Edcor customs

I received my custom transformers from Edcor and found that one had the wrong turns ratio and the other had a primary inductance that was too low. Here's a followup: I'm pleased to report that they called me back today and were very cool about the whole matter. They're going to send me replacements as soon as possible and I don't even have to send the "mistakes" back. They're even ordering smaller wire and larger bobbins to be able to wind to the primary inductance I need. I'll report back when I get the replacements.

Everyone makes mistakes, and the mark of a good company is how they rectify those mistakes. The moral of the story here is that when ordering custom components, from anybody, be sure to bench-test before incorporating them into your circuit.

See updated post above.

Can you use the "mistakes" for anything else?
Stephen

Yeah, probably. One was supposed to be 2400:600 (2:1 turns ratio), but what I got was a 4:1 ratio. The unloaded primary L on that one is 63H, so it might be OK for 10K:600 service if the source impedance feeding the primary is low enough.

The other was supposed to be 10K:100K. The turns ratio on that one was correct, but the primary inductance is way too low (12.6H). It might work as a 1K:10K or 600:6K. I gotta test it and see.

These are "EM" series, which means they use the same core as the "WSM" series but have wire leads instead of quick-disconnect terminals. I ordered four of each type.

I think they are trying to do those on an M-6 core, which might explain the low inductance. They will need to wind hecka turns to get the same result as Ni. So your copper loss will go up, but should have clean bass response.

Yeah, their stuff uses M6 29-gauge lams.

By the way, I also bought some of their new PC-mount models. They're really cute! I haven't run tests on them yet.

> was supposed to be 10K:100K

I would not expect that shop to be able to make hi-fi 100K windings. As they say: they don't stock wire fine enough to get a few thousand turns in a winding, and the stray capacitance is going to drive the highs wild. And the low-current inductance will be low: power-core iron doesn't wake-up until fairly high Gauss.

Try specifying a VERY over-sized core. It will improve inductance and wire-fit, and may not add much to the cost.

10K should be practical.

As you learned, they don't dig impedance-ratio, they think in turns-ratio.