Big Pop when toggle switch engaged

[d_rom]

Not exactly a stopmbox, but goes to the heart of DIY music electronics:

I have a homemade rotating speaker setup (I call it a Frankenleslie) that has been giving me loud distracting pops when engaged.  I need to find a fix for this before an important gig on Saturday!

Here's the wiring:
Wall power>toggle switch> either fast or slow leslie motor.

Signal goes from organ>limiter>tube amp>speaker

The thing that gets me is that the signal path is not connected to the toggle switch wiring, except that they share a mylar connector (which does not show a short).  how could this pop be getting to the speaker from my switch?

Please help!  respond here or email pseudonym_23@yahoo.com
Thanks.

[ExpAnonColin]

Eek!  That's terrible for your amp...

Anyways, that can usually be solved by a well placed high value resistor.  Since you're switching to a powered circuit, with the 9v battery, there's a bit of a jump.. pretty common... blah blah blah.....

Someone else be more helpful, please.

[AllyP]

Try the FAQ.....I use it regularly...search for "pop" and you will find your answer there :wink: have fun!!!

[Paul Perry (Frostwave)]

The question is, 1. what causes the 'pop'?
and 2. why is it heard in the amp?
I would guess, spike on the mains that then couples thru to the amp via the mains.
I'm thinking, that maybe the leslie setup could be isolated by a plugboard with a mains supressor in it.
Or the amp. Or both.
I don't think the info at geofex regarding switch popping (excelent though it is!) is in any way relevant to this setup.

[Rodgre]

I have a very similar problem.

I have a modified Leslie that does a similar thing. It is a 122 that's been sawed in half, and is just the bottom rotor, connected to the fast motor. As for audio, it's a straight connection from jack to speaker (I use an external amp.)

The "leslie" effect is created by basically switching the motor on and off by cutting the AC to the circuit. When I do this, I get a pop as well. Again, the audio for the speaker is at least five or six inches away from the motor.

I thought about using an external control like a rhostat that you might use for a speed control for a Dremel on the motor, but I'm afraid to hurt the motor.

Roger

[Mike Burgundy]

Paul's right - this is caused by spikes that are put back onto mains by switching the motor. Old fridges do exactly the same.
filtering/isolating mains (there are "extension cords" that have this built in) should do it.

[gez]

You could keep the leslie on all the time and use a true bypass box.

Just a thought...

[Rodgre]

You could keep the leslie on all the time and use a true bypass box.

Just a thought...

That won't work for my application, as the whole "leslie" experience comes from hearing that rotating speaker ramp up and down.

Roger

[Nasse]

Circuits that can electronically connect your motor on/off exists, but where? I quess you can find some with some searching. Some kind of thyristor and switching at zero-crossing and filtering is probably needed to prevent spikes. Maybe even ready made dimmer or control circuits exist that can drive inductive loads.

[R.G.]

The comments are correct - your problem comes from motor switching spikes, which are getting into your audio path one of three ways.

1. coupled in on the AC power line
2. coupled in on the shared wiring bundles
3. coupled in on ground conductors

The solutions come in two flavors.
1. suppressing the noise transmission into the audio path
2. suppressing the noise at the source.

Solution 2 is better, of course. The simplest way is to control the motors with inductive load rated zero crossing activated solid state relays, and clean up any residuals with filtering on the motors.

Mouser will have the relays.