Building QuadVol

Step 1: Solder the SMD components

There are some options to do this:

  • Use hot-air soldering
  • Use a SMD tweezer
  • Use a small soldering iron

Test: Connect a current limited power supply (limit: 50mA) to +5V,GND,-5V. The current should be between 10 and 20mA.

Step 2: Solder all resistors and the optocouplers

Now you can start to solder the resistors and the optocouplers and the control connector. Do not solder the capacitors now! It makes the debugging easier if the capacitors are not in place. It is also easier to fix solder problems at the SMD circuits without the capacitors.

Test 1: Connect a current limited power supply (limit: 50mA) to +5V,GND,-5V. The current should still be between 10 and 20mA

Test 2: Connect 5V to each of the optocoupler inputs (pin 1/2, 3/4, 5/6 of the control connector). The current drawn should be about 15mA.

Step 3: Solder the connectors and capacitors

Now solder the electrolytic and the film capacitors. No new problems are expected now.

The circuit should now look like this:
quadvol-finished

Test 1: Connect a current limited power supply (limit: 50mA) to +5V,GND,-5V. The current should be about 15mA.

Test 2: Connect 5V to each of the optocoupler inputs (pin 1/2, 3/4, 5/6 of the control connector). The current drawn should be about 15mA.

 Step 4: Final tests

Now you can connect a real audio source. If you have an oscilloscope, use this for the first tests. You do not have a signal generator? Use an MP3 file from your computer or a cheap MP3 player on the input. This helps to see if everything is working correctly.

6 thoughts on “Building QuadVol

  1. Andreas

    Hi,
    i build two quad-volume…but both dont work :(…If i connect the device it is muted? I connect for testing a headphone output with 1V max output – is that ok? The OPA seems ok, but how i can test the pga?

    Reply
  2. Andreas

    I have only a DPS5315 Power-Supply and can’t start both voltages. If i connect first Ground, than +5 and than -5 can i damage the OPA or PGA?

    Reply
  3. Daniel Post author

    On startup the device is always muted. You have to set a volume first. How do you do this?
    You cannot connect a headphone directly, because the PGA is a line-level output device that is not designed to drive a low-resistance load like a headphone directly. You need an additional headphone amplifier to connect a headphone.
    Powering up the two voltages sequentially is not optimal, but should be no problem for the ICs.

    Reply
    1. Andreas

      Sorry, i use the Headphone as source. The Output goes to an Oszilloskop. The volume is set with a connected ardruino. By your example code.

      Reply
  4. Daniel Post author

    Looks like a software problem. Check the signals on pin 13 and 15 of the PGA4311. There must be exactly 4 bytes transferred from the Arduino to the PGA. The demo code should give you an idea, but you must be sure, that you output the right polarity and the correct data.

    Reply
  5. Charlie

    Your QuadVol PCB would be perfect for a project that I am doing with active loudspeakers. I would need a few of the PCBs, maybe 4 or 6 of them. But I noticed that they are out of stock. Can I order some through you? If you are not planning to sell more, please contact me about other options. I do not want to have to redevelop this board myself. Thanks!

    Reply

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