I tried a few Marshall DSL40CR amps, when they first came out. Several of them had an odd, windy, or rustling sound when I wasn't playing. Other than that, I really liked the amp. Does anyone know if Marshall identified a cause for this, and if the more recently produced models exhibit the same behavior? I'm kinda hoping to find a floor model, that isn't making the noise, and just buy that one, rather than ordering online or getting a boxed one at a shop. Thanks.