Hi. As I've begun using my Lemur4 Ultra for pro audio work, I've discovered that the stock AC power adapter appears to be a little noisy. There is a high-pitched background hum that is apparent only when the AC adapter is connected. I've been able to rule out that my USB audio interface is the culprit, since unplugging the laptop from the power adapter and running off the battery makes the noise completely disappear. As I own two AC adapters, I tried both of them to make sure it wasn't just a matter of a faulty adapter; both adapters produce the same problem. I've also purchased a Furman line conditioner to try to treat the noise, but the problem does not disappear. Trying the laptop in friend's homes doesn't change the problem, either, ruling out that something in my house is the culprit. I now strongly suspect the AC adapter itself as the only possibility.
Can someone recommend me compatible adapters made by other manufacturers I could try with my Lemur4? As things stand, this hum, while not very loud, effectively renders the noise floor too high for production level recording and live performance.
Thank you for your time!