DIY ACA mini

Dang, this thing sounds good! Thanks again to Nelson and BAF for the opportunity to win and build one of these.

So far I’m preferring the jumper in. Really fun to change on the fly! Hope to makes some measurements soon.

Nice work and I can tell you’ve modified it somehow...blue led instead of red..lol
Where are your JFET Q1,Q2...it’s hard to tell from the top view.

BR
Eric
 
WOW!!!

Nelson, you are unbelievable! How can you make something this easy to build sound sooo good??? Thanks as always for being awesome!!!

This thing sounds unbelievably good! Since everything is included, it took less than 3 hours to build and another hour to allow it to warm up and bias.

Jim, thanks for your recommendation for mounting the Mosfets to the heatsinks. It worked perfectly.

The fact that there's no need for a chassis is fantastic! Figuring out and paying for a chassis has always been a major albatross for my builds so it's great that this unit is self contained. I look forward to many hours of enjoyment.

🙂🙂🙂
 
Well done guys, this unit looks so cute and being chassis less is indeed a plus enabling lot of things (starting with leaving it like that)

How does it sound in comparison to other amps you have? What do you drive with it?

Many thanks for all this and again congrats!

Claude
 
They remind that I can get by with five watts for 95% of my listening. I’m driving 88-89db efficient Spendor 3/1’s, so not necessarily efficient either.

Definitely doesn’t sound like a ‘toy’ amp - I bet if I were blind testing at modest volumes with my other amps, I’d struggle to tell apart. The only real tell is a lack of deep bass, but that’s a tall order for five watts, at least with my speakers.
 
What grade Jfets are prefered ?

They shipped with 6 ma idss. For less they might need a larger value on the pot.

If you use more than 7 ma I recommend bridging the wiper and cw pins on the pot to keep the Vds of the jfets at an adequate voltage. The idss limit on the jfets would be that of dissipation, but there is little advantage to the higher values.
 
Listening impressions

I'm thinking that this is probably the best first amp project for anyone considering diy electronics. It is so easy that anyone who can solder should have no problem achieving fantastic results. What's even better than the ease of construction is that the resulting amp is anything but simple. The end result is a detailed amp with a holographic sound stage.

I've spent the day listening to it on fairly inefficient SEAS full range drivers mounted in foam core boxes. The amp's performance punches well above it's weight class. Morcheeba, Air, Koop, Gov't Mule, Leo Kottke, Mississippi John Hurt and more have provided a day filled with audio enjoyment!

If you've been tempted to dip your toe into the diy waters, this is the project for you!

The only thing I chose to "modify" was installing a blue LED. Red just didn't feel right to me for a Pass amp and I had some Cree LEDs laying around. I did however use the red LED for my 6-24 biamp crossover and it is really nice! 😀