Here's another sorta-tweak implementation of an NC400/SMPS600 combo...
1. Tightly twisted AC cable, harness from SMPS to module, and speaker cables
2. Ric Schultz's speaker wire clamp setup
3. Hard-wired AC cable, based on a PC Ric used to sell
4. Shortened, almost minimal-length input cable
5. Some damping material on the case
6. Placed on a TipToe'd maple cutting block with Herbies Iso-cups between the block & the cases and various damping weights & dampers on the case top.
7. AMB fuses
I have them wired with Bruno's preferred input setup, but my sources are single-ended. So I modified my cables to replace the output side RCAs with XLRs.
I also played with power conditioning... I have a PS Audio Soloist filtered outlet available in addition to straight into the wall and can add Hammond Chokes as desired in parallel with the AC. The NCore started being plugged into the Soloist, but ended up straight into the wall with no chokes.
Although they showed some promise from a detail & control perspective at first, the musical presentation was not very coherent compared to a pair of B&O IcePower-based EVS 500M's from Ric. The highs/mids/lows did not gell into single notes, but seemed disconnected. Also the highs started out a bit harsh & hashy to my ears.
On the good side, bass was impressive in control & depth, although they didn't seem to go lower than the EVS 500Ms.
Now I've got 250-350 playing hours on the NCores... Better, very good in many ways. The note-level musical coherence has improved to where I generally don't notice a disconnect anymore. Mids-through-highs are cleaner, maybe still a bit emphasized compared to what I'm used to. The ultra-control of the bass has moved into the mids and they are very clear and lifelike.
But they are still not blowing me away... basically, they are still not making music for me. Overall musical coherent, flow, and urge is still not there strongly and is very dependent on the cleanliness of the powerline. Some of this may be the a bit of midrange body missing that others have mentioned. Then there's still a bit of emphasis and sometimes glare in the upper mids-treble.
When I put the EVS B&O Ice-Power-based EVS500M's back in, the musical coherence, flow, and urge come back immediately. The NCores are technically better amps... but I don't feel disappointed putting the 500M's back in. That's not a good sign!
I'm planning to give them more break-in time... I was reminded that some equipment takes a long time when I ran across a review of the Bel Canto REF500M's in Positive Feedback. The reviewer said:
"The mid-range became gradually textured, and lost for good a certain forwardness that waxed and waned with periodic irregularity during the early weeks; REF500M's treble region, that problem child, initially akin to a young one suffering of an unhappy combination of pulmonary insufficiency with whooping cough, happily healed from its youthful malaise whence the amplifiers approached 1000 hours of operation, and commenced to bloom into a delightfully lyrical maturity, almost devoid of residual constrictions.
Totally unforeseen, the steadily growing authority of the REF500M remained my greatest surprise. Well past the 1000 hours mark, at least until 1500 hours of music making, REF500Ms kept maturing in ease, a general sense of expansiveness, a surprising comfort in handling complex and intense dynamics, and a considerable solidity even in the most demanding fff (fortissimo) orchestral passages."
I also have the same experience as Ric reported with warmup. My experience with most gear since the early '80s has been a 1-2 hour warmup. The NC400/SMPS600 combo does not come on song for me until after 5-6 hours. So they are on most of the time (just down for system changes or threatened thunderstorms).
I'm trying to come up with additional changes that will improve the musicality while preserving the good points of the NCores. My thoughts:
1. Change the input & output wiring. Even though its not fashionable today, I've liked MIT hookup wire for its ability to maintain note coherence. I've got some raw input connectors coming in and will rewire both the inputs and the outputs when they get here.
2. Try different input stage power. I think it's worth trying a linear supply on the front-end and driver supplies, at the very least adding some additional filtering as serengetiplains did.
3. Output filtering. Instead of modifying the board as Ric intends, I'll start with an inline choke/resistor filter. If that makes a positive difference I'll try Econotweaks Detail Magnifiers.
4. EMI Reduction using conductive foam between the module & PS & around the PS.
5. Since they sound their best when the powerline is at its best, I've got a PS Audio P10 coming that theoretically should produce 'weekend-clean' AC quality all the time.
If these produce good results, then I'll bridge them... sharp eyes might have noticed that my case layout allows room for a second NC400/SMPS600 combo. OTOH, James Romeyn's comments on the sound quality at various load impedences has me concerned... I don't know the actual impedence versus frequency of this speaker as the manufacturer made a limited number of them and never published it, but I'm guessing it's a 4-6 ohm load across the spectrum. As I understand it, bridging could worsen any sensitivity.
And I am gathering the parts to do a balanced DAC source, but that's a while away at this time.
Some likely extended-work travel may get in the way of this further experimentation until late fall. But if it happens, I'll arrange to bring them along and lend them out in that area (more details once I'm sure that it'll happen).
Greg in Mississippi
P.S. My 'as-minimilistic-as-I-can-get-it' system consists of:
1. A computer music server based on cics's cMP/cPlay setup (see monster threads on Audio Asylum on this) with the latest OpSys slimming tweaks and all-linear computer, sound card, and DAC power supplies. The sound card is the digital section of an ESI Juli@ that has been modified within an inch of it's life and the DAC is a small ESS ES9022-based DAC card available from poster EUVL over at DIYAudio.
2. A series stepped volume control based on a Daven broadcast-quality multiposition switch and using a nude-Vishay as a series element. Cables from the computer are MIT 330 Shotgun and to the amp are just a very short twisted pair of MIT hookup and all are hard-wired to switch. I generally use the music player's built-in SW volume control and run this physical control at full volume.
3. The amps.
4. A pair of Eminent Technology LFT-IV speakers, a sorta full-range planar magnetic with rebuilt crossovers. Speaker cables are nothing-special Monster Powerlines hard-wired at the speaker end.
5. A bunch of various AC, damping, and woo-woo tweaks that most of you really don't want to hear about.
