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I'm looking for a bluetooth receiver board to connect to the Tape In of my 60s stereo record player console. We've used our Android phones with a 1/8" to RCA Y cable into the Tape In, and it works great and plays at a similar volume to the other inputs (radio, phono) when the phone volume is all the way up. I've been through 3 cheap bluetooth reciever boards (THIS, THIS, and THIS), and they are all much quieter (by about half) than the other inputs, which leads to deafening sound if you flip to radio without remembering to turn it down.

I tried a 5W amplified version of the board (THIS), and even if I turn it way down, the scratchy buzzing noise over top of the music is extremely loud and awful.

I seem to understand that the headphone out of my phone is a higher level than the line level being provided by these boards. I'm happy to keep trying other devices to see if one is louder, but it looks as if they are all going to provide a line level that is too low. I'm also happy to buy/build something to solve this problem, but what would it be? I'm also happy to buy one of those cheap TFT digital oscilloscopes to help diagnose the problem and/or test new hardware options, but I'd need to learn how to use it for that.

Open to all suggestions!

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  • \$\begingroup\$ There is a difference between "line out" and "speaker out." I assume most converters are going to put out an unamplified line out, and it seems the input on your stereo is expecting it to be amplified. Using a cell phone helps prove that, since that's amplified. This is just a guess, so a comment. "amplified bluetooth receiver" may be the thing you're looking for. \$\endgroup\$ Mar 26, 2021 at 20:51
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    \$\begingroup\$ The 5W amplifier is completely wrong product, it is an amplifier that is meant to drive a speaker, with a D-class full bridge, which is completely unsuitable for connecting to a line input. What you need is simply an op-amp that amplifies the audio by say a factor of two. \$\endgroup\$
    – Justme
    Mar 26, 2021 at 21:47

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Justme's mention of an op-amp was the keyword I needed. Google informed me that "op-amps" are often used for headphone amplifiers. I found a board-based one with a volume pot built in HERE, and put it between the bluetooth board's line out and the console's tape in. Adjusted the volume to match other inputs wonderfully.

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  • \$\begingroup\$ There are multiple hobbyists and audiophile headphone amps available that would work nicely and may provide a better quality sound. If you ever want to dable in making your own, Google cmoy amp. Or line level amplifiers or "pre-amps" for normal line out/in usage. The one you got is generic so works too \$\endgroup\$
    – Passerby
    Apr 2, 2021 at 16:38
  • \$\begingroup\$ I do appear to have some strange noise artifacts that I hear when no music is playing, particularly when I first turn on the console. Is there some power isolation or something I should be adding to help with this? \$\endgroup\$
    – Eric
    Jul 23, 2021 at 2:37

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