Congratulations on very fine amplifier Anthony, it exceeded my expectations. You should be very proud of this design.
The grip it has controlling a speaker is quite remarkable and smoothness is outstanding. 4 hours straight, no bleeding ears, fatigue or head ache.
This review can also be found on the following link at Stereo.net.au http://www.stereo.net.au/forums/showpost.php?p=154573&postcount=62
Over the last few years I have tried a fair portion of the more popular DIY power amplifier designs on offer. The ones I admit to are from Aspen (AKSA 55, 55N, 55N+, Lifeforce 55), AudioSector (LM3875, LM4780), Aussie Amps (NX150), ESP (P3A, P101), SKA (GB150). I’m not going to compare the NXV200 to any of these amplifiers as they are well documented elsewhere.
I accidentally came upon the NXV200 after talking to Anthony on another matter and the entry price for a fully built amplifier module was very attractive. I do not run at super high SPLs but I do require the ability to run low impedance speakers (some of my designs dip less than 4R), so the amplifier I built uses 42V rails giving 80W into 8R and 130W into 4R which is more than enough for my requirements. The power supply differs to Anthony’s and consists of 6 - 4700uF Nichicon (KG) Gold Tunes in a "C" type arrangement with other little tricks. This was fed via a Harbuch 300VA 30-0-30 transformer and a standard 35A 400V bridge rectifier. Several input caps were tried starting with a 22uF BlackGate NX on the PCB, a 2.2uF Mundorf M-Cap at the RCA and 3.3uF Mundorf M-Cap Supreme at the RCA. In the end the Mundorfs might have had a slight edge in the higher registers but the BlackGate NX seemed to have tighter control, so is going to be used in the final amp.
The test system used a Cambridge 840C and a modded Sony CDP-990 as sources, a DIY Burson Buffer based pre and a NAD 106 pre amp, speakers were my designs with one a pseudo 3-way (Scan Speak S2905-970000, Scan Speak 18W8531 (coated), Vifa M22WR09-08) and the other a 2-way (Vifa XG18WH00-08, Peerless 810921). In other words, very capable and resolving.
Assembly of the module is a snap and the instructions cover most things that an experienced builder needs. If you have any doubts, Anthony is only an email away and does provide great support.
At startup and shutdown, there are no pops, thumps, farts, driver movement so all is well behaved and you don’t have to cringe when you fire up or shutdown.
The first thing that stands out is the amount of control and smoothness on offer. I have never heard an amplifier that controls the woofer so well and when the note finishes it stops on a dime. There’s no overhang at all and that really contributes to the fine bass tonal quality. The drive, dynamic capabilities, timing and pace are right on the money and allows the rhythm of the music to flow. A good example is Bélla Fleck’s "Flight of the Cosmic Hippo" which has some of the most awkward low bass known to man. The NXV200 controlled it extremely well allowing the timbre and strange quality of the bass to come through unimpeded which is very impressive as not many amps are faithful to it.
This amplifier majors on smoothness and there is no bleeding ears factor here. I’m a large fan of the great late Eva Cassidy and since a lot of the recordings are raw, lesser amplifiers can shred your ears when she hits those higher notes, but not the NXV200. It remained composed, the voice flowed and the presentation was completely musical allowing a good insight into this great performer’s music and voice. I’ve heard so many commercial amplifiers out there that get this so wrong and in the end, the user hardly uses them.
This smoothness does have a small downside and all amplifier designs are compromises. The top end can be a little polite at times and some of the detail in the background does not completely have it’s own space. It’s still there but in the mix. This by the way is not a bad thing and will only upset the detail freaks out there but if you value musicality, then it’s not an issue and I found it mattered nought. If I want massive detail, I have other amps for that but they sometimes can become fatiguing, especially with a lot of the later CDs.... you takes your choice. The overall presentation is very refined indeed you can’t seem to do critical listening as it just draws you into the music with it’s presentation. There is no fatigue factor at all and the first listening session was 4 hours and I just grabbed disc after disc with the foot tapping and a grin.
It’s important to get the combination of components right and that’s the hardest thing to do in this game. The NXV200 will be used in my office with some nearfield monitors so it’s smoothness and control is very important. An edgy sound in this location is not desirable. I would suggest that the NXV200 be partnered with equipment that are neutral or on the bright side of neutral as that would provide the best balance. If you have a system that is edgy and making your ears bleed, then this could be the ticket to happier listening. I would not put it in a dull system and that would degrade the sonics on offer and kill the overall presentation.
This next comment is not meant to be degrading but is a compliment. It’s a bit like the NAD philosophy where you get a nice full bass, open mids, refined presentation, paint a nice image and don’t let the top end offend. Not a bad place to be and a fine design choice which places musical enjoyment foremost.
All in all, a fine amplifier indeed and congratulations go to Anthony.
Peter from RZaudio (aka rabbitz) . NSW, Australia