Hi Axcelon,
Quote:
I now have the original StepDance + XP8000/WI15 setup.
[snip]
The WI15 adapter produces an audible hiss, implying a switch-mode voltage reducer. This means that the voltage it supplies (which is only designed to be good enough for a power supply for a laptop) is not a pure, near constant voltage, which is the point of using a battery (since there is no "noise" under those conditions). Worse, the fact that I can hear the hiss of the adapter implies that the distortion of its supplied voltage has significant components in the audible range. The buffering of the SD should mitigate this to a fair degree, however I was immensely impressed with the 12V source from the XP8000.
I know what the physics and EE predict in these situations.
Zilch0md, do you still have your 15V pure battery rigs? Would you be able to compare the WI15 to them? I'd be curious to hear what you have to say.
The WI15 might benefit from adding a pi-filter stage between the 15V output and the SD, for maximum sonic performance while supplying 15V over the discharge range of the battery.
Make sense?
I find your assumptions to be reasonable, given your observations, but to my knowledge, you're the first person who has heard a hiss coming from the XPAL Willy Cable WI15, when used with the Stepdance. Like ianmedium, and apparently several other WI15-equipped Stepdance users who have posted their findings to this thread, all I hear is an inky black silence with the WI15 (in the absence of a signal). In fact, that's all I hear with the Stepdance in any power-supply configuration I've tried. I need to qualify that statement, however, by saying that I have not purchased or used any switching power supplies - only regulated, linear power supplies.
It could be, as you have suggested, that the XP8000 + WI15 is indeed a switching regulator, but my understanding is that switch-mode power supplies don't generate heat the way a linear regulator does because they are inherently more efficient and I've always found the WI15 to get warm to the touch when in operation, which suggests that it might be using a resistor to induce ohmic losses for the sake of regulating the voltage, rather than pulsing the input voltage to generate a the desired 15-Volt output. Still, I'm willing to say that the fact that the WI15 gets warm to the touch, is not in itself proof that it is not a switch-mode device.
All that said, I think Jan Meier would agree that a switched-mode power supply is OK to use with the Stepdance, though not ideal, as long as it is regulated, and of course, does not produce an audible buzzing sound with your headphones. Unregulated switch-mode PSU's should be avoided entirely. Regulated linear PSU's are preferred.
Regarding your request that I compare my pure 15-Volt battery solutions to the XP8000 + WI15 solution, I can tell you I do so with great frequency, sometimes using the 15-Volt RC LiPo batteries (in my "walkabout" setup) when outdoors, or doing chores around the house, walking the dog, lying in the hammock on our deck, etc., but almost as frequently use the XP8000 with WI15 as my "desktop" power supply (disconnected from the AC charger) whenever I'm in my easy chair in the den. I also use the XP8000 and WI15 with my "travel rig" when away from home.
So... I go back and forth between both power sources frequently and I'm happy to say, I've never heard any difference between the two 15-Volt solutions - not with my LCD-2's anyway.
What headphones are you using?
Since you've ruled out the XP8000 itself as a source for the noise you're hearing (via the 12-Volt cable), it seems that only your WI15 is suspect.
I have a spare WI15 cable that I could lend you briefly if you'd like to compare it to the one you have. Send me a PM with your mailing address and I can have it in the mail tomorrow.
Mike
