Digital or analog? Hypex nCore 400 Amplifier discussion & Build thread

[JonMarsh]

This has been in the works for a while, but today I actually got around to ordering the nCore 400 modules and SMPS600 power supplies- I've already got the chasis, special power cords, and a variety of other bits.

Chasis are being sourced from an acquaintance at Hexateq in Belgium; this was an early set before they got into officially supporting this Hypex module set:













I've been wanting to get back to this for a while, I've had the other "pieces to the puzzle" for over a year, but as we often say around Hacienda de Juan, "Slow work takes time."

In the past, these have taken as much as 6-8 weeks after order for delivery; I'm hoping demand will have normalized a bit and these might be available a bit more quickly, even if I don't have much time for 6 weeks or so to spend on something like this. We'll have to see how that turns out.

One of my colleagues we hired a couple of years back (a very nice/smart Danish guy) used to design Class D amps for another company; I know his old boss from 20 years ago. he's a bit incredulous at the performance specs for the nCore 400 modules, but then he used to do fixed clock designs with high performance conventional modulators, not a 4th order self oscillating Class D with the output filter inside the feedback loop- and the feedback loop being a fundamental part of the comparator.

I'll post more background data on the nCore 400 and info about the actual build as I go along. I don't have any other working Class D amps at home for comparison, and let's face it, I'm not interested in how good a Classs D amp it is, I'm interested in how good an amplifier it is, period.

[wkhanna]

.......as we often say around Hacienda de Juan, "Slow work takes time."

LOL!

Maestro, you truly are the quintessential facilitator.
Just when I thought I had my game-end amp you tempt us yet again!
Time to raise my contributions in my clandestine (from The Wife) X-mas club account.

[JonMarsh]

Modules shipped already!

Good news- got email confirmation this AM of shipping from the Hypex Web shop, probably be here late this week or early next wee- UPS Express saver.

Now, these modules have been out a couple of years, demand is moderated I suppose, as the early adopters have already adopted! For those familiar with the nCore 400 story, you can stop reading and move on to another thread; for others I'll be filling in some highlights and some of the background theory in later posts.

I've developed Class D amps of both the self oscillating structure and the more conventional triangle ramped modulator structure, and it's Class D amps that got me into SMPS (switched mode power supplies), which is fundamentally what I work in, though specialized from the semiconductor side, both power discretes, modules, and controllers. So I am familiar with the challenges and base technologies, and therefore have a lot of respect for what Bruno Petsys, Hypex's chief designer, has accomplished.

For a good introduction, I recommend this AES presentation given in 2008, available on the Hypex web site in PDF:

http://www.hypex.nl/docs/papers/AES124BP.pdf

Bruno is a proponent of the self oscillating Class D, which is what I first experimented with in the late 70's, before moving on to more conventional approaches with triangle generators and ultra high speed comparators, culminating in an AES presentation in 1990 and an invited paper in the AES journal in 1991. I could probably get a drop box link setup if anyone is curious.. This was done via my current day job, because we were developing some ultra high speed (for that day and age) 250V MOSFETs with platinum doping to reduce the body diode Qrr by a factor of 10. Plans changed, that FAB was shut down, and the memory FAB we took over in Villach didn't have a platinum doping process.... (ironically, 20 years later, we do, and are making parts with that technology at 600V+ and now at 200V also). (concept was good, just a bit ahead of it's time...)

So, the reason I used "Digital or Analog?" in the title, is that really, this is an analog amplifier, a self oscillating design which relies on high speed analog circuitry to work, including an all discrete signal path, so one might justifiably say this is not a Digital Amp- certainly not like some of the products out now, considered more innovative, which truly are power DACs. Even our own Forte Class D IC falls in that category.

There is a lot of discussion about the sound, or lack of it's own sound, in this amplifier; whether it's synergistic with a specific system configuration compared with another amplifier of similar or different design is up to the end user to determine. What does seem very clear is that it will pass an audio signal with a high degree of fidelity.


For reference, here are some distortion plots:

First, the more conventional swept level at several frequencies- note carefully the Y axis values, as they go all the way down to truly minuscule values, and the downward slope basically represents the noise performance of a 2K resistor times an ideal forward gain, up to a power level of 20watts. So, yes, this is a pretty ideal "First Watt" type of design, but should be called the "First 20".



A real acid test is high level 18 kHz + 20 kHz, just below the clipping level- you don't want to see how most class AB solid state amps do on this, much less a high power tube design:




Note that all the distortion spectra spikes are at least -100 dB. Yes, this is SOTA.


Now, just for giggles, and because I'm really not a very nice guy when I encounter so-so engineering, here is the distortion spectra for a 500W/channel at 8 ohm Class D amp reviewed recently on Stereophile, which comes at a rather high price; this is for 4 ohm where it measured best:




Please note again the scale on the left and the difference in the Y Axis values; the distortion minima at 30 watts is a bit over 0.01%, and the 1W distortion is about 0.05%. Not terrible, but... for the nCore 400, at 30 watts, the distortion minima is about 0.0004%, and at 1 watt, also where noise dominates, it's a bit over 0.001%. Mmmm. Which would you want in your system, all other things being equal? Except they aren't.


Let's take a look at that 18 kHz + 20 kHz thingie....




My, my... not so nice, huh? Some pragmatists may undoubtedly argue that it's good enough, below the threshold of audibility, but in my experience, this high a level of IM is not a good thing. And I don't want it running through my diamond tweeters! :W

[Hdale85]

So are you saying there is an issue with the Ncore 400's? Or they are good? lol

[JonMarsh]

So are you saying there is an issue with the Ncore 400's? Or they are good? lol

My expectations are that combined with a good power supply, the nCore 400's should be pretty dang good for covering the 200-400 watt area- in fact, my challenge might be, show me something better!
About the early part of 2012 I was looking at my Aragons, thinking about doing a partial or complete analog gain stage mod, but then after the nCore 400's came out, I just figured that would be a waste of time...

[benthe8track]

How do you think one of these will work with the Wavecor Ardents? Any thoughts on running 2 NC400s with this guy: http://www.hypex.nl/product/2012-11-.../smps1200.html

[JonMarsh]

How do you think one of these will work with the Wavecor Ardents? Any thoughts on running 2 NC400s with this guy: http://www.hypex.nl/product/2012-11-.../smps1200.html

That version of the SMPS1200 is optimized/setup for the older UCD modules (yes, I have some of them, was playing with those a few years ago, but never finished a home use "product".) It's not setup for the specifics of the 400.

The SMPS600 has all the cables, interconnection, and specific regulators for the internal gate drive circuits of the 400, and many folks do power two 400's off of one SMPS600. Since I'm packaging my build as mono blocks, to allow really short speaker leads (shorter is better and cheaper, you don't want to know what a long run of Cardas Clear will set you back- I've already spent enough on Cardas Golden reference! Not interested in making George any richer! :W )

Even in one chassis, I'd go with an SMPS600 for each channel (dual mono) and the SMPS600 includes cable sets and mounting kit. It's pretty dang plug and play...

Note, another trick I'm doing I was planning on describing later: Input transformer coupling/isolation

The nCore 400 is a fully balanced active input, but the CMRR and isolation can be improved using a wide band Jensen transformer; this will also cut RFI at the inputs, which some other users report makes things sound sweeter, and I prefer also- my plan is to use the JT-6610 which has a bit of a voltage step down (no issue with my DAC, which has oodles of output voltage; a JT-11 or similar would work OK for something more 1:1, but the 6110 turns ratio allows really optimizing the input impedance seen by the amplifier (2 kOhm) while presenting a moderate input load resistance for the DAC to drive.

[Hdale85]

I've actually been looking at SMPS builds, but for car audio applications lol. Been contemplating building something for my car.

I actually found this nice guide, and schematics/PCB designs but it's a very lengthy read. I'm not sure if this is a good setup or not?

http://www.bcae1.com/switchingpowersupplydesign/switchingpowersupplytut01.htm

[JonMarsh]

That's pretty good- it is focused just on car SMPS but if that's what you're doing, then it's fine. I designed and built something like this back in 1984... it ended up helping me seal the deal to landing my current job, as I was using MOSFETs from the company I interviewed with and have worked for since. :T

[Hdale85]

Awesome! I'm just looking for something pretty clean that could drive 41hz kits or maybe some UCD's or something.

[JonMarsh]

Surprise, surprise! Modules arrived at GF's late yesterday afternoon! That was quick! There was an additional $75 charge for duty. Sigh... well, I figure the complete build will still cost less than the discounted price I got on my Cambridge Audio 850W. GF's all for the very low idle operating power compared to all my class A/B amps that tend to pull between 180W (Cambridge audio) and 250W (two Aragon Palladiums) in idle power. (she's proud of her low utility bills and PG&E rating as an exceptionally Eco electricity user for a single family home in northern CA.)

Well, these will be next in the project queue after the Wavecor Ardent crossover development and build.

[JonMarsh]

Parts is part...

I unpacked the modules yesterday evening after dinner with my GF- very nice build quality, of course they're done by a 3rd party ISO qualified contractor. The interesting question is how many hours of work to get these put together and ready to listen to? I'll be going for accuracy over speed, of course.

I'll be doing the Wavecor Ardent measurements and crossover design first, though, so I may not get back to these until the start of March. Sad... :cry:

I've got to decide too, if I need to tweak or change out the speaker connectors, or whether I can plug banana jacks direct in to the connectors. If so, we're probably OK for now.

I also got word from the distributor (Markertek) that the JT-6110 transformers should ship around Feb 13, so they'll be on hand before the end of the month... :T

[Finleyville]

I am looking forward to this build. If I didn't already decide on an amplifier for my Finalists then these nCore units would definitely be on the short list.

[JonMarsh]

For reference, here's my colleague's system in Munich, who also uses TotalDAC, but with units configured as mono blocks, and with JL1 Signature mono blocks for power. We're already discussing bringing my nCore build to Munich the next time I'm there...

[wkhanna]

I remember a little while back you said your colleague was getting these Eggleston Savoy's.......

[benthe8track]

[ATTACH=CONFIG]22944[/ATTACH]

For reference, here's my colleague's system in Munich, who also uses TotalDAC, but with units configured as mono blocks, and with JL1 Signature mono blocks for power. We're already discussing bringing my nCore build to Munich the next time I'm there...

That's unreal, what does that sound like?

I'm in for a set of these nCores, trying to track down a case half as pretty as those Hexateq cases.

[JonMarsh]

Well, this is a relatively new set of speakers for him- he's been fine tuning the electronics with a more modest set for several years, up until last November- he's my partner in crime for DAC hunting and evaluations with other digital components including re-clockers, and was an intermediary for shipping for my TotalDAC-D1.

That he titled this picture "Audio Nirvana" probably tells the tale of how he feels about the current setup- there's some more voodoo tweaks he's applied recently, and he's still updating some cables. He has good ears for not being a musician, and his wife, a doctor, is a fairly critical listener and is to some extent the final check for approving upgrades. So, from my own experience listening to his system at a variety of stages, the various voodoo bits he's adopted DO work, as regards the listening experience. I'm just not as well equipped financially to try out some of them myself! (he's on the managing board of our company at this point- but we've known each other for decades, since he headed up the Asian operations (from India originally) .


I looked at a LOT of cases before selecting those, and that was something of a fluke thing, as one of the guys there offered only a few of these for sale; I knew him from sending him plans for the M8ta years ago.

[JonMarsh]

The Jensen 6110 K transformers for extra input isolation which I special ordered from Markertek came in today, but didn't get a lot of loving- they were upstafpged by the new Les Paul Recording model. But the went into the parts bin for the build, and I'll get back to them once the Wavecor Ardents are sorted out.

[JonMarsh]

For those curious about the JT-6110K transformer (one of the finest line transformers money can buy!) here's the low down:



The bandwidth, phase performance, distortion, and CMRR are just stunning... and it enables very good noise performance for amplifiers with a low noise front end that reach their best S/N with driving sources in the range of 2K or less.

[wkhanna]

Impressive........

But i am sure the Les Paul is more fun to hold in your hands.

[JonMarsh]

Impressive........

But i am sure the Les Paul is more fun to hold in your hands.

well, yeah, that's a lead pipe cinch! Did a bit of that last night before reluctantly turning in to bed while GF watched more figure skating on Olympics- she wanted to be a figure skater when she was young, but was told she was too tall, especially for dance with a partner...

[bigjohn]

[QUOTE=I'm in for a set of these nCores, trying to track down a case half as pretty as those Hexateq cases.[/QUOTE]

I've been looking for nCore cases and ran across these:

http://www.audiocircle.com/index.php?PHPSESSID=v4bfcno3585dp2t6gm0eqa7oq7&topic=122198.0

[benthe8track]

I've been looking for nCore cases and ran across these:
http://www.audiocircle.com/index.php...topic=122198.0

They look nice but cost almost as much as the guts. I think something with a reasonably sturdy case with a removable front panel would fit the bill. That way I could waterjet something beefy/fancy looking for the front but don't have to do all the little design details. Also I haven't used a brake since Jr. High.

[JonMarsh]

Milled Chassis like Ayre MX-R

Yeah, I'm a fan of this kind of construction if you can afford it...




To the best of my knowledge, this type of construction milled from a single block of aluminum was pioneered by my friends at Ayre Acoustics in 2006, with the development of the MX-R amplifier- they've used it in several other top of the line products since, but as you can see, its a fairly pricey technique, though producing lovely results.

OTOH, I am with Ben, it's hard to justify spending nearly as much for the casework as for the guts!

Great shielding and thermals, but would be difficult to find room for the input isolation transformer I'm using. Still, I wouldn't blame anyone with some extra loose change in their pocket doing a "standard" nCore 400 build going this way...

[5th element]

It seems like you're paying a fortune for what is actually very little. They do look nice, but I am sure they could give you that for far less if they did things differently. I've got one of these



That has similar surface finish, with thick anodised aluminium panelling around the front and it costs a tiny amount compared to that. I am sure if cooler master used similar construction techniques as used in that case they could make something functionally identical with similar visuals for much less.

[benthe8track]

The high material cost, long machine cycle time and low volume are why they cost so much. I have something in my head that that would be similar in terms of 'beefyness' but waterjet cut, not anodized and maybe something like these for the corners:

http://www.carbonfibertubeshop.com/medium%20tubing.html

I'll have to find some time to sit down and draw it up.

[JonMarsh]

Semi DIY regulators and gainbuffer

I'm expecting that I "may" want to tweak the input gain, when using the 4:1 input transformers, so I've ordered some FAB4312 Non inverting amplifier modules with LME49710 opamps (very low noise and high performance) which I can tweak to any needed gain, and



And some Tenthall shunt regulators (+/-15V) to go with them.



Yeah, it would be much cooler to spend some time and design my own, but this is what happens when DIY stops being a relaxing little hobby and becomes something you try to squeeze maximum productivity and results in with a minimal amount of available time!

The SMPS600 has low power auxiliary PS taps for about +/- 18-21V available; this way the buffer will have a dedicated very low noise regulator (I'm a shunt regulator fan, due to superior bandwidth and response; plus, IMO, they sound better!)

This should be easy to dummy up on the bench and test...

net circuit for the buffer will look a lot like this:




with the output voltage capability of the TotalDAC-D1, this full buffer gain stage may not be needed... but I think at least 6 dB will be.

[JonMarsh]

After some online R&D I've determined that it should be possible to adjust the gain of the module upwards by changing one resistor; good design on Bruno's part. This will reduce the negative feedback slightly, but not enough to be a performance issue I think, and will make things much simpler to deal with. I can bump the forward gain up to 31 dB by swapping out R141 from 1200 Ohms to 680 ohms.

Let's try that first...

[5th element]

There's a laser cutting place in the UK called lasermaster that has very competitive prices and will cut several different types of metal/grades/thicknesses with very good accuracy. They also do metal folding too, so they could easily come up with the external shape of those expensive cases with some folded steel, you could then laser cut some internal shapes to screw it to and compartmentalise the insides + a laser cut top and bottom and you'd be done. They could presumably laser cut the steel before folding, so you'd have cut outs for all the connectors.

I recently had them cut me a 50x50cm shape out of 3mm thick aluminium with all sorts of complicated shapes cut internally that came to around £25. You simply draw up the shape to cut in a CAD program, save it in the correct format, send it to them and that's basically it.

[benthe8track]

Hey Jon, how hard is it to ad a VU meter like this?

https://www.youtube.com/watch?v=xr3WT9uZMgs

I started sketching ideas for enclosures and I think it ads a nice (if superficial) touch.

[Audio_ElF]

Yeah, I'm a fan of this kind of construction if you can afford it...

[snip]

To the best of my knowledge, this type of construction milled from a single block of aluminum was pioneered by my friends at Ayre Acoustics in 2006, with the development of the MX-R amplifier- they've used it in several other top of the line products since, but as you can see, its a fairly pricey technique, though producing lovely results.

Okay so I'm Hope I'm not just being pedantic .. but for information the Chord DAC64 predates the Ayre MX-R by nearly half a decade and uses a milled aluminium construction with the Mezzo power amp coming in 2002.

Eloise

[JonMarsh]

Okay so I'm Hope I'm not just being pedantic .. but for information the Chord DAC64 predates the Ayre MX-R by nearly half a decade and uses a milled aluminium construction with the Mezzo power amp coming in 2002.

Eloise

Hey, there's a place in the world for pedantic posts, as long as they help banish ignorance! I don't recall seeing Chord gear much over on this side of the pond back then, and I don't recall seeing them at CES in that timeframe- glad they're getting more distribution and recognition these days.


I do recall them having some growing pains back in that time frame- witness the disparity in performance measured by Stereohpile on two samples of the DAC64. There were also some peculiarities with measurements with the RAM buffer switched in - it appeared to be truncating the lowest couple of bits and there were some spurious tones in the spectral plot. Audible? Who knows... OTOH, the first sample they received had some major issues with jitter and distortion. Hopefully these kinds of problems have been ironed out in production quality control, because the average user doesn't have an Audio Precision to bench his new DAC on. In fact, the average dealer doesn't, either...

[DDF]

Rekindling an old thread to explore an earlier post from Jon: "That version of the SMPS1200 is optimized/setup for the older UCD modules (yes, I have some of them, was playing with those a few years ago, but never finished a home use "product".) It's not setup for the specifics of the 400. "

The SMP1200400 has 2 to 3 times the wattage of the SMPS600 but costs 30Eu less. Is it truly something for nothing or is the SMPS600 better matched (i.e. sound better within its limitations) to the NC400 by design? The SMPS600 nom Vout is 65V vs 63V for SMPS1200400 (both unregulated) but other than that I couldn't find any other juicy tidbits on why the SMPS600 warrants more than double the price/watt.

Any inside intel on this would be greatly appreciated!

Dave

[JonMarsh]

Those are very good questions- sorry I've been so busy this year that I didn't even get back to this thread until now... I've both on hand, the main issue for using the A400 is the necessity to modify the cable sets to get them to work- but there is a guide for that, I'll post that soon (just leaving for work now). There are some tests I want to do for both supplies, there's going to be more tests and evaluations starting probably around late December or next January- partly because of day job related stuff.

[TEK]

Rekindling an old thread to explore an earlier post from Jon: "That version of the SMPS1200 is optimized/setup for the older UCD modules (yes, I have some of them, was playing with those a few years ago, but never finished a home use "product".) It's not setup for the specifics of the 400. "

The SMP1200400 has 2 to 3 times the wattage of the SMPS600 but costs 30Eu less. Is it truly something for nothing or is the SMPS600 better matched (i.e. sound better within its limitations) to the NC400 by design? The SMPS600 nom Vout is 65V vs 63V for SMPS1200400 (both unregulated) but other than that I couldn't find any other juicy tidbits on why the SMPS600 warrants more than double the price/watt.

Any inside intel on this would be greatly appreciated!

Dave

I think benthe8track did a build powering two NC400 with one SMPS1200A400, if I recall correctly.

Jup - here it is: http://www.htguide.com/forum/showthr...ex-NC400-Build

[DDF]

Forgot this post as well, busy times. Hypex sent me the pinout to connect this together, must be a pretty common question. It's attached. I've been sitting on all the parts for this build since March, hopefully this break will free up some cycles to finally put this together. It required buying "Cable set SMPS1200" https://www.hypexshop.com/DetailServlet?detailID=3900.

With that, all the needed connectors are available given what comes with the nc400 modules. Depending on placement in chassis and layout, it may require some additional wire to make the harness but it all looks pretty straight forward. I'm using this case

http://www.ebay.ca/itm/JC2210-Full-Aluminum-Power-amplifier-Enclosure-DAC-case-preamp-case-PSU-case-/121138479133

to this module placement

http://www.audiocircle.com/index.php?topic=106187.msg1202762#msg1202762

The quality of the chassis is very good, with the faceplate very thick and clean.

I really liked the dynamics, lack of compression and lack of colouration below 5 khz that I've heard from IRS amp builds so excited to try this in my system. Should be a nice compliment to the irdac bought this year, which I really really like.

[JonMarsh]

Good luck with your build - how does the chassis base plate look for conducting heat away from the base of the nCore 400 module?

I've got that same reference chart- comes in handy, eh? And I'm hoping to make some progress on my nCore 400 build over the holidays, too- it's a good time of the year for catching up on projects.

There's also some other stuff in progress with another forum member with access to OEM modules- that will be time intensive, but might be very interesting. Just got in a small lot of JT10-KB-DPC transformers to support that, for optimizing the CMRR and interaction between source preamp and power amp. This is a technique employed with considerable success in the AURALiC Merak amplifiers, which use modified UcD technology; it will be interesting to see how this works out in this case. I believe it will be possible to further optimize the S/N ratio and CMRR and minimize any chance of HF carrier coupling back to the preamp, but even these high grade transformers will introduce an increase in low frequency THD. Well, it will just take some listening time and time on the bench to characterize and hopefully optimize the trade-offs.

[DDF]

Thanks, good luck on your build as well.

The base plate for the chassis is 3mm thick Al, anodized (black). Pretty beefy, I think it'll do the job nicely. I was also happy with the Hypex cheat sheet; it would have otherwise been a lot of leg work walking through the various data sheets and come up with this. Time better spent soldering!

The Jensen specs beautifully, I hope it works for you. I assume you have enough of gain in the pre-amp? The 4:1 loss is ~ 12dB through the transformer.

I came into possession of a number of Hammond 560Gs. They're 1:1 but the impedance mismatch into the Hypex will kill CMRR at high frequencies. The Hammond also has some issues with very low frequency roll off so not "Fi" enough for this work.

I'm also restricted in the transformers I can use as I run run a passive pre. I've tried a number of well regarded film pots and always found the usual drawbacks: lack of dynamics, loss of bass articulation. But the Bourns 3540S-001-103 are little beauties. They're linear 10 turn wirewounds, dead flat out to 20k as long as impedance is managed, transparent, dynamic and detailed. I can't detect any colour in my system, however I tried a relative of these in a second system and they had grain. No idea why (inductance is very low), but interested to see if the synergy also works with the Hypex. By running dual mono with verniers they provide almost infinite adjustment and balance adjustment. Lack of log rule has no day-day restriction, majority of listening uses 90 degree rotation and the few times that are needed to crank it up is just a couple spins. My pre switches input grounds so along with the lack of gain and passive pot, is dead quiet by removing all the other nasty antennas from the pre input, other than what's playing at that moment. Channel crosstalk <-90

The high input impedance of the Hypex should ensure minimal loss through the pot, but I'll need to verify roll off with my cables. Current Bryston amp has 68k input impedance and is 0.1 dB down at 20kHz so I think it'll be OK (on paper!).

I did a bit more digging on the differences between SMPS600 and SMPS 1200. No cause for concern, but interesting so thought I'd share:
- Jan-Peter, co founder of Ncore wrote: "In our Ncore demo set we use the SMPS1200A700. Basically there is no need to have a special SMPS, but probably we'll develop one to have a nice compatible set..."
- customer support has been great and responded to me with 9these are quotes):
- SMPS1200 lacks a compatible Vdr output voltage for theNC400. It'll work fine without this voltage but dissipate another 5 W of heat.
- The SMPS600 is a bit more high end than the SMPS1200. The SMPS600 has separate diodes in the bridge rectifier and has automatic mains voltage switching for example. It should sound a bit better than the SMSP1200. [I'm taking that with a grain of salt]
- If the wiring and higher dissipation is not an issue for you than it is fine to use the SMPS1200 or even the SMPS400

[JonMarsh]

Well, I have some of the SMPS1200A700 to test for compatibility reasons with another project, but the actual build I'm doing will be using an SMPS600 for each unit. I wanted the VDR supply separate from in the nCore; there it's a bootstrap configuration to get the power and that could result in a bit more EMI besides the power loss.

The feedback from customer support is interesting- thanks for sharing.

The rest, we'll just have to see. It will be some time in January or February before the financials will completely come together for the analyzer purchase, but I need something better than the 0.001% resolution I currently have.

[JonMarsh]

One other point worth making - the 4:1 step down of the transformers is a desired feature; (I like the 6110 transformer but wanted the PCB mount packaging of the JT10-KB-DPC) - though it attenuated the signal by the turns ratio, it provides an impedance transformation equal to the square of the turns ratio, and with the right front end provides a more optimum source impedance for low noise.

As to the gain structure, after living with the Benchmark AHB2 for a while, I'm in agreement with them that "normal" power amplifiers have too much gain to be optimized for SN and "high res" dynamic range- my Cambridge and AURALiC preamps have very low THD+N, and enough output voltage with the DAC source to easily drive the additional input voltage- this is working out fine with the AHB2's set for reduced gain. The transformer also gives me the option of using a different type of front end than the normal Hypex instrumentation amp; in this case, a single full differential input and output gain stage is what I'll be trying- but for that, the impedance matching on each leg is fairly critical, and only a transformer works really well as a source driving that.

We'll see how it all works out- many a slip twixt the cup and the lip and all that, but I think it's an interesting possibility for the OEM nCore modules.

[DDF]

The excessive gain of most amps is what allows the passive to work so well. With the pot at less than 10 percent of full scale, keeps source impedance low while still allowing 10k load.

I have a spreadsheet calculating pole of passive pot against the interconnect capacitance, and with 10k pots, no issue there. Also put xsim to a novel use by simulating response of a passive plus amp with interconnect impedance included before and after the pot. 100k pots dont work well, but 10k is a walk in the park.

Those tranies are a nice solution, hope they work well.

Btw further to amp gains being too high, I still keep an old modded Nad3020 amp around to measure speakers with, other amps I've tried have too much gain.

[DDF]

Can't be accused of rushing it, but the build is done, 2 NC400s + 1 SMPS1200A400 in a small chassis. The supply is heat sunk to the faceplate/bottom and the amp modules to the bottom, both lightly lapped and use of thermal thermal grease. Front gets a bit warm but nothing worse than a highly biased class A/B.

Sounds like most descriptions I've read of it: gobs of detail without being bright, refined, stronger bass (than the Bryston it replaced), great image separation, great tonal definition (walking bass lines, organic midrange), dead quiet even ear to tweeter with a 10kohm passive pre. Measures like the spec sheet, ~ 0.5 dB down and rolling at 20 kHz. Dc offset <12mA both channels.

Making the harness was a chore, but worth it. Cost effective and small. Front feet were mounted countersunk under the power supply (last pic).

[JonMarsh]

Nice build, good looking chassis and clean layout. My NC400 build is off to Steve Manning in pieces for him to play with, have some other things in the works from NCORE, but haven't gotten back to this due to business travel and other issues, plus a lot of speaker work going on right now. What you're saying about the sound is pretty typical- a lot of happy users. In general I think using the SMPS1200 get's you closer to the NAD M22 level of performance with the NC400's.

[wkhanna]

Wow!
that is one gorgeous build!
detailed to the max, it makes it look easy, which is the sign of tons hard work & planning!

[DDF]

Wow!
that is one gorgeous build!
detailed to the max, it makes it look easy, which is the sign of tons hard work & planning!

Thanks! It's a tight space so the two most challenging aspects aspects were trimming the cables to exactly the right lengths to avoid proximity to each other, and drilling the bottom plate. Microsoft Office isn't the best "CAD" tool for making drill-hole templates!