impedance switch

[rbc3]

I'm thinking about installing an impedance switch in my Paramount.  I saw an old thread where Paul (I think) posted a circuit diagram for installing one, but the image isn't in the thread anymore.  Can someone repost it?  Also can someone recommend a 2-pole 3-position switch that will work?

Thank you,
Robert

[Paul Birkeland]

Finding this image was pretty tough!  (PJ sent it to my on a prior e-mail account, so I had to go digging through the internet to grab it)

Do note that this will only work with the Paramount output transformer (Not the SEX, Stereomour, Mainline, etc.)

We had to buy several thousand 4P3T rotary switches for our kits to get what we wanted, I'm sure we could put together a little parts order for you. 

-PB

[Paul Joppa]

But the OP said Paramour.

Which version? What output transformer? There have been quite a few of them ...

[rbc3]

Sorry I mis-typed.  I have a pair of Paramount 1.1 300B.  The output transformer is labelled OT-1, but I suspect that is just for build instructions.  How can I ID it?

[Paul Joppa]

OT-1 is our designation for the stock transformer (my design). PB posted the correct circuit above for switching output impedances on that transformer.

[rbc3]

Today I finally got around to wiring up the rotary switches to my 1.1 Paramounts so that I can switch between 4 ohm, 8 ohm, and 16 ohm impedance.  I custom made some brackets and mounted them to the OT-1 output transformers so that the left position is 4 ohm, the middle position is 8 ohm, and the right position is 16 ohm.  Here are the details of how I wired them for anybody else who wants to add this mod using a 4P3T (4 pole 3 position) switch.

The pin connections for each position are:
Position 1 (left)
    A -> 1
    B -> 4
    C -> 7
    D -> 10
Position 2 (middle)
    A -> 2
    B -> 5
    C -> 8
    D -> 11
Position 3 (right)
    A -> 3
    B -> 6
    C -> 9
    D -> 12

Since the impedance switch only needs two poles here is how I wired my switch so that left is 4 ohm, middle is 8 ohm, and right is 16 ohm.

OT-1 terminal 1 -> switch pin B (red wire)
OT-1 terminal 2 -> switch pin 1 (black wire)
OT-1 terminal 3 -> switch pin 5 (red wire)
OT-1 terminal 6 -> switch pin 2 (black wire)
OT-1 terminal 7 -> switch pin 4 (red wire)
OT-1 terminal 8 -> switch pin A (black wire)
switch pin 6 -> switch pin 3 (black wire)

All together it looks like this:
Position 1 - left - 4 ohm
   OT-1 8 -> pin A / pin 1 -> OT-1 2
   OT-1 1 -> pin B / pin 7 -> OT-1 7
Position 2 - middle - 8 ohm
   OT-1 8 -> pin A / pin 2 -> OT-1 6
   OT-1 1 -> pin B / pin 5 -> OT-1 3
Position 1 - right - 16 ohm
   OT-1 8 -> pin A / pin 3 -> pin 6
   OT-1 1 -> pin B / pin 6 -> pin 3
 
Here are some picks:
https://www.dropbox.com/s/3c1ch25rsgtxjpr/20150913_142632_HDR.jpg?dl=0
https://www.dropbox.com/s/d36mzl0vxrwy7rk/20150913_142649_HDR.jpg?dl=0