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  1. #51
    Senior Member Pascal Hibon's Avatar
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    Quote Originally Posted by wtnh View Post
    Inspired by Pascal's designs from last year, I got around to finishing a similar unit. Originally, I was going to put the power supply in the same box as the player, but things got too cramped. So I built a separate box for the linear power supply.

    The player consists of a Raspberry Pi 3B, official Raspberry Pi touchscreen, Allo Boss DAC and an Allo I2S isolator.

    Finished unit looks like this:

    Attachment 25300

    Since I had room in the power supply chassis, I decided to add batteries for the I2S isolator and the DAC. This required a switching relay to connect the LiPo cells in parallel (for charging) and in series for running the DAC. The toroid is a 25VA dual 9 volt secondary unit connected to a dual LT1083 linear regulator, outputting 5 volts for the Pi and 7 volts for the charging circuits. The batteries will run the DAC for about 20 hours - but go into charge mode when I power off the Pi:

    Attachment 25301

    Here are the two units side by side:

    Attachment 25302

    Here is a closeup of the Pi stack. The Pi is on the bottom, the I2S isolator is in the middle, and the Boss is on the top.

    Attachment 25303

    How does it sound? To my ears, pretty darn good, particularly on hi-rez tracks like 24-bit downloads from HD Tracks. On batteries, it is dead silent (ear to speaker, max gain). I will probably upgrade to the new Boss DAC sometime soon sonce most reviewers find it sounding even better.

    Thanks to Pascal for the design ideas.

    Whit
    Wow, great work Whit!
    Glad to have inspired you.

    The switching of the batteries, does it happen automatically (by means of a GPIO pin acting on power ON / OFF)?
    Cambridge Audio 851D-S -> Focal MP1200 -> Focal Electra 1028 Be
    1 x SB Boom, 1 x SB Radio, 1 x SB Touch and 2 x RPI 2B
    1 x SB3 and 1 x SB Touch in storage
    ReadyNAS NVX running LMS 7.9.0.
    iPeng on iPhone, SqueezePad & iPeng on iPad.
    http://www.last.fm/user/phibon

  2. #52

    Still a work in progress :-)

    Quote Originally Posted by Pascal Hibon View Post
    Wow, great work Whit!
    Glad to have inspired you.

    The switching of the batteries, does it happen automatically (by means of a GPIO pin acting on power ON / OFF)?
    Not yet - it happens when I kill 5 volts to the Pi via the switch on the right (I try to remember to use the Jivelight gui to shut down PiCorePlayer first). With 5 volts off, the relay de-energizes and puts the batteries in parallel charging mode. The charging circuit is still on.

    The switch on the left gives me the option of either running on battery or +7 volts to the isolator and DAC - this is just in case the batteries have discharged and I feel like listening anyway. However, the battery-only functionality is so good (20+ hours) that I may simplify the supply and just eliminate the left switch. I would then only need a single 5 volt supply.

    Adding a power "kill" relay driven off gpio would be a logical next step - but I would still need a "restart" switch to bring the system back up.

    Beyond that, it would be interesting to add automatic charging. I may get fancy and have two sets of batteries - one set charging while the other supplies the DAC with auto switchover when the active one dies.

    Cheers

  3. #53
    Senior Member Pascal Hibon's Avatar
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    Quote Originally Posted by wtnh View Post

    Adding a power "kill" relay driven off gpio would be a logical next step - but I would still need a "restart" switch to bring the system back up.

    Cheers
    Not necessary, the Jivelite GPIO off becomes your "power button". It triggers the charging relay and you can have you display blacked out by the screensaver (when off = display off). Your PI is still running and powered but it looks like it is switched off. When pressing the power button, the gpio will trigger the relay to put the batteries out of charging mode.
    You might need a bit of changes in the way this is all wired up: for this to work it is important that the I2C isolater stays powered as well, even when the batteries are in charging mode. But that is probably a matter of a few additional diodes (note that I don't know how things are currently wired up).
    Cambridge Audio 851D-S -> Focal MP1200 -> Focal Electra 1028 Be
    1 x SB Boom, 1 x SB Radio, 1 x SB Touch and 2 x RPI 2B
    1 x SB3 and 1 x SB Touch in storage
    ReadyNAS NVX running LMS 7.9.0.
    iPeng on iPhone, SqueezePad & iPeng on iPad.
    http://www.last.fm/user/phibon

  4. #54
    Quote Originally Posted by Pascal Hibon View Post
    Not necessary, the Jivelite GPIO off becomes your "power button". It triggers the charging relay and you can have you display blacked out by the screensaver (when off = display off). Your PI is still running and powered but it looks like it is switched off. When pressing the power button, the gpio will trigger the relay to put the batteries out of charging mode.
    You might need a bit of changes in the way this is all wired up: for this to work it is important that the I2C isolater stays powered as well, even when the batteries are in charging mode. But that is probably a matter of a few additional diodes (note that I don't know how things are currently wired up).
    That's a great idea, Pascal. I do recall seeing some relay scripts in this forum for power control. I'll have to look into the practical aspects of doing this. One small issue is that the GPIO pins are covered up by the isolator - but a few are passed onto the DAC. And the Boss DAC exposes a few of these on the Allo Volt header which I don't use, so I will need to investigate if one of them could be used. Alternatively, I could break apart the stack and connect the isolator to the Pi with a ribbon cable and a gpio breakout to keep things tidy. Also - I want to keep strict galvanic isolation between the Pi and the DAC, so may need an addtional relay to keep the isolator powered (currently I use a DPDT switch to do this). If the isolator is off (and therefore the DAC) does this mess up Jivelite? Easy to test.

    If I manage to get this to work - I'll post some details - maybe a schematic others may find useful.

    Whit
    Last edited by wtnh; 2018-07-14 at 07:40.

  5. #55
    Senior Member Pascal Hibon's Avatar
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    Quote Originally Posted by wtnh View Post
    If the isolator is off (and therefore the DAC) does this mess up Jivelite? Easy to test.
    I suppose it would mess up the jivelite and or picoreplayer setup since it would loose its audio interface when the isolator is switched off.
    But yes, that's easy to test.
    Good luck (looking forward to see the results).
    Cambridge Audio 851D-S -> Focal MP1200 -> Focal Electra 1028 Be
    1 x SB Boom, 1 x SB Radio, 1 x SB Touch and 2 x RPI 2B
    1 x SB3 and 1 x SB Touch in storage
    ReadyNAS NVX running LMS 7.9.0.
    iPeng on iPhone, SqueezePad & iPeng on iPad.
    http://www.last.fm/user/phibon

  6. #56
    Quote Originally Posted by Pascal Hibon View Post
    I suppose it would mess up the jivelite and or picoreplayer setup since it would loose its audio interface when the isolator is switched off.
    But yes, that's easy to test.
    Good luck (looking forward to see the results).
    A quick test confirmed that powering off the I2S isolator and DAC did indeed mess things up.

    I used the power off button in Jivelite and then pulled the plug on the isolator and DAC. Plugging the power to the isolator and DAC back in and then using Jivelite to "power on" resulted in picoreplayer losing connection to the DAC (even though the interface looked OK - just no sound), so it looks like I will need to accomodate that in my re-design. This means another relay.

    The good news is that this gives me the motivation to re-do the power supply and get rid of the eBay (i.e. China-sourced) regulator board which I never really cared for, and swap in a lower voltage toroid with Schottky rectifiers and a bigger filter cap, plus a fixed regulator. This will make the supply more efficient and reduce heat dissipation, which right now is higher than I like.

    The bad news is I need to order more parts :-(.

    Whit

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