Arnold - thanks for the more technical explanation. Do you think that a DC blocker may help? Or any other remedy? Rotareneg - I have tried pressing on the case. I have tried removing the case and pressing on the transformer or PCB. No changes.Today I tripped all the switches on our consumer unit and left only the ring which contains the DAC open, switching off everything else on the ring to see if any other household appliance may be exacerbating it. No change unfortunately with the hum!
Today I tripped all the switches on our consumer unit and left only the ring which contains the DAC open, switching off everything else on the ring to see if any other household appliance may be exacerbating it. No change unfortunately with the hum!
..................................................................................Very simple question: have you actually taken your devices to a friend's house some distance away to check whether the hum is still present? If it is, the devices are probably at fault. If it isn't, your mains supply is the source of the problem. Until you've established this one way or another, you can't begin to find a solution.................................................................
Thanks for the ongoing insights here.I have 4 further small findings that might help in the quest to remove the hum;1. I took the case off (again) to see if the rod that holds the transformer needs tightening or loosening. What I found before getting to that however, was that the casing seems to be contributing to the noise. With the case removed, the noise is definitely less. It is still audible, though perhaps heading towards the level that would not be noticeable from the listening spot. I had tried removing the case before and don't remember a particular reduction in noise, but there you go. So I got some thin rubber pads and tried to insert them in-between the front panel and side casing. Once the screws were again tightened, this did not seem to improve the noise. Flexing or moving the top casing also seems to affect the noise somewhat, though inserting anything in-between this and the base is quite tricky. Either way I did not have the impression that inserting further bits of rubber would likely affect the noise, given my findings with the rubber at the front.2. Trying again to isolate the area that the hum is coming from, I think it is coming from a different component to what I had expected. I had thought that the noise was coming from the main transformer (a bit round thing which I have labelled 'A'), though it appears to be coming from somewhere nearby. The exact culprit is difficult to determine, though I'm wondering if it is coming from the component highlighted in my photo below (which I have labelled 'B'). I'm not sure what this component is but am wondering if it is also a kind of transformer?3. I noticed that one of the bolts/pillars holding the PCB to the casing appears to have current running through it (if that is the right term) - when I touched it, I felt a small shock. I can't remember if my other hand was touching the casing or not. I also don't know if this is normal/expected or not. The unit was powered on at the time. Maybe I was stupid to be prodding around inside with the power on. I don't know if the other 4 bolts are the same (I didn't fancy testing)! I have highlighted this bolt in the picture below also.4. I took the DAC to my workplace and plugged it in there. Same hum. It is however only about 3 miles away as the crow flies - don't know if this is relevant or not.Atmasphere - that is a good question. I don't remember it being there initially though I may not have noticed it at that stage or maybe wasn't looking out for it. Once you've noticed it, you can hear it. Thanks again for the help here.
You mention getting a new DAC - this remains an option, though I like the DAC and would rather fix the hum problem if possible. Remember that my other components are also affected by this hum (although to a somewhat lesser extent), and that the DAC did not hum at all on testing at the manufacturer. You mention "things that can be done" regarding the electricity supply - what did you have in mind?
@jsrtheta +1@extrcampine OK- so what is your line voltage? If over 245 it could be contributing to the problem.If you take the equipment elsewhere, bring the DVM with you to see what the line voltage is.The Lampizator DACs I've seen use both toroid and EI core transformers. Any chance you can get the cover off the DAC and start it up? I've used a plastic straw and also an insulated screwdriver to suss out mechanical noises by using them as a stethoscope; if you can sort out which transformer is noisy that might help.
Arnold B. Krueger,With all due respect, that Benchmark AHB2 amp is a beautiful amp, but when they say:"THE QUIETEST, CLEANEST AUDIO AMPLIFIER ON THE PLANET" and it sells for $2995.00Isn't that a little too "audiophile"? A Crown XLS DriveCore 2 Series amp is a lot cheaper.