Connect with us

Digital music player with a Tivoli Audio Model One

Discussion in 'Audio' started by jespers, Dec 20, 2017.

Scroll to continue with content
  1. jespers

    jespers

    6
    0
    Dec 20, 2017
    Hi everyone,

    I'm very new to DIY electronics and just learning, but enjoying myself so far!
    Currently I'm trying to build a digital music player from a Tivoli Audio Model One FM radio. The loudspeaker is quite good, and the FM radio signal is getting phased out soon where I live.
    The idea for the project is that powering on the player will make the Arduino choose and play tracks from the SD card randomly until turned off again.
    Adjusting the volume using the front knob and a potentiometer may be an improvement later, but for now I'm sticking to just having the system play.

    I've bought these components for the project:
    - Arduino Uno
    - Sparkfun MP3 Shield: https://www.sparkfun.com/products/12660
    - Mono amp to sit between the MP3 shield and the speaker: TPA3110 https://www.ebay.com/itm/TPA3110-1-...l-Audio-Amplifier-Board-DC8-26V-/262451711067
    - Tivoli Audio 4 ohm 5 w speaker: http://herculodge.typepad.com/.a/6a00d8341c6d1b53ef013483f52a21970c-pi (the one on the left)
    - All inside an empty Tivoli Audio Model One case: http://ecx.images-amazon.com/images/I/71X9w4J7BXL._SL1500_.jpg

    I followed this guide when assembling the MP3 shield onto the Arduino: https://learn.sparkfun.com/tutorials/mp3-player-shield-hookup-guide-v15
    Using simple Arduino programming, it is playing well through the jack output to headphones. So far I have powered the Arduino through the USB port.

    Scrolling down to the topic "Output Circuit Details" in the MP3 shield assembly guide, they mention that I should use "AC coupling" when not sending the output to headphones.

    My questions boil down to these:
    - Is "AC coupling" for the MP3 shield relevant in my case?
    - What is the best way to power the Arduino/MP3 shield and the TPA3110 amp simultaniously using the same power source?

    Cheers,
    Jesper
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,669
    2,020
    Nov 17, 2011
    If it's recommended, follow the recommendation. It is only a capacitor in series with the audio output, so no special effort is required.

    Use a power supply with enough output power for both the Arduino and the amplifier. A USB port may not deliver enough power (USB is rated at 500 mA max. only, suficient for 2.5 W, not more).
    Use decoupling capacitors at the power supply input of each module.
    Use a star point connection for wiring the power supply lines both for ground and +5 V. The star point should be at the output of the power supply.
    You may add a ferrite in series with the + 5 V line between power supply and amplifier to minimize switching noise on the power supply. This may or may not be necessary. Try without ferrite first. Do not place any impedance (ferrite, resistor etc.) in the ground wiring.
     
  3. jespers

    jespers

    6
    0
    Dec 20, 2017
    Thanks for your answer, Harald.
    For power supply I'm considering this: https://www.velleman.eu/products/view/?id=360752
    It has dual output, but I'm unsure if this is a good idea in this case. Would a star point connection work together with this?
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    9,669
    2,020
    Nov 17, 2011
    The link leads only to a transformer. You'll need rectifier, filter, regulator ...on top of it.
    I suggest you buy an off the shelf 5 V USB charger rated at 1 A or more. This should supply enough power for your circuit plus it is safe (no mains accessible).
     
  5. Audioguru

    Audioguru

    2,744
    621
    Sep 24, 2016
    The TPA3110D2 datasheet says it can drive one 4 ohm speaker in mono with both its amplifiers paralleled and shows a graph of its maximum output power at different supply voltages and it overheats if its output power is 30W or more when its supply is 17V or more. If an 8 ohm speaker is used then it can be driven to 30W when the supply is 26VDC.

    The Velleman power transformer is 12V-0-12V which is 24V total. When rectified and filtered it will make 32VDC when loaded and maybe 36VDC or more when not heavily loaded which is much too high.

    The little speaker's maximum allowed power is only 5W but the amplifier makes more power when it has its minimum of 8VDC.

    Then the amplifier and the power transformer are both wrong for each other and for the little speaker.
    I agree than a 5VDC power supply will be fine if you find an amplifier that works from only 5V and can drive a 4 ohm speaker.
     
  6. jespers

    jespers

    6
    0
    Dec 20, 2017
  7. Audioguru

    Audioguru

    2,744
    621
    Sep 24, 2016
    The Chinese amplifier has a Chinese IC and its datasheet is written in Chinese. The datasheet shows a graph of its high heating with a 5V supply and an 8 ohm speaker. It also shows high heating with a 3.3V supply and a 4 ohm speaker. The IC's mode can be switched to work in class-AB or in class-D but the ad does not say which mode it is made in and the switch is missing so we do not know its output power into 4 ohms and if it will overheat with a 5V supply.

    You should select a Western amplifier (Texas Instruments have many) that has a detailed datasheet written in English.
     
  8. jespers

    jespers

    6
    0
    Dec 20, 2017
    Thanks, yes it looks like XPT8871 is not well documented.
    Looking at the TI catalog, there is for example the TAS2555: http://www.ti.com/product/tas2555
    but I'm having a hard time finding an assembled board containing it.
    Adafruit has a similar option, although only powering 2.5W, but volume is not very important in this case: https://www.adafruit.com/product/2130
    Can you tell me if I am on the right track?
     
  9. Audioguru

    Audioguru

    2,744
    621
    Sep 24, 2016
    The Texas Instruments amplifier in your link is modern with a class-H voltage boosting feature, so that its max output power is much higher than a normal older amplifier. Its package is so tiny that it has BALLS (!!) instead of pins and will be impossible to solder unless maybe it is soldered in an oven. Ebay, Amazon or Ali might have an assembled Chinese product.

    The Adafruit assembled Chinese amplifier produces a minimum of only 1.8W into 4 ohms with low distortion (typically 2W max). Will that be loud enough? 2.5W is when it is clipping like crazy with LOTS of distortion.
     
  10. jespers

    jespers

    6
    0
    Dec 20, 2017
    Thanks again! Yes so the Adafruit part provides much too few watts for the speaker's needs.
    I have looked into using more than 5V, going up to either 7V or 9V, which the Arduino should handle fine. Then there are more interesting options, like this PAM8610 based board: https://arduinotech.dk/shop/pam8610-2-x-15w-dual-channel-stereo-amplifier-board-12v/ Datasheet here: https://www.diodes.com/assets/Datasheets/PAM8610.pdf
    It's a stereo amplifier, but I would of course use only one channel.
    Would this be a better fit for my project?
     
  11. Audioguru

    Audioguru

    2,744
    621
    Sep 24, 2016
    With a 9V supply, the PAM8610 amplifier will produce 6W into 4 ohms from one channel with fairly low distortion.
    But 6W sounds only a little louder than 2W or 3W. 20W sounds twice as loud as 2W because our sensitivity to loudness is logarithmic. If you play music and the peaks are 6W then the average level will use only about 1W.
     
  12. jespers

    jespers

    6
    0
    Dec 20, 2017
    Ok, so since I am using a 5W speaker, the PAM8610 should be a good fit?
    So when 5W is the speaker's max, then the average level is not going to cause problems, or have I misunderstood your point?
     
  13. Audioguru

    Audioguru

    2,744
    621
    Sep 24, 2016
    If you play acid rock at full blast all the time then your 5W speaker might be damaged with the continuous 12W. 6W at low distortion is 12W at high distortion (clipping like crazy) because all the distortion harmonics add another 6W.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-