CJ said:
you can make a BH tester with a 100 k resistor and a .1 cap,
use your scope in X-Y mode,
Ok, finally got back to this after being stuck over in g9 transformer land for a while.
I can't seem to get enough current to saturate these things. even on the lowest tap of a Pultec inductor (21mH) there are too many turns. The MPP toroids saturate at around 20dB when driven through a 120 (ish) ohm impedance. If the impedance is any less than that, the inductor just shorts out the driving amp, andy higher than that and it never clips (I can only provide 24 db, even when I run my little amp at 21V+- (chip rating is 18V +-).
I guess I need to test the cores with fewer turns.
But What I did find out so far is IF i compare saturation of cores, to the MPP toroid that is very similar to the pultec toroid, the following cores saturate within 1 dB or so of where the Pultec clone did (20dB through 120 ohm impedance).
These cores produce similar or higher db level saturation point ( but all saturated under 24db on the 21mH tap)
All AL values specified below are as published ( I wound with the actual measured values varied by 10% ).
All of the saturation was measured at 20Hz on the 21mH tap
RM7 core - AL 250 - N48 material
RM8 Core - AL 630 - N48 material
26 x 16 4 slot pot core - H6A3 material - AL400
I think the main thing is to have enough of a gap to raise the saturation point, or a big enough core.
I have also decided that the saturation point doesn't matter for the pultec clones, anything reasonably high is fine though because the levels inside the Pultec are really low, and NEVER see anywhere near 20db, and in the HF section where the inductor is used is behind a relatively high impedance input trafo, and the levels are so beat down that it probably doesnt matter.
I will say however that my tests with HI perm cores (AL 3000, 8000, reused computer motherboard toroids, etc) show that they are not good, and distort at very low levels due to saturation.
I do think however that I am done winding toroids. I am going to use the RM7/RM8 cores, easy to wind.