i received my native instruments komplete audio 6 in the mail today. i wasted no time plugging it in. i have a few first impressions:
build quality
this thing is heavy. not unduly so — just two or three times heaver than the audiofire 2 it replaces. it’s solidly built, so i imagine it can take a fair amount of beating on-the-go. knobs are sturdy, stiff rather than loose, without much wiggle. the big top volume knob is a little looser, with more wiggle, but it’s also made out of metal, rather than the tough plastic of the front trim knobs. the input ports grip 1/4″ jacks pretty tightly, so there’s no worry that cables will fall out.
i haven’t tested the main outputs yet, but the headphone output works correctly, offering more volume than my ears can take, and it seems to be very quiet — i couldn’t hear any background hiss even when turning up the gain.
JACK support
i have mixed first impressions here. according to ALSA upstream, and one of my buddies who’s done some kernel driver code for NI interfaces, it should work perfectly, as it’s class-compliant to the USB2.0 spec (no, really, there is a spec for 2.0, and the KA6 complies with it, separating it from the vast majority of interfaces that only comply with the common 1.1 spec).
i setup some slightly more aggressive settings on this USB interface than for my FireWire audiofire 2, which seems to have been discontinued in favor of echo’s new USB interface (though the audiofire 4 is still available, and is mostly the same). i went with 64 frames/period, 48000 sample rate, 3 periods/buffer . . . which got me 4ms latency. that’s just under half the 8ms+ latency i had with the firewire-based af2.
at these settings, qjackctl reported about 18-20% CPU usage, idling around 0.39-5.0% with no activity. i only have a 1.5ghz core2duo processor from 2007, so any time the CPU clocks down to 1.0ghz, i expect the utilization numbers to jump up. switching from the ondemand to performance governor helps a bit, raising the processor speed all the way up.
playing a raw .wav file through mplayer’s JACK output worked just fine. next, i started ardour 3, and that’s where the troubles began. ardour has shown a distressing tendency to crash jackd and/or the interface, sometimes without any explanation in the logs. one second the ardour window is there, the next it’s gone.
i tried renoise next, and loaded up an old tracker project, from my creative one-a-day: day 316, beta decay. this piece isn’t too demanding: it’s sample-based, with a few audio channels, a send, and a few FX plugins on each track.
playing this song resulted in 20-32% CPU utilization, though at least renoise crashed less often than ardour. renoise feels noticeably more stable than the snapshot of ardour3 i built on july 9th.
i wasn’t very thrilled with how much work my machine was doing, since the CPU load was noticeably better with the af2. though this is to be expected; the CPU doesn’t have to do so much processing of the audio streams; the work is offloaded onto the firewire bus. with usb, all traffic goes through the CPU, so that takes more valuable DSP resources.
still, time to up the ante. i raised the sample rate to 96000, restarted JACK, and reloaded the renoise project. now i had 2ms latency…much lower than i ever ran with the af2. this low latency took more cycles to run, though: CPU utilization was between 20% and 36%, usually around 30-33%.
i haven’t yet tested the device on my main workstation, since that desktop computer is still dead. i’m planning to rebuild it, moving from an old AMD dualcore CPU to a recent Intel Ivy Bridge chip. that should free up enough resources to create complex projects while simultaneously playing back and recording high-quality audio.
first thoughts
i’m a bit concerned that for a $200 best-in-class USB2.0 class-compliant device, it’s not working as perfectly as i’d hoped. all 6/6 inputs and outputs present themselves correctly in the JACK window, but the KA6 doesn’t show up as a valid ALSA mixer device if i wanted to just listen to music through it, without running JACK.
i’m also concerned that the first few times i plug it in and start it, it’s mostly rock-solid, with no xruns (even at 4ms) appearing unless i run certain (buggy) applications. however, it’s xrun/crash-prone at a sample rate of 96000, forcing me to step down to 48000. i normally work at that latter rate anyway, but still…i should be able to get the higher quality rates. perhaps a few more reboots might fix this.
it could be one of the three USB ports on this laptop shares a bus with another high-traffic device, which means there could be bandwidth and/or IRQ conflicts. i’m also running kernel 3.5.3 (ck-sources), with alsa-lib 1.0.25, and there might have been driver fixes in the 3.6 kernel and alsa-lib 1.0.26. i’m also using JACK1, version 0.121.3, rather than the newer JACK2. after some upgrades, i’ll do some more testing.
early verdict: the KA6 should work perfectly on linux, but higher sample rates and lowest possible latency are still out of reach. sound quality is good, build quality is great. ALSA backend support is weak to nonexistent; i may have to do considerable triage and hacking to get it to work as a regular audio playback device.
