feeding amp through XLR, so balanced (and bridged) - you're wiring speakers as per "Bridged Mono"
catch is, in fact, simple - hot output of each single channel is marked as "-", due to phase
so, if you connect speaker to "+" Right and "+" Left, nothing would happen - you'll get silence (both "+" are actually GND)
if you connect speaker to "-" Left and "-" Right, it'll sing
It depends on how you wire it... If you're doing it custom and ONLY doing XLR input and balanced / bridged.. and putting 4 amp boards in one enclosure .. I'd consider using only two speaker terminals for each.
Example for each channel.
XLR input pin 3 is goes to Board A, connect output to red speaker terminal
XLR input pin 2 goes to Board B, connect output to black speaker terminal
Connect speakers normally.
Edited b/c I am a goof and forgot ACA is phase inverting...
Example for each channel.
XLR input pin 3 is goes to Board A, connect output to red speaker terminal
XLR input pin 2 goes to Board B, connect output to black speaker terminal
Connect speakers normally.
Edited b/c I am a goof and forgot ACA is phase inverting...
Thank you very much to @NeilBlanchard, @rikiheck, @N Brock, and @twofires for those very helpful answers. I understand that in the context of a kit, there's the issue of the additional tool and skill (crimping) plus the additional cost of supplying the right types of connectors. Makes sense. Those issues aside for someone who has those tools and skills and who is willing to pay for good quality and the right types of connectors, there's the additional issue of reliability: point-to-point wiring, soldered at each end, being more reliable than going through connectors. Excellent answers. Thank you again.
Question- if building 4 boards in one enclosure eg two monoblocks, which single enclosure will adequately dissipate heat? And the assumption is a separate linear power supply.
Thanks super helpful I will go this route.
Question - did you go with the upgraded UMS substitute heat sinks? Also Any insight as to whether I will need to request custom drilling to mount the N Pass vs. 1.6 2018 PCBs?
^ You may be confusing 3U (height) x 400mm (depth) with 4U 300
UMS heatsinks are not a "standard" option for the 3U 400. You'd need to have them custom drilled/tapped.
https://diyaudiostore.com/collections/deluxe
https://diyaudiostore.com/collections/accessories/products/ums-heatsinks
From the product page for the ACA linked below it says:
"Heatsinks: 2 x 2U UMS heatsinks with the new 2U UMS 8 hole pattern drilled and tapped with M3 threads"
So, I'd assume the boards' mounting layout with the output devices are UMS compatible for other heatsinks. When the crew here says "Universal", they're pretty good. I haven't directly checked, so someone with more knowledge could confirm.
Any of the First Watt clone amps would be my choice. I lean toward the M2x or Aleph J, but those are personal preferences. They're all incredible, IMO.
UMS heatsinks are not a "standard" option for the 3U 400. You'd need to have them custom drilled/tapped.
https://diyaudiostore.com/collections/deluxe
https://diyaudiostore.com/collections/accessories/products/ums-heatsinks
From the product page for the ACA linked below it says:
"Heatsinks: 2 x 2U UMS heatsinks with the new 2U UMS 8 hole pattern drilled and tapped with M3 threads"
So, I'd assume the boards' mounting layout with the output devices are UMS compatible for other heatsinks. When the crew here says "Universal", they're pretty good. I haven't directly checked, so someone with more knowledge could confirm.
Any of the First Watt clone amps would be my choice. I lean toward the M2x or Aleph J, but those are personal preferences. They're all incredible, IMO.
So I’m here to give my listening impressions with the ACAs in monoblock configuration.
I’ve had these two amplifiers for around a month now.
My setup:
Focal Chora 826 towers
Sabaj A20D 2022 DAC
I previously owned a Denon PMA-A110 integrated amplifier ($5000 CAD) but sold it in favor of keeping my much cheaper set of ACAs.
Why? The ACAs simply sound exceptional in my system.
The soundstage has opened up in a way it never did with my Denon. I can hear so much more detail, definition and articulation that the Focal is capable of.
I look forward to building an Aleph J or M2X in the future.
For anyone wondering; these amps are worth way above their modest cost. Don’t be fooled by the size. They drive my Choras with authority and reach ear splitting levels in my living area.
I’ve had these two amplifiers for around a month now.
My setup:
Focal Chora 826 towers
Sabaj A20D 2022 DAC
I previously owned a Denon PMA-A110 integrated amplifier ($5000 CAD) but sold it in favor of keeping my much cheaper set of ACAs.
Why? The ACAs simply sound exceptional in my system.
The soundstage has opened up in a way it never did with my Denon. I can hear so much more detail, definition and articulation that the Focal is capable of.
I look forward to building an Aleph J or M2X in the future.
For anyone wondering; these amps are worth way above their modest cost. Don’t be fooled by the size. They drive my Choras with authority and reach ear splitting levels in my living area.
I just finished my ACA 1.8 which I bought as a complete kit. Set on stereo output, the B side output makes a fuzzy, static like sound which gets worse with higher volume. The music from the B side speaker is attenuated relative to the A side for any given volume setting. The A side output sounds terrific. I ruled out speaker and cable connections as the cause by changing cables, speakers, amps and speaker wires. I'm using a WHAMMY HPA as the pre-amp that works fine with other amplifiers. The Q1 middle pin voltages on both PCB boards were set to 12V for the 24V power supply using the adjustable pots. Both blue LEDs light up with power. There is no smoke or sparks and the amp gets warm but doesn't seem to be overheating. I don't see any loose connections or poorly soldered joints.
While building the ACA amp, I had to de-solder and re-orient the C3 capacitor on the B side PCB. Could I have damaged the 10microF 25V capacitor and/or the PCB during this process? Are capacitors prone to damage from the heat of re-soldering and de-soldering?
Any help would be greatly appreciated.
While building the ACA amp, I had to de-solder and re-orient the C3 capacitor on the B side PCB. Could I have damaged the 10microF 25V capacitor and/or the PCB during this process? Are capacitors prone to damage from the heat of re-soldering and de-soldering?
Any help would be greatly appreciated.
Possible but unlikely. You would have to be pretty determined to destroy it through unsoldering/soldering. Do check the continuity though from the cap leads to the board in case you have lifted the print around the pads.
What you describe sounds an unusual sort of issue. First thing is to recheck that the DC conditions are correct, that the 12 volts midpoint is OK (its not critical so don't worry if it drifts a little etc). Also are the FET's about as hot as in the good channel.
You should see about 0.37 volts across either 0.47 ohm resistor and around 0.54 volts across either of the 0.68 ohm resistors.
A common mistake is connecting the ACA speaker output to ground unintentionally. Check that the speaker output point which is from C1 really does go to the correct (negative) speaker terminal and that it does not connect directly to ground. The red terminal is the grounded one.
Thanks, Mooly. You were right, it wasn't the capacitor. The things you mentioned all checked out. In performing the analysis you provided, I noticed the B side input RCA connection pin was wobbly. The nuts holding the RCA connector in place were a tad loose, so I carefully tightened them, without stressing the soldered connections. The pin was now secure and didn't wobble. When I plugged in the ACA, the B side played beautifully. Does that sound like a plausible explanation? I didn't change anything else, I just tested the voltages you suggested and made sure the speaker output wiring was correct.
Hard to say without being there and seeing it but given it fixed your problem it seems highly likely you have found the issue
No, it's not.
As a minimum ACA runs on 24VDC at 1.5A approx. That's per channel.
24 X 1.5 is 36W
Multiply by 2 for stereo is 72W.
For safety margin of 2 you need 160W trani.
For safety margin of 3 it is approx. 225W.
Secondary voltage of trani needs to be at least 18VAC, preferably higher to account for losses.
As a minimum ACA runs on 24VDC at 1.5A approx. That's per channel.
24 X 1.5 is 36W
Multiply by 2 for stereo is 72W.
For safety margin of 2 you need 160W trani.
For safety margin of 3 it is approx. 225W.
Secondary voltage of trani needs to be at least 18VAC, preferably higher to account for losses.
