The new Oppo BDP 105 was mentioned recently in an un-related Salk Circle thread. What caught my attention was that, in addition to all the features of previous Oppo models, the 105 also featured a DAC that could function independently of the transport. In other words, it could function as a stand-alone DAC. And, supposedly, it could handle bit rates as high as 24/192.
The question in my mind was whether or not the USB input to this DAC was USB Class 2 Audio compliant. There are quite a few DAC's in the marketplace that will play 24/192 material. But many of them are not USB Class 2 Audio compliant and require special drivers in order to handle bit rates over 24/96. (I should note that all Windows computers require special drivers since the Win USB implementation does not have the bandwidth required for higher bit rates.)
I found one document that seemed to indicate that the 105's USB DAC was USB Class 2 Audio compliant. But Oppo's documentation specifically indicated that while no drivers were required for MAC computers, drivers were required for other systems and not available for Windows 8 or Linux. I found this a bit confusing. The fact that no drivers were required for recent MAC computers seemed to indicate that the USB DAC in the 105 was Class 2 Audio compliant. But if that were the case, no drivers would be required for an up-to-date Linux system either.
Since our StreamPlayer is based on Linux, it seemed to me that no drivers should be required for use with it if it was truly UBS Class 2 Audio compliant. But there was only one way to find out. So I ordered a unit.
There are a reasonable number of great USB Class 2 Audio DACs available these days. But they tend to be expensive. Ayre makes one for about $2500. The Wavelength DAC I often use is $3500. My modified AVA DAC probably runs about $1900. If the Oppo BDP really is USB Class 2 Audio compliant, it would be quite reasonably priced at $1200. Plus, you get a great transport for Blu-ray, SACD, etc. thrown in on the deal! So it was worth investigating.
The 105 arrived on Friday and Saturday I tried running it through its paces. First I used the Oppo itself to play files from my music server. This worked as expected. So I next hooked up a StreamPlayer and hit "play." I received an error "trouble opening audio device." I could see that the StreamPlayer recognized the "Oppo USB Audio" device, but for some reason could not open it. This was quite disappointing.
Next, I hooked up a MAC to the USB DAC input and played some music. No problem at all.
This made no sense. The MAC did not need a special driver. But it seemed that the Linux-based StreamPlayer did.
Then, on Sunday, I got to thinking. The StreamPlayer I was using was my very first prototype. Were the drivers up to date? The answer was no, they were not. So I updated the Linux audio drivers to the latest version of alsa, hit play and heard wonderful music! The Oppo 105 DAC worked perfectly with the StreamPlayer with current alsa drivers - no special drivers required!
I tested the combination with a series of musical selections ranging from standard Redbook 16/44 to 24/96 and 24/192. All worked flawlessly and seamlessly. There were no clicks heard as the DAC switched from one format to another (which I have found with some other DACs).
The combination of the StreamPlayer and the Oppo BDP 105 has been playing continuously for about 24 hours now with absolutely no hickups. So, it appears that the 105 is indeed USB Class 2 Audio compliant and does not require special drivers with up-to-date Linux systems. This means it is a perfectly acceptable DAC for use with the StreamPlayer up to 24/192, just as I had hoped. This totally eliminates the need for a stand-alone DAC for music reproduction in my home theater. Nice.
One question that was asked in the earlier thread related to the use of the Oppo itself to play music files. The poster wondered why you would use a StreamPlayer when the Oppo could access and play network-accessible music files by itself.
While this is true, there are a number of reasons why I feel the StreamPlayer/Oppo combination is superior. I won't bother to get into all of them here, but here are a few worth pointing out.
First, in order to use the Oppo to play music files, you will need to have your TV or projector on in order to use the Oppo remote to make selections. In my home theater, I would rather not fire up the projector (and put hours on the bulbs) just to play music.
Second, the Oppo interface is like a directory browser. The process of selecting music with the remote is slow and cumbersome compared to scrolling through albums, artists, etc. on an iPad (for example). I tried using it and it does work. But I find it crude and clumsy and would not be at all satisfied with its use on a long-term basis. It simply can't compete with an good MPD client like mPad or the like.
When used with the StreamPlayer, the Oppo 105 can also be put in "direct" mode. This supposedly improves the DAC performance by shutting down all the circuitry not required (video circuitry for example) and eliminating a lot of RF interference in the process. I have not tested this, but you obviously couldn't use the Oppo alone in this mode since you would no longer have access to an on-screen display.
An unrelated observation I found strange (but did not verify) is that the documentation on the DAC section seemed to indicate that the USB port was the only port capable of 24/192 reproduction. S/PDIF and optical are only spec'd to 24/96. I only mention this as a side note since my concern was only with USB anyway. I just thought it was worth pointing out.
OK, how does it sound? Well, I should note that most of the DACs I have preferred in the past have used Wolfson chips. The Oppo uses Sabre chips which are also considered cutting edge. In the past, I have read many comments from individuals who liked the detail of the Sabre chips, but found them to be a little bright and thin, somewhat lacking in the bass department. Never having spent any time with them, especially in direct A/B comparisons, I can't say whether I agree or disagree with this assessment.
I had read these same comments about the DAC implementation in the BDP 105. So I don't know if my first impression was based on sound quality or the fact that I had read comments to this effect in the past, but I did sense that the sound was somewhat on the thin side. Most owners who made these comments seemed to feel things improved quite a bit with a bit of break-in. So I will not pass judgement here at this point and leave the StreamPlayer/DAC combination playing 24 hours per day for a few days before I revisit the system. Later I will conduct a few comparisons with other DACs.
We now have an ABX switch that will allow us to directly compare two different (volume-matched) sources (two DACs for example), with two amps and three sets of speakers and instantly switch back and forth. When I have time to test it, I will be able to directly compare two DACs in the same setup in order to determine how the various DACs compare in terms of sound quality.
I'll have to find time to conduct these tests later...