Pass ACA Class A Power Amplifier Review

[almico]

I have no idea about @almico 's eatery, but in some places it's less about the 'sound' (really, how can anyone judge sound quality in a restaurant?) and more about ambiance with 'mystique'. A cozy atmosphere to relax and have a good time. Below is a link to a Japanese establishment (now closed as its owner left the planet). Lowther and Altec speakers, homemade tube amps, Garrard 301/Grace oil damped arm (with coins to add tracking force help)/Denon 102 mono cartridge and plenty of old jazz records. My impression was that the gear was more for exploring 'camaraderie' within a nostalgic setting.

Not sure about the electrical code in Japan-- exposed wires and high voltages might be considered a danger around all that high proof alcohol!

http://www10.big.or.jp/~dh/codo/tennai/tennai.html

I get the idea of 'pride of ownership' from something hand made. I've done that. As far as the little Amp Camp thing? If I'm going to spend time and effort with construction, I want the finished product to be something I can be proud of, I want it to be something that at least approaches practicality, and something that isn't on the borderline of ridiculous.

I love that! One of my coffee gurus, still with us, but retired, is in Japan. https://roadsandkingdoms.com/2013/daibo/

And the Amp Camps do sound pretty incredible on the 604Cs...for a SS amp that is They are dead quiet and push enough current to drive those 15"s smoothy and quickly.

 

[almico]

Outstanding! Where do you source your beans? I've been using a Hottop roaster for many years, and enjoy trying a few lbs of something new each time I order...

Treated myself to 5lbs of Kona that I'm working through, but my go-to's are Sumatra Mandheling, and the Tanzanian Peaberry. There is a lot of good coffee out there. Best of luck with the new shop!

Be very careful, the coffee rabbit hole is nearly as deep as the audio one. I've been chasing that "best cup ever" since I was 6. It got serious about 10 years ago. I was stunned to learn that people were waiting breathlessly for the next $2000 grinder offering to be released. When I asked: "don't you have a grinder already", they smiled knowingly thinking "you'll see". Now I own more than a dozen grinders, the least of which cost $2000. A grinder is a grinder you say, well, isn't a loudspeaker a loudspeaker. It plays music, what more do you want? Ha.

I started buying #s from Sweet Marias, but graduated to Roastmasters and Klatch. These days I'm buying coffee by the sack from a few large importers. Stuff's about to get real when the new roastery opens. It has a loading dock and I'm not afraid to use it.

Right now I'm sipping a wonderful cup from Aida Batlle's farm in El Salvador, Finca Kilimanjaro* and listening to a nice clarinet and xylophone jam away on the Amp Camps and Altecs.

*Flavor notes: white peach & marzipan, light cream-like body and clean lingering finish.

 

[Sal1950]

I think that arm would be a perfect match for my Presto Pirouette

I haven't seen one like in the picture in decades. It looks to have a REK-O-KUT style tonearm on it now.

 

[BDWoody]

Be very careful, the coffee rabbit hole is nearly as deep as the audio one. I've been chasing that "best cup ever" since I was 6. It got serious about 10 years ago. I was stunned to learn that people were waiting breathlessly for the next $2000 grinder offering to be released. When I asked: "don't you have a grinder already", they smiled knowingly thinking "you'll see". Now I own more than a dozen grinders, the least of which cost $2000. A grinder is a grinder you say, well, isn't a loudspeaker a loudspeaker. It plays music, what more do you want? Ha.

Once you are up and roasting, I'd love to buy a few lbs from you, both whole bean and ground with a super-special grinder... Would be a fun comparison.

I'm not deep in the hole, I just drink a LOT of it, and like playing with the roasts... Plus, green beans are a lot cheaper.

Cheers! Or, is there an equivalent in the coffee world?

 

[almico]

I haven't seen one like in the picture in decades. It looks to have a REK-O-KUT style tonearm on it now.

It does indeed. I've had it for a while, but the previous owner left the motor spindle engaged for 100 years and there was a depression in the rubber drive wheel. I'm waiting for it to smooth out by itself...or the right place to utilize it, whichever comes first. My fantasy coffee bar will have fire bottles, spinning discs and a rack with 2 dozen records on it. Maybe the next one.

As far as the A5s, much work went into that project. I can probably dig up the images, but I braced the 828 cabs inside very well so they don't resonate much at all and they are well-padded. I also ported them and the mid-bass really kicks. I can't get sub-sonic pipe organ notes on them, but bass drums really thumb.

I can't find my measured curves, but here is a link from Diyaudio https://www.diyaudio.com/forums/mul...re-freq-response-roll-bass-2.html#post3716430. GMs post has two links. The first are a typical A5 curves, the second is to my thread about adding subs to them. The subs are a long story, but they sound great, blend perfectly and even measure well! Here's a pic of the speaker, the subs and the dusty x-over. The alligator clips run to the Radio Shack "screaming meemy" Super Tweeters. They also blend very well and help lift the top end of the curve off the pavement. I should probably measure them again after all this time. But I think the software I used has long needed updating.

The link to the bucket sub page https://www.transcendentsound.com/bucket-sub.html. Don't laugh till you've heard them. I'm driving 4 in series with a Crown XLS1500, probably at 2 ohms and 750W/ch, but it hasn't blown up yet. IIRC, I'm getting 33Hz down 3 dB. The magic is you can't really hear them...until you turn the Crown off, then the bottom drops out. Turn it back on, and it's back, but you can't tell from where. Nice.

FWIW, the room is not ideal. It's 20' wide and 10' deep with a stone fireplace right behind my head and double glass doors make up the entire right wall. I pull the heavy curtains when I want to do some critical listening, but... The back wall is open on either side of the fireplace and lets some bass escape into the rest of the house, which is the room's only redeeming feature. It is what it is as they say. I stopped fiddling with it when it dawned on me that I like it the way it is.

And now I'm back to playing with small boxes again...good grief.

 

[LTig]

I have no idea about @almico 's eatery, but in some places it's less about the 'sound' (really, how can anyone judge sound quality in a restaurant?) and more about ambiance with 'mystique'. A cozy atmosphere to relax and have a good time.

Sounds like the perfect application for the Bose Waveradio - seriously.

 

[almico]

Sounds like the perfect application for the Bose Waveradio - seriously.

I have a Heos-7 that would work too. With their app I can play Apple Music, Pandora, Spotify etc. But surprisingly, it sounds phenomenal in a big room...much less so in a small space. But I'll try it before dropping more cash. The Amp Camps might be working their way into the bedroom system anyway.

 

[amirm]

Be very careful, the coffee rabbit hole is nearly as deep as the audio one. I've been chasing that "best cup ever" since I was 6. It got serious about 10 years ago. I was stunned to learn that people were waiting breathlessly for the next $2000 grinder offering to be released. When I asked: "don't you have a grinder already", they smiled knowingly thinking "you'll see". Now I own more than a dozen grinders, the least of which cost $2000. A grinder is a grinder you say, well, isn't a loudspeaker a loudspeaker. It plays music, what more do you want? Ha.

Hmmm. I am thinking for the next category of stuff to test, I should get into grinder testing! Wonder if Audio Precision makes anything for that!!!

 

[almico]

Hmmm. I am thinking for the next category of stuff to test, I should get into grinder testing! Wonder if Audio Precision makes anything for that!!!

Some grinder p()rn to keep you busy for an hour or more.

https://www.instagram.com/titusgrinding/

 

[richard12511]

If that's true, if that's what NP thinks, then how sad is that? I mean, if you're going to go to all the trouble to get a group together and show them how to solder, why would you not have them build something useful and helpful?

Compare with the thinking of David Hafler. Or Stu Hegeman. Or Hermon Scott and Harry Ashley. Or later designers such as Jim Bongiorno and Marshall Leach. I have one of Dave's 60 year old kit amps that runs circles around this little Ampcamp toy. Good grief!

I missed this reply. If I remember correctly, the idea is to make it so simple that they can fully understand what they’re doing at the fundamental level. They can then use that knowledge to help themselves learn more complex designs. Kinda like if you’re trying to teach a young kid calculus, you should probably start by teaching him algebra first. If you jump straight to calculus, he’s likely to just copy you verbatim and absorb none of what he’s writing down.

 

[anmpr1]

If I remember correctly, the idea is to make it so simple that they can fully understand what they’re doing at the fundamental level. Kinda like if you’re trying to teach a young kid calculus, you should probably start by teaching him algebra first

Yes. But using your math analogy, and with this little ampcamp thing, it's as if Nelson is starting out with the basic premise that 1 + 1 = 5. That is, an idea that if you take two very simple things and add them together (i.e., his simple circuit and Nelson's special magic) you will somehow get an extra three or four units of raw goodness and/or quality with the finished product, once you've added it all up.

 

[ElNino]

Yes. But using your math analogy, and with this little ampcamp thing, it's as if Nelson is starting out with the basic premise that 1 + 1 = 5. That is, an idea that if you take two very simple things and add them together (i.e., his simple circuit and Nelson's special magic) you will somehow get an extra three or four units of raw goodness and/or quality with the finished product, once you've added it all up.

I don't see Nelson Pass as promoting any kind of magic. He's honest that his designs have high distortion. He's basically an empiricist, experimenting with how high distortion can get (and with what distortion profile) before becoming "objectionable", and then designing the simplest possible devices to hit that point. By "objectionable", I don't mean neutral or transparent; he's fine if an amp has audible levels of distortion, provided it's largely euphonic from a psychoacoustic perspective for an average listener, basically a tone control. There was a period of time where he was shipping an distortion-generating buffer to people just to experiment with this.

His commercial amps are basically anachronistic now and not something I'd ever recommend, but I think a big part of the reason they gathered a following years ago is because they had decent distortion performance at low-power at a time when low-bias class AB amps with relatively high crossover distortion at low power were common.

 

[anmpr1]

I don't see Nelson Pass as promoting any kind of magic.

I don't want to disparage Nelson uniquely. He's part of a cadre or clique that includes the 'high end' press, dealers, and naive customers who do argue (one cannot deny it) that these designs are magical. They are magical because everyone associated with them tend to obfuscate their true electrical nature, and instead attribute to the gear properties that no one can quite explain logically. Speed, depth, pace and timing, color, slam, plankton, and all the rest. Those are 'magic' words that no one can explain very well, if at all. And while the designers may not come out and use those words, their followers do, and they themselves do not discourage it--at least as far as I can tell.

Again, I don't want to single Pass out. Other names can be included, such as John Curl, Bascom King (PS Audio) et al. Men who can be contrasted with names such as David Hafler, Stu Hegeman, Gordon Gow (off the top of my head)--men who represented the opposite. This is not to say that boutique designs are ipso facto not suitable for their intended purpose, or are necessarily snake oil, or that they wouldn't 'perform' well on the bench. It is just that what are often claimed for them, as designs, go above and beyond any rational explanation. Hence, my use of the word 'magic'.

 

[Lorenzo74]

Hmmm. I am thinking for the next category of stuff to test, I should get into grinder testing! Wonder if Audio Precision makes anything for that!!!

since you live in Seattle i assume did you know that starbucks founder was inspired by Caffe sant’Eustacchio in Rome?(or this is another metropolitan legend...?)

I have many friends from US that when came to Rome, buy there beans (wood roasted) for their high end coffee...
Happy to support this by product stream.
my Best
Lorenzo

 

[amirm]

since you live in Seattle i assume did you know that starbucks founder was inspired by Caffe sant’Eustacchio in Rome?(or this is another metropolitan legend...?)

I do not. I don't drink coffee. I drink tea! My two sons though are way into it with one working for a while in a coffee shop. We buy them stuff for Christmas related to coffee making which we have no idea about! They tell us what they want and we just order them.

 

[almico]

since you live in Seattle i assume did you know that starbucks founder was inspired by Caffe sant’Eustacchio in Rome?(or this is another metropolitan legend...?)

I have many friends from US that when came to Rome, buy there beans (wood roasted) for their high end coffee...
Happy to support this by product stream.
my Best
Lorenzo

Not saying I'm taking over Italy's coffee trade, but my coffee is enjoyed there.

As far as the amp camps...I'm not going to stop some numbers on a piece of measuring equipment to stop me from enjoying them.

But it is definitely not for the "trying to get 30Hz from a bookshelf speaker" crowd, or even a floor speaker for that matter. Hook it up to a pair of high efficiency speakers and it is as musical as it gets, certainly for the price. For near field desktops amps it would be ideal.

.

 

[mhardy6647]

I drink tea!

green? black? oolong? white? yellow?
enquiring minds want to know!
Mrs. H & I are big fans of fermented leaves of Camellia sinensis extracted with hot water -- although, Philistines that we are, mostly "English style" (strong black teas like Assams, adulterated with milk & sugar).

That said, I'll quaff pretty much anyting caffeinated, although I have - so far - drawn the line at yerba mate. I'm afraid I might schizo out after one hit.

 

[amirm]

green? black? oolong? white? yellow?

For everyday, it is black (Earl Gray and sometimes Darjeeling). With Japanese food, it is green. With Chinese, it could be green, or oolong. In Korea, enjoyed white tea a lot but have not sought it out in US. Yellow? I don't know about that. I have had Chrysanthemum flower tea which kind of looks yellow. Is that what you mean?

Have also had plumb tea in Japan as well.

 

[NTomokawa]

plumb tea

You mean plum tea, right?

Or maybe the Japanese make tea with plumb-bobs, in which case they are far more badass than I'd ever thought!

 

[mhardy6647]

For everyday, it is black (Earl Gray and sometimes Darjeeling). With Japanese food, it is green. With Chinese, it could be green, or oolong. In Korea, enjoyed white tea a lot but have not sought it out in US. Yellow? I don't know about that. I have had Chrysanthemum flower tea which kind of looks yellow. Is that what you mean?

Have also had plumb tea in Japan as well.

No, there are "orthodox" teas (as opposed to tisanes) called yellow tea(s). I've not had yellow tea -- but it exists. That's just about all I know, too!
https://marktwendell.com/huo-shan-yellow-sprouting.html

We lived about 15 minutes from Mark T. Wendell Teas' storefront/business when we lived in MA -- although, in full disclosure, our primary tea connection, umm, I mean purveyor is another Mass-based concern: https://www.uptontea.com/