Your laptop computer probably already has a headphone output — but does it offer low-latency 24-bit ASIO, GSIF, MME, Direct Sound and Core Audio drivers? Echo's Indigo does.
Echo Audio's small but perfectly formed Indigo is a Cardbus headphone output device for portable computers with a PCMCIA slot, which pretty much includes all but some sub-portables and Apple iBooks. The Indigo's feature set is sparse, with no line input, and no digital or MIDI I/O. Unlike more expensive and full-featured Cardbus interfaces such as Digigram's VXpocket, it does not employ flying leads or a breakout box — the Indigo's useful bits are contained within an unobtrusive grey plastic widget adjoined to the credit-card sized adaptor itself, giving access to two 1/8-inch stereo output sockets (one at either side) and a rotary volume control. This means that regardless of where your laptop's Cardbus slot is located, there is a headphone socket pointing towards you. A blue LED shows you the Indigo's ready to go.
You may be wondering what this £100 headphone socket can do that the standard one on your portable cannot. Well, it's capable of playing back 24-bit audio at 96kHz, and Echo claim that it will thus give you superior sound quality for your CDs and DVDs. While this may be true, the big selling point for musicians will be the inclusion of ASIO 2 and GSIF drivers for low-latency operation. On paper, the Indigo would seem perfect for composing on the go with self-contained music software.
Echo's web site suggests as a minimum requirement a 500MHz Pentium III, though this seems to refer more to the optionally bundled WinDVD software then the card itself, and I would venture that for those already content with the performance of their audio software any Pentium II or Apple G3 should suffice ('Lombard' Powerbooks excluded). You will, however, need to be running a relatively recent operating system — Windows ME or higher for PC users and OS X for those on a Mac. Installing the Indigo in Windows XP Professional was straightforward, though perhaps not quite as simple as for a USB device. The driver setup program presents the option of installing 'professional audio support' (yes please!) before prompting you to power down your computer and insert the card. On startup the new device was detected by Windows, which ran the familiar Add New Hardware wizard. After selecting Install Automatically and OK-ing that annoying 'Driver not electronically signed' warning, the blue LED sprang pleasingly into life.
A quick look at Windows' Device Manager revealed the Indigo to be listed as only one device, which was sharing IRQ 9 with the USB controller. Those of us who have wrestled with resource conflicts in the past will reflexively find this cause for concern, but in the event it was not in the least problematic. On installation the Indigo becomes the default output device, so it'll play all of Windows' annoying chimes, bells, and 'tada's. A discreet Indigo control panel is added to your Start menu, containing the buffer size settings for the GSIF drivers and the option to spoof an audio input — a necessity for programs such as Sonar that refuse to work without one. This is disabled by default, which had me scratching my head for some time wondering why the Indigo had disappeared from Sonar's audio preferences panel after installing a later driver revision.
Playing a familiar test song through my Sennheiser HD565 headphones made it clear, even to my less-than-golden ears, that the Indigo could boast significantly better quality than my Thinkpad's built-in Crystal Sound Fusion chip. The biggest factor in this comparatively increased fidelity was probably the headphone amplifier, which was capable of driving my studio headphones with far more 'oomph', yielding a much more controlled bass and a crisper mid-range. By far the most startling improvement, however, was the increased definition of the stereo image, which I'll venture has a lot to do with the relatively low jitter of the D-A converter. It made it possible to place instruments far more accurately in the sound stage, and revealed problems with songs I was mixing.
By default the Indigo's ASIO drivers are set with a buffer of 512 samples, which equates to a theoretical latency of around 12ms. Playing software instruments in Sonar and the demo of Cubase SX felt very snappy indeed, and I only noticed any hint of lag when playing staccato bursts of fast-attack drum sounds — nothing that would bother me in practice. I was also able to go about my business glitch-free and happy at the lower buffer setting of 256 samples (6ms), though on my somewhat antiquated Thinkpad this did slightly increase the processor usage. For those who like to impress their friends, a 128-sample (3ms) buffer is available, though it wasn't practicable on my system. WDM performance in Cakewalk's Sonar was particularly impressive: latencies of 2.9ms were usable, albeit with a performance hit. The optimum setting on my PC for a 16-track song with a couple of DX Instruments appeared to be around 10ms, though I've no doubt that those with more powerful systems will be able to significantly improve on this. To put these figures in perspective, my Thinkpad's Crystal Sound Fusion chip (with WDM drivers) could manage a 10ms latency only with a comparative CPU hit of about 25-30 percent, as measured by Sonar, and dropouts were very easily incurred.
Praise notwithstanding, my experience with the Indigo was not entirely free of troubles. One driver problem revealed itself upon waking my Thinkpad from Sleep mode, when the Indigo began replaying my 44.1kHz songs at 48kHz. Fortunately Echo's tech support was able to direct me very quickly to a driver revision that fixed this bug. I also noticed that the Indigo emitted stuttering, droning sounds when pausing clips played with Windows Media Player after having used an ASIO application. Thankfully, no such artifacts were apparent in any of the serious music creation programs I tested.
A less anomalous but more irritating problem is the Indigo's lack of ASIO drivers capable of sharing the stereo output with standard Windows interfaces. This means you can't run more than one audio application simultaneously if ASIO is used. It is possible to run two or more programs at the same time if they use standard Windows interfaces, such as Direct Sound or MME, but not, for example, Cubase and Wavelab using Steinberg's far more efficient ASIO protocol. It's extremely annoying to see the 'Audio hardware in use' message years after I thought it had been banished, and I hope Echo will fix this soon.
With the Indigo's high-quality headphone amp and low-latency ASIO drivers, musicians who prefer to compose or play live exclusively using soft synths and samplers might find that Echo's baby provides all they need. Using the Indigo's ASIO drivers in Propellerhead's Reason proved to be a wonderfully painless experience. With a UK MSRP of a penny under £100, the Indigo's closest rival in features is probably M Audio's Sonica — a USB device that also provides an optical digital output. Although the Sonica has greater surround sound capabilities, it currently lacks the Indigo's comprehensive driver support for professional audio applications, and for many the choice will depend on whether they have a free USB port on their laptop. Personally, I was most enamoured with the Indigo's unobtrusive Cardbus design, and the fact that it didn't add to the metres of cable I already have to lug around. Aside from my gripe regarding the current lack of true multi-client ASIO drivers, the Indigo is an excellent product at an attractive price, which could do wonders for the musician who yearns for a slimmed-down studio and the right to roam.