Fosi Audio BT20A Bluetooth 5.0 Stereo Audio 2 Channel Amplif...

Unlike other posters for this product, I did NOT use the FOSI BT20A as my primary amp. Instead, I used it to wirelessly connect my old circa 1979 2226B Marantz amplifier to my old 1985 JBL 4312 speakers.To do this, I also bought a Bluetooth transmitter/receiver dongle which I attached, in TRANSMITTER mode, directly to my Marantz speaker outputs.I then hooked up my JBL speakers to the FOSI unit using banana plug adapters. The FOSI will accept either banana plugs or bare wire. My speakers are bare wire, but I opted for the plug adapters as they seemed the cleaner alternative. The FOSI amp is a Bluetooth RECEIVER, so whatever gets transmitted from the dongle attached to my Marantz in TRANSMITTER mode will be caught by the FOSI RECEIVER amp and pumped thru the speakers. And there’s your wireless connectivity!I have had this setup for only about a week now, and I’m still experimenting with different settings.The first thing I discovered is, that if you’re using another amp as the primary amp (the Marantz, in my case), you had better turn the bass and treble controls on the FOSI down to a bare minimum (or altogether off), otherwise you will have a tremendous amount of distortion, especially in the midrange. I’m using the Marantz amp to control the bass/midrange/treble, and the tone boost the FOSI provides can be painful. If, like me, you’re using the FOSI to resurrect an old stereo system, I would recommend youstart with the FOSI bass and treble at zero (6 o’clock) and the volume at a quarter (9 o’clock) and adjust both your primary amp as well as the FOSI from there. Currently, I have my FOSI bass and treble at just a bit over the minimum, while its volume is at the halfway mark (12 o’clock). I may slightly readjust, but this is working well for me now.The FOSI sound quality is somewhat on the bassy side. Its volume is tricky. I suspect it’s 50 watts per channel, totaling to the advertised 100, but that’s still a lot! Midrange can be tricky, especially at louder volumes, where you may get a blaring distortion, unless you really play with bass and treble. This is why I recommend fine tuning the tone and volume controls on both your old amp and the FOSI, if you’re planning on using it to make an old stereo system Bluetooth. Small increments/decrements on either end will produce noticeable changes.I primarily use my stereo to play old vinyl, and this is where I’m still struggling with the sound.I have also adapted my old Marantz to be a Bluetooth receiver (with a separate receiver dongle) and play my phone thru it. The Marantz captures my phone tunes from the receiver dongle, transmits them thru the transmitter dongle to the FOSI receiver. The sound quality is admittedly better in 100% digital format.The FOSI is only about 12-14 feet away from the Marantz primary amp, so I cannot speak on range. However, my amp and its components are in a closed cabinet and there is a wall between it and the FOSI. I have not had any issues with connectivity. Sound is clean and uninterrupted no matter what else we have running.Bluetooth connection is a snap between my transmitter dongle and the FOSI, especially if the transmitter is ONLY used with the FOSI, as in my case. Once first contact is made. both units will remember their last connection.Hope this helps if you’re trying to bring new life to your OLD stereo system!