sorry.....
Good evening, I am entering this discussion because I have a problem. I built my mini ACA exactly following the 6L6 guide on DIY audio guides, made changes on V0 (11.47 volts) and VB (0.303 mV) on both channels, the heatsinks heat up as they should but one channel makes distorting noise. I don't have the possibility to take any other measurements and so I ask what could it be and what can I verify?
thank you Giampiero
Good evening, I am entering this discussion because I have a problem. I built my mini ACA exactly following the 6L6 guide on DIY audio guides, made changes on V0 (11.47 volts) and VB (0.303 mV) on both channels, the heatsinks heat up as they should but one channel makes distorting noise. I don't have the possibility to take any other measurements and so I ask what could it be and what can I verify?
thank you Giampiero
Think I got it. I did not know i could decrease the VO reading by turning the pots clockwise. I am close to the target values, VB 0.30V & VO 11.5V. the probes on my MM leads are too fat to stay in the test holes so it is harder than it should be. Q3 & Q4 are in the correct spots.
Again, thanks for the help. I have 3 builds done and the last two went smoothly!
Again, thanks for the help. I have 3 builds done and the last two went smoothly!
I got one of these assembled, biased and working. It sounds great but I'm having an issue with some input devices. Specifically, a couple of Raspberry Pi players running Moode. I'm hearing a dirty ticking sound at approximately six clicks per second. The noise is constant, no matter what the volume level on Moode is. At low music levels, the ticking is plenty apparent. When I power down the Pi, it stops. There also is some audible hash that seems to follow the activity of the pi, with short bursts, etc. I have two players that facilitate this behavior when plugged into the ACA Mini, but they sound noise-free elsewhere. One player is a naked stack with an fully enclosed power supply. The other is in a metal box with the PS completely enclosed and the Pi and DAC in a section with some plastic "windows to let the WiFi signals through. FWIW, both have Inno-Maker DAC (marked "Skylark" on the board) hats based on an ES9038Q2M chip, on a Pi4 or Pi3 running the newest version of Moode. My Astell & Kern portable player sounds fine, with no notable noise.
The amp board is currently sitting on a base, screwed to the stainless steel perf sheet below it. I'm planning on surrounding the sides with woven stainless grid, but was planning on leaving the top open. I see a lot of pretty much naked players on this thread. Although it's all sitting on a table saw for now, everything is well insulated from it. You can see from the photo what the present setup looks like.
Any thoughts on what might be happening and how to address it?
The amp board is currently sitting on a base, screwed to the stainless steel perf sheet below it. I'm planning on surrounding the sides with woven stainless grid, but was planning on leaving the top open. I see a lot of pretty much naked players on this thread. Although it's all sitting on a table saw for now, everything is well insulated from it. You can see from the photo what the present setup looks like.
Any thoughts on what might be happening and how to address it?
Attachments
Both channels, yes, meant to say that. Circuit ground on the board and the perf below it are attached via the four screws on ground pads into small aluminum risers that are screwed from below (two screws each) onto the perf material, so a pretty solid connection there. Perf is also screwed into right-angle connectors holding the small black channels around the perimeter together, but since both the corner connectors and the channels are powder-coated, I doubt there's much of an electrical connection to that rim at present. As I said, this is just work in progress, and I will install a ground screw on one of the channels at the next stage.
The PS is the SL Electronics 24v one that came with the completion kit. I could scrounge around and see if I have another one here to try, but as I say, my A&K portable player sounds fine with this setup, so it's hard to understand how that could be causing the problem.
Toys4Boys, there is a wireless mesh unit in a room on the other side of a wall, in my office. Never caused any kind of interference issue with any other audio equipment. Evey the pi player shown in the photo works flawlessly within a few feet of it. Some of the noise/hash is clearlyrelated to activity of the Pi--when I push "play" and I know it's accessing the SSD where the files are, I get a burst of hash.
I was not having this issue when I had a little Tripath class D amp, burning in my new pair of speakers there.
The PS is the SL Electronics 24v one that came with the completion kit. I could scrounge around and see if I have another one here to try, but as I say, my A&K portable player sounds fine with this setup, so it's hard to understand how that could be causing the problem.
Toys4Boys, there is a wireless mesh unit in a room on the other side of a wall, in my office. Never caused any kind of interference issue with any other audio equipment. Evey the pi player shown in the photo works flawlessly within a few feet of it. Some of the noise/hash is clearlyrelated to activity of the Pi--when I push "play" and I know it's accessing the SSD where the files are, I get a burst of hash.
I was not having this issue when I had a little Tripath class D amp, burning in my new pair of speakers there.
Still worth trying, different equipment will exhibit no or different problems related to WiFi.
OK, more information. In checking my grounds, I noticed that in my excitement to get the thing playing music, I inadvertently left the plastic insulating washers in place on the threaded shaft of both RCA panel jacks--stupid mistake. You can plainly see them on the photo I sent. I was sure this would fix the problem, but no. Still the same tictictictictic as before, clearly audible on BOTH channels.
I have tried with different input cables and checked the input solder connections, but all seems fine. Meter shows a 0 ohm connection between the body of the panel jacks and the perf grid under the board. Not a lot of other things to check here. I did turn off the wireless mesh router in the next room--made no difference. Remember, amp plays fine with another source, and the RPi DAC plays fine through another amp. It's something about this combination.
Thoughts as to what to try next, anyone?
I have tried with different input cables and checked the input solder connections, but all seems fine. Meter shows a 0 ohm connection between the body of the panel jacks and the perf grid under the board. Not a lot of other things to check here. I did turn off the wireless mesh router in the next room--made no difference. Remember, amp plays fine with another source, and the RPi DAC plays fine through another amp. It's something about this combination.
Thoughts as to what to try next, anyone?
I got a "ticking" sound in both channels of my Mini when I tried to use a couple of different step up transformers in front of it to get a little more gain. One was a Hammond 124b and the other was a small toroidal transformer wired backwards. Didn't like how they sounded otherwise so I didn't try to track down the reason.