Hi, I'm new here - forgive me if this has been covered before, and please point me to the right thread. A search on "LA3A" has just brought up a single hit with a short mention. I guess most people that go for the electroluminiscent type of opto compressors go straight for the LA2A - the step from using high voltage for the opto to also using high voltage for tubes isn't that big probably.
Anyway, I've made some experiments with a night light recently, and I plan to go for a transistor version a la LA3A, where a step up transformer is needed to drive the electroluminiscent foil.
So my question is: Does anybody have data for the original transformer? (A tapped inductor, actually)
So far, I've just made experiments with a 1W rated 100V ELA speaker transformer - no way to drive the capacitance of the foil with a flat frequency response.
And last night I've tried a O.E.P. Microphone transformer.
1+1:6.45+6.45, 150R primary impedance parallel wired,
secondary wired in series to get ca. 1:12 step up ratio.
The catch is that these transformers are really low power
(100mW @ 300Hz, 1mW (!) @ 30Hz), so it's probably the worst abuseto use them in a circuit like that.
However, it works remarkable well at high frequencies,
and just the low end has seriously distorted waveforms. (The latter
was to be expected.) But the night light glows just fine, and
distortion in the CV path may not be all that important.
I just fear I might destroy the little transformer.
Also, I have no idea what the step up ratio of the original transformer is.
The driver circuit is clever, as it has two feedback paths, pre and
post xformer, so a relative wide range of winding ratios maight be used without much altered closed loop gain. (?)
Anyway, knowing the original winding ratio (and power rating or core
size) would be nice.
Best Regards,
JH.
Anyway, I've made some experiments with a night light recently, and I plan to go for a transistor version a la LA3A, where a step up transformer is needed to drive the electroluminiscent foil.
So my question is: Does anybody have data for the original transformer? (A tapped inductor, actually)
So far, I've just made experiments with a 1W rated 100V ELA speaker transformer - no way to drive the capacitance of the foil with a flat frequency response.
And last night I've tried a O.E.P. Microphone transformer.
1+1:6.45+6.45, 150R primary impedance parallel wired,
secondary wired in series to get ca. 1:12 step up ratio.
The catch is that these transformers are really low power
(100mW @ 300Hz, 1mW (!) @ 30Hz), so it's probably the worst abuseto use them in a circuit like that.
However, it works remarkable well at high frequencies,
and just the low end has seriously distorted waveforms. (The latter
was to be expected.) But the night light glows just fine, and
distortion in the CV path may not be all that important.
I just fear I might destroy the little transformer.
Also, I have no idea what the step up ratio of the original transformer is.
The driver circuit is clever, as it has two feedback paths, pre and
post xformer, so a relative wide range of winding ratios maight be used without much altered closed loop gain. (?)
Anyway, knowing the original winding ratio (and power rating or core
size) would be nice.
Best Regards,
JH.