want to focus on content that would show its impact on frequency response. If that impact is in bass and you pick content without much of it, then you won't hear the difference.

As differences become smaller, it is critical that we know what to focus on and don't randomly shoot at the board to find differences. For this reason, we train listeners ton what to listen for which goes even beyond having measurements. This is all codified in international standards such as ITU-R BS1116, METHODS FOR THE SUBJECTIVE ASSESSMENT OF SMALL IMPAIRMENTS IN AUDIO SYSTEMS INCLUDING MULTICHANNEL SOUND SYSTEMS

Measurements allow you to know what the artifacts are so that you are familiar with them and search for them.

Remember, our goal is to find the truth not to fool ourselves. If there are differences to be found, we want to find them. Because if we don't and declare such gear transparent, and then someone conducts a blind test using above training and shows audibility of artifacts, we just became fools. And fools we don't want to be.

So slow down. Read the answers as given and ask questions if you don't understand them. I used to do this kind of thing for a living so am not just throwing arguments at you. It took me almost 6 months to train myself to hear compression artifacts and that most definitely involved understanding the algorithms involved to know what to listen for.

 

[Xulonn]

I have had the Lepy sitting to be tested for months. I can put it on the bench now if there is interest.

I have a feeling that the Lepy might test reasonably well, because those old Tripath "Class-T" chips were pretty good. It will be interesting to find out for sure.

As is often the case, it's the implementation and quality of the other parts on the board that determine the overall performance, reliability, and longevity of these cheap little amps.

My 1993 Classé amp still works like new, but the Lepy will have long since been corroding away in a landfill 25 years from now.

I believe that my Trends TA-10.1 uses the same chip - and it cost about $160 about ten years ago, and sells for about $200 from a Netherlands dealer these days.

 

[audimus]

They can be a touchy group; you know how it is when an entire forum revolves around one person and what they say is the gospel

Are you talking about this forum? The description is ambiguous...

 

[amirm]

Would using this amp in a speaker with an imedance in the 12-16 range change the distortion?

Here is the same bridged test with 16 ohm load added:

As you see, it doesn't get you much distortion wise but cuts your power way down. Given how little power you have to play with as is, I don't see using high impedance load as a good thing.

 

[Azookey]

Here is the same bridged test with 16 ohm load added:

As you see, it doesn't get you much distortion wise but cuts your power way down. Given how little power you have to play with as is, I don't see using high impedance load as a good thing.

That's interesting, according to their sheet on operation modes, it should be putting out close to 15 watts at 8ohm or higher, in balanced bridged mode

https://cdn.shopify.com/s/files/1/1006/5046/files/ACA_Monoblock_Operation_RevA.pdf

 

[tomchr]

As requested, here is the bridged performance:

Awesome. Thank you. I was expecting some cancellation of the even-order harmonics. Good to see it in action.

Tom