Originally Posted by M Code
We know those NAD components well, and have visited many times their subcontractor factory in Nanjing, China, they are solid, well designed/built products. To eliminate the hiss, you need to do more troubleshooting..1.
If you disconnect the pre-outs > main-Ins, does the amplifier still hiss?2.
What source is connected when the hiss is most audible?3.
Is there any cable box, Sat tuner or PC connected to the preamplifier?4.
Have you ran a direct independent ground between the reamp and amplifier
Over the years, we have installed many, many systems many costing up to $100K and we will not accept an audible hiss. If you have an audible hiss, then I would suggest that you should have each component checked carefully.. Hopefully with a shop that has an AP system, as you may have a defective component with an out-of-spec noise floor... If not, take your preamp and amplifier back to the store and try it with another unit..
Just my $0.02... 👍😉
I agreed with your claim that NAD are well designed and well built "physically" products because it reflects on the actual unit that is solid, has good appeal and even nicely packed. I think many of us are attracted by such factors hence "jump ship" to them. However, why is it that we have audible fan noise on these well designed and built models and for a few of us here at AVS that actually own the M15HD and HD2 have the "Check DSP" problem? My ex system was the Rotel. They also are Made in China but Rotel claimed they "own" the factory themselves whereas NAD seems to "oem" their manufacturing to the "chinese" without "owning" the factory. That can makes the different where sub standard parts are dropped into the production and resulted in end users feedback over the glitches that's concerning, annoying and even very frustrating.
The previous hissing case i have did all the check and the results are as follows :1.
If you disconnect the pre-outs > main-Ins, does the amplifier still hiss? Lower hiss;2.
What source is connected when the hiss is most audible? All components were disconnected from the pre-amp;3.
Is there any cable box, Sat tuner or PC connected to the preamplifier? Nope;4.
Have you ran a direct independent ground between the reamp and amplifier? Yes. I have added additional ground using the ground out from the amp connecting them to different ground but i heard no different in the hiss generated. Frankly i thought different grounding can only solve the humming issue and up until now, i dont have hum problem in any of my system setup (keep my fingers crossed for future ones);
Lenbrook initially want to deploy their technician to my place to check on the hiss but upon i told them to bring a new replacement unit over and swap the one which is confirmed to have excessive hissing that needs attention of replacement/repair of components within, they decided to rather deploy another "factory A stock" over which has a paper tape attached at the bottom with some Chinese wording written on it (too bad i didnt took a photo of it so i have nothing to proof on this) and at that point of time, i have a bad feeling on this replaced unit and unfortunately my guts feeling is right, it has gone completely malfunctioned with the "Check DSP" initially displayed and now, it only make the "buzzing" sound.
The critical point here is if you have good design but the end products cant even live up to the basic specifications, then it's kind of wasting the whole effort. The best manufacturer who stands by its products that dares to admit their products issue, make rectification and provide total customer support and satisfaction will earn the business over long term ultimately.