Graham Slee Voyager headphone amp in Review – plastic surgery done right

As HiFi headphone listening evolves, so does its component base. Chic design has influenced many market heavyweights – even boutique audio companies have opted to create sexy. But whereas amps like the ALO Rx is a masterpiece of steam and industry, the Graham Slee Voyager is plastic and comparatively bulky. Thankfully, looks are deceiving. This amp really takes off, surpassing all of my expectations.

Update: Feel free to discuss about the Graham Slee Voyager in our forums

Dimensions: L. 12.5 W. 6.7 H. 2.8 (cm)
Weight: 180 grams approx. (700 grams with plug top PSU)
Battery life: 50 hours continuous play, 2-3 weeks average usage
Output: 12mW rms into 32 Ohms, 10mW rms into 600 Ohms
Frequency Response: Flat: 13Hz to 34.5 kHz (-1dB), 5.5Hz to 69 kHz (-3dB)
Contour: +9dB at 45Hz and 20 kHz, Turnover +3dB at 260Hz and 2.85 kHz
Channel Balance: 0.5dB*
Hum & Noise: -94dB CCIR Q-pk 20Hz-20kHz, better than -100dB “A” curve weighted
Stereo Crosstalk: -52dB
Distortion (THD+Noise): at 80Hz: 0.03%, at 1 kHz: 0.03%, at 5.6 kHz: 0.05%, at 16 kHz: 0.13%
Power sources: [1] Battery, 9V (MN1604; 6LR61), [2] USB via “mini-B” 5VDC (with internal 9VDC analogue voltage conversion), [3] Mains adapter, 12-18V AC or DC unregulated (internal rectifier for AC use) (Polarity protection on all)

Build and Package
The Voyager sports a friendly retro style which ain’t erotic, but has some very real advantages. Firstly, unsightly scratches don’t show up as glaringly as on shiny metallic bodies and secondly, the large Hammond case fits in a lot of high-powered, high-quality components. From Alps to SWC, and Jalco to Analog Devices, Graham Slee has spared no expense with his portable headphone amp. In particular, the smooth ‘kachaa’ of a stereo miniplug sliding into either of the audio ports is pure pleasure.

Don’t worry though, this much pleasure comes well-protected. Four substantial Phillips’s bolts keep the case safely shut and are easy-breezy-beautiful to remove for access to the insides . And under the bonnet, things are laid out quite well for DIY efforts. Even outside, the centre-aligned input makes the Voyager perfect use with massive Line Out Docks and headphone jacks. Switching the Voyager between power sources and the two hardwired EQ settings: contour and flat, is relatively simple. Overall, it is a very well laid out amp, but if kept in a protective pouch, getting at the power and EQ switches is somewhat of a hassle.

You are probably asking yourself, ‘how big is this bugger?’. It’s not small. From the top down, it is a little smaller than the iDevice, but from the side, it dwarfs the iDevice at 2 or 3 times its thickness. Pocketable? If you are an army lad or lass with massive pockets, yes. But if not, this device is a tight fit when paired with your designer jeans. Fortunately, God invented jackets and nearly any jacket pocket will comfortably fit the voyager, your iDevice, and connecting cable. Oh yes, a purse should work well.

Features in Review
While a bit tubby, the Voyager is a delight to use. The battery is easily removed and lasts about 50 hours per charge, but the amp can also be fed from the mains, or powered via USB. In case you are wondering, battery power is this amp’s sweet spot with USB falling behind, especially when the Voyager drives lowΩ earphones. NOTE: the Voyager does NOT charge batteries.

Voyager Battery, USB, mains compared

Graham Slee has kept things simple; instead of adding circuitry (and ostensibly, noise) to automatically detect the power source, power source is user-selectable. When set to a source which isn’t in use, the amp effectively, is off. When on, a red light glows faintly from the front plate.

On the other side, the same sort of Alps switch enables a user-selectable EQ. Contour, quite like its sounds, bents both extremities upward so that bass and treble grab that extra bit of ‘hell yeah’. In case you are wondering, ‘hell yeah’ translates into around 9 decibels of fun in either frequency. As with all amps which use volume pots, there is a little channel imbalance at low volumes, but even with sensitive earphones, it isn’t problematic though IEM users will need to keep the volume pot low.

The Voyager also sports interchangeable op-amps for DIY sound tweaking. The short of it is that you can tailor sonic/power aspects of the Voyager by changing out op-amps.

Audio Performance
Graham Slee is a wonderman when it comes to designing audio circuits. The Voyager in many areas is hands-down the best sounding portable amp I have heard. Paired with the right mid-high impedance headphone, it sings with lustre and considering that it’s battery-powered, has capable low-reaching lungs. It is equally phenomenal with the formidable Beyerdynamic DT880 and the comparatively low Ω Ultrasone DJ1Pro. Even after shrinking down to iems, it provides power and resolution aplenty. But it isn’t capable of driving balanced armature headphones very well other than making them bloody loud. While the Voyager won’t implode or anything, music may suffer bass roll off, channel narrowing and otherwise, distortion spikes. The Voyager isn’t designed to amply support impedance swings which balanced armature earphones buffet about. On the other hand, highly sensitive low-Ω dynamic (moving coil) earphones are run more or less with aplomb, though they too, can suffer some distortion.

FitEar333 looks sad

But does better with cross talk

By aplomb, I mean fun and power. The Voyager may look like the amp next door, but it sounds like the hot rocker up the street. Bass is taught, mids are smooth, and highs nigh on perfect. Even with highly sensitive earphones, hiss is minimal and channel balance is overall, quite good. It is smooth and warm and free of grain and discord.

The Voyager supplies the best control over the oddly hard-to-drive Ultrasone DJ1Pro of any portable amp I have heard. Even plugged into an iPod, the DJ1Pro slams. But naked, it lacks deep waves of bass. Enter the Voyager: and hello bass! Bass stretches incredibly low with massive slam and space. The DJ1Pro is taken 90% of the way to the performance of a good home headphone amp for a stunning audio experience. On the opposite end, the high end is well controlled and uber-smooth. Both the ALO Rx and Voyager compare well for technical driving of the DJ1Pro, but the Voyager’s smooth, yet fun signature matches these DJ phones more perfectly.

Needless to say, volume can go over-the-top with the 64Ω Ultrasone. A twist of the volume pot to 12 o’clock is beyond what my ears can take. The 600Ω Beyerdynamic, a headphone described as ‘monster’ by some, is almost as well-driven as the Ultrasone. It is however, much quieter than the DJ1Pro. Even when set to about 2 or 3 o’clock, it is just a little beyond too loud. In other words, it won’t be too loud for the person who has gone to way too many concerts in her life. But that out of the way, tonal quality is simply phenomenal. Plugging the single ended DT880 into a powerful home amp reveals a deeper bottom end and better instrument separation, but the Voyager is so well-matched to the DT880 that it it may pack some home amps into their shipping boxes. Its warm, powerful output is excellent for bright, energetic headphones as it ‘tames’ them much like a valve-based amp would.

With the contour EQ circuit engaged, things get wild. 9 decibles are added to the bottom and the top for a truly dynamic sound. Bass light earphones such as the Audio Technica CK100 and the Final Audio FI-DC1601SS are perfectly mated to this circuit, becoming more engaging, more fun. The earphone which gains most from this circuit setting is the Final Audio 1601 SS; it simply sings and confirms my impression that this quirky earphone is unmatched. My wife tends to think that this combination is better than listening live! But overall, the Voyager is a better headphone amp than it is an earphone amp. Low Ω earphones can drive it to distort/roll off bass.

Just when you thought the Voyager was going to get off nearly clean, a wrench is thrown into the works: this amp suffers thump. When switching ON/OFF or engaging the EQ, there is a loud pop from the headphones which borders on painful. It isn’t as loud as the the FUBAR IV’s pop, but shames the ALO Rx. When using sensitive headphones and earphones, it is particularly annoying.

And, when fed from powerful sources, it loses amping power pretty quickly, defaulting instead to distorted renditions of bass and channel blurring. The same thing happens no matter the source with low Ω earphones.

Chart Disclaimer
This review’s RMAA measurements reflect the performance differences between the naked iPod touch 2G and the same iPod when paired with the Graham Slee Voyager and ALO Cryo line out dock. Since they are taken with my equipment, they should not directly be compared to other technical data. The data represents the ability of the amplification circuit to drive headphones. It is NOT the headphone response data.

Sound Conclusion
This amp surprises. As long as balanced armature earphones are taken out of the equation, the Voyager is simply one of the best if not the best portable amp in its class. It hits hard, but is warm and fun and has a few great features. Somewhat difficult to drive headphones such as the DJ1Pro roar, and ‘monsters’ like the DT880 are deep, smooth, and excellently layered. With high-end energy comes control and maturity. Space and separation aren’t quite as impressive as some competitors; the Voyager spins a detailed, relevant stage, but it isn’t dwarfing as it is with some amps. The smooth Voyager signature is addictive and moving. But if you’ve had it up to here (cue the metre-stick) with maturity, flip the CONTOUR switch for bat-out-of-hell bass and poppin’ treble. The Voyager transforms into wall-of-sound loud for those who want it, but otherwise is greedily mature for those looking for class.

Tame looks aside, the Voyager is a respectably powerful, yet mature beast. But when maturity fails, it delivers ear-slamming fun for bashful headphones, and for Audio Technica’s CK100 or Final Audio’s 1601 series, is a grace-filled resurrection of bass. It is easy to open and swap op-amps out, has good balance and is easy to use. Right, the Voyager is tubby, but it is otherwise godly. The best part is that it isn’t as expensive as many of its colleagues. With the proviso that it isn’t the best amp to drive balanced armature earphones, and prey to thump when engaging power or EQ, it is beautiful.

Headphone Amp Summary
Title: Graham Slee Voyager Developer: Graham Slee Projects
Connection: Stereo Mini (mini TRS)
Price: £160.43 (~250$) Application: Portable
  • Scratch-resistant
  • Lots of power
  • In-built EQ circuit is distortion-free, sounds great
  • Smooth, textured sound – amazing
  • Great battery life
  • 3 power sources
  • EQ, power engagement thump
  • Is not good for balanced armature earphones

Headphone amps and DACs help your headphones get the most out of their transducers. Take a look through our headphone section for suggestions of good upgrade/sidegrade options, and our headphone amplifier section for suggestions on how to wring out the best performance from your beloved phones.

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