What is the NAD C390DD?
Here we have the C390DD (Direct Digital) amplifier from NAD. This is an interesting product for several reasons.
Firstly it is not an integrated amplifier in the traditional sense; it is not Class A, Class A/B or Class D – it is digital. It performs digital to analogue conversion (DAC) but has volume control and drives your speakers. You might think of it as a “power DAC”. Everything is digital. NAD say that this eliminates distortion, noise and phase shift – giving you a purer sound as a result. They also claim that this is one of the most accurate DACs available.
Secondly the amplifier has a modular design. NAD call this design MDC (Modular Design Construction). There are a number of MDC modules available that you can install into slots inside the amplifier. Think of it as being like adding a graphics card or sound card to a PC. This allows people like us to customise the amplifier to include things we need. The same concept is also in use in NAD’s Masters Series – so we are talking high tech here.
Thirdly, as the whole thing is digital – it is also programmable. You can apply EQ tweaks within the settings that provide rudimentary room correction (called Room EQ). You can rename inputs and change their gain levels. You can use the electronic crossover and send separate signals to the speaker and subwoofer.
Very impressive so far!
Features and specifications
The base model has digital audio inputs in the form of 3x Coax RCA, 2x Optical Toslink and 1x AES/EBU. There is a single Optical Toslink out (should you need it) and 2 pairs of speaker terminals (this can be used for bi-amping).
Also included are two USB inputs – one Type A for connecting an iPod and one Type B for connecting to a computer.
The C390DD outputs 150W into 8 ohms. Like all NAD amps (I think), this one includes Soft Clipping technology which is designed to prevent damage to speakers when the amplifier is driven too hard. Included is a remote control.
This all seems to good to be true! Lots of boxes ticked so far…
Modular Design Construction (MDC)
The MDC concept gives the ability to customise the functionality of this amplifier. NAD will sell you little modules which slot into the C390DD and expand it’s capabilities. Each module is like a little circuit board that fits into the amp.
There are 3 MDC modules available: DD BluOS, DD HDM-1 HDMI and DD AP-1 Analogue Phono. The BluOS module allows you to add Bluesound into the amplifier; think of Bluesound as being a bit like Sonos (but better). The HDM-1 HDMI module provides 3 HDMI inputs and 1 HDMI output meaning that the C390DD can sit in the centre of a high quality 2 channel TV / sound system. Finally there is the AP-1 Phono module which provides 1x balanced audio input (XLR), 1x unbalanced audio input (RCA) and 1x phono input for a turntable.
When I ordered the C390DD I also ordered the BluOS and AP-1 modules. The C390DD was going to be the centre of my music universe and I was genuinely excited about the possibilities. This is where things start to go wrong.
What NAD don’t tell you is that there are two sizes of MDC module, look on their website – it isn’t mentioned anywhere. The sizes are not named so we will call them small and large. The C390DD has 2 small and 1 large MDC slot (the USB ports occupy 1 of the small slots). Both the BluOS and AP-1 modules are large – this means you cannot use both BluOS and AP-1. I could live with that if NAD actually made it clear, but they don’t! After trying for a good hour to cram them both in, I had to give up.
I had to send back the BluOS module because I need the phono / vinyl input. So the MDC concept is not that flexible after all.
What a shame.
(Incidentally the HDMI module is small so you can combine that with either BluOS or AP-1.)
I have always been interested in room correction; it is a big, complicated topic that is out of scope of this article. Audio geeks like myself know full well of the effects a room can have on the hi-fi system playing music. You can end up with too much bass, not enough bass, too much treble (bright) or poor sound staging all due to the room. Most of us have to compromise in our listening rooms: we have partners / children / housemates and must accommodate furniture, TVs, book cases, etc.
The C390DD comes with a feature called Room EQ. This allows you to cut or boost specific frequencies in order to try and correct any problems you may have from the room. To make use of it you have to get the NAD to play a series of test tones (beeps); these are downloaded from the NAD website, placed onto a USB stick and inserted into the C390DD.
You then use a sound pressure level meter (or an equivalent app on your smartphone) to record what happens when you play each tone. The results will show that some tones are too loud and some are too quiet. What you are aiming for is to get an even response on each tone. The idea is that you reposition your speakers and/or tweak the Room EQ settings to do this.
Its a nice feature but I found to be hit and miss. It is nowhere near as sophisticated as the room correction systems you get with AV receivers or something like the Dspeaker Antimode.
Listening to the C390DD
Things go further downhill at this point. I have listened to other direct digital amplifiers before (e.g. NuForce DDA-100) and I find it hard to get on with them.
First the good stuff: there is plenty of power here. The NAD outputs a really good bass sound, very deep, clean and precise. The bass notes start and stop with ease. There really is no distortion or noise. You can turn this thing up to full volume (with nothing playing), put your ears to the speaker and you can’t hear anything! Most “normal” amplifiers would carry a slight hiss or buzzing sound.
However I just can’t get excited about this sound. It is so boring! The C390DD pulls off an amazing trick in managing to suck the enjoyment out of whatever I play through it. Yes it can go loud, yes it is clear and yes the sound is well balanced but . . . it just isn’t fun.
The sound stage is quite flat – there is no 3D sound-staging effect here. The music sounds like it comes from behind the speakers. I found myself skipping through tracks to different music genres in an attempt to find something it was good at. I failed.
It is such a shame that I don’t like the sound that the NAD C390DD makes. I love the idea of the MDC system. I love the idea that I can tweak the amplifier. I love that it includes Room EQ (even though its very basic). However I just can’t make myself like the noise that it makes – which at the end of the day is the most important thing. I want my music to entertain and excite me, not send me to sleep. This product promises so much but delivers so little. I really wanted to like the C390DD but I just don’t. Sorry NAD.