Not sure what you're asking. What does not make sense about the rear pins on the switch?
... if wired properly, and with the switch in the correct position (up)
the signal goes in through channel A's input,
get's amplified on the channel A amp board
in addition to the signal being on the black output post of channel A, it get's routed back through the 39k resistor to attenuate the amplified signal
over to channel B's input
through channel B's amp board where it's inverted yet again.
Now you have two amplified signals at each black terminal. One in-phase with the input signal, and one inverted. (Simple diagram attached).
Since this is an SE Class A amp, it should not matter at all re: the switch position for the devices / sinks to get warm. They're warm even without a signal.
So, two things are odd....
1. That the mode selection switch seems to turn off one channel (very odd to me).
2. That it worked in stereo. That's good. At least you know you've got something to work with and that both channels actually do work.
More pics, please, and please indicate which channel is "turning off". Please use A and B vs. L and R for ease. Please just say red or black speaker terminals for ease also. They're not 'negative'.
... if wired properly, and with the switch in the correct position (up)
the signal goes in through channel A's input,
get's amplified on the channel A amp board
in addition to the signal being on the black output post of channel A, it get's routed back through the 39k resistor to attenuate the amplified signal
over to channel B's input
through channel B's amp board where it's inverted yet again.
Now you have two amplified signals at each black terminal. One in-phase with the input signal, and one inverted. (Simple diagram attached).
Since this is an SE Class A amp, it should not matter at all re: the switch position for the devices / sinks to get warm. They're warm even without a signal.
So, two things are odd....
1. That the mode selection switch seems to turn off one channel (very odd to me).
2. That it worked in stereo. That's good. At least you know you've got something to work with and that both channels actually do work.
More pics, please, and please indicate which channel is "turning off". Please use A and B vs. L and R for ease. Please just say red or black speaker terminals for ease also. They're not 'negative'.
Attachments
For 'RCA bridged mode' the two inputs are Not connected together. You use the White input, that feeds the White channel, the White channel output then feeds the Red channel input via the 39kΩ resistor.
(You join the Red and White channels for Parallel mode.)
(You join the Red and White channels for Parallel mode.)
^ Who are you replying to, and who said that?
If you're noting Allan's statement that "inputs should be common", then I think I had already addressed that in my previous post. Are you just re-affirming what I've already said, or are you replying to Allan?
If you're noting Allan's statement that "inputs should be common", then I think I had already addressed that in my previous post. Are you just re-affirming what I've already said, or are you replying to Allan?
^^^^ No problem.
I was specifically responding to Allan's post #11240. Your post just beat me... and we are saying the same thing - yes.
I was specifically responding to Allan's post #11240. Your post just beat me... and we are saying the same thing - yes.
no false observation.. while testing the ACA output in RCA bridged mono its phase threw me when I inadvertently used the scope earth on the load, so the output was a dead short to ground yet I still got 7 watts at that too, though thankfully a smokeless 7 watt. When I saw only 7 watts I then felt the sinks, the left channel was quite a lot warmer than the right so I shut it all down. Have since tested it again in all modes but this time with a floating probe earth, thankfully its fine. I get full power in all modes as per spec 
Ahhhhh - thanks for sharing. 😀 Greatly appreciated. I was puzzling over how one channel would "turn off" under a measurement circumstance or just with the flip of the mode switch. I just couldn't square the circle.
Simply turn on ACA CG3060 AMP CAMP 5W-8W = 9.5 bias with 2x single rail xformer 2x15v CC 10000x4 50V = 22.5
Headsink 24cm - 5,5cm
Is so hot normal? ... (The sound is very good)e)
What is best for PSU 22.5V? ...
Headsink 24cm - 5,5cm
Is so hot normal? ... (The sound is very good)e)
What is best for PSU 22.5V? ...
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I have my scope floating for eons
first time when I wasted handful of fuses on big PA amp which I just finished repairing, without exactly knowing why is popping them as soon I connect scope
then I realized that red and black on back side of amp are actually having some meaning
it wasn't even bridged ... but my brain was
first time when I wasted handful of fuses on big PA amp which I just finished repairing, without exactly knowing why is popping them as soon I connect scope
then I realized that red and black on back side of amp are actually having some meaning
it wasn't even bridged ... but my brain was
Yes hot is normal. Each channel is dissipating about 36 watts. If you can hold a finger on the heatsink for 5 seconds all is well. Or measure the temp and read back through the thread for other peoples temperature readings.
DC balance (it’s not bias) should be 1/2 the PSU voltage, so 11.25v
Hi, Just finished my first DIY project the ACA!! Well, not exactly finished... So, when I turned it on after the build in stereo the left channel has about half the volume as the right channel; however when I drop the switch down to mono both speakers have the same level, but mono signal... looking for a place to start with troubleshooting!! Halp!!!
Attachments
With the switch in normal stereo poke around the input wiring and see if you have a loose connection or cold solder joint.
Look at the wire going to the second terminal on the left row of the switch...it looks like it's touching the third terminal on the left (right below).
@KevinHeem and @6L6 I am good... turns out the issue was with the source... although not sure why... I was using a macbook pro secra 2015, with a dragonfly blue plugged into usb.... when I used regular headphone out the issue went away... what is odd, is I checked the dragonfly with my headphone w/ no issue... anyway, the amp appears to be working as described... thanks again.
ZTX450 can be replaced with BC560, isn't it, guys?….
any recommendation for replace ZTX450?…
any recommendation for replace ZTX450?…
ZTX450 is low noise npn medium power, try BC337 but noise performance is not as good.