Pass ACA Class A Power Amplifier Review

[Thomas Savage]

Thank you for your kindness, Tom. Are you the Tom with whom I should be seeking conversation? Neurochrome Tom?

I'm not Neurochome Tom , iv not quite worked out what I am but I definitely can't be trusted around high voltages.

 

[wow77459]

My experience may parallel you to a degree which makes this even more exciting. I will let you know once I commit to something and prayerfully I will live through the experience and enjoy the new sounds.

 

[DonH56]

I'm not Neurochome Tom , iv not quite worked out what I am but I definitely can't be trusted around high voltages.

FIFY. (From the "takes one to know one" group of fans.)

 

[mhardy6647]

I'm not Neurochome Tom , iv not quite worked out what I am but I definitely can't be trusted around high voltages.

Just remember -- one can be shocked many times... but one can only be electrocuted once.


Measuring high voltages -- Just follow Alanis Morissette's advice:

Spoiler: YT video within

One Hand In My Pocket

EDIT: PS If my name were Neurochrome Tom -- I think I'd have it tattooed somewhere prominently.

 

[wow77459]

Took me about 3 and a half minutes to understand your advice. Certainly enough time to get shocked many times over.

I kept waiting for her to say her hand was in an insulated glove.

Neurochrome Tom has identified a number of weak points on my end that I haven't properly thought through. I may not even get out of the starting gate on this one. That's probably a good thing to know now rather than later.

You cautioning me about high voltage, and keeping a hand in a pocket and Tom's partial of my possible tool purchases and offering suggestions that have me questioning whether or not I want to make a proper investment into tools I may only need this one time.

On a side note, I did just get my Caintuck F-15 open baffles and I am enjoying them even though they are supposed to not be in their prime just yet.

You may have given Tom something to consider.

 

[ta240]

If you want build something and it is for speakers and have little to no experience perhaps start with encasing a class-D amp and its power supply using the better class-D amps.

The ACA is not very powerful. Depending on your speakers, the size of the room they will be used in and how loud you occasionally want to play the ACA might disappoint.
Sure you would have built something (populated a board) and made a casing for it but would likely be a waste of money.

The Neurochrome kits are more likely not to disappoint.

I would not recommend to go down the tube-amp build route as there are lethal voltages involved and when tinkering with it a charged capacitor is not a good place to be.

My first build was an ACA. I just bought the boards, then sourced the components separately so I didn't have a lot invested in them. I don't think I spent over a couple hours listening to it. I've always wondered if I did something wrong based on the glowing reviews it receives. Even at low volumes I wasn't impressed. Although, one time I fed it with the 02 Headphone amp on high gain as a preamp and thought it sounded better.

My second build was a single ended tube amp. I don't know if a lot of it was the fun of building it but when I was done it sounded exquisite. Then I chased tweaks, capacitors and tube rolling down the rabbit hole and it never sounded the same. With one set of tubes the highs would sound good, with another the lows sounded good. Whenever I turned it on I'd think it sounded great, but I don't know if it was always in the back of my head that a different tube might sound 'better' but I was never happy long term with it. And when a song would come on that I'd like and turn it up I could hear it struggling. Even a low powered SE like it used 90 watts continuously and put out a fair amount of heat in the summer. Now that I run the stereo 12-16 hours a day and use music to drown out the neighbors, it just doesn't seem optimal.
That amp was in a wood case (treated with fireproofing) so I never got a bad shock off of it. However one I did get careless with one that I used in the garage and sent 400v down one arm, through my chest and out the other. That did not feel good and I probably should have seen someone about it.

I built Rod Elliott's PA3 and I still enjoy its 'smooth' sound. I don't think it is really a high fidelity sound but it is quite pleasing. Only when I turn it up do I find it not as good.

Later after a few other builds I did the Akitika GT-102. To me that is the perfect beginner DIY amp. Bulletproof instructions, no sourcing of parts, no drilling, no figuring out power supplies or adding speaker protection or and of the other tasks that most builds take. It sounds good.

A few more builds down the road and I finally did the Modulus-86. The boards and instructions were very good, but it requires sourcing a case and power supply and speaker protection. Then fitting it all and making sure it is solidly and safely constructed. To me it seems to sound a bit better than the GT-102 but I may be imagining that. I generally found myself listening to this amp the loudest out of any of them. I wouldn't think about it but would notice after awhile that I had it pretty loud. It is clear and strong at higher volumes.

I also build Rodd Elliott's P101A and it is clear and punchy but I'd kind of like a tone control to up the low end a bit on it.

And then finally, after all those years, all those builds and all that money.... I've decided I really like having a remote control for the power, volume and input switching, plus tone controls are nice. So, tomorrow a Yamaha R-N600A is due to arrive. I really enjoyed the building, the planning, the sourcing parts on the DIY builds. I find the process very Zen and I do miss it. However, looking back, I could have bought a really impressive 'forever' amp for the money I've spent. Instead I have a tote full of completed amp boards and a few completed amps in cases that have no resale value.

 

[GK.]

When you enter the world of audiophilia you are stepping into an alternate universe.

Consider this kind of bullshit in an alternative context. Suppose that I took on a commission from the local HAM radio club to present a design for a basic transistor tuned radio frequency receiver. This is to be an introductory project to give club newbies and novices in electronics something to build and to get them listening to whats on the airwaves.

Imagine that I subsequently turned up to the following committee meeting with my example development. It is this stupidly miss-engineered heap of crap that consumes 300W of power, weighs 50kg and won't even come close to matching the performance of a basic crystal set unless it is paired with some kind of boutique or obscure headphones that nobody actually owns. Oh, and I am going to generously charge the newbies and adolescent novices about $400 AUD for the basic kit.

Would this design be a raging success? Would the grown men of the committee and all of the other club members grovel at my feet and start lovingly calling me their Papa?

No! Idiots and weirdos aren't the norm in this arena. I'd be rightly laughed out of the room and likely ejected from the premises with scorn and contempt.

 

[ta240]

That is a lot of anger about audio reproduction.

As far as I'm aware he doesn't make anything off the sales from DIYAudiostore.com He does have PassDIY.com with 3 items for sale. Those ship from his warehouse and come with a nifty PASSDiy sticker His designs that are for sale on DIYAudiostore site are routinely 'knocked off' by people on the forum that freely distribute the gerber files for their version's of the PCBs, and he will even chime in and give them advice on their designs.

On the subject of stupid, old technology shouldn't all those HAM radio people be ashamed of themselves because they aren't using zoom, facetime or teams to communicate instead of the ancient low quality communication method they are using?

 

[voodooless]

On the subject of stupid, old technology shouldn't all those HAM radio people be ashamed of themselves because they aren't using zoom, facetime or teams to communicate instead of the ancient low quality communication method they are using?

Those people would not claim that their HAM radio gives superior audio quality, though.

 

[dtaylo1066]

And ICEPower or Hypex amp kit is a good and easy way to learn DIY and also get a quality measuring and sounding unit.

 

[rdenney]

Those people would not claim that their HAM radio gives superior audio quality, though.

But they would claim that they complete their communications of often planetary distances without using publicly available infrastructure, which is frequently enough not available in circumstances extant at one end or the other.

And for them that’s the challenge, and doing it well isn’t that easy.

Rick “whose ham radio gives close to the best audio quality for communications from here to the other side of the planet when limited to using only two radios, two antennas, and two portable generators” Denney

 

[solderdude]

My first build was an ACA. I just bought the boards, then sourced the components separately so I didn't have a lot invested in them. I don't think I spent over a couple hours listening to it. I've always wondered if I did something wrong based on the glowing reviews it receives. Even at low volumes I wasn't impressed. Although, one time I fed it with the 02 Headphone amp on high gain as a preamp and thought it sounded better.

My second build was a single ended tube amp. I don't know if a lot of it was the fun of building it but when I was done it sounded exquisite. Then I chased tweaks, capacitors and tube rolling down the rabbit hole and it never sounded the same. With one set of tubes the highs would sound good, with another the lows sounded good. Whenever I turned it on I'd think it sounded great, but I don't know if it was always in the back of my head that a different tube might sound 'better' but I was never happy long term with it. And when a song would come on that I'd like and turn it up I could hear it struggling. Even a low powered SE like it used 90 watts continuously and put out a fair amount of heat in the summer. Now that I run the stereo 12-16 hours a day and use music to drown out the neighbors, it just doesn't seem optimal.
That amp was in a wood case (treated with fireproofing) so I never got a bad shock off of it. However one I did get careless with one that I used in the garage and sent 400v down one arm, through my chest and out the other. That did not feel good and I probably should have seen someone about it.

I built Rod Elliott's PA3 and I still enjoy its 'smooth' sound. I don't think it is really a high fidelity sound but it is quite pleasing. Only when I turn it up do I find it not as good.

Later after a few other builds I did the Akitika GT-102. To me that is the perfect beginner DIY amp. Bulletproof instructions, no sourcing of parts, no drilling, no figuring out power supplies or adding speaker protection or and of the other tasks that most builds take. It sounds good.

A few more builds down the road and I finally did the Modulus-86. The boards and instructions were very good, but it requires sourcing a case and power supply and speaker protection. Then fitting it all and making sure it is solidly and safely constructed. To me it seems to sound a bit better than the GT-102 but I may be imagining that. I generally found myself listening to this amp the loudest out of any of them. I wouldn't think about it but would notice after awhile that I had it pretty loud. It is clear and strong at higher volumes.

I also build Rodd Elliott's P101A and it is clear and punchy but I'd kind of like a tone control to up the low end a bit on it.

And then finally, after all those years, all those builds and all that money.... I've decided I really like having a remote control for the power, volume and input switching, plus tone controls are nice. So, tomorrow a Yamaha R-N600A is due to arrive. I really enjoyed the building, the planning, the sourcing parts on the DIY builds. I find the process very Zen and I do miss it. However, looking back, I could have bought a really impressive 'forever' amp for the money I've spent. Instead I have a tote full of completed amp boards and a few completed amps in cases that have no resale value.

The journey can often be more rewarding than the final destination.

The money (and time if that were converted to money) I have spent on the headphone hobby itself could probably have bought me a HE-1 but would not have had the experiences that I have accumulated over decades.

The ACA is a fun educational thing when actually building it rather than buying a finished one. It can even make itself useful and will give pride of builder/ownership.

 

[voodooless]

But they would claim that they complete their communications of often planetary distances without using publicly available infrastructure, which is frequently enough not available in circumstances extant at one end or the other.

And for them that’s the challenge, and doing it well isn’t that easy.

Sure. But this is a tangible and measurable metric. They won’t go:

So, yesterday, I talked to Phil from Antarctica. His voice was 300 dB down in the noise, but I could still make him out, clear as night and day!