What is an "HT" transformer?

[ianderso]

While I've built many 9VDC solid-state projects (think effects for guitar players), I'm starting to test the waters on making some tube-driven devices. I was looking over some old schematics and kept seeing a reference to an "HT" attached to the plates of the tubes (usually ECC83s or similar) in the schems. I know it's a transformer reference, but what, exactly, does the "HT" mean?

Thanks,
IZA

[Papabravo]

Originally posted by ianderso@Apr 26 2006, 11:14 AM
While I've built many 9VDC solid-state projects (think effects for guitar players), I'm starting to test the waters on making some tube-driven devices. I was looking over some old schematics and kept seeing a reference to an "HT" attached to the plates of the tubes (usually ECC83s or similar) in the schems. I know it's a transformer reference, but what, exactly, does the "HT" mean?

Thanks,
IZA

Quoted post

I think it might mean "High Tension". This arcane terminology still shows up in high voltage circuits. It generally takes a step-up transformer to go from 120VAC to a typical +300VDC plate supply.

[windoze killa]

Originally posted by Papabravo@Apr 27 2006, 02:32 AM
I think it might mean "High Tension". This arcane terminology still shows up in high voltage circuits. It generally takes a step-up transformer to go from 120VAC to a typical +300VDC plate supply.

Quoted post

You are correct. HT means High Tension and EHT is Extra High Tension. EHT transformers are generally in the KV range.

HT transformers can have an O/P anywhere from about 100V to about 1KV. Some are multi tapped to provide voltages for the screen grid and supressor grid as well as the plate supply.