Strange intermittent humming when using L/Pinkie

[jonp]

Ever since I owned my first Little Pinkie (with my previous XCan V3) - and now with my Little Pinkie SE with XCan V8, I have noticed a strange intermittent 50 hz humming problem (like bad valves) whenever I use a source that is powered by batteries rather than the mains.

So for example, if I use a portable music player or a laptop computer into a USB DAC as a source, I will get this "bad valve" humming sort of intermittent sound, unless I actually run a grounding cable from the spare line output grounding terminal to one of the ground connections on the mains sockets in my power strip.

This phenomonen has happened with both my previous X-Can V3 and my current X-Can V8s (both) and is also independant of the mains supply (happens at different houses), power strip or no power strip, the valves I use and the source (DAC / transport) - but only so long as the source is battery powered. And the problem does not occur with the stock wall-wart supply.

As I say, I can get rid of this problem by running a ground connection between the X-Can amp line out socket and the mains ground, but I have discovered that this is - for some reason - quite injurous to the sound.

Now, this problem never ever occurs if I have the X-Can connected to a source that is mains powered, such as the line outputs of soundcards in my main PC, or even when connected to a battery powered USB DAC which is connected to the mains-powered PC). But if that DAC is connected to a laptop on battery power, the intermittent hum comes back.

Does anyone know why this is happening (the intermittent part seems strange - I would have thought I'd get it all the time or not at all).

I really would like to use the X-Can with a DAC and laptop without having to make this extra ground connection between the X-Can and the mains power strip.

[Deleted]

Jonp
A remote possibility is that the battery leads are picking up "frame buzz" from Analogue TV transmissions, Are the battery leads tightly twisted together ?
Alex

[Deleted]

This sounds silly, but is it the casing? I had an intermittent noise from mine which was fixed by tightening the screws that hold it together.

Ian

[jonp]

Hi,

Thanks for the replies. It isn't any physical issue with the power supply. It is dead quiet and the humming comes from the headphones - so it is part of the analogue audio signal.

It also would not be due to battery wire configuration, etc, since this problem occurs even when using a portable music player that has an internal / proprietary battery housed within the unit.

I did some further tests today and noticed that if I put my fingers on the casing of the X-Can V8 when the humming starts, it is greatly attenuated, however not as much as if I run a dedicated grounding wire back to the mains (in the latter case the hum is eliminated, but the sound seems to suffer quite a bit in doing so).

The other thing to note is that the stock wall-wart has an insulated ground pin, so it is not earthed - this is different to the Little Pinkie which is earthed. And as mentioned before, the problem does not occur with the stock wall wart - it only occurs with the Little Pinkies.

Perhaps Mike can chime in here. As I say, in summary:

1. It has happened with all three Little Pinkies I have owned (curently own two SE versions).

2. It has happened with my earlier X-Can V3 and with both my current X-Can V8s.

3. If I connect the X-Can V8 to any mains powered source that is connected with a grounded mains plug (i.e my main PC) then there is no intermittent hum problem.

4. It does not happen with stock wall wart for the X-Can V8, regardless of how the original source is powered and whether it is grounded or not.

[Deleted]

jonp
USB can cause all kinds of weird hum and noise issues, especially from Laptops. Sometimes even mouse and keyboard clicks can come through.
Have you been able to see if it happens with the Laptop running on battery ?
Alex

[mrarroyo]

If you are running windows in your laptop, set the music player as "high" in the priorities. This should remove most of your noise, and close as many of the other applications you may have open. As an option make sure you have sufficient ram.