ACA Redux

[kenzo3]

Absolutely totally cool! Great idea! Design is very creative and clever. If they were available, I would have bought two instead of the more expensive ACA pair I recently purchased. I would bet a paycheck you will sell out of every kit you can make available.

 

[A Jedi]

I would have bought two instead of the more expensive ACA pair

You would need 4 for the same amount of channels and power

 

[quadtech]

Mark, an idea for an "evo" version - if you could create "mirrored" Left and Right amp PCBs, a
cylindrical amp enclosure could be used, with a toroidal transformer and
a round power supply PCB in the middle, with the left and right channel amps at the ends, heatsinks facing outward.
The cylindrical enclosure might be made of perforated metal sheet, for ventilation.

 

[Mark Johnson]

Member @peppennino alerted the thread to (this heatsink) . Maybe you could use it as the widest portion of an inverted Egyptian pyramid, with amplifier PCB and daughter-card PCB stacking to form the pyramid shape. You could dedicate the daughter card PCB to SMPS DC filtering and nothing else; then install a more elaborate filter circuit with much greater HF noise attenuation. Spend an extra six dollars on the filter and save thirty five dollars by using a cheaper alternative to the Mean Well PSU brick. Oh and by the way, musical signals wouldn't travel vertically, back and forth between amp PCB and daughter PCB; only +24VDC. You could even put ferrite beads on the vertical mounting legs that hold the daughter PCB.

The splayed pins of the radiator design, would allow much more visible light from the "glow" LEDs. The perfectly vertical pin fins of RACAM's cylindrical radiator, unfortunately block all optical paths except perfectly vertical. Delightfully, splayed pins allow a nice wide cone of glow light to escape. Maybe amber or orange LEDs would complement the red aluminum nicely.

_

 

[N Brock]

I've been playing around in KICAD. 😁

I'm closing in on a layout that turns a pair of these monoblocks into Version 1.8, that is, it gives you the option to configure them for bridged or parallel operation. It's looking like the additional cost will be less than $5, so well worth including in the kits for the versatility it provides.

 

[Mark Johnson]

Hi Nelson, I assume that a stereo amp where the Left channel is bridged and also the Right channel is bridged, is going to require 4 PCBs, 4 hedgehog heatsinks, and 4 SMPS power bricks?

 

[audiosteve]

Hi Nelson, I assume that a stereo amp where the Left channel is bridged and also the Right channel is bridged, is going to require 4 PCBs, 4 hedgehog heatsinks, and 4 SMPS power bricks?

Good question!

 

[kenzo3]

You would need 4 for the same amount of channels and power

I see, thanks. that does change the equation. But the design under discussion here sure looks simpler to build. Definitely an issue for a non EE like myself.

 

[N Brock]

Hi Nelson, I assume that a stereo amp where the Left channel is bridged and also the Right channel is bridged, is going to require 4 PCBs, 4 hedgehog heatsinks, and 4 SMPS power bricks?

Yes, that's correct. A bridged (or parallel) channel is made up of 2 "regular" ACA circuits. So to get a bridged (or parallel) stereo setup you need 4 PCBs, heatsinks, and power supplies.

 

[sal_cats]

Hi,

Thanks for this design! I have two of these PCBs and intend on starting the build next week. I'd love to see some pictures of people's DIY enclosures for these if anyone's built some?

Thanks

 

[A Jedi]

Hi,

Thanks for this design! I have two of these PCBs and intend on starting the build next week. I'd love to see some pictures of people's DIY enclosures for these if anyone's built some?

Thanks

Given that it's round, a soup can will probably do lol.

 

[N Brock]

Hi,

Thanks for this design! I have two of these PCBs and intend on starting the build next week. I'd love to see some pictures of people's DIY enclosures for these if anyone's built some?

Thanks

I'd love to see what you come up with, but one benefit of this design is that an enclosure is not needed. 24V is touch safe, just don't lick it or drop bits of metal on the PCB.

 

[peppennino]

Proudly Single Ended 😄

 

[peppennino]

As I'm using a 24V brick, I have to adjust P1 to 12V, right?

 

[N Brock]

As I'm using a 24V brick, I have to adjust P1 to 12V, right?

Yes, that's right, it can be within a few tenths of a volt and it's fine.

 

[peppennino]

Thanks! Done 😃

 

[peppennino]

PunkACA running

 

[sarathssca]

It might be fun to revise the circuit, to take advantage of now-available-again, very low cost J111 N-channel JFETs in thru hole packages. They are substantially cheaper than Toshiba 2SK170 and Linear Systems LSK170. J111s work very well as source followers, which is exactly how the 2SK170 is used in the ACA. And since the ACA circuit already includes an adjustable resistor (trimmer) to deal with manufacturing variability of this JFET, it's practically a drop-in, plus adjustment of ancillary resistor values.

At USD 14.00 per hundred transistors, they're a bargain. So compelling in fact, that I've purchased 500 for my own experiments and future projects. And the Pchannel J175 is now available again too -- I've bought bunches of them as well. Just in case of continuing spotty supply.

Mess around on octopart dot com and/or findchips dot com, you'll see loads of thru hole, non Toshiba JFETs at wonderful prices. Example below.


_

can we use the pair of J111 + J175 JFETs in ACA mini amplifier in place of toshiba/Linear system JFETs ..

 

[peppennino]

As I used ZTX451 instead of ZTX 450, have I to change something? I see that it has half of the current gain...

 

[peppennino]

David and Goliath 😄