BSR turntable switch makes loud pop

I am using a late '70s era BSR changer in nearly perfect condition. It uses a ceramic cartridge, and is connected via a Lehman Black Cube SE pre-amp. (Yes it's a yardsale item connected to a $700 pre-amp. I am doing this for nostalgia, as the turtable was my grandmother's and I used to play with it often as a child. I had to steal the pre-amp away from my Stanton because the BSR's ceramic cartridge seems to require the special 470 ohm impedance setting.)

My issue is that the turntable makes a very loud pop, of random intensity, when switching off. The randomness of the intensity seems to imply that the pop is caused by the arcing action of the microswitch as it disconnects the motor at a random point in the AC waveform. Hence, a disconnecting at the full 120 volt point means the switch opens with the full current of the motor arcing across. Disconnecting while crossing at 0 volts means the switch opens with the no current arcing across. Use of ferrite chokes on the incoming lines of the pre-amp eliminates the "spike" of the noise, but the dulled pop is still quite loud.

Could this issue be resolved by the use of a zero-switching solid state relay? Basically, I am thinking of re-wiring the unit so that the microswitch carries only a couple milliamps and the the relay would switch the motor off at the zero point every time. What do you think?

Here is the relay I'm talking about:
Digikey part# Z166-ND

(P.S. I am not concerned about the acoustical/ mechanical noises. I am well aware that it's a cheaper machine and makes a good bit of whirring and a loud clunk when it switches itself off.)
I had to steal the pre-amp away from my Stanton because the BSR's ceramic cartridge seems to require the special 470 ohm impedance setting.)

Ceramic cartridge? If memory serves me right a ceramic cartridge does not need a phono preamp. You should be able to connect the cartridge to just a line level input on a preamp.
Try that and see if that helps the popping sound from the switch.

If the popping sound is still heard you can put a snubber circuit around the switch contact. It consists of a capacitor and resistor in series, paralleled across the switch contact.

Post back if it still pops using a line level input on the preamp. Somewhere I have the info for the values for the cap and resistor....

You are correct. Ceramic cartridges do not require a pre-amp. Only magnetic cartridges do.


Thanks for the conformation.

Hooking the Ceramic cartridge up to a phono preamp would really amplify the signal from the cartridge I would think. Enough I would guess to pick up the arc from the power switch when switching it open.
Dear Jea48/Rar1: Could you tell me how ( with out a phono stage ) the cartridge signal is " compensate " for the RIAA de-emphasis eq. used on the recording process?

Regards and enjoy the music,
Usually with ceramics cartridges, which are constant velocity, part of the RIAA response is built-in. The rest comes from a 'ceramic' input that has a resistor/cap combination at its input. If you use a regular AUX input, the EQ will be incorrect.
Dear Atmasphere: So, we need that " ceramic " input: right?, in that case a regular phono stage does not works due that the ceramic cartridge already has part of the RIAA response.

Thank you.

Regards and enjoy the music,