Home of the Squeezebox™ & Transporter® network music players.
Page 1 of 2 12 LastLast
Results 1 to 10 of 16
  1. #1

    JustBoom DAC HAT / Amp Reviews?

    Hi Folks,

    I've read a bit about folks creating fairly decent systems using DAC HATs for the rPi. I'm in Canada, and a bit limited on which boards I can get without having to use international shipping, potential duties, and long delivery delays, so I'm looking to use what I can get locally. BuyaPi carries a couple JustBoom boards - I'm looking at the DAC HAT and their AMP, along with an rPi 3B. I could power this from one single power supply which would help keep it simple. I already have an LMS - or might consider setting up a portable one to go with using a WD wifi drive, for example.

    What I'm wondering is whether anyone else has a similar build, and what sort of quality I can expect out of the DAC HAT. It uses the:

    "Burr-Brown / Texas Instruments PCM5122 DAC chip – 384kHz / 32 bit. Please note that due to Linux driver restrictions, max frequency is limited to 192kHz on the Raspberry Pi"

    and I'm wondering whether this is a decent DAC? Also - has anyone used the JustBoom amp? Not looking for extreme hi fidelity, but does it sound reasonable, with the right set of speakers?

    Alternatively, JustBoom has an 'Amp+' that can connect directly to the rPi, I believe without the DAC HAT. Does anyone have any experience with this, and if so, any idea what the difference in sound quality would be like?

    Thanks,
    Brawny

  2. #2
    Senior Member
    Join Date
    Apr 2008
    Location
    Paris, France
    Posts
    2,109
    I have a few amp HATs since a few weeks. I don't know the other products but this one does sound good, and it is really powerful (I use a Mean Well LRS75-24 76W, 24V PSU. 90W or 100W wouldn't have been out of place.) Wrt the DAC, I don't have much high-def files, but evidently it can handle anything I throw at it. I use piCorePlayer, it is absolutely plug and play.

    Some parts of the amp get fairly hot when it runs at high volume in a non-ventilated enclosure, but the parts in question are rated for over 100°C operating temp, so I don't think there is anything to fear. In my early opinion the product is well built and probably worth the money.

    The IR header is unpopulated, a Vishay receiver is included. Soldering required. Justboom sells an accessory IR remote.

    Various GPIOs are available through the amp, I haven't got to that yet.

    There are 3 ways to power the amp: with a 5V PSU powering the Pi (2x3W max in this configuration, AFAIK), with an 8 to 24V PSU powering the amp and backpowering the Pi: via a 5.5/2.1 barrel connector, or via a 2 pole 0.1 inch male header.
    Finding a DC plug is easy but finding the matching connector for the header is more difficult. I've been told by Justboom support the connector is an AMP-TE CST-100 II.
    For my part I've gone the DC barrel route because I use a wire thicker than the max the connector can accommodate.

    Four of these elusive M2.5 standoffs are included with the amp. They are nylon, I've replaced that with brass standoffs for the Pi and the amp. Theoretically heat exchange improves and sensitivity of the wifi antenna degrades due to grounding. I'm not using wifi so I didn't research the subject. If you procure your own standoffs, you'll need 11mm ones.
    (I use M2 standoffs, they are tiny but cheap and available compared to M2.5. Better to use M2 washers too to cover the M2.5 hole.)

    Bonus, a pic of an early form of my build
    HTH
    Name:  IMG_1361.jpg
Views: 569
Size:  183.5 KB
    Last edited by epoch1970; 2017-05-13 at 04:46. Reason: Best standoff size is 11 millimeters, not 12.
    3 SB 3 • Libratone Loop, Zipp Mini • iPeng (iPhone + iPad) • LMS 7.9 (linux) with plugins: CD Player, WaveInput, Triode's BBC iPlayer by bpa • IRBlaster by Gwendesign (Felix) • Server Power Control by Gordon Harris • Smart Mix, Music Walk With Me, What Was That Tune? by Michael Herger • PowerSave by Jason Holtzapple • Song Info, Song Lyrics by Erland Isaksson • AirPlay Bridge by philippe_44 • WeatherTime by Martin Rehfeld • Auto Dim Display, SaverSwitcher, ContextMenu by Peter Watkins.

  3. #3
    Senior Member
    Join Date
    Dec 2008
    Location
    Alexandria, Va USA
    Posts
    165
    Is that a rPi 7" touch screen or another screen?
    2 Duets controllers, 1 X Boom, 1 X Radio
    1 X Receiver + Audioengine A5
    1 X Receiver + Yamaha RX-A2000, Polk M70
    1 X Receiver + Boston MicroSystem CD
    Raspberry Pi 2 B, HiFiBerry Dac+ & Max2play
    Nexus 7 w/ Squeeze Ctrl
    ReadyNAS 516 LMS 7.9

  4. #4
    Senior Member
    Join Date
    Apr 2008
    Location
    Paris, France
    Posts
    2,109
    Quote Originally Posted by mark wollschlager View Post
    Is that a rPi 7" touch screen or another screen?
    Oops. No sorry that is not part of the build, it's an iPad running iPeng.
    This player is meant as a "rugged" package, there is not a single control on it.
    As it's running pCP, powering in it up and down by plugging/removing the mains cable is possible without harm to the machine so I even forego using a switched power receptacle which is much more expensive than a passive, fused one I use here.
    I expected to get the player to netboot but that plan went poof after some reliability testing, so unfortunately there is still an SD in the Pi.
    In the future I might add some way to interact with the machine, but I doubt there will be a screen.

    Then of course, with this much electrical power available anything is possible. This very PSU has a single 24V DC output line, but the model just above (LRS100-24) offers two.
    I've seen this machine briefly peak over 100W DC when playing at +90% volume a particularly dynamic song...
    3 SB 3 • Libratone Loop, Zipp Mini • iPeng (iPhone + iPad) • LMS 7.9 (linux) with plugins: CD Player, WaveInput, Triode's BBC iPlayer by bpa • IRBlaster by Gwendesign (Felix) • Server Power Control by Gordon Harris • Smart Mix, Music Walk With Me, What Was That Tune? by Michael Herger • PowerSave by Jason Holtzapple • Song Info, Song Lyrics by Erland Isaksson • AirPlay Bridge by philippe_44 • WeatherTime by Martin Rehfeld • Auto Dim Display, SaverSwitcher, ContextMenu by Peter Watkins.

  5. #5
    Senior Member Julf's Avatar
    Join Date
    Dec 2010
    Posts
    2,451
    Quote Originally Posted by brawny View Post
    "Burr-Brown / Texas Instruments PCM5122 DAC chip – 384kHz / 32 bit. Please note that due to Linux driver restrictions, max frequency is limited to 192kHz on the Raspberry Pi"
    It is worth noting that the 32-bit floating point format has a resolution of 24 bits, so it provides no improvement over the more common (and more efficient) 24-bit integer format (and in any case, I have not come across any commercial recordings with a dynamic range exceeding 16 bits - vinyl does 12 bit on a good day). There is also not any real evidence of sample rates beyond 96K providing any audible benefit.
    "To try to judge the real from the false will always be hard. In this fast-growing art of 'high fidelity' the quackery will bear a solid gilt edge that will fool many people" - Paul W Klipsch, 1953

  6. #6
    Quote Originally Posted by epoch1970 View Post
    There are 3 ways to power the amp: with a 5V PSU powering the Pi (2x3W max in this configuration, AFAIK), with an 8 to 24V PSU powering the amp and backpowering the Pi: via a 5.5/2.1 barrel connector, or via a 2 pole 0.1 inch male header.
    Finding a DC plug is easy but finding the matching connector for the header is more difficult. I've been told by Justboom support the connector is an AMP-TE CST-100 II.
    For my part I've gone the DC barrel route because I use a wire thicker than the max the connector can accommodate.

    Four of these elusive M2.5 standoffs are included with the amp. They are nylon, I've replaced that with brass standoffs for the Pi and the amp. Theoretically heat exchange improves and sensitivity of the wifi antenna degrades due to grounding. I'm not using wifi so I didn't research the subject. If you procure your own standoffs, you'll need 12mm ones.
    (I use M2 standoffs, they are tiny but cheap and available compared to M2.5.)
    That's a very cool setup! I had visions of putting everything in one of the little pi-sized plastic cases, and using a laptop type power supply, but I like your design a lot too! It makes sense that the amp would get hot if it was driven hard, so a tight fitting plastic case may not be ideal after all. I have a metal box that might work for me - it looks like a metal lunch box, but was a promotional item from a local beer company that came with a 6 pack of tall cans inside, with their logo all over the outside...

    You say you don't use wifi, but in my case I will be. I suspect that putting everything inside a metal case might make for a great faraday cage, so I'd have to use some sort of dongle mounted on the outside of the case, attached by USB cable.

  7. #7
    Quote Originally Posted by Julf View Post
    It is worth noting that the 32-bit floating point format has a resolution of 24 bits, so it provides no improvement over the more common (and more efficient) 24-bit integer format (and in any case, I have not come across any commercial recordings with a dynamic range exceeding 16 bits - vinyl does 12 bit on a good day). There is also not any real evidence of sample rates beyond 96K providing any audible benefit.
    Thanks Julf. I'm not really an audiophile, but wanted to make sure that the DAC provided reasonable conversion. Really, just looking for confirmation that this DAC HAT does a reasonable job, and there aren't any serious shortcomings. I appreciate your input - I'm happy to take advice from folks who know more than I do!

    Brawny

  8. #8
    Junior Member
    Join Date
    May 2017
    Posts
    1
    Hey brawny,

    Aaron from JustBoom here.

    Just wanted to check in and say hi and let you know that if you have any questions or anything we are here to help :-)

    Think you will be pretty pleased with the DAC HAT. We designed them here in the UK and they are made about an hour down the road from us in Hastings so we can easily keep an eye on the quality.

    Thanks

  9. #9
    Senior Member
    Join Date
    Apr 2008
    Location
    Paris, France
    Posts
    2,109
    Quote Originally Posted by brawny View Post
    You say you don't use wifi, but in my case I will be. I suspect that putting everything inside a metal case might make for a great faraday cage, so I'd have to use some sort of dongle mounted on the outside of the case, attached by USB cable.
    I have not researched the topic, simply at a point I had 2 machines in the same area, one naked going wireless and the proto in its box with wifi not yet disabled. The first one was reading something like 75% signal strength, the other 40%.

    However, you can find threads about people trying to kill the wifi signal, and even putting the Pi in a microwave oven (not operating...) isn't enough unless everything is shut very tightly. Small ventilation holes could make a difference, I believe.
    The Pi 3's built-in wifi is IMHO very nice. It's small, it's 'free', and it works reliably. It is certainly worth experimenting how signal strength fares inside your box with cover closed and with cover open... Adding ventilation holes/louvers would probably be a good idea, at least in a domestic environment. This alone could affect reception strength.

    With a metal box and a modular PSU as I am using, you must take care of properly grounding the case/chassis and protecting live wires from direct access. There is real vital danger of electrocution from touching even the outside of the enclosure if things go wrong.
    A large electric connection plastic box would be safer; DIN rail chassis mounts are available for Pi and so are PSUs. I don't think it looks as romantic, but wifi reception would probably be better. I believe a setup like that can be slightly more expensive than using a tin (or wooden) box, but still cheaper than using a large laptop PSU and a separate enclosure for the Pi.

    In any case, I would highly recommend to have the contraption cross-checked by a trained electrician before putting it in operation. Besides, after the audit you can give a sound demo and help the LMS/DIY cause

    BTW. I think you mentioned something like carefully chosen speakers in your OP. I went the big power route because I wanted to use any speakers and cables. I have driven 4 to 8Ω bookshelf speakers and 8Ω floor standing speakers. I lent the device for a while to a pal who connected 4 speakers using common electric cord... I am no audiophile, but given enough current I think this amp is really capable and does sound good with quality audio gear. Not a gadget but a real system.
    Last edited by epoch1970; 2017-05-09 at 00:38.
    3 SB 3 • Libratone Loop, Zipp Mini • iPeng (iPhone + iPad) • LMS 7.9 (linux) with plugins: CD Player, WaveInput, Triode's BBC iPlayer by bpa • IRBlaster by Gwendesign (Felix) • Server Power Control by Gordon Harris • Smart Mix, Music Walk With Me, What Was That Tune? by Michael Herger • PowerSave by Jason Holtzapple • Song Info, Song Lyrics by Erland Isaksson • AirPlay Bridge by philippe_44 • WeatherTime by Martin Rehfeld • Auto Dim Display, SaverSwitcher, ContextMenu by Peter Watkins.

  10. #10
    Quote Originally Posted by JustBoom View Post
    Hey brawny,

    Aaron from JustBoom here.

    Just wanted to check in and say hi and let you know that if you have any questions or anything we are here to help :-)

    Think you will be pretty pleased with the DAC HAT. We designed them here in the UK and they are made about an hour down the road from us in Hastings so we can easily keep an eye on the quality.

    Thanks
    Thanks Aaron! I'm looking forward to receiving my rPi3, DAC HAT and Amp tomorrow. I still need to locate a power supply, a memory card, and give thought to speakers. I may very well have some questions for you - but I'll wait until I've had a chance to look over the documentation, first. I appreciate your offer to assist!

    Cheers!
    Brawny

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •