EL Panel autotransformer vs standard step-up?
- Thread starter jwhmca
- Start date
Help Support GroupDIY Audio Forum:
Auto-transformers are smaller-cheaper. The primary winding current is not lost but flows in the secondary so the magnetic flux only supplies the additional secondary power, while the secondary voltage rides on top of the primary voltage.
Of course you give up, isolation.
JR
Of course you give up, isolation.
JR
Smaller/cheaper.... but there's, what, a 1:4 step-up? ATs are great for 90%-110% ratios (size is 1/10th), even 1:2 ratios (size is half). Much over that the difference is minor.
Isolation... but the EL panel naturally "floats" and you won't be putting finger on it.
Knowing that there is no isolation, the transformer designer can skip inter-winding insulation, even interleave all turns, for best high frequency extension. In an LA-3 this seems moot: we seldom limit on >>2KHz overtones (listener's ears would burn even before the tape/MP3 overloaded).
I would guess the original used an AT because they had something suitable on hand, or the custom design was a penny cheaper as an AT. I'd figure it "unimportant" in a DIY build.
Note that any 2-winding transformer can be connected as an autotransformer, though with a different ratio. (600:10K 1:4 2-winding becomes a 1:5 or 1:3.)
Isolation... but the EL panel naturally "floats" and you won't be putting finger on it.
Knowing that there is no isolation, the transformer designer can skip inter-winding insulation, even interleave all turns, for best high frequency extension. In an LA-3 this seems moot: we seldom limit on >>2KHz overtones (listener's ears would burn even before the tape/MP3 overloaded).
I would guess the original used an AT because they had something suitable on hand, or the custom design was a penny cheaper as an AT. I'd figure it "unimportant" in a DIY build.
Note that any 2-winding transformer can be connected as an autotransformer, though with a different ratio. (600:10K 1:4 2-winding becomes a 1:5 or 1:3.)
