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ACA-Nelson Pass's Amp Camp Amp


The Dude

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I started doing parts count and a little test assembly on my kit last night, and I can see why the chassis costs what it does. It's quite impressive. Unfortunately, the person packing the chassis parts must have been in a hurry to go to lunch because they only gave me three of the four rails needed to attach everything. Good thing I'm not in a hurry.

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  • 2 weeks later...

Jeez! I had to buy new tips for my soldering station and special solder to assemble this darned thing. It better be worth it...LOL

 

Seriously...DIYAudio really impressed me with their customer service. They had the missing chassis rail sent from the supplier in Italy within three weeks.

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  • 2 weeks later...

The ACA is underway! My audiophile brother-in-law is coming to visit this weekend and I have to have it finished so I have someone to share it with. Every time I do or buy something new, my wife tells me to, "Call Dennis", so I hope to have it finished before he gets here.

 

The boards are finished and it is just a matter of doing all the wiring. I expect to finish that tomorrow. Keep your fingers crossed that nothing smokes when I power up. Can't wait to hear this thing!

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It's up and running! The sound is stunning. Much warmer than the Class D amp with a more spacious soundstage. The volume leaves a bit to be desired, though. Running my Node full out it hovers around 70 - 80 db on what should be fairly loud passages.

 

I was going to say that it sounds less detailed than the Class D, but I'm not sure that is an accurate statement. There is still a lot of detail...it's just somehow different.

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Does your pre have enough output to drive the ACA to full output? The one I built years ago that had plenty of power for my LaScala's in my room. It is an amazing sounding class A amplifier for what it cost to build. If you continue to like the sound you may want to go to another level and build the complete full version of a SE class A amplifier, the BA-1. More refined and taken to the next level. 

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11 hours ago, babadono said:

Are you running it stereo full bandwidth into your Forte IIIs?

I'm not sure I understand what you mean when you say stereo full bandwidth? I am running it in stereo mode and it is the only amp driving the speakers, if that is what you mean.

 

1 hour ago, henry4841 said:

Does your pre have enough output to drive the ACA to full output? The one I built years ago that had plenty of power for my LaScala's in my room. It is an amazing sounding class A amplifier for what it cost to build. If you continue to like the sound you may want to go to another level and build the complete full version of a SE class A amplifier, the BA-1. More refined and taken to the next level. 

 

After a few hours of operation, I need to amend the results. Last evening I measured maximum peaks of 94db at 1 meter on axis. For me, that is significantly louder than I usually listen. I'm generally more in the 50-60db range. I noticed something else, though. When I lowered the volume to what I thought was my more typical listening level, it was actually in the 65-75db range and it sounded wonderful. I'm sure a big part of that is just my brain adapting, but I think there is also a purity to the sound that makes it really easy to listen to. I think I'm going to love this thing.

 

As for building a BA-1, I can imagine more projects in the future. For now, I have some experimenting to do with what I have on hand. I've learned that the maximum output from the Node is only about 2 volts. That works, but may not be enough to get the full potential from the ACA. I want to try running everything through the preamp on my Marantz 1060 to see what that does. I also want to try bi-amping with the Aiyama chip amp on the bottom and the ACA for the mids and high. I should have enough to keep me entertained for awhile.

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2 hours ago, CWelsh said:

I'm not sure I understand what you mean when you say stereo full bandwidth? I am running it in stereo mode and it is the only amp driving the speakers, if that is what you mean.

Roger that's what I mean...that you are not just driving the tweeters/ mids or the woofers. So 8 watts into a full 3 way speaker. Depending on how dynamic your source material is that may sound a bit anemic. IMHO of course...I never listen over 75dB SPL:D

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Hooked up the ACA to the preamp out on my 1060 and it makes a significant difference. Also, while the Node offers the ability to boost or cut bass and treble by plus or minus 6db, but I think the tone controls of the 1060 offer more flexibility.

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  • 1 year later...

I know this thread has been dormant for quite a while, but I'm starting to think of next steps for my system, still keeping the ACA as my power amp. I'm looking for thoughts and suggestions for a preamp. I need a minimum of two line level inputs and a phono section. Ideally, I would like something I can build from a kit, but it won't be a deal breaker if not.

 

I'm attaching to this thread because I would like to hear from those who are using (or have used) the ACA. Let's discuss!

 

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I had a good experience with a tube line stage from Tubes4hifi.com.  I ended up selling that line stage to fund a new project, but do have a similar line stage that I will be building into a pre amp with phono section.  All of this comes from Tubes4hifi.com.  Note, this is running a tube pre/line stage into a solid state, some frown upon it and prefer to run SS pre into tube amps, YMMV.   If I was going to go SS, I would look at Diyaudio again for something from Mr. Pass. 

 

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9 minutes ago, The Dude said:

I had a good experience with a tube line stage from Tubes4hifi.com.  I ended up selling that line stage to fund a new project, but do have a similar line stage that I will be building into a pre amp with phono section.  All of this comes from Tubes4hifi.com.  Note, this is running a tube pre/line stage into a solid state, some frown upon it and prefer to run SS pre into tube amps, YMMV.   If I was going to go SS, I would look at Diyaudio again for something from Mr. Pass. 

 

I've looked at Tubes4hifi.com. Very interesting stuff and the prices seem reasonable. I have to admit, I find the website a bit difficult to decipher. I've also looked at Elekits. What tips me to Tubes4hifi is the remote control option.

 

As for tubes into SS vs. SS into tubes, I have no bias either way. I would love to be able to try a nice little SET amp sometime, but I have an old Fisher integrated that I've hooked up to my Fortes, and it does sound good, but I definitely prefer the ACA. Maybe it is just that it is Class A. I don't know.

 

I've looked at various options from Diyaudio and will likely go that way if I stick with SS. I snagged one of the active crossover/bi-amp kits and want to see what that does. I have the technical skills to handle the assembly of kits, but I'm not sure I have the knowledge necessary to combine various pieces into a whole. I think I need a mentor...LOL

 

My goal is to have a great sounding system, but I have no illusions that it is going to be the creme de la creme... that is beyond my means and even beyond my ability to appreciate. However, being able to say I built it adds significantly to my appreciation.

 

Sorry for rambling so much. I really appreciate your feedback.

 

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52 minutes ago, CWelsh said:

@The Dude If you don't mind me asking, what are you planning for your new preamp with phono section project? That sounds a lot like what I want.

I'll be using the Tubes4Hifi ph6 and pc5. They were designed to be replacement boards for the Dynaco PAS3.  I once had them installed in and make shift chassis. It's been a while since I've heard it, so I can't recall the characteristics of the sound, but that it was dead silent and good sounding.  I don't even recall what amp I used at the time. Hoping for similar results with ACA. There are 2-3 stereo setups I will keep and rotate through and this will be one of them.  That pre is currently under construction, so it won't be until later this year that I get to enjoy it again. 

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