My first DIY build is finished, I had zero prior knowledge. I have used youtube to learn how to solder, after it was built I had put the diode the wrong way, after a while I found the error and finally connected B1 to the system. Uses it on the F5 turbo and it sounds very good. In case of vibration, a high-frequency sound comes from the nutube, in my case it is only 5 seconds after it is switched on or the input is changed. It's very pleasant to listen to, if you're not a hi-fi freak and just want to enjoy the music that flows out of the speakers, you don't need anything more and for the price it's a bargain! Not least, it's fantastic fun to have made it yourself.

The build was very enjoyable and with the guide it was pretty straight forward. I changed the configuration on my build one input and 2 outputs works like a champ. This is a high gain pre-amp and works well in my setup. I plan to upgrade the power supply and change some caps.

Great and robust design. No hickups during build, very well supported by the excellent documentation. Delivers a clear and powerful sound with my Dali Epicon 2 speakers.
Very much recommended to diy an excepional amplifier. Just wonder when the Wolverine PCB`s will be available at the DIY store.

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.

I have not finished. the assembly yet so I cannot comment on the sound, but I have the Pearl 1 and that sounds very nice.
The Pearl 3 PCBs are professional and very well designed. All parts of very good quality and the instructions are clear and very-well made.
I was afraid of soldering the surface mount components, but after watching some supporting videos I was more confident and everything went fine. I can highly recommend this kit to anyone.

Easy to build (approx. 3h), very good sounding kit.

Kit came nicely packaged with all the parts. Read Papa's article and follow the instructions in the build guide and you will be rewarded with a wonderful bit of audio kit. The ACA+ will drive an amp nicely too. When using headphones I run my digital source through a Schiit Modi dac and the sound is fantastic. Perfect set up for a home office or late night use

Great historic reference.

Very compact and with transparent sound, perfect for desktop setups.

I built an SE version first, as I could get hand on an early kit from another DIYAudio member. The build is really easy to do, even more when using the dedicated case from Hifi2000.
The Iron Pre sounds so natural, and so airy, that I was totally happy when I tested it. So happy that I ordered the balanced kit, which is yet waiting for me to build.
It's probably the best pre-amp I own. No, it is the best pre-amp I own.

Just what I needed. It eliminated all hum and hiss from NuTube harmonic generator board so I could use standard wall wart for 12VDC power. Its small size allowed it to be mounted in a wooden cigar box that I mounted the NuTube in.
DIY store was great to work with when the USPS lost it in the mail the first try.

These Fets are the best I ever tested and heared in my MC Preamp. They are very well matched and they give the highest amplification with the lowest Noise. Thanks for fast delivery to Germany.

Excellent board and parts. Service was great and not exactly sure yet how I will modify them to use with a full range driver and the sub from the LX521. still working to modify the values.

Received the matched jfets fast. Have not used them in a personal project yet. But glad to be able to get jfets again. I prefer solid state for its reliability vs tube. I look forward to building a turn table record player with moving coil pre pre amp for my line level preamp instead of a Step Up Transformer (SUT) All battery to avoid AC hum etc...

I purchased the newer back panel kit and installed on the newer 4U Deluxe kit for a FirstWatt F5 amp. Now I have standoffs for a number of builds. I cut down a leftover nylon computer desk plug to make spacers for the binding posts. Fairly easy to do and cut a small notch for the part of the key that extends through panel. I do like the new heavier binding posts and the Neutrik RCA jacks.