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  1. #21
    Senior Member
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    Yesterday I opened mine up again and tried running without the display at all (physically removed, no connections at all).

    Wow! This made a significant improvement. Way more spaciousness, room ambience etc. Everything sounds more organic, full bodied etc.

    Of course there are some problems, you can't initialize the Touch from startup or after a factory reset without the display. You also need the display to turn on remote login. Once you have remote login working you can do almost everything else, albeit you have to edit configuration files for most of them.

    After hearing what it sounds like without the display its hard to go back!

    This was through the analog outs, It did make some difference on the digital out but not as much as it did on the analog outs. This was with a Peachtree Nova which uses the Sabre DAC which is fairly immune to variances in digital ins, so it might be a bigger difference on other DACs.

    While it was open I decided to try bypassing the output caps. Again this made an improvement. Not nearly as big an improvement as taking out the display but still definitely there.

    As a reference, with the caps bypassed and the display removed the analog outs are now better than the DAC in the Nova. I was listening to the Touch driving the Nova both over coax and analog. Listening to the preamp outs of the nova. The analog from the Touch was definitely better. And that had an extra set of interconnects as well.

    So the Touch with a linear supply, no display and output caps bypassed is a REALLY good DAC.

    John S.

  2. #22
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    Funny.

    Now all you need to do is get another Touch and turn it into a controller for the headless neutered Touch. You should remove the wireless while you are in there

    Obviously, you have some very subjective comments there. From a technical point of view what do you think removing the screen (vs turning it off) is doing to the system to cause the difference you are noting as improvement?

  3. #23
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    Quote Originally Posted by pounce View Post
    Funny.

    Now all you need to do is get another Touch and turn it into a controller for the headless neutered Touch. You should remove the wireless while you are in there

    Obviously, you have some very subjective comments there. From a technical point of view what do you think removing the screen (vs turning it off) is doing to the system to cause the difference you are noting as improvement?
    That is the plan. I'm going to get another Touch and use it as a controller. I also have an old HP tablet as a large now playing screen mounted on the wall.

    My guess is the un-mounted display is either cutting down on noise on the supply traces or cutting down on radiated EMI from the panel itself. I'll do some tests on the supply rails and see if that changes. The EMI is going to be a little tougher since in normal use the screen is about 1/4" away from the board, that makes it a little fun to measure. The EMI could be picked up by the analog output traces, in which case it should be easy to measure. But it could also be picked up by things like the crystal oscillators. I have to figure out how to measure such things with the board and display in their normal positions.

    Hmm, that would make a good first test, try the display connected but swung away from the main board. If the sound stays the same its probably PS issues, if the sound improves its probably EMI.

    John S.

  4. #24
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    hi john

    wow! i haven't tried the analog output but went straight for the spdif output.

    if the problem is emf/rfi, could stick some of those ers emi/rfi absorbent paper at the back of the touchscreen. but of course, nothing beats distance...

    when you say bypass the output caps, you mean shorting the big electrolytic caps at the output right? i didn't measure anything but this cap is meant to block dc voltage. you mean there's no dc voltage at the output of the akm dac?

    thx!

    yeo

  5. #25

    Headless Touch

    John, that is great news. My plan now is to remove the Touch circuit board from its cramped confines and mount it in a box with some room to work, without the controller. With the observation that the analog outputs are so good, I will plan to optimize those as well as my previously planned mod to bring in external clocks and output I2S, all via LVDS signalling through a DVI connector, as I did with the Receiver. Since I will be preserving the analog outputs, that answeres my earlier question about using a clock-doubler circuit to provide the clocks for the Touch. I'm gonna have to buy two more high frequency clocks from Guido Tent (good thing the euro is weak right now...)

    Can you think of any other functionality that will be lost without the controller, other than the ones you mentioned? I presume even another complete Touch elsewhere in the system would not allow recovery from a factory reset. I will use SlimControl with my WinMobile phone to control the system, as I do now. Would there be a way to recovery from a factory reset using SSH?

    Pounce, I like the term headless Touch, but NOT neutered, thank you. It may be ghostly, but still a beast!

    Jack

  6. #26
    Senior Member Phil Leigh's Avatar
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    I can't detect any RFI with my (ELFIX) sniffer from the screen itself...
    You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal...
    Touch(wired/W7)+Teddy Pardo PSU - Audiolense 3.3/2.0+INGUZ DRC - MF M1 DAC - Linn 5103 - full Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend Supertweeters,VdH Toslink,Kimber 8TC Speaker & Chord Signature Plus Interconnect cables
    Stax4070+SRM7/II phones
    Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything.

  7. #27
    Senior Member CharlieG's Avatar
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    Smile Headless Touch

    Quote Originally Posted by JIJ3 View Post
    Pounce, I like the term headless Touch, but NOT neutered, thank you. It may be ghostly, but still a beast!
    Jack
    Wouldn't a Touch without the touch screen be "Touchless"?

    Or maybe "Untouch(able)"

    Maybe it's a Receiver:-)

    Actually I would have bought a touchless Touch (Receiver II?) had it been available when I bought my Touch (at a cheaper price of course).

  8. #28
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    Quote Originally Posted by Phil Leigh View Post
    I can't detect any RFI with my (ELFIX) sniffer from the screen itself...
    I couldn't either when I ran such tests with the spectrum analyzer. What I'm worried about is the flex cable, it has no shielding. When its all assembled its laying right against the board and could very easily be contaminating the analog signals or maybe the oscillators etc. Fortunately the flex cable is on the back side which means the board ground planes should provide shielding to the parts and traces on the "top" side.

    John S.

  9. #29
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    Quote Originally Posted by JIJ3 View Post
    Would there be a way to recovery from a factory reset using SSH?

    Jack
    Probably yes, IF you could SSH into it. The problem is that SSH is turned off by default. You need the screen to turn it on!

    Hmmm, actually there might be a way. The OS looks for initialization files on external media at boot time, you could probably write a script that modified some internal files such that it turned on SSH, and bypassed the initial setup step. You would have to make sure that this script modified configuration files to the state they would be in after you ran the normal setup.

    So after a factory reset you plugin a USB stick or SD card with the appropriate file and you are up and running without the display.

    The other option is a custom firmware designed for headless operation. I'm not sure if Logitech is going to support that.

    John S.

  10. #30
    Senior Member
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    Now we gotta DUET II (respectively a stripped down Touch) at 3 times the price of a Duet receiver.

    I am asking myself - who is the actual winner in that game?

    I am wondering if Logitech guys are reading this.

    It must be frustrating for these guys - at least for the technicians.
    I mean, this discussion sounds like pretty bad press to me.

    Just to summarize what's being said over here - the message is:

    "Take out everything what makes a Touch a Touch.
    The community will be more than happy about it - at least the ones who
    look for great soundquality.
    There is no way that you can go back once you're done with the tweaks."

    ---------------------------

    Dear Logitech.

    Pleeease - build a DUET II - no frills. Half the size of the old DUET should be possible. You might even skip Wifi (or built in a switch to turn it completely off), since Wifi messes with the sound anyhow. Just focus on sound quality. You might think of an I2S output. (I am not asking for USB on purpose) . And 24/192. Stay with 5V on the DC side. We'll take care on the linear supply.You might consider GBIT ethernet.

    If the quality is good enough you'll be able to sell it at 199$ and probably
    come out with an even better margin than you'll see with the Touch.
    For sure you'll have much less trouble compared to the Touch, with such a product.

    And for sure you'd turn the traditional "High-End-Audio" world upside down, with such a product.

    TX for listening.

    Best regards
    SC


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