ESL auto switch-on bias power supply

[pidigi]

Hi all!

My Monoliths II are always powered and I have quite often to vacuum them. I would like to implement a tweak of the bias power supply in order to have it automatically switching on when music is applied to the speakers (and, of course, OFF after some time, say 10 minutes, after the music ended).
Any suggestion/schematic available?

Thanks!

Paolo

[CharlieM]

I'm not familiar with the Monoliths but I assume their bias supplies plug into a 120v wall outlet. If so, then why not just plug them into one of the switched outlets on the back of your preamp or receiver? That way, they would power on and off via the front panel power switch on your preamp/receiver.

[pidigi]

Hi Charlie,

nice idea, but:

1. my preamp doesn't have any switched outlet (diy preamp, never thought I would need them)
2. each loudspeaker has its own plug, this means I would need two switched outlets
3. two more cables (I'm biamping them, so I already have quite a few) laying on the floor in the living room (if you know how big Monoliths are, you can imagine that waf is already on the borderline )

In any case this is really not a bad idea, except for the last point. But I'm planning on building a mains filter, and a "must have" will be some switched outlets with timers in order to perform automatically the turn on sequence. This will be very appreciated by my beloved one, so maybe it could help in accepting two more cables on the floor!

Thank you for your help!

Ciao

Paolo

[CharlieM]

My hybrid electrostats are bi-amp'd too. Both my bias supplies plug into a common extension cord, which plugs into a single switched outlet on my preamp. Absent an outlet on the preamp, plugging the bias supplies into a switched power strip outlet would work too.

I sounds like you have a great setup with great speakers.

[bolserst]

Charlie's solution is simple and effective. I've used it for years

But, in case you want to try something a little more complicated and want it built into the speaker, you might check out Rod Elliots web page on the subject:
Signal Detecting Auto Power-On Unit

If you are feeling really ambitious, you could try copying the setup Martin Logan used on the SL3 (see attached schematic and pic).
Personally I think it is overly complicated, but it works.

[Fabien Lefebvre]

There exists some (affordable) commercial products that make this possible: power strips with auto switch on.

Example:
Amazon.com: Smart Strip LCG3 Energy Saving Surge Protector with Autoswitching Technology, 10-Outlet: Home Improvement
"Smart" Power Strips: Helping to Stop Idle Current Now! : TreeHugger

I never used such thing but it should correspond to your needs.

[bear]

Probably not a great idea.

ESLs one would think charge up very quickly - but this is not really the case.
...they get most of the way fast... but not all the way...

There can be an audible difference between turn on and a day or so later. I'd keep them on. Besides IF you want to vacuum them, the best thing to do is to turn them off and then SHORT out the cells! That would be both stators to the HV, so that the charge is bled off. That's fast.

So what you may want to do is to devise some electromechanical means by which you can short the cells down in the interface area where the bias supply hooks up. This sort of thing is frequently done in electrostatic air cleaners, where you want to pull out a highly charged cleaner cell and not get zapped. It is just a bit of phosphor bronze (springy) that a plastic button is positioned to cause it to move to a contact or place across the HV and the stator of the cell. You could recycle a suitable contact leaf from a large industrial contactor or relay, or else make the thing rotary, so that you can just use brass or copper to do the job, kind of like a rotary knife switch where there is no spring in the knife part... just the contact end...

So, short out the cells when and if required, don't turn off the bias supply and expect it to bleed down.

_-_-bear

[tyu]

Bear

Probably not a great idea.

ESLs one would think charge up very quickly - but this is not really the case.
...they get most of the way fast... but not all the way...

There can be an audible difference between turn on and a day or so later. I'd keep them on.

Bear thanks for your info on this, All the ML that i have sound much better with the panels left on all the time. But most dont get it,on old ML panels there are spots on the panels that drop out,if the panel is left on for a day or two the dropouts go away,ML makes big money on panels an then when you do get newone thay dont ever get fully charged an dont sound beter than the old ones.
Only good thing to come out of this is you can get some Great deals on ML Then you can redo the panels an you have for the money some of the best ESLs ever.

[pidigi]

Hi Charlie,

thanks four your answer

Originally Posted by CharlieM

My hybrid electrostats are bi-amp'd too. Both my bias supplies plug into a common extension cord, which plugs into a single switched outlet on my preamp. Absent an outlet on the preamp, plugging the bias supplies into a switched power strip outlet would work too.

....still needs to fight with too many cables on the floor...

I sounds like you have a great setup with great speakers.

Charlie, YOU own great speakers! I really like the beam splitter idea!
I've been in ESL DIY several years ago, then I had the chance to have the monoliths for a very good price....

[pidigi]

Originally Posted by bolserst

Charlie's solution is simple and effective. I've used it for years

But, in case you want to try something a little more complicated and want it built into the speaker, you might check out Rod Elliots web page on the subject:
Signal Detecting Auto Power-On Unit

If you are feeling really ambitious, you could try copying the setup Martin Logan used on the SL3 (see attached schematic and pic).
Personally I think it is overly complicated, but it works.

That's great! Thank you very much for the schematic and pictures!!!