I recently acquired a 2007 ES 350 and have been struggling with the ground loop coming from the aux input when using a powered source (I'm using the BB bluetooth music gateway). I had an alternating whine that increased with RPM. The usual advice is buy a ground loop isolator for the aux input side. First I tried the "PAC" model on amazon, and that completely killed the volume and bass. Next I tried the Kensington, and that worked much better, but I think it still affects sound quality and ideally I wanted to clean up the power source instead of the analog audio out.

So next I tried a " " from amazon (not affiliated, in fact it took three weeks to arrive). Thankfully, this powered the BB and eliminated the ground loop. It has three settings (low, off, full), but it doesn't matter what position the switch is in. I don't know what kind of electronics are inside, but whatever it is, it's allowing me the highest possible audio quality by cleaning up the power before it has a chance to affect the analog signal.

Afterward, the whole device chain seemed kind of vulnerable at the bottom of the console, so I reinforced it with a paint mixer.

Anyway, this is just an FYI for anyone suffering from this problem. Assembled contraption attached.

 

Awesome post! Will give this USB isolator a try after I order it from eBay.

Also, I agree with you that many people blame the AUX input to cause the hissing/whistling sound when accelerating but it's actually from the cigarette lighter.

My Lexus ES 350 was also experiencing the same problem as you of the alternating whine (I'm also using the Blackberry Bluetooth Gateway Streamer).

Will provide an update if this USB Isolator works.

 

I was actually using an external USB rechargeable battery pack. Definitely isolated!

Nice job on the isolator.