I received a replacement amp plate from Ed Mullen (Director, SVS); it came very well packed and with new screws too. It is the first time when a manufacturer sends me a replacement board or any kind of electronic devices (due to RMA/warranty) with the DDP Incoterms (all taxes paid by the manufacturer). TNT/FEDEX just left my package in the yard after a short talk on the cellphone, telling me that I have nothing to pay. A huge CONGRATS to SVS for such a customer service and they way they deal with their customers!
I installed the board yesterday and had it briefly tested. I have noticed a slight decrease in the background noise, indeed, but only by a small margin, with 1.1 dBA. However, the noise was cleaner to my ears and from the listening point I wasn't able to hear it, so I am happy after all.
Perhaps there is still room for improvement on the design and I'm sure that future versions of subwoofers the schematic will be redesigned to further eliminate the background noise completely, but meanwhile, for those having hiss noise issues with SVS subs or with any other subs, just rotate them with 90 or 180 degrees (so the sub to not fire into listeners face), then adjust the phase with +/-90 or +/-180 degrees and remeasure the output with REW. This will definitely lower the audible noise on the listening point so it will not be audible any longer.
The attached pics represent the noise for:
- original board (35.5 dBA)
- replacement board (34.4 dBA)
- room ambient noise (23.9 dBA)
Measurements were done with DecibelX on iPhone 12 Pro from identical distance. Several measurements were done and I got same results. I also used REW + Motu M4 + EMM999 and I got the same 1...1.2 dB difference in noise.