ok, mains bulb tester done, works a treat. If you plug in 2 CFLs you can make yourself a strobe light, and when the capacitor bank is discharged, its a bit of a rush in current limiter with incandescent lamp.
Anyway, with inlets closed, its completely quiet, and with inlet open a bit of hiss and something that sounds like a small plastic fan, really quiet. More a buzz than a hum. The transformer is still outside the housing, like in the photo yesterday
Anyway, with inlets closed, its completely quiet, and with inlet open a bit of hiss and something that sounds like a small plastic fan, really quiet. More a buzz than a hum. The transformer is still outside the housing, like in the photo yesterday
-I think CFLs have rectifiers in them. One is charging thus short circuiting. This swithces the other one on. Essentially I put a CFL onto the power point and one in the socket. So they flickered alternating. But I got a 60W incandescent as well and that works. Just tried first with a CFL work light and a CFL bulb that was hanging around.
-amp does not have any cable on it just yet, just set a jumper. With a cable there will be some more noise. Will check tonight. Essentially, if there is a cable just hanging off the amp, its noisier than when the cable is connected on both ends. The other end being the xover, not some external device. Just want the amps sorted by themselves before I connect them to the outside world.
-amp does not have any cable on it just yet, just set a jumper. With a cable there will be some more noise. Will check tonight. Essentially, if there is a cable just hanging off the amp, its noisier than when the cable is connected on both ends. The other end being the xover, not some external device. Just want the amps sorted by themselves before I connect them to the outside world.
I can twist the cables that go into the housing, for now its flat cable (some offcut from domestic wiring).
Earth comes in separately. But its pretty sure interferences. I rewired it for star ground, did not change a thing. Plus if the earth would be messed up, there would still be noise, if I close the input via a jumper? Then again, then earth and input floating are at the same, no signal there. Jumper closed only proves, from there to signal in of the TDA there are no interferences. Inlet open, then that pin is an antenna? Can put short and long cables on to check.
All this still just one of the small PCBs with the TDA on it, no extra bits.
Earth comes in separately. But its pretty sure interferences. I rewired it for star ground, did not change a thing. Plus if the earth would be messed up, there would still be noise, if I close the input via a jumper? Then again, then earth and input floating are at the same, no signal there. Jumper closed only proves, from there to signal in of the TDA there are no interferences. Inlet open, then that pin is an antenna? Can put short and long cables on to check.
All this still just one of the small PCBs with the TDA on it, no extra bits.
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the 240V cable being incl earth of course. That earth that meets the N in the switchboard. This earth is then connedted to the outlet of the PSU and so on.
Reg attenuation, just an open cable, not connected to anything. I suppose the signal cable needs to be twisted as well. Bit trickier to find shielded twisted cable, as twisted cable by itself did not cut it. I do not need the return/ground as that will just introduce a ground loop.
Reg attenuation, just an open cable, not connected to anything. I suppose the signal cable needs to be twisted as well. Bit trickier to find shielded twisted cable, as twisted cable by itself did not cut it. I do not need the return/ground as that will just introduce a ground loop.
No hum with the input shorted proves that the power supply ripple voltage at very low power is not audible. I think we can call that a small step. It would be interesting to measure the PSU and the output to confirm this. You could also try increasing the current load of the PSU to see if the amp remains quiet with higher ripple voltage.
You could try coax cable.
You could try coax cable.
damn, the images from yesterday morning are too blurred to see what the scope was at. Was it really 1V per cm? I put the 100 ohms on, got 200mV ripple, was it really 2 V yesterday then?
Gotta multism it. Edit: gets the same results, about 200mV
With jumper on inlet, no noise. No jumper imagine a very small propeller or ball bearing very faint. Some sine wave with not too many overtones. Not like a saw tooth buzz. But I had to stick my ear into the speaker to hear that. So not concerned. The buzz it normally does has a lot of high frequency overtones and can easily hear it 1 foot away.
Gotta multism it. Edit: gets the same results, about 200mV
With jumper on inlet, no noise. No jumper imagine a very small propeller or ball bearing very faint. Some sine wave with not too many overtones. Not like a saw tooth buzz. But I had to stick my ear into the speaker to hear that. So not concerned. The buzz it normally does has a lot of high frequency overtones and can easily hear it 1 foot away.
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I would try a plain cable, thats where the noise comes in. The more amps interconnected, the worse it becomes
Can use the laptop, thats floating. At work now, have to wait until tonight.
Found something how to bild near field probes, that may be worth trying. Guess have to reduce the radiation from all the wiring and transformers and then reduce the audio cables playing antennas.
Also it may have helped to connect the 2 centre taps of the toroid first and then put into the PSU. This would be 2 separate coils in the toroid, so the currents between them would otherwise have flown on the beginning of the PSU PCB.
Can use the laptop, thats floating. At work now, have to wait until tonight.
Found something how to bild near field probes, that may be worth trying. Guess have to reduce the radiation from all the wiring and transformers and then reduce the audio cables playing antennas.
Also it may have helped to connect the 2 centre taps of the toroid first and then put into the PSU. This would be 2 separate coils in the toroid, so the currents between them would otherwise have flown on the beginning of the PSU PCB.
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