Spinet 1/4" Line Out MEE Switch

[theseacowexists]

So I've got it down how to build a 1/4" line out from spinet, and how to build a switch for switching between the internal speaker and the line out. Done several of these already. But I want to take this a step further and have a switch that acts as a main/ensemble/echo switch. I was about to just use an on/on/on DP3T switch to do this. Then I got thinking about how the line out needs to have the 8ohm resistor for the amp load. So in the ensemble position, wouldn't the amp see a different load than 8ohms? I don't want to try this until I get some input from the experts here. Is a DP3T even the right switch for this?

[muckelroy]

Study the Leslie 7271 kit schematic. The M-E-E switching is set up in such a way that when in ensemble, your amp would see 2 8 ohm loads in parallel, so be 4 ohms.

It is fine for your M3 amp to be running a 4 ohm load. What's dangerous is running it open for too long, or a very high load.

They are DP3T, but are set up in an unusual way. You'd have to find a DP3T switch that has opposite normally open and normally closed contacts. That can get finnicky if you don't know precisely the right switch to get from the vendor. It's very easy to find a stock 3-wire M-E-E switch. Then, you can construct something resembling the 7271 kit quite easily.

[theseacowexists]

So I guess it is almost as simple as I initially thought. I'll get a DP3T switch and see if it does the trick or not. From your experience, how can you tell if the switch has contacts that match an MEE switch?

I saw another post that suggested just using a typical 3-way guitar pickup selector. A Telecaster switch actually bears a close resemblance to a half moon switch, and maybe this circuit would work too?

[muckelroy]

Yes, a 3 way rotary switch commonly sold for guitars would work, but the only issue is the size and how to mount it in something.

As for compatibility, you only need it to do as follows. (Each position shown, dashes show connection being made, and has two lines. One for one throw, one for the other throw)



MAIN X-X X
.....X X X
ENS. X-X X
.....X X-X
ECHO X X X
.....X X-X


The middle "X" in all of these is connected to the other middle X. Just study the 7271 schematic and it will make more sense.

[enor]

A Telecaster switch actually bears a close resemblance to a half moon switch, and maybe this circuit would work too?

The halfmoon switch _is_ the 3-way telecaster switch.

[theseacowexists]

Here’s the finished product! Thank you for pointing me in the right direction for figuring out how to wire the MEE switch. I fit both the MEE and Leslie switch into one project box. The knob on the front controls the line out volume. One jack on the side is the mono line out, and the other is for the TRS cord to the Dr. Fishsticks Leslie Controller (which is permanently mounted inside my 130). The box has Velcro on the bottom and back sides and is supported by two Velcro’d brackets underneath. When the box is removed, the brackets swivel under the lower manual. The lines from the amp and to the internal speaker are hooked up to the bottom of the box via a molex connector. A strip of Velcro hidden under the percussion box allows the wires to be neatly stowed away when the box is removed. I’ll post my wiring diagram if anyone is interested in copying this design. Thanks again for the help fellas!