mystery power

i posted the following letter to dana at m-l. perhaps members have come across this before?

hi dana
sorry to be such a nuisance, but i am sure you can clear up this mystery!
in my quest to find the reason for the slight unbalance in the two sl-3's, i disconnected the bass speakers with amp output to electrostatics only, and to my amazement found the the two electrostatics happily kept on playing with the 230v power plug removed!!
little difference in sound with power plug in or out. i use a 115w naim transistor power amp with dc protection.

regards
leon

Hola Leon..this is normal. Usually they can sing without the electricity for 5 minutes...remember that the panel acts like a big capacitor, and when you plug them into the mains AC, what happens is a woofer singing first, then, in less to one second, the panels starts to sing. This is because they were out of charge. If you unplug them, depending of the musical material, they can last over 10 minutes or more...but you can listen this after 1 minute, they start to loose SPL and the highs too. This shows to you that the PSU is working on both speakers.

hi roberto
thanks for your response, my thoughts exactly except that they continue playing for hours. all i can think is ac sound leakage from the music sense circuit to the eht transformer which then powers the walton-cockcroft eht circuit.
what i did find on closer inspection is that there is little difference in volume with power plug in or out at low volumes, but at high volumes there is an appreciable difference indicating, as you say, that the eht supply is working.
my next step is to give the low volume diaphraghm a good shower .
regards
leon

Its impossible to work, even with a leak, for hours. From where the PSU is going to get the energy for keeping the panels charged? But depending of the type of the music material, they could last some time, but I doubt hours.
Happy listening!

roberto said:

Its impossible to work, even with a leak, for hours. From where the PSU is going to get the energy for keeping the panels charged? But depending of the type of the music material, they could last some time, but I doubt hours.
Happy listening!

Click to expand...

The electrostatic charge does not 'power' the speaker, it just provides the attraction and repulsion potential for the audio signal, in much the same way the magnet does not power a normal speaker, it also just provides the attractive and repulsive forces. If there was no leakage current, the speakers would stay charged indefinitely, much like the magnet does. There are slight leakage currents for the high voltage, however, so the speakers charge will slowly bleed off. It's not only the charge on the panel itself that has to be drained, but also the charge on all the orage high voltage capacitors in the high voltage multiplier circuit, which is many times the charge held by the panel, and can indeed last for hours.
Humidity is one of the main sources of high voltage leakage, in Costa Rica, you may only get several minutes of play time, but in a dryer climate, they can go hours. In the cold, dry winter here, mine still play quite well, even after being unplugged overnight (and can still give you a heckuva jolt, if you get across the orange caps).

Peter