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Gazjam
30-07-2009, 18:12
Been reading up a bit about best ways to mod my Squeezebox 3 / 7520 system.

Been asking about here and there, and if using the SB3 as a digital transport only (i.e. no analogue out) then the suggestions I got here were very interesting.

This one in particular, but not being an electronics wiz I thought id ask here for opinions?

...and I quote;

"If you STILL want to hack the SB hardware, and REALLY make a difference, you need to get your DAC modded to allow clock out or I2S in. Then you need to mod your SB to provide clock in or I2S out.
The point is that you need the transport(sb in this case) to be wordclock locked to the DAC so that the DAC clock circuit "drives" the timing of the transport and you do not need to recover a clock from the spdif/toslink signal. Many people believe that the recovery of the embedded clock is the most fragile part of the entire spdif/toslink methodology. This approach will minimise transport/spdif induced jitter.

I believe it is harder to create a wordclock out from a DAC - you need advice from experts here. The SB is the "easy" part."

So,
any technical input on the viability of this mod on the 7520 BDac? Stan, any thoughts?
Is this kind of thing do-able with the 7520?


Thanks for any replies.
:)

leo
30-07-2009, 20:30
Some reading, saves me trying to explain it;)

Actually I think the dac chip used in the 7510/20 can be used with I2S left justified so should be easier to use with the SB3
We don't have the schematics for the 7510 or 7520 so it makes things a little harder to work out

I don't have a SB3 so somebody else will have to try it, the Duet receiver I have uses plain old I2S

http://images.google.co.uk/imgres?imgurl=http://audiogestalt.files.wordpress.com/2008/06/twin-tda1541a-pcb3.jpg&imgrefurl=http://audiogestalt.wordpress.com/&usg=__2jb7EJ9XrJCqbRjwnMXbs1yCs_k=&h=1495&w=1995&sz=112&hl=en&start=1&um=1&tbnid=z2Ukr1_hwCB1CM:&tbnh=112&tbnw=150&prev=/images%3Fq%3Di2s%2Bmod%2Bsqueezebox%2Btda1541a%26h l%3Den%26rlz%3D1R2GGLL_en%26sa%3DN%26um%3D1

You probably already seen this

http://images.google.co.uk/imgres?imgurl=http://audiogestalt.files.wordpress.com/2008/06/twin-tda1541a-pcb3.jpg&imgrefurl=http://audiogestalt.wordpress.com/&usg=__2jb7EJ9XrJCqbRjwnMXbs1yCs_k=&h=1495&w=1995&sz=112&hl=en&start=1&um=1&tbnid=z2Ukr1_hwCB1CM:&tbnh=112&tbnw=150&prev=/images%3Fq%3Di2s%2Bmod%2Bsqueezebox%2Btda1541a%26h l%3Den%26rlz%3D1R2GGLL_en%26sa%3DN%26um%3D1

leo
30-07-2009, 20:41
BTW, I intend on doing a I2S out with the Duet Receiver at some point, mainly because I faff about with dacs it makes trying some diy types a little easier (no need for a SPDIF to I2S receiver if you have I2S to start with)

Unless you plan on running the 7520 very close or better in a same case as the SB3 it may not offer any benefit ,theres the clock to mess about with, infact if your not careful it could perform worse.
Not an easy mod tbh, best left to the fiddler:)

Gazjam
30-07-2009, 21:21
Thanks Leo.

I've a fiddller intersted in the mods, I'm a numpty when it comes to this!


Interesting article, will read in depth soon.

Covenant
30-07-2009, 22:05
Personally that mod is a no-no for me Gaz as you loose internet radio.

Tony Moore
31-07-2009, 07:14
If you use I2S without reclocking then it'll work on both 44.1 and 48khz.

There could well be some benefit of driving a DAC I2S direct from the SB3 but as Leo says the lead lengths must be very short and sometimes it's easy to in fact end up with worse performance. Soldering the wires on to pick up the I2S signals is not for the faint hearted either.

I did do this in my TDA1541A based dac, first with the SB3 (which needed the format changing to work with the standard I2S input of the 1541, hence the X shaped board)

http://i296.photobucket.com/albums/mm168/TonyMoore300B/DAC.jpg

You can see the 4 connections soldered onto the SB3 for the I2S. (bit clock [BCLK], word clock [WCLK], data and ground)

Then I got the Duet Receiver which is standard I2S so I could manage without the conversion board.

http://i296.photobucket.com/albums/mm168/TonyMoore300B/DACWithSBR.jpg

With this I glued down a 4 pin header strip and then wired over to the smt resistors using very fine strands of wire.

As Leo says, the SB3 is "left justified" which assuming the 1520 can handle this format then it should work. You'd have to break the current connections from the receiver chip in the DAC though, assuming that there are no jumpers or that the receiver chip is not socketted.

My setup _is_ reclocked at 11.286Mhz so I can't listen to 48Khz material. I guess it would be possible to use two superclocks, one for each sample rate and switch between them but for the amount of 48Khz material that I've come across it's not been a problem for me.

Cheers,
Tony

Gazjam
31-07-2009, 07:26
Thanks tony.

Cov, didn't realise I'd lose Internet radio either, so it's a no from me too.
Just gathering info at the moment anyways.

leo
31-07-2009, 15:07
If you use I2S without reclocking then it'll work on both 44.1 and 48khz.

There could well be some benefit of driving a DAC I2S direct from the SB3 but as Leo says the lead lengths must be very short and sometimes it's easy to in fact end up with worse performance. Soldering the wires on to pick up the I2S signals is not for the faint hearted either.

I did do this in my TDA1541A based dac, first with the SB3 (which needed the format changing to work with the standard I2S input of the 1541, hence the X shaped board)

http://i296.photobucket.com/albums/mm168/TonyMoore300B/DAC.jpg

You can see the 4 connections soldered onto the SB3 for the I2S. (bit clock [BCLK], word clock [WCLK], data and ground)

Then I got the Duet Receiver which is standard I2S so I could manage without the conversion board.

http://i296.photobucket.com/albums/mm168/TonyMoore300B/DACWithSBR.jpg

With this I glued down a 4 pin header strip and then wired over to the smt resistors using very fine strands of wire.

As Leo says, the SB3 is "left justified" which assuming the 1520 can handle this format then it should work. You'd have to break the current connections from the receiver chip in the DAC though, assuming that there are no jumpers or that the receiver chip is not socketted.

My setup _is_ reclocked at 11.286Mhz so I can't listen to 48Khz material. I guess it would be possible to use two superclocks, one for each sample rate and switch between them but for the amount of 48Khz material that I've come across it's not been a problem for me.

Cheers,
Tony

Can't help but be impressed with all the work gone into that !
You still using AYA Tony?

Tony Moore
31-07-2009, 19:50
Hi Leo,

Well, it was the version that pre-dated the AYA but yes, I'm still using Pedja's DAC and it's still very, very good!

Not much time these days for any DIY though. Still, I enjoy the results of the labours every day so that's fine!

Cheers,
Tony