Wiring secondary on Freed (Scully) transformer

Hi all,

I have a Freed transformer that came out of an old Scully's tape machine preamp:



I want to use it to experiment with "color" (see this thread).

I can't find any wiring diagram for it to be wired other than 600 on the secondary (pins 1+5 tied C.T., with legs on 4 and 6). However, I wish to wire the secondary to reflect other impedances, like 150 ohm.

Could I assume the following would give me that?

pins 1 + 4 one leg, pins 5+6 the other leg

Looks like four identical windings.  you can try 1:1, 1:2, 2:2, or 2:1 by using additional windings in series.

For example, if you went in on 2 hi 3 low for a balanced input (3 to signal gnd for unbalanced) and then out 4/5 that’s 1:1.

Same as above except out 4 high, tie 5 to 1, and 6 low you’re 1:2.

A 600 ohm load on 1:2 is reflected as 150 ohms to the primary side (divided by the square of the turns ratio, so 2 squared = 4, 600/4=150).

I think I understand. I think I got it right. I want to use the two windings on each side in series.

I want to go in on 2 high and 8 low with 3 + 7 C.T. tied for 600 ohms in.

Goal is to go 150 out, again with the two windings in series.

Would that not be pins 1 + 4 on the high and pins 5 + 6 on the low?

Similarly, to go 600 out with the two windings in series.

Would that be 4 high and 6 low with 1 + 5 C.T. tied?

If you go series on the primary and parallel on the output you’ll get a step down.

If you go series on both, you get 1:1.

dogears said:

If you go series on the primary and parallel on the output you’ll get a step down.

Click to expand...

So, 1:2? 600:150?

for 600 strap the center taps,  for 150 wire paralegal while observing phase,

if you want some saturation, wire the front as 150  tie 2 and 7, tie 3 and 8

be sure to use both coils as this is a dual coil design,

fazeka said:

So, 1:2? 600:150?

Click to expand...

2:1, but yup

Thanks CJ! Should have just checked with you first! 

CJ said:

for 600 strap the center taps,  for 150 wire paralegal while observing phase,

if you want some saturation, wire the front as 150  tie 2 and 7, tie 3 and 8

be sure to use both coils as this is a dual coil design,

Click to expand...