Maximum stand-off voltage of WSM/XSM series

Posted: 5 months ago Quote #861
I'm looking into building a single-ended amplifier that will need about 900 volts of plate voltage (a VT327A - electrically similar to a 100TH).  The current thought is to use a CXS25-10K.

It would appear that the CXSE series can be safely run up to 600 VDC, 350 VAC - a spec that does not seem to be in the transformer information, but I was able to find elsewhere in this forum.

(I do note that at the 10k-8 ohm ratio, 25 watts into 8 ohms implies 500 VAC RMS - is this actually above the rating, or is the 350 VAC a voltage rating between windings/the case?)

The "solution" would seem to be to have a bipolar supply for the amplifier - +/- 450 volts about the chassis to keep the inter-winding and winding-to-core voltage to a reasonable level.

In doing this, it will be necessary to have a coupling transformer somewhere along the way - perhaps a WSM/XSM - to electrically isolate the input stage (which would have its signal ground at -450 volts or so) from the rest of the world.

Are the ratings of the WSM/XSM sufficient for this voltage, and if not, is there another recommendation?


Posted: 5 months ago Quote #862
What determines the maximum volt of a transformer from winding to winding it really the breakdown voltage of the wire coating. On all of our CXSE we use heavy coated wire. This give a 1000V breakdown voltage between the windings.

The WSM and XSM use a wire with a thinner coating. Their breakdown is about 500V.
Brian Weston
Tech Support
EDCOR Electronics Corporation
Posted: 5 months ago Quote #863
Thanks for the reply - that is valuable information.

To expand my understanding of options, what would be the maximum suggested DC current for WSM and XSM if used as an interstage (plate-to-grid) coupling/matching transformer and still (reasonably) minimize issues with saturation, distortion and frequency response?  Should one even consider using one of these transformers this way?

My primary interest would be a single-ended (triode) driver stage (say half of a 6SN7) but knowing similar numbers for differential (e.g. push-pull) would be informative as well.

(Since the tolerated flux/current could vary depending on specs, let's assume a 10k winding.)

Posted: 5 months ago Quote #864
The maximum DC current would be 10mA. They are not gapped for DC current, but we do have many costumers using them as interstage transformers.
Brian Weston
Tech Support
EDCOR Electronics Corporation
Posted: 5 months ago Quote #865

Please consider including this sort of information (stand-off voltage, DC current, general comments about proper impedance termination, etc.)in either the product data sheet itself and/or in general information about the product or product line - perhaps via a linked "FAQ" about such info that gets asked/answered in the forum that could provide a single-point reference (e.g. only one document for you to update) on such things.

Again, thank you for your willingness to answer questions and provide this useful information!