I noticed a hum and pulsing noise coming from my DAC even though it wasn’t on. I speculated it could be DC on the AC line. I tracked it down to a heating pad on the circuit. While I have no idea how accurate my testing was, I measured 10 millivolts with the heating pad off and 200 millivolts with it turned on. With it off the hum and pulsing stopped. That’s great because there’s nothing wrong with my DAC. Can anyone tell me definitively whether I’m somehow damaging the transformer when I use the heating pad? Would this cause a degradation in sound when the DAC is in use? Is there a relatively easy was to remove any DC on the AC line? Thanks for any answers you provide.
Is the heating pad the type with half-wave rectification to get half-power? If so its bad news period.
I don’t know. It has four heat settings and appears to dump the same amount of DC into the AC line regardless of the setting. Why is it bad news?
You were suggested a possible explanation, which also looks reasonable to me: heavy unsymmetrical load on your mains line *will* create a significant DC component, which *may* affect your DAC.
You discarded it.
Fine, but then I can´t imagine a different one.
IF somebody has another idea, be certain he will post it here.
If not ......
You discarded it.
Fine, but then I can´t imagine a different one.
IF somebody has another idea, be certain he will post it here.
If not ......
I posted and asked some questions. I received a response which asked me a question. I responded to the question and the post died. What do you mean I discarded it? There was no explanation provided. An explanation requires a statement, not a question. . .
A good power conditioner removes DC, EMI, surges, etc. Monster Cable makes one as do many others. Or you can make your own. But I'd suggest anyone using a DAC of any kind be using a power conditioner.
If the power supply in your source equipment has been properly designed, you wouldn't have trouble with a little DC and or noise on the AC mains. No need for a "power conditioner" then.
Designers just have to learn to do their jobs when it comes down to a power supply in their products.
-Chris
Designers just have to learn to do their jobs when it comes down to a power supply in their products.
-Chris
If there is DC through the transformer and it is toroidal then it can hum.
You possibly need a mains DC blocker.
You possibly need a mains DC blocker.
Which could probably be quite small for a low power component like a DAC (the designs you see on the web are generally intended for big power amps needing hundreds of watts, here I would imagine sub-1000 µF and a small DIP rectifier would do), but would still have to be built safely of course, with double insulation. "I see lots of heatshrink tubing in your future..."