It is my considered opinion that the ACA sounds much better with a linear CLC or CRCRC supply. (Without an LM1084 or other such regulator.)
I have tried the regulator approach and found it lacking in bass extension and definition. I have used the set of PCBs from Rudi with the the regulator eliminated, and bypassed with a thick copper wire between pin2 and pin3. The regulator support components are also omitted. In this case the 0R22 resistors were 3W metal oxide (film) power resistors. Wirewound power resistors would also work in those locations.
I have tried a sufficiently sized Meanwell chassis mount SMPS set to provide 27V to the amplifier channels. It also sounded inferior to the linear supply when compared side-by-side.
A 300VA transformer with dual 20V or 22V secondaries makes a good choice for the ACA. Each secondary provides the raw AC voltage to each channel. Sounds like a good dual-mono implementation.
I have tried the regulator approach and found it lacking in bass extension and definition. I have used the set of PCBs from Rudi with the the regulator eliminated, and bypassed with a thick copper wire between pin2 and pin3. The regulator support components are also omitted. In this case the 0R22 resistors were 3W metal oxide (film) power resistors. Wirewound power resistors would also work in those locations.
I have tried a sufficiently sized Meanwell chassis mount SMPS set to provide 27V to the amplifier channels. It also sounded inferior to the linear supply when compared side-by-side.
A 300VA transformer with dual 20V or 22V secondaries makes a good choice for the ACA. Each secondary provides the raw AC voltage to each channel. Sounds like a good dual-mono implementation.
Ok. Thats interesting tests and observations 🙂
Im running my twin ACAs with the stock SMPS power supplies and added big filter caps inside of the amps, and after the SMPS DC filters P089Z on the incoming supply wires outside of the amps.
Hmmm. Makes me thinking it possibly could be fun and worth it to upgrade to linear supplys 🎷🙂🎸
Thanks for the information. I’m not so convinced we all hear the same way. I’ll try it both ways. I plan to use PLC power supplies surprised they were never mentioned the ones I got from Omron have less than 80mV p/P of ripple noise.
If the PLC supplies can be set for a higher voltage, I can recommend trying 27V up to 30V. When combined with IRF140 or FQH44N10 output Mosfets, the ACA is a very fine sounding amp, capable of driving larger speakers to verify satisfying levels.
Check out the work described by several builders earlier in this thread.
Check out the work described by several builders earlier in this thread.
Using Ohm's law we know that P = V x I
therefore P = I x I x R
assuming that I = 1.5A calculates as
1.5 x 1.5 x 0.22 = 0.495W
for piece of mind a 3W resistor will be just fine
Attachments
I have the opportunity to secure a few expensive Z-foil resistors at no cost and have decided to try to replace 3-5 of the resistors in my ACA with Z-foils now that I have the opportunity. I tried years ago to replaced a few of the resistors in my simple diy RIAA amplifier with Z-foils and at the time I thought, that I could hear a small but definate improvement. I now wonder if I can repeat the magic or if it was just my imagination. Which of 3-5 resistors on the ACA PCB would you suggest that I experiment with? (I know full well that the topic is controversial, but as an old medical researcher, I like to test the unthinkable).
I would suggest the input and feedback resistors (R11, R12) as the first candidates for that experiment. Maybe the gate stopper resistors next.
C1 should be 4700 uF, and preferably one of the Kemet or Rubycon parts that will fit in the footprint on the PCB.
The choice of output Mosfets will have a much greater impact on the sound of the amp.
Have fun!
C1 should be 4700 uF, and preferably one of the Kemet or Rubycon parts that will fit in the footprint on the PCB.
The choice of output Mosfets will have a much greater impact on the sound of the amp.
Have fun!
When adding R16, how deep does the trace need to be cut? While my continuity check no longer beeps when going from V+ to C4+, I measure a resistance of 3kohm between the two. I feel as though this has been cut really deep, and I can't figure out what else to do. Am I missing something? I haven't actually added R16 yet so the resistance should be "infinite", right?
If a close inspection of the cut looks sufficient (use a magnifier), then go ahead and try adding R16.
Could simply stop beating around the edges and Build one of the proven Excellent ; Firstwatts.. instead.
ACA is a trainer aircraft. ACA With Premium Parts is a trainer aircraft with chrome plated exhaust pipes and a gold plated propeller.
FirstWatt F4, F5, F6, AlephJ, and M2x are high performance fighter aircraft with afterburning jet engines, supercritical airfoils, air-to-air missiles, radar, and aerial refueling capability.
FirstWatt F4, F5, F6, AlephJ, and M2x are high performance fighter aircraft with afterburning jet engines, supercritical airfoils, air-to-air missiles, radar, and aerial refueling capability.
+1
As much as I absolutely adore ACA, and it’s completely different and totally worth building as well ACAmini, ACA in any format, in any configuration will be completely eclipsed by any of the Firstwatt designs. This is not to say that the ACA is a bad amplifier or poor performing, not at all. The Firstwatt are just a clear, distinct and superior move forward, as they should be.
As much as I absolutely adore ACA, and it’s completely different and totally worth building as well ACAmini, ACA in any format, in any configuration will be completely eclipsed by any of the Firstwatt designs. This is not to say that the ACA is a bad amplifier or poor performing, not at all. The Firstwatt are just a clear, distinct and superior move forward, as they should be.
@tungsten, @Mark Johnson @6L6: The premium ACA is my current reference, using an SMPS no less. I wonder what epiphany I will experience soon when my sissySIT is finally finished. It does help that the rest of my system is very revealing and sensitive enough so the ACA is not running out of steam.
A comment on amplifier quality and figther jets. It is also a question on subjective preferences. I have been playing with hifi and diy for some 45 years and if I were to sum up my personal experience it is, that (when succeesfull !!!) I get the most realistic, involving sound reproduction from simple/short circuits with excellent components. Complicated long electronic chains seem to take life, realism out of the music - don't ask me what it is, I can't name it. That is why I am trying the build the ACA-Tungsten with the best possible components, just to see if it will replace my present power amp TTSA (The Totally Simplistic Amplifier). Maybe, deep down, I am an oldfashioned balloon skipper?
You might be thrilled with the (in active production today) First Watt F8 amplifier. It has three transistors per channel, one of which is a silicon carbide power JFET manufactured by SemiSouth. Owners Manual .