I have the original DacMagic and have enjoyed it very, very much. In the Q&A on Cambridge's website, it says that connection via USB cables limits the sample rate to 44 or 48 kHz due to inherent limitations of USB cable. Don't know if I buy into this. The DacMagic LED was showing 48 kHz in when the file playing was 96 KHz, so I thought the USB was the cause. Later I found I just wasn't aware that the iMac output has to be set to 96 kHz and 2-Ch. 24 bit via Audio MIDI Setup in Utilities. I haven't gone back to USB but have been using optical port on iMac ever since the initial problem. Maybe you know whether the USB output represents by-pass of all processing in the digital stream? I'm not sure it does, although it bypasses the internal DAC. Pretty sure the optical output bypasses any processing of the digital file. Do you have any thoughts regarding Mac processing with either UBS or optical outs?

I have been A/Bing the optical and USB of the DMPlus for a bit now. Both are going into the DMPlus. I simply change the sound out between the optical and the DMPlus USB in the Mac's sound control. Then I switch from USB to optical input on the DMPlus. I prefer the USB to the optical. It is subtle, but I find the USB to be fuller than the optical only. Whether this is due to the internal MAC circuitry or not I cannot say. I have read everything I can find on the apple site about sound processing from the Mac's various devices and they simply don't focus on the stuff e=were are interested in. Computer company, go figure..
After messing with the settings for awhile I am going to reconnect the optical out to the Denon AVR-4311ci receiver again and have my choice of DAC's. Denon uses the AKM Semiconductor AK4358VQ DAC's (2 of them). Naturally, the Denon forums tell me I am nuts to use any other DAC, but I find I really like the Cambridge when I compare the two. Both are very nice, but the DMPlus gets my vote for primary listening choice.

Nice review!
I enjoyed reading it.
Thanks, Chris

Thanks for elaborating on your comparisons of USB vs. optical. I think I'll be doing the same and just elect for the one that sounds best without further concern about what the iMac is doing internally. Just got in a Matrix M-line amp and have it connected to DM. Using Audeze LCD-2 phones. Sounds really good and I will compare to another amp in A/B comparison shortly. Also I bought the dual OPA 627A opamp to roll for the stock in this amp, but will wait to evaluate the sound a while before swapping out the opamp.

Chris J, thanks for the kind comments!
Audiofan4life, Isn't this the best part of this hobby! Experimenting with different gear and combinations is always a big part of the fun for me.

longbowbbs,
Yes, indeed! When we hit the combination that makes good music sound real and we are immersed in it- wow. My family doesn't get it- they just say, oh that sounds nice, and go on with their conversations. They'd be just as happy with whatever gear they could get at Walmart.
Just compared an Audinst HUD-mx1 headphone DAC/amp by running the DAC's output to the Matrix M-line amp, bypassing the Audinst headphone amp section. While I've been impressed with the sound the little Audinst can produce for the money, it was unquestionably a step up to the DM. Better imaging, warmer vocals, smoother overall.
So far, I can't really hear much difference at all between the USB and optical outputs from iMac to the DM. Have you noticed that using USB cable the DM cannot be set higher than 48 kHz sampling or higher than 16 bit? Maybe it's different with the new DMP model. With the optical, the DM is set to 96/ 24, but as I said, I can't really hear a difference at first listen. Maybe the DM does a great job of upsampling, making a difference in the formats very small in terms of audible differences, if any. But since I'm paying for 96/24 so to speak, I think I'll probably stick with optical. Awesome either way. BTW, have you listened to Audeze LCD-2 phones through your gear? I'm in love with them. I'm fond of very solid, detailed, controlled (musical) bass. These phones reproduce whatever bass is there, down as far as audible. No smearing or distortion at all. Listening to Patriot's Dream by Jennifer Warnes right now and the big bass drum whacks sound so real and clean. Aaron Neville's "Everybody Plays the Fool" has great percussion and bass that's a perfect arrangement. And there are no trade-offs: mids are detailed and accurate, as are highs which do not have the brightness which I find annoying in some phones. But I guess I'm getting off subject. Let's enjoy our DM's.

I did find that using an Audioquest cable made a nice difference from a generic computer USB. The Forest is the least expensive. I have the Cinnamon as well. Big improvements fir the USB. The DMPlus indicates the sampling rate at 44.1. The DMPlus may be different from the DM in handling USB audio. Here is an excerpt from the DMPlus manual:
Up to 24-bit content is now supported via both the USB Audio and Digital Inputs.With Windows PCs the DacMagic Plus can operate driverlessly (i.e. use Windows own built-in driver) at up to 24-bit/96kHz resolution.In addition our own Windows driver (downloadable from www.cambridge-audio.com/DacMagicPlusSupport) allows up to 24-bit/192kHz operation and supports both kernel streaming and ASIO.Mac PCs already support up to 24-bit/192kHz USB transfer natively.:If the file is up to 192K it will play in its native rate via the DMPlus' USB. k00l!!All my files are AIFF lossless ripped directly from the Mac Mini's internal DVD-Rom drive via iTunes...(That took weeks!!)I have been enjoying my handful of SACD's and DVD-A discs via my Denon DVD-5900 to AVR-4311ci through the Denon Link. I listen through the Denon's HP jack or I listen to the M&K S-150's...Sweet either way!...

OK...another thing to play with on the Mac...
http://www.benchmarkmedia.com/wiki/index.php/OS_X_Audio_Playback_-_Setup_Guide#Audio_MIDI_Setup
Set the output to 192k (Or whatever from 44.1, 48, etc) It will not change the sample rate from it's native, but if you know you have something in say, 96, then you can force the playback. If it is not correct your speed will reflect the newer, incorrect sample rate. (Chipmunks anyone!..

longbowbbs, Sorry for slow response to your post. I'm new here and I couldn't find the reference to this thread in my list of posts. Don't know why. But just now I came across the emailed link to the thread.
Okay, that's great info and I appreciate it. Seems as though the the DMP is an improvement in USB support of 24/192. Until I upgrade to DMP, I'll be running optical in. I saw a new Cambridge DacMagic 100 advertised for under $400 which appears to have some of the features of the DMPlus. It supports 24 bit/192 via USB and has its own clock, bypassing the Mac's clock. I'm not familiar enough with DAC manufacturers and models, but I would assume the DMPlus has a DAC that's better than 100. Did you buy your DMP before the model 100? Right now I've been moving my DM back and forth from computer to main stereo system, so I'd consider the 100 if it is an improvement over the original DM. Any opinions on that?

Oh, and the DM100 does not have selectable filter type. I hope it is similar to the min filter setting of the DM, which is my preference.