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Squeezebox I2S mod

Paddy

pfm Member
Hi I have a SB+ made by Patrick Dixon a member here and am bringing it back into service.

It has a modified digital out that i plan to use into a P1a/P3a upscaler and DAC combo. The DAC also has an I2S input and I believe it is possible to get such a thing out of a SB. What I'm not sure about is which flavour of I2S is involved in some of the mods that are reported on the net.

The pin configuration on the upsampler / DAC is below. Apparently it is the "standard" used by Audio Alchemy



I can't do the work myself but wanted to try to understand what is involved and to be able to provide some pointers.

Any thoughts gratefully received

Regards

Chris
 
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I think the way its usually done is via some sort of buffer stage which would allow for greater transmission distance. I'm not sure that this is a good idea, or that it solves anything that couldn't be solved by aggressive reclocking on the receiving end, but it sure sounds cool.
 
Thanks, I'm way out of my depth here but, the P1a/P3a are apparently right up there as a Redbook combo and they owe me little and i already have the SB+ so i set to thinking. Dangerous i know.

Plenty of other mods for consideration as well. Output stage of the P3a can be significantly improved by changing out some op amps or alternatively i'm quite taken with the idea of some sort of valve output stage a la Lampizator.

All would need to be done at a cost by my friendly local repair guy but, i doubt he is interested in researching options, hence the questions.

Thanks again

Regards
 
Here's an example of I2S output for the Squeezebox Receiver, though other Squeezeboxen would seem to have something similar. http://db.audioasylum.com/cgi/m.mpl?forum=pcaudio&n=64672&highlight=sabre+i2s

Now, this gent is taking it about 3 inches to a DAC inside the same case, so I'd expect some problems over a longer distance (more than about 6").

SBR has a Wolfson WM8501 and SB+ has a Burr-Brown PCM1784E. On the BB the I2S pins are BCK - 1; Data - 2; LRCK - 3; GND - 4. http://www.ti.com/lit/ds/symlink/pcm1748.pdf

So you should be able to get it out, but I don't know how far you'll be able to make the signal go in a satisfactory manner without some sort of buffering, which would almost surely produce significant amounts of jitter. I've seen some mention on the forums of people who got it to work without a bunch of noise through months of effort, only to find the results not worth it.
 
Although I imagine you are very fond of your SB+ you can now create a Squeezebox with much better performance using a Raspberry Pi, and it's own USB interface, or a HAT with SPDIF output. The HATs use the I2S interface on the Pi, which may be superior to the USB, in theory, though I use USB and it's bit perfect and sounds 'perfect' to my ears. The SB+ is limited to 16/44 I believe, which is ok, but I do have quite a lot of 24/96 material, so being able to play that, and future formats (maybe DSD will be mainstream one day), is quite useful.
 
Hi Jem,

This is a bit of a side project as my main source is still vinyl. I

I recently got hold of the P1a/P3a combo for not a lot of money and although it is pretty old to say the least, it has potential to be a very good Redbook combo, up there with the best at the time. This lead me to finding a suitable source. I had looked at the Pi i2s route but, as i have the SB+ already and am only looking for Redbook, I thought i would investigate. The SB+ has an improved S/PDIF using a transformer-coupled balanced output (whatever that means) so it seemed like a worthwhile investment. http://free-12415f14c3a-124e539428a-12d517bd9a9.force.com/spdif

I originally bought the SB+ when i lived in a house but, having moved to a flat years ago it fell into disuse and its only now with the P1a etc that I'm giving it a go. Winter evenings and all

Regards

Chris
 
Just worked out who is behind the P1a/P3a - I had an Audio Alchemy DAC many years ago, and loved it. They were big fans of the I2S interface, and hoped it would be adopted as a replacement for SPDIF. As a project, I think it's a worthwhile experiment.
 
I did get the PT gear working using the I2S input working with a Squeezebox Touch via the USB output and a small USB to I2S adapter purchased for a few £ on eBay. Worked well with a short home made cable and given the PT stuff works up to 96kz allowed some high Res material to be played using the SBT software mod.
 
Thanks ntom,

I'm using an older SB+ so don't expect any of the hi-res stuff. That's fine with me to be honest as i have a Hugo which I will also press in when i get finished so i can do some comparisons. I think I will stick with the existing connections and concentrate now on whether to mod the output stage of the P3a (Burr Browns, caps etc) or to get a valve output Lampucera type thing made.
 


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