I built two: paralleled the inputs and driving each section of a set of Klipsch RP-8000’s crossover inputs (2 way) with each output section. Biased at .400 with no problem!
I’ll steal a line that you have to make it to the build guide to read:
“This amplifier sounds fantastic, if you have any interest at all, you really should build one. :)”
Highly recommended!
This was my fist experience building anything electronic. The build was pretty easy and the sound is really impressive. I made a little base out of a wood box from the craft store. I am using it with some old KLH Model 33 speakers and it has plenty of power to drive them in a small room. I also got great customer service from the store. Thanks!
This was my first time building an amp. After some research and advice I settled upon the ACA Mini. The build process was straightforward and not difficult. I ended up making a custom case for this, as well and using different power switch and plugs. I think it came out pretty good. But man o man the sound…this little thing sounds incredible. It’s my new go to amp for my sensitive horns and coaxials. Highly recommend
A real class A amp built in an evening, ideal for beginners and a great replacement for class d desktop amps. Big thanks to NP. Nearly finished a b1 pre to go with it and full range speakers after that to complete the picture. Don't wait on, just get a kit and build one :)
Pros: Really surprised at the sound quality out of this lil amp. I built it as a curiosity but it gives an amazing soundstage that easily outclasses my vintage amps. When paired with efficient speakers and keeping the volume below 75db, it might be the best sounding amp I own.
Cons: my kit did not come with all the correct resistors. Luckily my engineer neighbor came to the rescue and got me the parts I needed to finish. Directions are good, but not dummy proof. It is limited though and really doesn’t like to be pushed above 1-2 watts. But lets be real, its punching way above its weight for its cost.
Overall, I would highly recommend this amp to anyone who is DIY amp curious. Fun to build, great to listen, excellent learning experience. Thanks Nelson!
Thanks to Papa's generosity, we can build this amazing amp with his hand-selected and matched essential parts. What a bargain! It has displaced my 50 wpc Millett NuClassD as my new my desktop amp.
Note that the power switch is really a standby switch, so if you have a tube or other preamp you want to power down along with this amp, you will need a way of switching off the ACA Mini's SMPS to prevent a 'thump' in your speakers when the preamp is powered back on.
I elected to do this by adding a power switch to a version of Mark Johnson's SMPS filter design I had as a separate device. The 'off' side of the SPDT power switch also takes the Mini's power caps voltage down to ground via a bleeder resistor in about 5 seconds.
The performance of ACA Mini comes as a most pleasant surprise - but then again, not really. Coming from our friend and generous contributor, Nelson Pass, the ACA Mini truly delivers with outstanding performance. Coupled with the also magnificent Korg Nutube B1 preamp, the amplifier projects a solid soundstage of width and depth, creating a realism within the music which belies the diminutive size of the amp footprint and component count. Clearly, Nelson's pursuit of the First Watt principles are demonstrably manifest in the ACA Mini.
Thank you, Nelson.
Thank you also to the DIY Audio Store team who take such good care in completing our purchases.
There is little more to say beyond my strongest recommendation of this amplifier. A straight forward build with a caveat to ensure that Nelson's excellent note is carefully followed on the crucial process for the bias settings. There will be no issue with this process if the designer's clear instructions are respected.
This is my first complete kit, I've made.
Using:
- Full ACA mini kit and binding posts from the store
- diyaudio fire metal solder
- Araldit standard
- Ohmmite Heatsinks (8 x VM1-038-1AE)
- Aluminium plate (dimensions 250 x 190 x 15mm)
- Some small material
The amplifier sounds wonderful and it will be used with 6 x 9inch and 12inch full range speakers (another one is planned:-)). The adjustment for biasing was a little time-consuming but at the end it's a very nice experience.
(see my post #2,255 at the ACA mini thread)
Once again the ACA mini as a kit with essential kit components
At all documentation descriptions 5 stars ⭐️ ⭐️⭐️⭐️⭐️
I’ve build this amp over the past weeks, sourcing the PCB kit from DIY Audio store and the other parts from DigiKey and other sources. The parts kit was sold out at the time.
I bought a LRS 100-24 to embed the power supply in the total package and used an SMPS DC filter because off the good reviews. Based on what I hear, it certainly doesn’t hurt.
I have 2 ACAs that I use in bridged mono and everyone knows (or can read) what that delivers in sound quality.
I’m therefore so happily surprised about the sound quality off this little amp. In certain ways, it delivers more details or maybe dynamics than the ACAs do.
I would have to do more listening sessions switching back and forth to know. But not doing that right now. Just enjoying what I hear :)
Without any formal knowledge, extended experience or measuring instruments, my impressions are that this little amplifier reaches way lower in the bass region as well as the high frequencies without a roll off. The sound is full and complete. I am excited anticipating how it will sound after some use. The kit is simple and easy to build. Would suggest two multimeters for the biasing - makes it easier. The kit was flawless (as always), the build guide by 6L6 was excellent and we must thank Nelson Pass for his generosity to all of us. If you are thinking about building this amplifier, please don't hesitate! Highly recommended!
For my first kit amp project this thing is mindblowingly good. With the online guide, a little verification with a meter, fun soldering and bam! A little giant killer is born! So much fun. Sounds WAY bigger than it should….
Thank you for making such a great, easy to build, “DIY” package available. Now for some woodwork and aesthetics. This one is worth something nice! If I could give it ten stars I would.
⭐️ ⭐️⭐️⭐️⭐️⭐️⭐️⭐️⭐️⭐️
I bought this kit simply because I like building kits. If they are inexpensive, I build them and give them away. At the time of this review the kit was $125. Cheap enough. But once I built it and connected it to my Magnepan LRS and KEF LS50 Metas, as a bi-amped system, using the ACA Mini above 70hz.....This little amp ain't going anywhere! I have a Pass Labs First Watt F5v2 that is my absolute reference amplifier. I've tried dozens of A,AB,D, Tube amps and nothing sounds as good as the F5v2.....but other than raw power, this little guy holds its own. Easy to build and fun to set the bias as it is a little challenging. You really need two VOMs and solder in a few little pieces of wire at the test points to allow easy connection with small alligator clips and you'll be in "High Cotton"......A nother issue is reading the resistors so you insert the correct ones. You need a good OHM meter and I recommend a auto calibration version. About $50 at Home Improvement Big Box stores or Amazon. If you are into this kind of stuff you should have one anyways. I mounted mine in an aluminum cabinet I built out of scrap, but I didn't like the looks. Finally I mounted it exposed on a wood base and added a level control to make balancing with the subwoofer easier. Get one and build it...You'll LOVE it!
amazing quality A++
from a 30 year + experienced audiophile / DIY builder
Arrived in the UK well packaged along with the B1, easy to assemble. Amazing Sound for the cost, thanks Nelson & the DIY team
& community. Made the Ash box with speaker terminals on the rear will house a filter inside.
If you're reading this, you are curious about this little amplifier. Build one (or many)! You will be amazed. Make sure all transistors are soldered where they should be, take your time to set the bias--and enjoy! The sound is amazing with plenty of bass. Cheers!
Best sounding for the buck. Thanks for the design Papa Nelson.
