ACA-Nelson Pass's Amp Camp Amp

[CWelsh]

2 hours ago, The Dude said:

I have not, still in the hunting and gathering part in regards to components.  Since I have other projects that take priority, this is on the back burner until fall/winter.  

 

Have you considered the SP14?

Hi have, but the price increase is substantial to get the SP14 with a remote and I haven't gotten beyond my bang-for-the-buck tendencies. Especially since I plan to buy a second ACA.

[CWelsh]

I just ordered my second ACA. Going to see just how far I can go with them.

[CWelsh]

The new ACA is up and running! In each of the available options (bi-amp, bridged mono and parallel mono) there is an improvement over the single ACA. The essence of the sound doesn't change, but there is more detail, the sound stage seems to have greater depth, and the bass is tighter. What I found with the parallel mono mode, is how all the improvements are very noticeable at lower volumes. This is a pretty big change from the single amp.

 

These things seem to be made for Klipsch speakers. For less than $750, I have 15 wpc of single ended pure class A amplification. Not too shabby, if you ask me.

[The Dude]

8 hours ago, CWelsh said:

The new ACA is up and running! In each of the available options (bi-amp, bridged mono and parallel mono) there is an improvement over the single ACA. The essence of the sound doesn't change, but there is more detail, the sound stage seems to have greater depth, and the bass is tighter. What I found with the parallel mono mode, is how all the improvements are very noticeable at lower volumes. This is a pretty big change from the single amp.

 

These things seem to be made for Klipsch speakers. For less than $750, I have 15 wpc of single ended pure class A amplification. Not too shabby, if you ask me.

That's good to know, I'd be interested to know how one would handle gain matching each channel to insure accurate levels out of each amp. I know some of the Tubes4Hifi pre amps have individual channel gains, so I assume one could accomplish it by that means.

[CWelsh]

13 hours ago, The Dude said:

That's good to know, I'd be interested to know how one would handle gain matching each channel to insure accurate levels out of each amp. I know some of the Tubes4Hifi pre amps have individual channel gains, so I assume one could accomplish it by that means.

That's a good question. I spent a fair amount of time doing an A B comparison to make sure there were no glowing differences, but that isn't the same as taking measurements. Maybe someone with more technical know how that I have will chime in with a suggestion. Do you suppose measuring voltage at the speaker terminals might do it?

 

At some point, I intend to build and try the DIY Audio active bi-amp crossover, which I believe should offer the same capabilities for individual channel gain adjustments. In the amp itself, I think minor tweaks to the bias pots might do it. I'm guessing, here.

[geezin']

Recently looked on ASR to see how the Pass ACA fared. Not well by his standards. What am I not (hearing) seeing?

[The Dude]

2 hours ago, geezin' said:

Recently looked on ASR to see how the Pass ACA fared. Not well by his standards. What am I not (hearing) seeing?

What is ASR? 

[Edgar]

2 hours ago, geezin' said:

Recently looked on ASR to see how the Pass ACA fared. Not well by his standards. What am I not (hearing) seeing?

It just shows that something can measure poorly but still sound pleasing. I used "pleasing" intentionally, to emphasize subjectivity.

 

@The Dude, ASR is Audio Science Review.

[The Dude]

2 hours ago, geezin' said:

Recently looked on ASR to see how the Pass ACA fared. Not well by his standards. What am I not (hearing) seeing?

You're comparing a $300 diy kit to $4000 commercially built amplifier. I'm not an engineer, but I'd guess it's more than $300 in parts to get to high fidelity.  That being said, having the enjoyment of building one and still having it sound pretty good regardless how it measures is something I am ok with.

[Edgar]

3 minutes ago, The Dude said:

That being said, having the enjoyment of building one and still having it sound pretty good regardless how it measures is something I am ok with.

It used to be that one could build things more cheaply than buying them. Modern economies of scale have pretty much ended that. For example, I'm currently building a set of speakers that roughly compare to the Klipsch Chorus, in terms of components. Because I have to purchase them at retail prices, the cost of components is a significant fraction the price of the Chorus itself. In other words, I'm not really saving much by building them myself. However, what I end up with is mine, both in design and in execution.

[CWelsh]

11 hours ago, geezin' said:

Recently looked on ASR to see how the Pass ACA fared. Not well by his standards. What am I not (hearing) seeing?

I did read the ASR review, but it has been a couple of years or so. My memory is, he didn't like it because of the high distortion ratings using his measurement tool. Even Nelson Pass acknowledges that it has second order harmonic distortion numbers that look high. Apparently, the same is true of virtually every tube amp in existence. Whatever the case, I can tell you the thing sounds pretty freaking amazing through high efficiency speakers.

 

I watched another reviewer on YouTube absolutely trash the ACA. However, what he was really testing was a Chinese clone he picked up on Ebay for cheep and playing it thorough not terribly efficient speakers. Crazy people!

[CWelsh]

9 hours ago, Edgar said:

It just shows that something can measure poorly but still sound pleasing. I used "pleasing" intentionally, to emphasize subjectivity.

 

@The Dude, ASR is Audio Science Review.

You make an excellent point. My enjoyment of the amp is subjective. Others may find it less pleasing than I do. And, I will admit that the cost and the fact that I assembled the kit contribute to my evaluation. Still, for less than $750, I don't know that you can beat it. I've tried some Class D amps and agree that they sound great, especially for the price, but the ACA has something I really like, and that makes me happy.

[CWelsh]

@The Dude Did you ever finish your preamp project?

[The Dude]

16 hours ago, CWelsh said:

@The Dude Did you ever finish your preamp project?

No, still collecting parts, plus, It hasn't gotten cold enough for me to focus on inside projects. Probably going to be a January project.  I'm starting to feel the itch, especially since I have a new work bench and new work area.

[CWelsh]

HA! I can totally relate. I've got a guitar build that I started a few months ago and haven't done a thing with while the weather has been good enough for golf. And, before I started, all of the components sat in a box for over two years waiting for me to finish my work bench.

 

[The Dude]

41 minutes ago, CWelsh said:

I've got a guitar build that I started

Nice, what kind of guitar?  I would love to build a couple of electrics myself or find some trashed bodies that I am after and refurb to my liking. 

[CWelsh]

It's a copy of a Martin D28 from Stewart McDonald. This is my second and the rosewood is gorgeous. I've built several electrics from either kits or just assembling parts from various sources. I've also picked up a few damaged or non-working guitars that I've rehabbed. Now I have a bunch of guitars hanging on my wall that I never play...LOL

 

 

[The Dude]

On 10/24/2024 at 3:45 PM, CWelsh said:

Now I have a bunch of guitars hanging on my wall that I never play...LOL

Thats me as well, I like to collect certain bodies/colors.  I dabble, but never really play.  I have always had an interest in different gear such as amps, cabs, etc. 

[CWelsh]

I finally pulled the trigger on a preamp. Picked up a Pass designed ACP+ from the DIY Audio store. Hell of a nice preamp for $250, and pairs really well with the ACAs. I see this as a foundation to build on. I'm thinking I will ultimately add a phono section, a selector for four inputs (including phono), and a remote volume control in a single chassis. I could have had all that by just going with the Tubes4HiFi SP 10, but I think this will be more fun to build.

 

Now I want to play a little with the different non-balanced options for running the ACAs in mono.

[The Dude]

That looks like a decent option, i like the headphone section. I would look at the pearl phono section.  I always wanted to try that nutube as well. I received the remaining parts for my pre, now I just need to start building the chassis.