Jimster480
Major Contributor
The performance is so poor I can't see the purpose of this existing.... you can build so many amps with breadboards today with off the shelf IC's and they will all stomp this amp into the floor....
-
WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!
Pass ACA Class A Power Amplifier Review
- Thread starter amirm
- Start date
maty
Major Contributor
Because many are not properly informed and do not make the necessary calculations to know what power they need for their speakers, listening distance, position, kind of music (DR) ...
Any intellectual effort is systematically shunned. Satisfaction must be immediate and with the least possible effort.
Any intellectual effort is systematically shunned. Satisfaction must be immediate and with the least possible effort.
captain paranoia
Active Member
- Joined
- Feb 9, 2018
- Messages
- 293
- Likes
- 218
Is that Nelson Pass website?
No, it's diyaudio
https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218
You mention that $327 price tag in your OP. It might be worth linking that to the source of this price, and the source of the kit you have tested. The only provenance you have in the OP is Nelson Pass. It might also be worth pointing out the $15 BOM from the original article.
I'm not a 'hi-fi personality'. I have some designs published that are intended as cheap, simple toys to demonstrate the principle. I don't think it would be fair to judge me if someone started selling kits of those designs at inflated prices. Judge the people selling the kits as something more than the design was intended for.
Last edited:
solderdude
Grand Contributor
That's all quite correct. In fact one of my (purposely designed) designs has been tested here as well.
About this being a Nelson Pass design but secretly a DIY audio as it cannot be bought on the Pass website.
On the front of the amplifier it says 'PASS ACA CLASS A AMPLIFIER'
It was designed by Nelson Pass (for whatever reason) and he gave permission to market it by DIY audio.
I reckon it is a design N. Pass stands behind otherwise it would have not been called 'PASS ACA CLASS A AMPLIFIER'
Besides, may of his designs will measure similarly because N. Pass designs this way and likes it (so do his customers)
Most of these devices will be audibly transparent enough to sound good with music under normal circumstances.
There is no 'magic' in there. The magic that is there (the distortion) is designed in there on purpose.
So while the comments may be harsh the measurements are justified as far as technical performance is concerned (well aside from proper adjustment not being verified).
That doesn't mean many afficionados won't like how it sounds.
Stefano_Milano
Member
It costs less this amp already assembled with HYPEX modules UcD250LPOEM
https://www.amazon.it/dp/B00J8LBYGQ
https://www.amazon.de/dp/B00J8LBYGQ
https://www.amazon.it/dp/B00J8LBYGQ
https://www.amazon.de/dp/B00J8LBYGQ
- Joined
- Oct 11, 2018
- Messages
- 3,739
- Likes
- 6,448
I guess enough is enough, and I've piled on my share. So I'll move on. As a last word, I'd have no problems if Nelson invited a group of fans over for a 'lunch 'n learn', and said, "I know you guys aren't techies, so here's a free bag of parts. Bring your own soldering gun and we'll have some fun. The product will most likely wind up in your closet, because it's just meant for a fun outing." I sort of get that (although I really don't know why, if someone is going to go to all the trouble to build something, they wouldn't make the project more useful).
However, if later I found out that one of the attendees started selling my bag of parts, a case and power supply for three bills, and then had the gall to put my name on it... well, in that case I'd be on the phone with the guy selling it, or my lawyer, that same day. The fact that he hasn't done it tells me he must approve of what's going down under his name. Or just doesn't care. That part of the equation I just don't get. Next...
However, if later I found out that one of the attendees started selling my bag of parts, a case and power supply for three bills, and then had the gall to put my name on it... well, in that case I'd be on the phone with the guy selling it, or my lawyer, that same day. The fact that he hasn't done it tells me he must approve of what's going down under his name. Or just doesn't care. That part of the equation I just don't get. Next...
solderdude
Grand Contributor
Pass is fully aware of this and give his permission. The fact that he sells amps that are close in distortion numbers tells me he has a different approach to what is good enough and or 'good sounding' than that of most ASR members. Pass states specifications and has explained his builds often.
Those wanting perfect measurements simply should look elsewhere. The facts about this amp are known.
Now if someone would be brave enough to send a 'First Watt' amp to Amir for testing we can seen what Pass really has up his sleeve.
Nelson is a big supporter of diyaudio and Burning Amp. No secret there. And he releases stuff to them without compensation for them to be able to raise operating funds.
I think you miss the point of the project. It's for entertainment purposes, there's no false claims being made, it is exactly as advertised. If that doesn't interest you, fine- it's not interesting to me either, but I'm not bent out of shape or pissed at Nelson because that idea of entertainment isn't mine.
- Joined
- Nov 6, 2018
- Messages
- 1,448
- Likes
- 4,812
There's that one, for example
https://www.stereophile.com/content/first-watt-sit-3-power-amplifier-measurements
Not fundamentally different from ACA when one thinks about it.
Now, while I am very much in the "transparent signal, eventually DSP/modify to taste" camp vs "be stuck with a non-transparent signal you won't be able to fix (aka 'house sound')" I still think that people are free to have their own preferences. Transparent is a better starting, or endpoint is a rational opinion to hold but it doesn't mean listening in that mode is mandatory.
I own excellent devices by ASR standards, but also own very poor devices by the same standards and I enjoy listening to all of them. There's a particularly awful (in terms of measurements) solid-state/tube hybrid I have kept using now and then for 16 years now and I still love it.
Also, could my transparent systems be DSP'ed into emulating that device? I guess it could, yes. But this would be time-consuming, possibly beyond my ability and would probably require hardware/software more expensive than that crappy device was.
¡Yo también!
One thing about NP (and I'm a self-admitted fanboi) is that he shares information, designs, and design principles with the community and does so freely. Nelson doesn't hide information or measurements and talks about the goals for his designs. What initially attracted me to his ideas was the conceptual simplicity, the short signal path, very few active components. That's also what makes his designs great for DIYs and tinkerers.
Good to see that I am not alone in trying to make my point twice and people are too busy to beat the dead horse to notice there is a reason and place for this mini class A amp.
So to your point (again that I tired to make twice before..), I built this thing and had run it against my other amps including a 4B SST and Halo A21, also ran REW to compare the FR. Obviously I took precautions by putting two ACinfinity fans on top of the heat sinks, and ran REW at low level, about 70 dB from about 8 ft. The fact is:
- From where I sat, 0.1 W average was enough to get almost 70 dB average from my pair of KEF R900 that has sensitivity of 90 dB.
- For the Jazz music (Patricia Barber, Diana Krall etc...), there were probably peaks of up to 12 dB, but mostly well below that.
So for those listening sessions, as expected I really couldn't tell a difference between using this mini and my much larger amps such as the A21, the only clue was the bass, but even that wasn't very obvious. Now, if I play something like 1812 overture, then the difference would be obvious lol..
I also tried using my AVC to drive it so I could get some help from a sub, and that did help the bass to be more acceptable.
So I am going to say for those who built this as their DIY amp, try to find use of it in a small room, like a bed room, use speakers with sensitivity of at least 88 dB/2.83V/1m, 8 ohms nominal, sit within 8 ft and I can assure you if you just focus on the music you can pretend it is a $2,000 100 W/Ch amp, just don't go for higher than 70 dB spl average. You can obviously go louder if you sit closer, like 2 meters, and stick >=93 dB sensitive speakers.
Imo this thing should not have been rated 8 W or even 5 W, but may be 2-3 W is fair..
solderdude
Grand Contributor
Technically is remains a poor performing design.
There simply is no way around it.
Good enough under some circumstances ... yes.
There simply is no way around it.
Good enough under some circumstances ... yes.
maty
Major Contributor
When you buy an amplifier you have to make sure that it is able to play high quality recordings with high DR. 80 dBSPL is too high in an usual room, but it is a useful value for estimate the power required. We want the amplifier to always work in its comfort zone, where it has the best measurements.
At 70 dBSPL I can clearly differentiate between my two audio systems, with the type of recordings I usually listen to,
that is why I love my little mod coaxial (true 85 dB/W/m) so much in front of my Big 3-way boxes, 91 dB/W/m.
At 70 dBSPL I can clearly differentiate between my two audio systems, with the type of recordings I usually listen to,
that is why I love my little mod coaxial (true 85 dB/W/m) so much in front of my Big 3-way boxes, 91 dB/W/m.
This shows how big a scam this is. That power supply is $49, should be $18. 172% overpriced! https://www.amazon.com/s?k=24V+5A+POWER+SUPPLY&ref=nb_sb_noss_2
To me, transparent means "does not modify the signal in an audible way."
What do you mean by "audibly transparent enough"?
maty
Major Contributor
solderdude
Grand Contributor
I have yet to encounter an individual that can tell added distortion products below -80dB from say added distortion products of say -100dB using real music in normal to comfortably loud listening conditions.
So to me THD < 0.01% is 'transparent enough' which doesn't mean that technically a device with distortion products below -120dB is not better.
So Technically the design is poor but when not used above say 1W I don't think one can audibly tell it apart from any other reasonably well designed amplifier. In those circumstances I consider it audibly transparent enough.
I would not buy nor build this device and when I got one for free would rip out the PCB's and build something more decent in there with a more usable range of output power.
Similar threads
- Poll