Hiss and Noise
While reading this thread I've been smirking to myself about hiss being the noise of system and what the noise floor of most equipment measured here is. But if NC400 hisses, be it in 110dB horn, then it is a real problem.
Amplifier amplifies hiss from preceding devices, did you experience hiss from 26 dB gain with DLCP or just with miniDSP?
Did you try to attenuate with resistors after amplifier? That's one method to reduce hiss.
Hypex electronics are world famous of failing, even the new FusionAmps (the amp modules themselves are fine, it's there accompanying other stuff). Have you had any reliability issues?
It would be greatly appreciated if users posted about this aspect of their products, good or bad. I own Hypex amps, but turned away from DLCP because fear or immature failing. My amps have been running great!
Hypex DLCP has a signal/noise ratio of 113 dB and is specified to 7,4 uV noise on the outputs. I don't know what that is, but an online calculator says something like -129 dBu.
https://docs.google.com/viewer?url=...load/doc/dsp/dlcp/Documentation/DLCP_04xx.pdf
The hiss from either Minidsp was not tolerable, so changed to DLCP. That hiss was far less, but still enough for me to be annoyed by it with the standard 26 dB gain in the Nc400 while sitting around 3.5m/11 feet from the speakers.
Since I have Nc400 with both 26 dB gain and 13 dB gain laying around, it was easier for me to just switch them than to try different remedies. Now I can't hear any hiss unless I stick my ear next to the tweeter.
Doing it this way will cost you gain headroom, meaning you need to turn the pre-amp way up to reach the same spl level, but you gain signal/noise ratio out from the pre-amp and you amplify less of that pre-amp noise in the amplifier stage.
If you have enough gain to reach desired spl, it's a win-win.
Oh, and all electronics will hiss. Even if you turn off the pre-amp the amplifier will hiss. It's just a question of how much and how sensitive you are to it. I'm very sensitive, it seems. But I also usually listen to music at around 65-70 dB.
Hypex reliability;
I've had amplifiers from Hypex fail in both of the Kii Three speakers I had. The software in Hypex DLCP has gone AWOL on me on two occasions, both happening while I'm adjusting dsp settings and uploading it to the DLCP. Bloody infuriating because you need a total reboot of the whole shitbox with fresh installment of the operating system.
The Hypex Nc400 monoblocks I have (I use 4) have so far been reliable. I never turn them off and they are placed inside a small space with limited ventilation. They have been at work like this for around 10 months, but I expect them to fail eventually. They don't really get very warm, at least not compared to those inside the Kii Three's that share the space with 6 modules without ventilation.
I would not expect any Hypex to survive for 20 years, but let's see.