Electronic – Bluetooth receiver board into 60’s console stereo Tape In

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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!

Best Answer

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.