Hi everyone,

I'm Antonio from Italy and I'm quite new to this foru and electronics in general, so please forgive me if I'm making some basic mistakes.

I'm converting an old, non-working Commodore 1541 5.25" floppy drive into a self-contained audio player.

Inside it I have installed:
-a Pioneer IDE CD/DVD-ROM drive, used to play audio CDs;
-a small IDE CD-ROM audio controller with display and remote control;
-a TPA3118 mono Class-D amplifier;
-a small Bluetooth audio receiver;
-a 3.5 mm AUX input;
-a 3-position source selector to choose between CD / Bluetooth / AUX;
-an internal loudspeaker.

Everything is powered from a single switching PSU originally intended for an external hard disk. It provides:
+12 V / 2 A
+5 V / 2 A
common GND

The CD-ROM uses both 12 V and 5 V. The amplifier is powered from 12 V, while the controller and Bluetooth board use 5 V.

I have attached some pictures of the components and a hand-drawn diagram of my current power wiring.

The problem
Everything works, but I have significant noise problems.
There are three situations that may help identify the problem:

1. AUX input selected with nothing connected
If I select AUX while there is no cable/source connected to the 3.5 mm jack, I get a very loud hum/noise from the speaker.
When a cable/source is connected, the noise disappears or is greatly reduced.

2. Noise when the CD-ROM is running
When the CD-ROM motor starts spinning or is reading a disc, I can clearly hear interference/noise through the speaker.
This happens even when another audio source is selected, for example Bluetooth or AUX.

3. Noise even when no input is running to the amplifier, I can still hear some noise from the speaker.

I'm very new to electronics and I don't own or know how to use an oscilloscope, so I'm having difficulty understanding where the noise is coming from.

I fear I may simply have made some basic mistake in the way I connected the power supplies, grounds or audio signals.

Could someone have a look at my wiring diagram and suggest how I should troubleshoot this?

If necessary, I can also draw a more detailed schematic showing exactly how the audio connections and the 3-position source selector are wired.

Thanks in advance for your help!
Antonio
Attachments

 

"NOISE" is quite a vague description ofan unwanted signal. HUM, BUZZ, and HISS are descriptive terms thatpoint towards sources. xz