[timequest]

I am not an experienced DIYer, so I am looking for advice on where/who can mod my Duet output by eliminating the S/PDIF and tapping directly into the I2S source.  My objective is to be able to feed the Duet into an I2S input (which utilizes HDMI as the connection).  I don't know how doable this mod would be?? Experienced advice will be greatly appreciated.

Thanks.

[JoshK]

This is a very worthy endeavor, however, it is far from trivial.  I have read a fair bit about how to do this, as I'd love to do the same. 

Aside from the connector, which I will for the sake of this argument assume it is simply a matter of matching the pins/conductors for what you desire, there is the sending/receiving interfaces.  If your DAC is expecting a particular source load, then your I2S needs to be that load or you will have a lot of reflections and then you might as well just use SPDIF. 

John Swenson seems to have done some work on tapping the I2S in the Squeezebox.  Elso Kwak also has shown how he transmits I2S.  Kwak's method looks the most straightforward to my eyes, but Swenson only spelled out in words what he did, never showing a schematic.  The devil is in the details, so I am leary of going off words.

The problem as I see it, for a relatively inexperienced (in digital/RF transmission) DIY'er is the lack of proper measurement tools to verify that all is groovy, and the lack of knowledge of tricks of the trade to deal with potential pitfalls.

You can hire someone like Emipirical Research to do said mod for you, but last I inquired the quote was an order of magnitude off what I was willing to spend for such a mod.  (I am not saying it isn't fair pricing, just not at all consistent with my perceived value.)

Still all that said, at some point in the future when other projects have been completed it is something I want to explore.  I am just willing to sacrifice a SB up to learning if something goes wrong.

Maybe if enough of us have interest and agree upon a single format for transmission (HDMI cable perhaps) then we can bribe someone with the know-how to layout a (sub)board for us that taps the I2S and properly drives the sending side.  I, for one, though, would need a receiver (sub)board designed as well. 

For me, I'd love to re-adapt my AES digital input on my DEQX to be an I2S input for my Squeezebox, but I'd need to receiving side too.  This might be relatively simple if the DSP wants to accept the same format of data the SB sends (no bit shifting or rejustifying needed).

[timequest]

Thank you, Josh.

My DIY skills are not in line with this type of project, and I too am limited as to how much I can pay someone else to do this for me.  For me, a music server is the way to go - there are just so many benefits.  If I could get my server to the Proverbial "next level," I would be satisfied and done... (Are you laughing?  We're never done!).  Anyway, I am interested in purchasing the new PWD from PS Audio, which utilizes true I2S input by way of HDMI conductors.  The I2S capability of the PWD is really one of the main features that I am interested in though.  I have also been reading about tapping into the I2S source, which is obviously not a simple mod.  If you come up with any viable options let me know, and I will do the same

[JoshK]

I am not very familiar with PSAudio's offerings.  Are you referring to the PerfectWave DAC (@$3,000)?  The reason I ask is that this is already a media player, so one wouldn't need a Squeezebox with this player/dac.  Or are you referring to something else?

[timequest]

Yes, I am referring to the Perfect Wave DAC.  There is a bridge that must be purchased to be used in conjunction with the PWD for it to function as a server.  My budget will not allow that.  PSA is offering a trade-in program for up to $1,000, so I can just afford the unit at $2,000, but that's it.  Additionally, I'm not sure it will work in conjunction with the way I?ve set up my PC-based server and I would not want to have to re-rip all of my CDs.  It would be so much easier to simply feed the Duet into the PWD.  I'll have to read up on the details.  Regardless of the DAC used, I2S is the way to go. 

[JoshK]

Then I'd just go with the Slimdevices Transporter if I were you.  You get the Squeezebox like control and hi-end dac in one.  You can probably get this less than $2000 and you wouldn't have to deal with I2S.

[timequest]

Believe me, I've thought about this option.  Here's why I don't think I'll go that route; I had the opportunity to do direct A/B comparisons between the Transporter/native DAC and the Transporter/Cullen Stage IV PSA DAC on a very high-end system at my local audio dealer.  Everyone in the room clearly heard an improvement with the modded PS DAC.  The new PS DAC is supposed to be miles ahead of the aforementioned DAC.  Once I get a chance to hear it for myself, I will know for certain.  I have a feeling it is going to be something very special.  If I can't achieve an I2S mod, then the Transporter option is more viable.

[JoshK]

I just don't know many DIY'ers who've attempted this mod.   In theory it seems like a straightforward mod to tap the I2S.  But how would you know if you terminated everything correctly without a TDR?  By ear?  I just don't think this would be reliable enough.

If you get Empirical to do it, I think you'll realize you went way over budget.  I seem to recall a number not so far off the price of that upgrade for adding the receiving end to my DEQX.  In theory that is the easier side. 

My little knowledge of the subject leads me to think that the idea is simple and requires rather inexpensive parts, but verifying whether you did it right involves using expensive test equipment that I don't own or have access to.

[timequest]

I know...you're right.  I wish money wasn't such a damn option.  I do hope that more manufacturers will begin adopting I2S as their native interface connection.  They?ve all known about jitter for so long, you would think they?d have addressed this issue by now.  Instead, you have companies selling expensive re-clocking devices and charging an arm-and-a-leg for mods.  Hello?there?s a market for this!!

[JoshK]

I think it boils down to no standard interface.  One manufacturer's interface is different than the other's.  Unless you buy components that were meant to match that interface, i.e. from that same manufacturer then you are up a creek.   Consumers were generally ignorant for so long and complacent with what they had that they didn't make much of a stink about it.

[JoshK]

Someday, when I get a "round tuit", I am going to try Elso's method (emitter followers for each of the 3 streams for the sending side into 3 seperate 50 ohm BNC'd coax cables). 

By the way, if you really want to learn up about this, you should hang out on this forum.  They know what they are doing.  I don't.

The aforementioned Elso Kwak method is on that forum somewhere.

[Occam]

Some links that may be of interest -
http://forums.slimdevices.com/showthread.php?t=24800
http://forums.slimdevices.com/showthread.php?t=38967

http://audiogestalt.wordpress.com/

FWIW,
Paul

PS - I can't vouch for these threads veracity, but IMO John Swenson is very knowledgable.

[JoshK]

Thanks Paul for the links, I had seen the 1st and definitely hadn't seen the last.   I agree Swenson is a smart cookie.  His creativity in tube audio is inspiring and his work here is also inspiring.

[timequest]

Cullen Circuits has announced that they will be offering I2S mods (via HDMI connection) to DACs and transports.  I sent an email to Rick, who said he was going to look at the SB receiver to see if he can design a board that will fit inside - which would be great.  As I know more, I will post.  The price factor will obviously come into play; I have no idea what that will be yet.  At least there are some options.