ACA MinMax Parts Kit
This parts kit contains the parts you need to complete two channels of the ACA MinMax amplifier. For builders that have their own chassis and PSU, this is for you.
- 2 x PCBs
- Transistors (Toshiba JFETs and IRFP9140/140 MOSFETs)
- All resistors and trimmers
- All capacitors, including two 1F super capacitors
- All Jumpers
- All LEDs
- All Switches, screws, nuts, washers (separate from chassis hardware).
- XLR and RCA jacks along with two pairs of binding posts
- Hookup wire
It does not include the ACA chassis and 36V power supply included with the complete kit.
The ACA MinMax combines Nelson Pass’ ACA Mini with the HiFi-2000 Amp Camp Amp chassis to get the most out of this design. Strategic part upgrades enable a 36V power supply and 850mA bias current per channel. This kit is for those who want a bit more power out of the Amp Camp series while keeping the original design philosophy of an easy to build, safe, and great sounding class A amplifier.
Can be operated in stereo, balanced mono, or parallel mono configurations.
Features:
- Larger heatsinks of the Amp Camp Amp chassis allow for higher bias current
- Left and right “mirrored” PCBs for simplified chassis wiring
- Power supply voltage increased to 36V
- Capacitors upgraded to 50V
- 2SK170 / 2SJ74 input JFETs and IRFP140 / 9140 MOSFETs sourced directly from Nelson Pass
- Larger TO-247 output transistors and alumina thermal pads help keep parts cool
- Multi-turn potentiometers for finer control when setting bias and offset voltage
- Optional gate resistors (100 ohm provided)
- PCBs support TO-247 and TO-220 footprints for diy-ers who want to experiment with MOSFET variations
Key Information
- Power Amplifier Project
- Designed by Nelson Brock
- Intermediate Difficulty
- Complete Kit Available
- No Build Guide
Highlights
- A more powerful ACA Mini with a new twist
- Compatible with the existing ACA chassis
Links, Discussion & Files
Power Output:
| Impedance | RMS Power, Stereo | RMS Power, Parallel Mono |
| 4 Ω | 25 Watts | 30 Watts |
| 8 Ω | 15 Watts | 16 Watts |
| 16 Ω | 8.4 Watts | 8.4 Watts |
Please be aware, the ACA chassis has markings on the back panel which do not correlate to this design. The panel can be installed normally and markings can be ignored or blacked out with a marker. Alternatively the panel can be flipped putting the markings on the inside, however two 1/8” (3.2mm) holes must be drilled to mount the XLR connector.
First, let me say that I bought the ACA/MinMax chassis and power supply at the same time. It great to have everything you need to build an amplifier from the start.
So you are building two mirror image boards that are otherwise identical. Someone pointed out that the wiring was the most difficult part of the build. The wiring diagram is excellent. So if you do have difficulty in wiring, it's perhaps due more to your ability to execute. But that's why we are building....to get better at it. Really, this is an easy build.
I was amazed at the sound of this thing. Of course Papa designed it. I am currently driving it with a Mellow Tones Amps Rocket 6N1P tube preamp. Speakers are CSS Audio Criton 1-TDx that I built. Source is CD player feeding its digital output to an ANK DAC I built from a kit. Now those speakers are only 86 dB efficient so I wasn't expecting much. But the room that system is in is relatively small. That little amp can lift the ceiling in there. There is something about the sound of the ACA/MinMax that makes me want to keep listening.
Nits: Naturally I prefer a linear power supply. The Meanwell 36 V supply is a large brick. Shutting off the amp at the front panel only kills the bias circuitry......not my favorite thing. So I have the amp plugged into a switched power strip that cuts all power to the amplifier.
I love this little amp. I bought two of them because I plan to run them as balanced mono blocks at twice the rated power.
The amp went together without any problems - worked first time I turned it on.
It fits perfectly into the Modushop Amp Camp Chassis and looks great.
Gets a full 15 watts per channel - gives me enough volume to fill the room!
Sound is exquisite and detailed. Highly recommended!
Good Day,
I keep coming back to this store to buy up as much as I can! What neat stuff. I’m a complete amateur but this store has forced me to buy a scope and a function generator!!! I have wanted these machines for 30 years. I’m an audiophile enough to know the difference between common and plain to state of the art. For us mortals DIY is truly the only way to achieve this. With a little learning, and help along the way, what a beautiful system one can have real pride in. My immediate project is going to be a dual mono NOS TDA1541A from a tube 6X5 rectifier into a John Broskie high gain aikido using Soviet made 6N16B miniature tube output stage. Just need to learn some clocking techniques and find a suitable I/U conversion ( mono to double the current and geez if I have enough gain I may just use a low value resistor (20 ohms max). It will be built a bit modular so I can tweak things like the resistor as I learn. Once going, I will play it through my VTA SP-14 preamp, my Minmax 10w class “A” amp with my 100db efficiency dual transmission line speakers! All the while I’ll be working on the Aleph J. THANK YOU Neslon and all the gifted folk on the forum. You all are Class A.