That is the crux of the matter, transparent sound ie. sound with low distortion which is not linearly related to distortion of the amp. A negative phase H2 correctly applied will cancel some of speaker generated distortion. How much distortion does the ACA made through the speaker you measured and how much distortion the so called tranparent amp at 88 dB SPL? Did you measure distortion at reversed speaker polarity to make sure correct phasing that cancel speaker distortion? Did you even measure?
As you repeat this often, you seem to believe it. How does it apply to all kinds of intermodulation distortions introduced by the amp with high H2, do they also cancel speaker generated intermodulation distortions? How about phase of distortion components to be cancelled? Do you speak based on your opinions, or you have done some research and real world measurements that would support your opinion written here above?
Coming soon, a work in progress. 🙂
In the mean time, you can look at what Circlomanen has done here and Diegomj1973 here.
Won't work well for you since your speaker is multiway crossed close to 1kHz with phase inversion. The phase inversion will add distortion after crossover freq like what happened to Plasnu here.
To judge the amps we play with in this forum the ACA is not the right amp to judge. It should be a Class A amp without global NFB like M2X, Korg Nutube etc.
The goal has never been to design an amp with 0.000001% distortion on paper but an amp that sounds subjective better compared to the 0.000001% amps. As Nelson says…..it is entertainment not dialysis. It seems that even in recording studios H2 is added to make it "sound better"?
To my ears instrument sounds more natural and better after I sold my Nad M3 with damping factor of 150 etc. and got a small SE tube amp. After this I found out I could get same listening experience with FETs and the DIY fun part of it.....to build something simple that subjective sounds better than expensive commercial amps. What have impressed me with these amps is how good a string sounds when it fades out and we are down to mW into the speakers. I care much more about how the amp sounds at 5 mW than 500 W ……
A pianist I know has approved the sound of piano music from my speakers with Pass forum amps. A Steinway D is a bit of a challenge to reproduce at home.....
Even at the big HiFi shows around……a lot of the so called "high-end" equipment sounds awful to my ears.
The goal has never been to design an amp with 0.000001% distortion on paper but an amp that sounds subjective better compared to the 0.000001% amps. As Nelson says…..it is entertainment not dialysis. It seems that even in recording studios H2 is added to make it "sound better"?
To my ears instrument sounds more natural and better after I sold my Nad M3 with damping factor of 150 etc. and got a small SE tube amp. After this I found out I could get same listening experience with FETs and the DIY fun part of it.....to build something simple that subjective sounds better than expensive commercial amps. What have impressed me with these amps is how good a string sounds when it fades out and we are down to mW into the speakers. I care much more about how the amp sounds at 5 mW than 500 W ……
A pianist I know has approved the sound of piano music from my speakers with Pass forum amps. A Steinway D is a bit of a challenge to reproduce at home.....
Even at the big HiFi shows around……a lot of the so called "high-end" equipment sounds awful to my ears.
HA! ACA is almost too loud!
After a few days with many hours of ACA-bliss (it needed a little run-in time), I am caught up in a conflict:
After a few days with many hours of ACA-bliss (it needed a little run-in time), I am caught up in a conflict:
- ACA running in "classic" mode as a Stereo-Amp is already too loud for the setup I have at the moment: Mac -> Herus DAC -> ACA -> Kef 101/2 (86dB / 1m / pink noise input of 2.83V) — I run the mac somewhere between 20% and 50% which is really loud.
- On the other hand, I am sooo tempted to get me a second unit and run them in bridged (or parallel, once the gear is built) mode, though this'd be a total overkill in loudness (amplification).
- How can I enjoy the full potential of this little gem? (Am I already enjoying it even when it's running low, since it's a class A, and I should get a proper/better attenuator at input-level (B1) 😉?)
- How big a chassis should be used to run a dual-mono one-case ACA? (mini dissipate 3-U sufficient?)
- If I'd stack 2 mini dissipate 2U, would the upper unit overheat? (What is the impact of lower/higher temperatures anyway?)
- What happens if I run ACA on a lower BIAS, like 9V, would this only limit the Dynamic range of ACA, but not the amplification, right? And I guess this probably wouldn't be recommended without changing the Meanwell (or tweaking components)?
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I had this problem with my Audio Innovations Valve amp just too much gain for the new speakers I'd built. The solution was to split the incoming signal before the volume pot. Hi Fi Collective sent me this sketch and then because I only needed a couple to do the job I bought some flash Z foil resistors to do the job.
The expensive high end alternative would be a pair of these NB Price is for one and you'll need a pair:
Fostex R100T Transformer Type Attenuator
I'm running a pair of ACA and the Korg preamp with no problems and I ran the ACA direct from Cambridge DAC magic before that without volume control issues.
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Those speakers are gorgeous! Very pretty. Bet they sound great too.
Also, my favorite movie of all time is Blade Runner.
Also, my favorite movie of all time is Blade Runner.
Authorised replica of these out of production for a long time:
http://www.audioevidence.com/pdf/Hi-Fi News Review.pdf
Kit of CNC parts from here:
Home
Build log: Carfrae Little Big Horn Build - DIY Audio Projects - StereoNET
Very efficient max recommended Watts 20 hence my interest in the ACA.
you are explaining yourself over and over again.
it can only mean one thing - you are not doing it very well.
not sure how critical your listening skills are but judging by your so called "review" you are not very good at that either.
don't know what your job requirements are and don't care, it is irrelevant here on this forum.
you do not know me or anything about my listening skills so...make your own conclusions.
at the end you achieved your goal - gaining cheap publicity slagging the work of much more knowledgeable and tolerant people than yourself.
please don't waste our time with more drivel.
To everyone else - apologies for the outburst, I will retreat now from this discussion and concentrate on something positive.
So many thoughts in my head... but I will try to mention only a few:
- I am an old fashion guy and I like to pay due respect when I see a man of stature, dedication, willing to help DIY community, willing to sacrifice his own time
- I like the minimalist approach idea, especially if it has only two gain stages; second of which operates in a single-ended pure class-A mode
- I have two ACA's and I am very happy with the sound; can I hear the distortions - definitely. The ACA's are supposed to introduce the un-initialised to sound of two transistors clapping. Many liked what they achieved, and moved forward to Aleph's and other designs. Again, these designs have been shared with the whole DIY audio community, unselfishly. This here, on its own, deserves re-reading my first paragraph over and over again.
- Would I like to see thing done differently? Well, I can not really ask for a better community of DIY-ers than this one here.
To amirmaj
- I do like your website, at least I used to…. I head the respect for your measurements and technical acumen I felt was present whenever I read your reviews. However, the way you presented the ACA is disrespectful. You completely omitted/missed to identify the sole purpose of ACA existence, and that is an introduction to possible great many listening pleasures that a two gain stage, pure class-A single-ended design can provide. With proper, very sensitive speakers, one can stop right there, at the ACA’s. With less sensitive speakers, an initialised one can now move to Aleph’s and have an excellent amplifier.
- If the specs don’t look good, then instead of trying to emphasize how awful the ACA’s are -> please provide an alternative… that are of the same topology, same sound, come in full (beautiful) kits, have the backing of such a wonderful bunch of people, the designer included!!!
- I am an old fashion guy and I like to pay due respect when I see a man of stature, dedication, willing to help DIY community, willing to sacrifice his own time
- I like the minimalist approach idea, especially if it has only two gain stages; second of which operates in a single-ended pure class-A mode
- I have two ACA's and I am very happy with the sound; can I hear the distortions - definitely. The ACA's are supposed to introduce the un-initialised to sound of two transistors clapping. Many liked what they achieved, and moved forward to Aleph's and other designs. Again, these designs have been shared with the whole DIY audio community, unselfishly. This here, on its own, deserves re-reading my first paragraph over and over again.
- Would I like to see thing done differently? Well, I can not really ask for a better community of DIY-ers than this one here.
To amirmaj
- I do like your website, at least I used to…. I head the respect for your measurements and technical acumen I felt was present whenever I read your reviews. However, the way you presented the ACA is disrespectful. You completely omitted/missed to identify the sole purpose of ACA existence, and that is an introduction to possible great many listening pleasures that a two gain stage, pure class-A single-ended design can provide. With proper, very sensitive speakers, one can stop right there, at the ACA’s. With less sensitive speakers, an initialised one can now move to Aleph’s and have an excellent amplifier.
- If the specs don’t look good, then instead of trying to emphasize how awful the ACA’s are -> please provide an alternative… that are of the same topology, same sound, come in full (beautiful) kits, have the backing of such a wonderful bunch of people, the designer included!!!
Spot on E_B.
I've been a life long music lover, both playing and listening. I used to buy all my gear. I eventually began building my own speakers because I knew I wouldn't electrocute myself doing it. I then eventually moved to the B1 buffer and preamps with gain.
Still afraid of building amps (I am an arts guy), I stumbled across the ACA. I built a pair and I couldn't believe how good it sounded - with the right pair if speakers.
Since then I've built the F6, M2, the Aleph J, and many preamp designs, and I still don't consider that I know much about electronics.
However, I do know that my system has never sounded as good when it was being driven by expensive, high powered commercial gear. The First Watt style amps were a radical departure from my previous amps, and I am consistently amazed at the sound emanating from my speakers.. It all started with this community and the ACA.
I don't want to jump all over someone with a different opinion about what an amp should do, but it would be a shame if someone read that ACA review and decided not to embark on DIY amp building because of it. It's been an immensely satisfying hobby for me, and my ears have never been happier.
I've been a life long music lover, both playing and listening. I used to buy all my gear. I eventually began building my own speakers because I knew I wouldn't electrocute myself doing it. I then eventually moved to the B1 buffer and preamps with gain.
Still afraid of building amps (I am an arts guy), I stumbled across the ACA. I built a pair and I couldn't believe how good it sounded - with the right pair if speakers.
Since then I've built the F6, M2, the Aleph J, and many preamp designs, and I still don't consider that I know much about electronics.
However, I do know that my system has never sounded as good when it was being driven by expensive, high powered commercial gear. The First Watt style amps were a radical departure from my previous amps, and I am consistently amazed at the sound emanating from my speakers.. It all started with this community and the ACA.
I don't want to jump all over someone with a different opinion about what an amp should do, but it would be a shame if someone read that ACA review and decided not to embark on DIY amp building because of it. It's been an immensely satisfying hobby for me, and my ears have never been happier.
First, I am that way with all the reviews I do. I am not interested in the back story, flowery reviews from others or owners, etc. I run a set of objective measurements against every piece of equipment and that is that.
That aside, I don't understand your criticism. Here is the second sentence in the review: "It is a DIY design by the famous designer, Nelson Pass, meant to be starter amplifier for people new to audio electronics to build."
"Listening pleasure" is not something that is discussed in the context of audio measurements. I can get listening pleasure out of a clock radio with my favorite album. That is neither there, nor here.
Again, I am not involving emotion in these reviews. They are strictly based on objective facts. In this case, the ACA produced the worst response of any Amplifier I have ever measured:
As a person who strives in engineering excellence and most transparency in audio gear, you can't expect me to try to spin the above into something positive. I would be called on it by the membership immediately.
As to other kits, that is not my job to provide. I review what is sent to me as a service to audiophile community.
You can suggest other kits I highly recommend Neurochrome kits. That is how you build high performance amplifiers. Tom is an active member here and really knows his stuff. Here is my review of his Modulus-256: Review and Measurements of Neurochrome Modulus-286 Amp | Audio Science Review (ASR) Foruml]. It finish fourth in the graph above.
Yes it is more expensive but he has lower cost kits. And the one I reviewed comes in the same case as ACA I reviewed. Except that the power supply is internal so you don't have a big brick hanging from back of it.
And let me be very clear: I am NOT reviewing Nelson, his life, or his knowledge. I am reviewing a piece of audio gear which had to stand on its own two feet. Sadly it did not. That's all.
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Granted, the ACA does measure poorly.
….. but that doesn’t matter.
The power cables made out of litz copper wires and solid-core copper wires will sound completely different, but this CAN NOT be measured. I suppose you will eventually get that the measurements… are not important if something sounds really nice to an individual.
It is also about the concept –> the simplistic, no SMD-approach, where the delicate analogue signal is amplified in its purest, unconverted form (no digital amplification), only by two discrete transistors (no amp-on-a-chip IC’s).
We all know that ACA distortions creep in at max output. But, it still sounds great. It conveys emotion, rhythmic drive and ease of musical presentation in the way that amp-on-a-chip can't approach. It does not matter how poorly it measures (it actually measures okay at 1Watt output, which is plenty with appropriate speakers).
The reason why the ACA has an external power supply, instead of an internal, is to ensure the DIY beginners do not have to deal with mains voltages. But, the power supply can go inside, the wires can be shortened, the litz cables can be replaced….and the whole package will sound much much better.
2A3 designs will also measure poorly at their max output of 3 W. But their first watt sounds so wonderful. Even driven into soft clipping, they will still sound wonderful. The best. The ACA can be wired in a pseudo-bridged config, that will amplify the H2 - which will bring the ACA sound even further towards the valve sound. The Korg pre-amp is designed with this in mind as well.
The ACA concept is the result of a FirstWatt “movement”, where the fist watt matters the most. It is an introduction to a two gain stage design. Almost all DIY-ers who built it, move on to outstanding designs such as Aleph J.
You are comparing an amp-on-a chip design with a 2 gain-stage single-ended pure class A design. One will sound pleasing and relaxed, the other clean and clinical. These two can't be further apart sound-wise.
With this in mind, it’s irrelevant what the measurements (yours, or for that matter – Nelson’s) say. The poor measurements have not stopped the hordes of DIY-ers from building these amps.
….. but that doesn’t matter.
The power cables made out of litz copper wires and solid-core copper wires will sound completely different, but this CAN NOT be measured. I suppose you will eventually get that the measurements… are not important if something sounds really nice to an individual.
It is also about the concept –> the simplistic, no SMD-approach, where the delicate analogue signal is amplified in its purest, unconverted form (no digital amplification), only by two discrete transistors (no amp-on-a-chip IC’s).
We all know that ACA distortions creep in at max output. But, it still sounds great. It conveys emotion, rhythmic drive and ease of musical presentation in the way that amp-on-a-chip can't approach. It does not matter how poorly it measures (it actually measures okay at 1Watt output, which is plenty with appropriate speakers).
The reason why the ACA has an external power supply, instead of an internal, is to ensure the DIY beginners do not have to deal with mains voltages. But, the power supply can go inside, the wires can be shortened, the litz cables can be replaced….and the whole package will sound much much better.
2A3 designs will also measure poorly at their max output of 3 W. But their first watt sounds so wonderful. Even driven into soft clipping, they will still sound wonderful. The best. The ACA can be wired in a pseudo-bridged config, that will amplify the H2 - which will bring the ACA sound even further towards the valve sound. The Korg pre-amp is designed with this in mind as well.
The ACA concept is the result of a FirstWatt “movement”, where the fist watt matters the most. It is an introduction to a two gain stage design. Almost all DIY-ers who built it, move on to outstanding designs such as Aleph J.
You are comparing an amp-on-a chip design with a 2 gain-stage single-ended pure class A design. One will sound pleasing and relaxed, the other clean and clinical. These two can't be further apart sound-wise.
With this in mind, it’s irrelevant what the measurements (yours, or for that matter – Nelson’s) say. The poor measurements have not stopped the hordes of DIY-ers from building these amps.
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i would like to seek for any experience on in sensitive speaker pairing like atc, dynaudio speaker. hows is the experience.
however, driving a speaker well and driving it loud is 2 different thing i assume?
however, driving a speaker well and driving it loud is 2 different thing i assume?
With two ACA's in monoblock, pseudo-bridged configuration (more voltage, more H2 distortions), I do not have ANY trouble achieving unpleasant sound levels with my 86dB sensitive Dynaudio Contour 1.3 speakers.
ACA's connected in parallel config will have a better bass drive, but I like the bridged sound better. A matter of taste...
See here for an easy flick-of-a-switch bridged <-> monoblock configuration change:
Monoblock ACA bridged mono <=> parallel mono at the flick of a switch
ACA's connected in parallel config will have a better bass drive, but I like the bridged sound better. A matter of taste...
See here for an easy flick-of-a-switch bridged <-> monoblock configuration change:
Monoblock ACA bridged mono <=> parallel mono at the flick of a switch
to amirmaj:
I know you did not start this diversion of the main topic here but you keep feeding into it.
AFAIK this thread is about building the ACA amp, difficulties, experiences, so on.
If you want to talk about your review open a new thread and see if you'll attract any interest.
The way I see it you are trying to hijack the thread here to promote your activity, knowing that the ACA thread has a great following.
In my book that is called trolling.
It's no different to the behavior of the eBay sellers who promote PCBs based on FW designs.
So, either stick to the topic (build an ACA) or move your nonsense to a different thread.
Or maybe the moderators should look into it.
I know you did not start this diversion of the main topic here but you keep feeding into it.
AFAIK this thread is about building the ACA amp, difficulties, experiences, so on.
If you want to talk about your review open a new thread and see if you'll attract any interest.
The way I see it you are trying to hijack the thread here to promote your activity, knowing that the ACA thread has a great following.
In my book that is called trolling.
It's no different to the behavior of the eBay sellers who promote PCBs based on FW designs.
So, either stick to the topic (build an ACA) or move your nonsense to a different thread.
Or maybe the moderators should look into it.
wow, that was cool. by the way , what do u mean pseudo-bridge configuration? is it same as the former bridge mode?
It is not a true bridged mode, where you feed the differential signal in and get the cancellation of H2
You take the output from one ACA module, reduce the amplitude, and feed it to another ACA module... as shown in the original Build Guide. I call it a pseudo-bridged mode of operation
You take the output from one ACA module, reduce the amplitude, and feed it to another ACA module... as shown in the original Build Guide. I call it a pseudo-bridged mode of operation
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amirmaj is typical engineer with ingrained mixed up assumption, he talked about transparent sound which he clearly did not show any measurement. Perhaps he loves to listen to his speaker distortion so much he wants to listen to it as pristine as possible.
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