While various bargain HV supplies have appeared in posts here, anybody have an opinion of the industrial standard brand, EMCO?
http://www.emcohighvoltage.com/pdfs/fseries.pdf
Any thoughts on applicability to ESL bias? Distortion? Any issues with using EMCO centre-tapped modules? Heat? Safety concerns? Buying 'em used on eBay?
Not just speculation, I have a 6kV CT module that seems to work fine with a panel of Dayton-Wright cells.
BTW, testing charging time as influencing loudness. Been running 9 hrs and gaining 2-3db with each doubling of time and still growing.
Thanks.
Ben
http://www.emcohighvoltage.com/pdfs/fseries.pdf
Any thoughts on applicability to ESL bias? Distortion? Any issues with using EMCO centre-tapped modules? Heat? Safety concerns? Buying 'em used on eBay?
Not just speculation, I have a 6kV CT module that seems to work fine with a panel of Dayton-Wright cells.
BTW, testing charging time as influencing loudness. Been running 9 hrs and gaining 2-3db with each doubling of time and still growing.
Thanks.
Ben
Thank for the info.................. bias bias bias....more time an money needs be put into the setup..... to get the best sound out of any ESL....
I feel that I get better sound with a bias tran that can pass more current also not just Volts...like the old stock 121 Acoustat........... an is setup so the use can set the bias.....anytime any room.
I feel that I get better sound with a bias tran that can pass more current also not just Volts...like the old stock 121 Acoustat........... an is setup so the use can set the bias.....anytime any room.
What? Are you saying a HV transformer is better than a doubler-ladder?
DATA: my panel of DW XG8 cells is within 2dB of full charge in 400 minutes. In the air, seems to vary a dB or two with the weather. My home-brew panels of 6 cells each has 40-60 MOhms in series with bias supply and connected at both ends of cell.
Ben
Just from a sound standpoint.................the old Acoustat tran...secdary is at 750AC...............I use these tran in the bias on my ML esl panels....what a diff in sound... runing the same bias v...as the stock ML bias...it not a small change..
looks to me like the bias is not vary important to most esl bilders....look at the $20k soundlabs..this is just one......you an I can buy one of there type bias ..for less than $20.
there a bizz...thay cant pay more than $5ea.....that what I mean...it like it has nothing to do with the sound.....I think one big reasons I don't care for SL sound.....
I know an do work for people that SL esls....but there not in to diy are mods............are I would have tried the diff bias setups in the SL..years back
looks to me like the bias is not vary important to most esl bilders....look at the $20k soundlabs..this is just one......you an I can buy one of there type bias ..for less than $20.
there a bizz...thay cant pay more than $5ea.....that what I mean...it like it has nothing to do with the sound.....I think one big reasons I don't care for SL sound.....
I know an do work for people that SL esls....but there not in to diy are mods............are I would have tried the diff bias setups in the SL..years back
I'm having a lot of trouble making sense of your personalized writing style.
Contrary to your experience is the belief in high resistance diaphragm coatings whose purpose is to keep the charge from migrating/changing except very slowly. Likewise, if only for safety reasons, cells have lots of megOhms between the bias supply and diaphragm, again a big buffer between the bias supply (transformer or ladder or in the case of EMCO oscillator and other bits) and the cells.
Ben
Contrary to your experience is the belief in high resistance diaphragm coatings whose purpose is to keep the charge from migrating/changing except very slowly. Likewise, if only for safety reasons, cells have lots of megOhms between the bias supply and diaphragm, again a big buffer between the bias supply (transformer or ladder or in the case of EMCO oscillator and other bits) and the cells.
Ben
I have used those units for a bias supply - work fine. I went right to manufacturer to purchase and paid way way too much - you can find these on ebay cheap
Many thanks for confirmation.
These units are designed for 1-15v DC input/control voltage which generally results in up to rated output, say 3000v at maybe 1 mA. BUT, as a bias supply, the output draw is tiny and therefore, if you input 15v, you'll get an output substantially larger than the rated expectation (which is also the rated max).
Therefore, you must run a lower input (control) voltage and so as to not exceed the rated output max.
...and keep one hand in your pocket at all times.
Ben
I just slapped together a simple LM317 voltage regulator with a pot to dial in my input voltage to feed the HV unit - then I was able to dial in my bias voltage...
But in all honesty, if you don't need a bias voltage over 3kv, why not just pick up one of these with a LM317 feeding it?
http://www.goldmine-elec-products.com/prodinfo.asp?number=G17350
Works perfect for my makeshift ML CLS 2kv Bias supply (feed 3vdc in) - may not be able to handle the 5kv of a Acoustat...and get rid of that cap across the output - rated at 2k, and not needed for an ESL bias supply.
But in all honesty, if you don't need a bias voltage over 3kv, why not just pick up one of these with a LM317 feeding it?
http://www.goldmine-elec-products.com/prodinfo.asp?number=G17350
Works perfect for my makeshift ML CLS 2kv Bias supply (feed 3vdc in) - may not be able to handle the 5kv of a Acoustat...and get rid of that cap across the output - rated at 2k, and not needed for an ESL bias supply.
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Just to offer my own version of an all together inconceivable bargain device for driving an EMCO module with 1-15vdc:
New LM317 Adjustable Voltage Regulator Step Down Power Supply Module LED Meter | eBay
Add a wall-outlet 22vac transformer and it is just like a bench power supply with a 3-digit voltage read-out! For $10. (OK, I bought 3 for $27 but one had a faulty display, so that's still $13.50.)
Absolutely inconceivable bargain.
Ben
New LM317 Adjustable Voltage Regulator Step Down Power Supply Module LED Meter | eBay
Add a wall-outlet 22vac transformer and it is just like a bench power supply with a 3-digit voltage read-out! For $10. (OK, I bought 3 for $27 but one had a faulty display, so that's still $13.50.)
Absolutely inconceivable bargain.
Ben
i really dont think you can hear a difference. maybe the same difference you hear if you upgrade a digital cable to a gold plated one.............................
i use an inverter(like the ones in laptops or lights) with a small ladder as well. works like a charm. cost 3 euro
i use an inverter(like the ones in laptops or lights) with a small ladder as well. works like a charm. cost 3 euro
No technical issues at all using the EMCO modules(single output or center-tapped) for ESL bias supply. Obviously the modules can output orders of magnitude higher current than is required for biasing an ESL with typical amounts of leakage paths. Placing the high resistance charging resistor physically close to the module rather than the panel, would go a long way in addressing potential safety issues by localizing/minimizing access to the (high voltage + high current) output of the module.
Concerning tyu’s advice regarding bias supplies and charging resistors:
From his many posts elsewhere on the subject, I believe his statements and preferences are valid for his particular situation. Living on the coast, his ESLs are exposed to humid salty air resulting in much higher than normal leakage currents. In this situation, to get your ESL’s to operate at their best, you need to have a bias supply that can handle the leakage current without the voltage sagging. Also, you need to use lower value charging resistors to minimize voltage drop from these leakage currents. Alternatively, instead of changing the resistor value you could increase the HV supply output voltage. Either way, the end goal is to get the proper amount of charge(ie voltage level) on the diaphragm coating.
Let's talk DIY.
An EMCO (second-hand, about us$40-70 on eBay) replaces a fist-full of diodes and high voltage capacitor and related bits.
What you get is an output proportional to the DC input/control voltage, roughly 1-15vdc. So you can experiment with bias voltage and adjust it as needed with the weather or living near the sea-coast. Your bias voltage is reliably predictable from the input voltage (once you measure it once).
Having said that, for my tweeter array I made the usual ladder and at the end, a wire and alligator clip so I could short-out the highest steps in the ladder if I wanted a lower bias.
Thanks Bolserst. My system has loads of resistors in all directions (including 20megOhm inside the cells at each end)... made possible by the big spacing of DW XG8 cells and the high resistance of the coating*. I'm likely to put another 20megOhms adjacent to EMCO module, as you indicate.
Ben
*which is why you need 400-500 minutes to charge these cells.
An EMCO (second-hand, about us$40-70 on eBay) replaces a fist-full of diodes and high voltage capacitor and related bits.
What you get is an output proportional to the DC input/control voltage, roughly 1-15vdc. So you can experiment with bias voltage and adjust it as needed with the weather or living near the sea-coast. Your bias voltage is reliably predictable from the input voltage (once you measure it once).
Having said that, for my tweeter array I made the usual ladder and at the end, a wire and alligator clip so I could short-out the highest steps in the ladder if I wanted a lower bias.
Thanks Bolserst. My system has loads of resistors in all directions (including 20megOhm inside the cells at each end)... made possible by the big spacing of DW XG8 cells and the high resistance of the coating*. I'm likely to put another 20megOhms adjacent to EMCO module, as you indicate.
Ben
*which is why you need 400-500 minutes to charge these cells.
Update on the charging time for those super high-resistance Dayton-Wright panels.
In this case, I had one mostly charged panel and below I present the time it took a second panel to catch up. The second panel was last in service about 35 years ago*.
After 6 hrs, the newly charged panel was 12.2 dB softer than the other panel.
After 16 hrs, 2.7 softer.
After 22 hrs, 1.4 which is borderline detectable on music.
After 28 hrs, .8 softer
It is possible my system (including the panels) is favouring one side or another and I may know that in 48 hrs. Likewise, I can't be sure how much the baseline panel was charged (which would minimize the difference). But as of 28 hrs, that's my data which shows significant bias build-up for almost 24 hrs.
The other side of the story is that these cells must hold their charge quite a long time... yet not be dangerous because of all the high resistance.
I was told you could put 10kV bias on these cells, 8kV in damper summer weather.
Ben
*special advice to long-term DIYers: consider buying a 21 room house.
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