I purchased this holiday card sound recording module: Link.

It's hooked up to a 0.5W 8Ohm speaker, and the IC is shielded from the outside world, so I really only have access to the outputs to speaker positive and negative. The sound is pretty poor, and it crackles at higher volume (not sure if it's because of mic being poor as well).

I have one of these HeadRush Pop-up speakers. Sound is pretty good, not sure of specs of speaker but back of it says "A K 7I14" and it's for sure better than the recording module (which is made of a piece plastic and a magnet).

I have access to L/R/GND here, as well as output of its amplifier stage to speakers (positive/negative).

What I want to do is hook up the output of the recording module, over to the L/R/GND of the HeadRush speaker (L/R connected to positive, GND connected to negative), so that I can record at a lower volume and avoid crackles but still play recording at a higher volume. I only need about 10 seconds of recording that's not horrible or even stereo.

Is this feasible? Or is there a better way of chaining? Or should I not do this at all?


2 Answers 2


Yes. you can do that so long as it's an 8 Ohm dynamic speaker and not something weird like an electrostatic or a piezo. The way you have described the connection is correct. If you happen to get a lot of distortion when you do this, it means that it was being driven by a class D amplifier. Solve that by adding a 0.5W 8 Ohm resistor in parallel (your new amp will have to do way more work if this is the case, but that shouldn't be untenable).

  • \$\begingroup\$ The 8Ohm resistor should be in parallel with which component? I'm assuming parallel with the holiday card output, as to reduce too much power going to the HeadRush input. \$\endgroup\$
    – PGT
    Feb 17, 2016 at 18:37
  • \$\begingroup\$ @PGT yes, you're using the resistor to mimic the speaker because class D filters (this is actually a valid reason). \$\endgroup\$
    – Dave
    Feb 18, 2016 at 6:04

Class D audio outputs should be properly terminated like Dave said .It would also be good to filter out the switching frequency to stop it playing havoc with the rest of your chain.A RC filter with a cut frequency of 20KHz would be cheap insurance.I think you should attenuate the speaker Audio by say 10 to 1 to avoid the possibility of amplifier overload .If you have ground loops which i dont think you will have then an Audio isolation transformer is called for .They are small due to the low power needed and at low power sound fine .


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