The Pioneer A-40AE has a line output (RCA) that can be used to connect an active subwoofer. This line-out is the appropriate connection as the amplifier itself does not have a dedicated subwoofer output socket with an integrated low-pass filter. You can therefore connect the subwoofer via the RCA line-out and connect the speakers directly to the speaker terminals. This allows 4 speakers and an active subwoofer to be operated simultaneously, with the subwoofer receiving the signal from the line-out.

With this amplifier you don't need plugs, but an open cable to connect the two components. Here you can find the suitable cable: Oehlbach SP25 (10m, 2.50mm²) The instruction manual explains how to connect the two components, but unfortunately it is only available in English, French and Spanish: https://intl.pioneer-audiovisual.com/manuals/docs/SN29403415_A-40AE_EnFrEs_180528_web.pdf

There could be many reasons for this, but it has to do with the electrical signal being disturbed somewhere. The most plausible cause could be the old cable since it is the connectors that influence the audio signal the most. We strongly recommend using a new cable with gold plated pins like this one for example: Goobay Plus Cinch - Cinch cable (0.75m, Premium, RCA) As the record player also has a 3.5mm output, you could also use the following cable: Goobay Plus 3.5mm plug - RCA cable (1.50m, Premium, 3.5mm jack, RCA) The contacts are very sensitive, especially as they age. If the sleeve has holes and releases parts of the copper inside, you will also have problems. Both situations can cause this effect. The gold contacts conduct the signal much better, so we are convinced that a new cable will solve your problem.