I'm battling some RF noise on my ACA when using it on my desktop setup, and wondering if anyone could help troubleshoot. Setup: Macbook Pro -> Sony TAZH1es Pre-out -> ACA -> Coral Holey Basket open baffle diy. I'm getting bad RF noise when moving things on the desktop of the computer, ie moving the mouse makes noise through the system. Swapping out the ACA For a cheap topping tripath amp completely removes the issue, so I'm fairly confident its coming from the ACA and not my non-sheilded speakers. So far nothing i've tried has worked including:Appreciate any suggestions, these speakers sound great with the ACA and I'd like to use them together
- Moving ACA and Sony onto a filtered furman power strip
- physically moving the speakers
- physically moving the components +- 3' (within range of the cabling)
Dgcoffee, I read your post and am curious about what you are using for your input wires and how you configured them from the RCA to the inputs on the board. I do assume your wires are twisted at a minimum.
Personally, my background is from an area that had high levels of UF, RF, and magnetic field mubojumbo in the environment.
I recently finished my second ACA, adjusted the bias after its 16 hours of music to 12V and both of the ACA’s are completely silent around other noisy power supplies.
I used shielded silver plated copper for both my power supply and input wires, oh the led leads are also off the same construction of wire but are of a smaller silver plated copper wire diameter. The shield of both is only attached on one end and that is to the ground bus. My power supply also has a 15000uF cap in each amp that connects to two P089ZBs 1/per side. I have no noise leaking in via the power line nor in my inputs.
I’m burning in the parallel mono resistors currently. Everything sounds nice so far on the midlevel bookshelf speakers I’m using. I wanna drag all this hobby stuff to my hotel room while I’m at AXPONA next month. I’m sure I may have typed that here before. Hummmm.
I just bought a 115v pri/35v sec transformer from eBay. A dedicated power supply for the two ACA’s is currently tempting me.
Personally, my background is from an area that had high levels of UF, RF, and magnetic field mubojumbo in the environment.
I recently finished my second ACA, adjusted the bias after its 16 hours of music to 12V and both of the ACA’s are completely silent around other noisy power supplies.
I used shielded silver plated copper for both my power supply and input wires, oh the led leads are also off the same construction of wire but are of a smaller silver plated copper wire diameter. The shield of both is only attached on one end and that is to the ground bus. My power supply also has a 15000uF cap in each amp that connects to two P089ZBs 1/per side. I have no noise leaking in via the power line nor in my inputs.
I’m burning in the parallel mono resistors currently. Everything sounds nice so far on the midlevel bookshelf speakers I’m using. I wanna drag all this hobby stuff to my hotel room while I’m at AXPONA next month. I’m sure I may have typed that here before. Hummmm.
I just bought a 115v pri/35v sec transformer from eBay. A dedicated power supply for the two ACA’s is currently tempting me.
Another issue of note is the ferrous nature of the kit’s connection hardware. The speaker posts are highly magnetic and the rca jacks are mildly magnetic. I switched those out for audionote’s silver hardware as all wire is solid silver except as noted previously.
I do admit that the last few hours of music have really started to reveal some top notch sonics. When I enter the room and step in front of the small speakers I feel an immediate urge to connect the ACA’s to my full range OB’s to see…, urrr hear, what I really have with these and find out how they compare to my adcom 555 and my modded ST 70.
I may finally finish up the Zen amp I’ve been toting around since the 80’s.
I do admit that the last few hours of music have really started to reveal some top notch sonics. When I enter the room and step in front of the small speakers I feel an immediate urge to connect the ACA’s to my full range OB’s to see…, urrr hear, what I really have with these and find out how they compare to my adcom 555 and my modded ST 70.
I may finally finish up the Zen amp I’ve been toting around since the 80’s.
It always bugged me why the numbers I got from "Bridged Mono" as it's called on the back panel of the ACA 1.8 kit didn't match the numbers Nelson got when he ran an amp that he borrowed from Variac. See posts 8788 and 8810 in this thread. The numbers I got were from the ACAs I built at home on Vector Board running on a bench power supply.
Well, here's the story. Somewhere along the line R12 was changed from 68K to 39K. I know I was aware of the change, but might not have incorporated it into my builds. I don't think I used the extra 39K resistor that is wired to the switch on the back panel of ACA 1.8, I probably just stuck a trim pot in the circuit and tweeked it for a gain of minus one because looking at it with a scope, I could see the gain was off. Variac's ACA must have had the 39K. The 39K does not take into account the 10K R11 on the ACA circuit board. So the gain is less that unity by about 2dB. ( I used the math, not an actual measurement which will be lower still.) This means side A clips before side B with it's low gain. Just guessing, I think the resistor on the switch needs to be 24K to 27K.
Well, here's the story. Somewhere along the line R12 was changed from 68K to 39K. I know I was aware of the change, but might not have incorporated it into my builds. I don't think I used the extra 39K resistor that is wired to the switch on the back panel of ACA 1.8, I probably just stuck a trim pot in the circuit and tweeked it for a gain of minus one because looking at it with a scope, I could see the gain was off. Variac's ACA must have had the 39K. The 39K does not take into account the 10K R11 on the ACA circuit board. So the gain is less that unity by about 2dB. ( I used the math, not an actual measurement which will be lower still.) This means side A clips before side B with it's low gain. Just guessing, I think the resistor on the switch needs to be 24K to 27K.
^ Nice! Thanks very much for sharing the details of what prompted the investigation, the work, and the fix.
I've never run mine in that mode or measured it, but for the 'price' of a 100k resistor from the stash, I'll go ahead and pop one in each of my ACAs before I forget.
Edited to add - Takes less time to modify two than the site allows for editing... See below. Not my finest work, but it'll do. Thanks again!
I've never run mine in that mode or measured it, but for the 'price' of a 100k resistor from the stash, I'll go ahead and pop one in each of my ACAs before I forget.
Edited to add - Takes less time to modify two than the site allows for editing... See below. Not my finest work, but it'll do. Thanks again!
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Hi
As you can See here in step 16and 17, there is no mounting hole drawing. the pcb is "just" screwed with the MOSFET´s nd the middle hole.
https://guides.diyaudio.com/Guide/Amp+Camp+Amp+V1.6+Build+Guide/5
chris
As you can See here in step 16and 17, there is no mounting hole drawing. the pcb is "just" screwed with the MOSFET´s nd the middle hole.
https://guides.diyaudio.com/Guide/Amp+Camp+Amp+V1.6+Build+Guide/5
chris
Thanks @ItsAllInMyHead thats a great diagram much clearer. I will check out that thread for resistor values has there been any benefit by placing a pF cap across the resistor. Also for the output + are they just connected to ground in ur diagram.