I have both (4490 & Multibit) and hope to do a comparison soon.
Soon has finally arrived! Today I spent a few hours comparing my upgraded Bifrost 4490 with my Bifrost Multibit. Several weeks ago I posted my impressions of the Über to 4490 upgrade (Posts #60 & #67) which to my ears was a pretty noticeable and impressive upgrade. I liked it so much that I decided to purchase a Multibit for my 2 channel system and move the 4490 to my night stand setup which includes a recently acquired Vali 2.
My original motivation to purchase a DAC was in an effort to improve the sound of my 2 channel system. I purchased a Bifrost Über shortly after it's release and it unequivocally took my audio system to a significantly elevated level. I was completely thrilled with the outcome. Since I know how these Bifrost DAC's sound on my 2 channel system, naturally this is where I was going to do my comparative listening.
So cutting to the chase, I must say that I'm somewhat disappointed that there weren't more obvious differences between the 4490 and Multibit. There
are audible difference in my audio system, albeit minor in my humble opinion. While the Multibit is a better sounding DAC than the 4490, in my opinion the differences aren't as significant as the Über to 4490 upgrade. The Multibit definitely does a better job of spatially separating instruments in the soundscape as well as providing slightly more detail than the 4490, however these 2 DACs are more similar sounding than different. I must stress that the differences between the 4490 and Multibit aren't that stunningly significant.
Predominantly on good recordings it did become apparent that the Multibit was able to produce a more live-like sound. The 4490 had a slightly "trowelled over" sound that just wasn't as "airy" sounding as the Multibit. Both DACs maintained a very nice wide soundscape, the 4490 maybe just a tad better, but the Multibit was able to present depth to the sonic image that reproduced a very nice 3D-like sound. I would give the 4490 the edge when it comes to delivering slightly more pronounced bass but the Multibit reproduced a more natural and tight sound that allowed me to follow the bass notes more effortlessly. The Multibit is just a bit better when it comes to providing clarity, detail and air that leaves you with a more realistic presentation. Perhaps your audio system has greater resolving capability than mine in which case you may hear a more significant difference than I was able to in my setup. Regardless, each Bifrost DAC has a place in their respective setups in my home and are sounding very satisfying indeed.
From a value perspective, if you have a first generation or even the Über version I would not hesitate in ordering the 4490 board and do the swap out yourself. The audio improvement is simply a "no brainer". Although the upgrade path of an existing Bifrost to Multibit is definitely more expensive especially when you have to add the cost of shipment to and from California. If you have the equipment to squeeze out the capability of the Multibit and have no issue with this more costly upgrade path then by all means go for it.
Just a final note, my 2 channel system also includes a Lake People G109S headphone amp. This amp combined with my original Bifrost Über and HD650 and HE500 headphones sounded absolutely terrific. Having introduced the 4490 upgrade into this headphone setup for a very brief period I did hear a noticeable improvement (as mentioned on the adjacent 2 channel system) but it was only there for a very brief period before it was replaced by the Multibit. I did not take the opportunity to do a direct 4490 and Multibit headphone comparison because these DACs are residing and being enjoyed in separate systems, however the Multibit certainly trounces the Über on all levels. The Multibit has taken these headphones to another level all together.
