Power supply noise in record player output lines

I have a 12 V powered record player which has a regular hum being fed from the power supply . Not having a pioneer amplifier with 12V out to feed the recorder I picked up a spare parts bin one and fed that in . Not sure of the innards but it looks perhaps solid state

If I use a regulated 12V power supply of the old transformer type there is no hum . Using this flattish box type gives the hum . I Want to use it up, but I know nothing of Audio frequency noise .

Would I put a capacitor across the pos & neg or build in some sort of choke filter arrangement? What are typical values for Audio? I can'tafford to use any resistance as the signal is already minimal . There does not seem to be any amplification in the pioneer player itself.

It appears that the power supply you are using is not adequately filtered for the application. That can be taken that you are pulling more current than was originally intended. For instance, if you are pulling 100ma @12v the effective impedance is 120 ohms. A 30 microfarad cap will also have about 120 ohms at 60Hz reducing the ripple by about ½. 60ufd would drop it by ¼ and 300ufd would drop it to a tenth of its current value. So the game becomes one of how much ripple can you tolerate verses how large of a cap you can get your hands on or fit in the box. Warning: make sure the WVDC rating of any cap you select is at least 17 volts or more. Most 12 supplies I deal with have filter caps rated 25WVDC.

Some Wall-Wart power supplies are no more than a transformer (AC output).

Some have a half-wave rectifier, some have a full-wave rectifier, some have a rectifier and a small filter capacitor. (These are DC output, but not regulated)

A few have an electronic regulator, linear or switchmode. Only these are suitable for powering audio projects; none of the others are!