Audio-gd NFB-5.2 DAC/Amp

For a while now I’ve been using a Creative X-Fi USB soundcard as my quality DAC and amplifier and it’s done an amazing job, but as a USB-powered amp, it was never going to shine with any truly high quality headphones. And so it came to pass that I decided on my first step into the realm of dedicated headphone amplifiers – the Audio-gd NFB-5.2

I decided on the NFB-5.2 because it is a combination digital-to-analogue converter (DAC) and headphone amplifier. Reviews I read seemed good and it was available from the great crew at Addicted to Audio where I buy a bunch of my stuff (often with their wise advice).

Specifications

Signal to noise ratio:  119dB
Output power:  3500mW @ 25 ohm – 150mW @ 600 ohm
Output impedance:  2 ohm (headphone out)
Sampling support: 44.1kHz – 192kHz (16-bit or 24-bit)
Inputs:  Optical, Coaxial, USB

I’ll review the NFB-5.2 in 3 stages: first a quick overview, then the DAC, and then the amp.

Overview

The front panel of the Audio-gd NFB-5.2The NFB-5.2 is quite simple and that’s good. On the front of the unit is:

  • A power button (left)
  • Volume control (right)
  • 6mm stereo headphone socket with a securing system to keep the plug in place
  • Simple, 4 character, blue display
  • 4 control switches (under the display)

All of the buttons and the volume knob are brushed metal and the case of the unit is also all metal. It’s not super heavy, but seems very well built.

The 4 buttons under the display allow you to select different options.

Button 1: Filter

The “Filter” button lets you select from a number of filters used to remove unnecessary frequencies from the DAC output. It’s generally not something that you’ll notice in the sound and is used more to remove subtle digital artefacts and noise from the signal. I played around a bit and now leave my NFB-5.2 set to filter #6 which has creates an output that looks like this:

A graph showing the effect of filter #6

Filter #6 frequency response chart

As you can see, it only starts to affect the sound at around 20kHz and above – all frequencies which are beyond normal human hearing limits, but it should help to clean up the overall signal.

There’s a full listing of the possible filter options here.

Button 2: DAC/HP

This button has 4 options. Options 1 & 2 activate the headphone amplifier output either without (option 1) or with (option 2) the OP amp. Options 3 & 4 activate the RCA line outs on the back of the NFB-5.2 and allow you to use it as just a DAC with a separate dedicated amplifier. Once again the two options are for the OP amp being used or not used.

The OP Amp

The OP amp (OPA) is modular circuit that can colour the sound to suit individual tastes. Audio-gd supply the NFB-5.2 with their OPA-2134 model, but you can buy 3 different options as aftermarket (or custom) options. The 3 other OPAs offer neutral sound, warm sound, or dynamic sound. I hope to review the OPAs separately in the future.

In relation to the OPA-2134 that comes standard, my feeling is that it’s better left switched off. Engaging the OPA using setting 2 or 4 of the DAC/HP switch results in a flatter sound with less depth and a weaker sound stage. There’s really no improvement that I can discern.

Button 3: Gain

A very simple option here: “high” or “low”. The “high” option apparently adds a 12dB boost across the range (from the DAC, not the amp). When I’ve used high gain, the sound seems to become a bit edgy when compared to the equivalent volume on low gain. I’m sticking to the low gain option, but others might like the extra energy delivered by the high gain.

Button 4: Input

3 options here: USB, Optical or Coaxial. Very simple.

All work the same although I have read claims of slight sound variations between the 3 inputs. As I don’t have a source with all three outputs I can’t do a fair comparison.

NFB-5.2 DAC Stage

The DAC in the NFB-5.2 is really nice. I’ve run my Bang & Olufsen BeoLab 3 speakers using the line out of the NFB-5.2 and the sound is beautifully clean, well-layered with plenty of separation between instruments and creates a stunning sound stage through the BeoLab 3’s acoustic lenses.

As I’ve already explained, the filter system is a nice feature for those who are more technically inclined, but once it’s set you’ll probably not think about it ever again so essentially the NFB-5.2 DAC stage is a set-and-forget affair and it does a fine job.

The TE8802 Chip

The NFB-5.2 is an upgraded version of the NFB-5. The only difference (according to what I’ve read) is the inclusion of the TE8802 USB chip. The TE8802 allows for asynchronous transfer… yeah, I didn’t understand either!

What all this really means is that the NFB-5.2 should be less susceptible to minor issues with errors created by the USB chip in your computer slowing down or running inconsistently. In short, it’s a minor upgrade that’s nice to have, but likely won’t be a game changer.

Compatibility

The NFB-5.2 worked perfectly with my laptop running Windows 7 (64-bit) and MediaMonkey as my media player. The Audio-gd drivers, combined with the TE8802 chip allow the NFB-5.2 to work all the way up to 192kHz/24-bit. After doing some reading, I believe there’s no real benefit (and possibly some disadvantages) to using 192kHz output sampling so after testing that it worked, I reverted to 96kHz sound and it’s brilliant!

It’s worth noting that ASIO drivers seem to give the best sound and best compatibility with the NFB-5.2. I started out using WASAPI drivers, but they created some nasty cracks and pops from the computer (not the NFB-5.2’s error) and the sound seemed better when using ASIO.

NFB-5.2 Amp Stage

The amplifier in the NFB-5.2 is probably slightly weaker than the DAC. Where the DAC seems to be beautifully clean and crisp, the amp strikes me as just a touch soft around the edges. Perhaps it’s just a warm sound signature when I prefer a more analytical sound in general. There is also a hum that’s audible through my Shure SE535 LE in-ear monitors, but read on because that’s not necessarily a bad sign.

Power

The NFB-5.2 has plenty of grunt. I’ve just received my new Sennheiser HD650s (thanks Gavin!!) and the NFB-5.2 volume control only just clears 50% (on low gain) to drive the 300ohm HD650s. There are very few (if any) conventional headphones that the NFB-5.2 couldn’t drive. Obviously there will be much more expensive amps that will sound better, but it’s got the power.

Noise

This is a tricky one. With the 300ohm HD650s, the NFB-5.2 sounds pitch black – no noticeable noise. On more sensitive cans like the Audio Technica AD900s, there is some hiss when you turn the volume right up (>75%), but none at normal listening volumes. From this perspective, the NFB-5.2 is nice and clean.

What put me off slightly here is the noise I heard when I connected my Shure SE535 LEs. The Shures are hyper sensitive (119dB SPL/mW) and this showed up a background hum from the amplifier. The NFB-5.2 is listed with a 119dB signal to noise ratio so there’s a good chance the SE535 is picking up the end of the NFB-5.2’s quality control limits and that’s OK – it’s not meant for driving hyper-sensitive IEMs. The main reason for my concern was that the hum isn’t balanced – it is louder in the left channel. That might not mean anything, but I look forward to testing the SE535s on another NFB-5.2 next time I visit Addicted to Audio. Maybe the right channel on my unit is just slightly cleaner than Audio-gd’s quality control standards, but I’m keen to make sure there’s not an error somewhere in the circuitry of my amp.

NOTE: It’s important to note again here that an amp like the NFB-5.2 is not really designed to drive super sensitive, low impedance monitors like the SE535s so this isn’t a major flaw, but until I can test a few other similar amps, the unbalanced hum leaves a tiny doubt in my mind.

Control

The NFB-5.2 amp is really well controlled. My Ultrasone HFI-680s can be quite bassy and that can cause them to lose clarity and control if not well driven. The NFB-5.2 does a great job of tightening the bass and keeping it punchy and full.

I mentioned earlier that the NFB-5.2 amp seems slightly soft around the edges and while that is definitely the case, there is no doubt that it does an amazing job for the cost. It’s an incredibly good amp for the cost (especially when you get a great DAC built-in).

Overall Conclusion

Would I buy the NFB-5.2 again if I had my time over?

Absolutely!!

For less than US$400 plus shipping costs (about AU$480 here in Australia) you get a really nice DAC with a solid, powerful amp that will drive anything very well. The amp may tend towards being slightly warm, but it reveals detail well and definitely won’t create fatiguing edginess in the sound. Being able to bypass the amp in the future while maintaining the really nice DAC stage of the NFB-5.2 is a massive bonus!

The high gain mode seems to bring some unwanted distortion or edginess to the sound, but there’s so much power on tap that you don’t need to use it if you don’t want to.

Of course, there’s also the fact that you can buy different OP amps for around $40 each and modify the sound to your tastes. I look forward to trying these out and sharing some thoughts in a future blog post.

If you’re looking for a nice entry point into DACs and amps, the NFB-5.2 is an excellent option – well priced, clean, powerful and simple to use – I’d recommend it.

Massive Portable Player Shootout

I’ve been using an iPod Video 80Gb (5.5 generation) for years now and have loved it, but my music collection continues to grow and I’m a fan of lossless audio (ALAC and FLAC) so it’s no longer large enough to hold all my tunes. I’m now at a major crossroads when it comes to finding the right combination of quality, capacity, and ease-of-use. There are a few options I’ve considered and I’ve been lucky enough to try all of them so I’m sharing the results here. I’d like to extend a massive thanks to Wing and the team at Minidisc.com.au for providing the Cowon J3 demo unit and outstanding customer service in my purchase of the Cowon X7 unit.

What’s Being Compared:

  • Apple iPod 80Gb (5.5 Generation) – middle of image
  • Apple iPod 160Gb (late 2009)  – top right of image
  • Cowon X7 160Gb – top left of image
  • Cowon J3 – bottom left of image
  • Sony 460 Series Walkman 4Gb – bottom right of image

If you’ve spotted the odd one out here (yes, the Walkman) and you’re wondering why I’m comparing a little 4Gb player to three hard-disk behemoths and a large-scale SD-based player, it’s purely thrown into the mix as a reference point to see how the expensive players compare to a relatively cheap option.

I’m comparing the players on 4 key factors:

  1. Sound quality (including power output)
  2. Size
  3. Interface & Ease of Use
  4. Customisation & Flexibility

Sound Quality

It’s very hard to conduct a subjective test of sound quality on audio sources because the only real way (short of complicated and expensive setups) is to keep switching your headphones or line-out cable from source to source. Because each of the player’s has a slightly different volume scale, it’s also hard to match the volume exactly and that can influence our perception of quality, too. I’ve done everything I can to minimise the impact of volume, delay between sources and personal preference. All players were tested with no sound “enhancements” (i.e. no BBE effects on Cowon products and no EQ or Sound Check on iPods). All testing was done using 320 kbps MP3 tracks to avoid any potential difference between ALAC and FLAC files. I used my Audio Technica AD900s, Ultrasone HFI-680s and HiFi Man Re0s with each player for a thorough sample.

The order of performance here is a little tricky, but essentially it’s:

First Place: Cowon X7 & J3 – Clean, rich sound with a massive open sound stage and all of the details perfectly presented. My only criticism of the Cowons is that they actually are a little under powered from a volume perspective. They have no trouble getting great sound quality out of the higher impedance HFI-680s and Re0s, but they are at more than 95% volume in order to create an energetic, exciting listening experience.

In addition to their naturally awesome sound quality, the Cowons offer the range of BBE features to further enhance your listening pleasure and although I normally steer clear of “sound enhancements”, the BBE suite is exceptional. The EQ settings are widely adjustable and powerful, the BBE bass boost seems to do a great job of boosting the bass without all the added distortion of many systems and the compressed music enhancement (MP Enhance) is quite effective at bringing the brilliance of lossless music back to a compressed track. Finally, the winning feature for me on the Cowons is their stereo enhancement (equivalent to crossfeed in RockBox). This feature replicates in your headphones the effect of listening to speakers. It’s a simple process and doesn’t mess with the source signal and sound quality, but does result in a beautifully focussed stereo image.

The only key sound quality feature missing (which could also be considered ease-of-use) is ReplayGain. The Cowons don’t normalise the volume for you meaning that you may have to regularly adjust your volume from track-to-track and that’s an issue when you try using the volume controls, but more on that later…

Second Place: iPod Video 5.5G – Solid, clean sound with good depth and good detail. The iPod Video is a great no-frills player. I’ve used it with RockBox and also the regular interface. Either way, the natural sound is great and it seems to have more oomph than other players (volume at 85-90% for higher impedance headphones).

The EQ on the iPod is horrid and introduces all kinds of distortion, but I don’t feel it needs equalising if you have decent headphones. It also lacks a quality volume levelling feature in its original Apple guise (RockBox fixes this). The iPods do have the Sound Check feature, but I find it fairly useless and have heard many reports of degraded sound quality from its use.

Third Place: iPod Classic & Sony Walkman (tied) – These players don’t sound the same, but it’s hard to split them based on their differing shortcomings. The iPod Classic lacks depth in the bass and has a touch of harshness at the high end combined with a lack of very high end detail. It also suffers from the same lack of sound enhancements as explained for the Classic (above).

The Walkman actually has an enjoyable sound for a cheap device (<$100), but it can’t match the others in terms of detail and soundstage. That said, the sound enhancements offered are quite good and quite effective. It’s a perfect exercise player for me (i.e. when I want fun sounding music that I’m not listening to for quality).

Size

I’m not comparing the Walkman here because this is about capacity. Very simply, the J3 is the smallest, but not by much. The iPod Classic is next, followed by the iPod Video and the Cowon X7 is easily the largest and quite bulky. All but the X7 could comfortably fit in a pocket, but the X7 would require a bag of some sort to carry around. It fits nicely in the palm when you’re using it, but the X7 is definitely a bit bigger than the alternatives. That said, if you want to match the sound quality of the X7 you’ll need to add an external amp to the iPods meaning that they just got a bunch bigger and have extra cables sticking out… I’ll be doing a post about the pros/cons of external amplifiers soon.

Interface & Ease of Use

The iPods are the easy winners here – that’s just what Apple do – make things easy. There is no doubt that the Apple interface and synchronisation protocols work well. My only complaints are the lack of effective volume normalisation and the restriction to ALAC as the lossless format. Having recently converted my entire library to FLAC, I really don’t want to have to undo it now. RockBox on the iPod Video allows the use of FLAC, but the Classic can’t use RockBox so it’s slightly more limited.

Another bonus for the iPods is the massive range of accessories available. Being able to drop your pod into a dock and have instant, remote controlled music is a great plus and something that no other player can offer without significant fiddling and expense.

The Walkman comes second because it just works. There are limited bells and whistles and the synchronisation with MediaMonkey was easy and painless. It can’t play lossless formats, but with 4Gb capacity and just-above-average sound quality, 320kbps MP3s are fine. The menus are easy and obvious and the buttons are easy to use and well-placed. Perhaps the best thing about the Walkman though is the SenseMe feature which scans your library and sorts them into mood-based groups. The system isn’t quite perfect (it put a slow song into an upbeat category), but it’s a great, quick playlist solution.

I’m a big believer in working with industrial design rather than fighting against it. If it doesn’t work how I initially expect, I take the time to understand it and learn it, but the Cowons are a long way behind in the ease of use category because of some crazy design decisions. Both players have the volume controls on the side down the bottom of the players. When you’re holding the players you’re fingers are nowhere near the buttons so it’s awkward to adjust the sound (and you need to because there’s no volume levelling).

The menus in the Cowons are quite good and you can access all the important settings direct from the “now playing” screen so this is a plus for the Cowons, but it doesn’t make up for the killer…

You can’t auto-sync playlists to a Cowon player!! That’s right, the Cowon X7 will hold 160Gb of your music, but it won’t let you easily transfer the playlists from MediaMonkey (or Winamp or WMP, etc.) to the player. When you do ask the media player to transfer the playlists, they appear in the X7 (or J3), but when you click on the playlist it says “no file”. I’m sure there’s a fix, but from everything I’ve read it’s a manual fix not an automated one – very frustrating and possibly a deal breaker for me.

Customisation & Flexibility

There are a bunch of custom interfaces for the Cowons and this makes them more customisable than the others. Combine this with their ability to sync with any system and play any type of sound or video and you’ve got a very flexible and customisable player.

The iPod Video can run RockBox and that gives it plenty of flexibility. I rate it only a fraction behind the Cowons because RockBox can be a bit unstable.

The Walkman and iPod Classic tie for 3rd place for different reasons. The Walkman can’t play lossless audio, but it can sync with lots of different systems. The iPod can play lossless audio, but only ALAC so they’re pretty even. The iPod might win by a hair thanks to its ability to play lossless and sync with MediaMonkey.

Summary

What’s the player of choice then? For a collection up to 80Gb, I think I’d take the iPod Video, but over 80Gb it has to be the Cowon. The sound from the iPod Classic just doesn’t cut it for this type of premium player. If you have a huge library and need a large capacity player, there’s a good chance you also appreciate the quality of good music.

I’ll be adding a line out adapter and portable amp to my iPod Classic in the near future and will be sure to report back on the results. In the meantime, I actually think the best answer is to have the Classic for dropping into a dock, using in the car, etc. and having the Cowon X7 (or J3 if you want a small pocket-sized option with killer sound) for mobile portable listening direct to headphones.