Amp Camp Amp - ACA

Hi all. I have just completed a set of ACA monoblocks and wishing to run them as balanced monoblocks only ie: 0ne dc inlet, one set of speaker binding posts and one XLR per monoblock and no switches at all. Could someone please provide a wiring sketch for this arrangement as my skillset not sufficiently developed to nut this out. How could I wire up just one led on the front panel for both channels?
 

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wire power wires to both "channels" in case, as usual

take -Out from one pcb to one output terminal**

take -Out from second pcb to second output terminal**

connect XLR pin 1 to GND input pads on both "channel" pcbs

connect XLR pin 2 to one "channel" pcb + Input pad

connect XLR pin 3 to second "channel" pcb + Input pad

simple as that

**due to phase invertion of amp stage, Pa declared hot outputs as "-"
 

Plott

Member
Paid Member
2021-09-12 6:34 pm
Vienna, Austria
Wired as per advice. One heatsink seems to get quite warm (LH) after 30 seconds while the other remains cold (RH).
You have two different transistors in the Q4 position, one flat and one round - are they of the same type? The same applies for your Q3s, one flat, one round. Q3 is a ZTX450 (flat), Q4 is a 2SK170 (round).
 
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Plott

Member
Paid Member
2021-09-12 6:34 pm
Vienna, Austria
Can someone explain to me how the parallel mode works? If I'm reading the wiring diagram right, we're connecting the output of one side through a 32K resistor to the INPUT of the other side. Is that right?
No, that's the balanced mode with RCA input, the second input uses the inverted signal of the first output.
In parallel mode the two inputs are connected to each other and also the two outputs.
 
Just signed up to say that I just built 2 of these back to back to run in a monoblock config for my office and had fun nearly every step of the way (I'm guessing flux could've made soldering the bigger resistors easier and soldering 3 wires to a single point took some acrobatics)! These sound absolutely incredible and really seemed to open up my Kef Q150s.

Now to sit back and help out here as best I can.
 
Playing around with a passive preamp this week, but am getting ground noise. The passive is a simple circuit with a 50K Alps Blue Velvet pot, RCA input jacks and XLR output jacks. The noise only occurs in the middle range of the volume. So fart I have only tested the output of a Dynavector P75 Mk3. I suppose I should check another source later today.

I have wired the positive RCA through the pot to pin 2 of the XLR, and the negative to pin 3. I am only using a twisted pair inside the unshielded case, so no shielded cable. The left and right ground/negative are not connected together.

I am using the ACA in balanced input mode, so the switch is in the middle position. I see on the internal wiring diagram for the 1.8 ACA that pin 1 is connected to ground. I don't think connecting pin 3 to pin 1 is the right choice...or is it? I imagine there is something else I am missing.
 
Playing around with a passive preamp this week, but am getting ground noise.

This one is totally on me. The TT cartridge goes through a K&K step-up transformer which, incidentally, has a few ground configuration settings I had forgotten to change. In the meantime, the CD player sounds great. At this point I might work towards building a balanced B1.
 
I really butchered a wiring question previously, and I'm going to try again.

I want to wire this up in dedicated Bridged Mono mode (with the one RCA input). I see on the wiring diagram, the left channel RCA is the only input in this mode. I see that RCA input is wired to the left channel input. But I don't understand the 3-way toggle, how does input get to the right channel? How would I wire that up?

Thanks much,
Dan
 

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