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Today I tried running my touch without a display, not just turned off, but with the display physically removed.
It works! It plays music and can be controlled remotely. BUT you can't set it up after a factory reset, that HAS to use the display. You need the display to turn on SSH so you can remote login. Many other configuration options are really difficult to do without the display. Once you have SSH running you CAN change most settings by editing config files.
Now on to the sound. Wow, another significant leap forward. This was probably the biggest improvement yet. Still not as good as my own DAC, but getting quite close. Significantly more sense of space, room reverberation is permeating the experience rather than being painted on. (it wasn't THAT bad, but that gives the sense of it). The sound is much more organic and "whole".
OK so now I have to figure out how to do this through software so I don't have to physically take the screen off.
John S.
Follow Ups:
John: do you have a good link with instruction on how to set up the Squeeze Server to stream PCM from FLAC?
Thanks Rich
see this post and following replays
chris
.
Hi John,
Thank you very much for your ongoing effort in improving the Squeezebox Touch. Can you please give us a list of mods that you have performed on the SBT so far, or is it too much to ask?
I try really hard "track down" your posts across different forums (here at AA and slimdevices), but I want to make sure that I'm not missing out on anything.
Thank you!
"We should no more let numbers define audio quality than we would let chemical analysis be the arbiter of fine wines." N.P.
While I had the Touch opened up I decided to try bypassing the output caps. The DAC is already ground referenced so I'm not sure why those caps are even in there. I measured 4mV on the DAC output which shouldn't be much of a problem in any system.
So I soldered some wire around the caps (the caps are still there, just bypassed). This improved things even more, but not as big an improvement as no display. This is now sounding REALLY good.
I have a Peachtree Nova on the bench so I tried running the analog and digital out to it and comparing. With the Touch out of the box the Nova's DAC was better, not by a lot, but definitely better. With no display and the caps un-bypassed, it was a toss up. With the caps bypassed the Touch is definitely better than the Nova's DAC.
So right now with a linear supply, no display and caps bypassed this is one REALLY good sounding device.
Of course that is with PCM streaming from an external server, if you start decoding flacs on the Touch, all bets are off.
John S.
Hi John,
Very interesting. Yes killing it in SW would be the handiest iffins you can do it. I still haven't bought one but, speaking from fairly recent experience doing a much larger touchscreen design, LCD displays are a notorious problem for emissions and part of the problem might just be internal EMI.
I understand from your previous posts that the design is really tight so this probably isn't practical but, just in case, I finally tamed ours by putting small series resistors (~150ohms) in every clock and data line feeding the display. It doesn't really matter where, the idea is to just reduce the edge currents without without manging the signal. While Pclk is of course the biggest spur emission-wise all the signals need damping, it's hard to believe what large circulating currents the 'signal level' excitations manage to produce. Sigh. There are some mighty small resistor packs these days and they might be fitable on the main board where the display flex connector fans out if they decide to rev the layout.
Yes, it's inelegant HW, but so's the problem.
Rick
Just make a separate little board with the FPC connectors and the resistors. Plug the display into the new board and then use FFC jumpers from the new board to the main board. It would also make it much easier to take apart. It would also make it easy to put in a new box with the display, touch board and linear supply all in one box.
It wouldn't be hard to put together the layout for such a board.
John S.
Setting the Now Playing screensaver to 'Screen off' doesn't accomplish the same thing?
No, the screen off screensaver just turns off the back light, the clock and sync signals are still going to the LCD.
I tried the screen off mode and I couldn't hear any difference. But getting rid of the screen altogether made a big difference.
John S.
Are you sure that disabling the driver or whatever you might do in software at the OS level would be any different?
The screen off screensaver still leaves signals going to the display, but I'm sure you CAN turn off the signals to the display by setting certain registers in the CPU. This will probably have the same affect as unplugging the display. To my knowledge there is nothing in the Touch software that does this. Its going to take some digging in the CPU documentation (which is several thousand pages long!!) and coming up with a way to tweak those registers.
John S.
Can you say what processor it uses? I think I may have read it someplace but didn't pay much attention. I'd suppose the Ap. sets the registers at power on reset.
Using a separate board for display damping resistors works fine, I actually put them on an intermediate board we used to allow multiple LCD brands. I take it both end use a FFC.
Tnx Rick.
Its a Freescale MX35 series, I don't remember which exact model, its sitting open on my bench right now so when I get home I can get out the magnifying goggles and look!
The Touch has a bunch of /sys interfaces for access to other parts of the processor, I'll see if there is something in there for the display. If not I'll add one!
If the resistors really work that would be nice, so you can keep the display usable and still have the sonic benefit.
John S.
Didn't we expect that? ;) I said before that a DUET II would have been the better approach - at least soundwise.
How did you do it? Did you just left the internal connection ( back/front panel disconnected?)
What a pity that automatic upgrades can not be avoided.
Cheers
Hi John,
Thank you for sharing your continued experiments with the Squeezebox Touch. Because you mentioned comparing it to your DAC I am wondering if you are talking about the sound improving through the analog output or the digital output or both when the screen is disabled.
Thanks again,
Aaron.
This was through the analog outs.
I did check it with digital to a Peachtree Nova and my own DAC. With the Nova there was a difference without display but not nearly as big a difference as with the analog outs. With my DAC I had a hard time telling if there was any difference or not.
John S.
I have built a Buffalo II with the Sabre32 DAC that is a step up from the one in the Nova. It is supposed to be fairly robust when it comes to differences between transports. I haven't dug in and compared the Squeezebox to my Oppo, or any of the other silver disc players I have lying around, want to get more familiar with it and get it working reliably via ethernet and an external server.
What DAC are you using? I know that you probably built it, just curious about what you selected.
Best,
Aaron.
My main system DAC is a prototype for the Bottlehead DAC which has a S/PDIF receiver and transmitter in an FPGA. Its designed to be used with interfaces that will sync their S/PDIF out to an input stream. The receiver has no PLL, its driven by the local low jitter clock, it "assumes" the input stream is already synced to the local clock.
The FPGA drives a pair of 1704 chips, which drive transformers (I'm using a pair of Audio Note SUTs I've had for years). The transformers are a major part of the low pass filter after the DAC chips. My version is currently driving a JFET based amplifier I have been working on for a couple years. Of course the real one will have a tube output stage.
In my normal setup I have a fitPC slim running linux and squeezeslave driving a EMU 0404USB which is connected to the DAC (right now with TOSLINK). I have not found any difference with TOSLINK or coax. Of course I have homebuilt linear supplies running everything.
I can use this DAC with the Touch even though it doesn't sync to a S/PDIF input stream. The FPGA in the DAC has a buffer and I can run asynchronous and reset the buffer at song boundaries. This works as long as the the frequencies are not too far off. I've also done it without syncing at boundaries which every now and then drops or duplicates samples. The interesting part about this is that I really can't tell when this happens, there is no click or pop.When the clocks are really far apart such that even with the buffer I'm dropping/duping multiple times per second, then I can get some hint that something is a little different.When it happens every couple minutes, I have no clue its happening. (I have a red and green light on the board I can use to let me know when there is a under/over run)
I'm currently working on a digitally controlled crystal oscillator to track non-synced inputs but that is not up and running yet.
This is a very good sounding DAC.
John S.
Thank you for taking the time to explain your DAC, that is very intriguing work. I have built a Hagerman Chime, which is BB1794 + Tube output stage based, and it is an excellent sounding DAC. I bet that with the clock sync it sounds fantastic. I have been wondering why there isn't a clock sync DAC that doesn't cost a fortune, and I'm happy to hear that you are working on one. I'll definitely be checking the Bottlehead website for more information. Don't know if I'll invest in building another DAC since I just got the Twisted Pear Buffalo II running and I have two rather spendy DIY's already, but I might. Your design definitely standouts out among DACs available DIY or otherwise.
Aaron.
This is not available yet, its still under development.
John S.
.
John, I forget if your dac is capable of 192/24 or 96/24. Have you compared material other than 16/44?
regards ~ Michael
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