Hi
So I have been planning to get into Electrostatic Headphones. I am pretty confident I can design the headphones. But amplifier is another issue. Only experience prior to this in DIY audio have been with PAM 8610 and TPA3116 class D boards.
So my question here is, is this feasible?:
Audio Source (Phone) >>>> PAM8610 >>>> (Audio-transformer + Bais) >>>> ESL Headphones.
Diaphragm area will be less than 70sqcm (10x7cm) per cup. Estimated lowest Capacitance will be 30pf (it can vary based on diaphragm movement). If above is not a good idea, can you guys please direct me to a simple schematic which can achieve good results.
So I have been planning to get into Electrostatic Headphones. I am pretty confident I can design the headphones. But amplifier is another issue. Only experience prior to this in DIY audio have been with PAM 8610 and TPA3116 class D boards.
So my question here is, is this feasible?:
Audio Source (Phone) >>>> PAM8610 >>>> (Audio-transformer + Bais) >>>> ESL Headphones.
Diaphragm area will be less than 70sqcm (10x7cm) per cup. Estimated lowest Capacitance will be 30pf (it can vary based on diaphragm movement). If above is not a good idea, can you guys please direct me to a simple schematic which can achieve good results.
So basically you want to use an amplifier meant for low-impedance loads and a step-up transformer. I'm sure that can work. A disadvantage compared to a specially-designed high-voltage amplifier is that you can't accurately limit the current driving the headphones to non-lethal values, so you will need to ensure by some other method that a failure of the insulation between the stators and your ears won't do any harm.
Thanks, this gives me more confident.
Few more questions:
1. Would a current limiting resistor on bias supply not reduce the lethal amounts of current?
2. Also Currents should be high at very high frequencies only, I lack a proper oscilloscope (mine is bust right now). Would it be possible for some one to test if PAM or the TPA chip can handle loads at-least till 20Khz ?
3. Also found these transformers: 10pcs 1300 : 8 Ohm Audio Transformer EE14 Transformateur Audio POS Transformador Sale - Banggood.com
Will these work for headphone. I know they are not center Tapped so am planning to use 2 per channel. That should help with Saturation too I guess.
Few more questions:
1. Would a current limiting resistor on bias supply not reduce the lethal amounts of current?
2. Also Currents should be high at very high frequencies only, I lack a proper oscilloscope (mine is bust right now). Would it be possible for some one to test if PAM or the TPA chip can handle loads at-least till 20Khz ?
3. Also found these transformers: 10pcs 1300 : 8 Ohm Audio Transformer EE14 Transformateur Audio POS Transformador Sale - Banggood.com
Will these work for headphone. I know they are not center Tapped so am planning to use 2 per channel. That should help with Saturation too I guess.
For headphones, current limiting resistors (with high enough voltage ratings!) could indeed reduce the current into the stators sufficiently. With 30 pF, a 100 kohm resistance would limit the bandwidth to 50 kHz, which is still OK. Since you probably need only a few hundred volts, the short-circuit current is then a few milliamps, which is quite unpleasant but not lethal.
The high-voltage DC supply for the membrane need not be a problem at all. Normally these are high-voltage cascades with quite low short-circuit current. To further reduce the risk and to minimize distortion, you can indeed put a couple of large resistors in series with the supply (making quite sure the voltage ratings of the resistors are high enough). (I assume you make a balanced transducer with a high-ohmic membrane charged to a high DC voltage between two stators driven in antiphase.)
By the way, if I were you I'd ask a moderator to move this to the "Planars & Exotics" or the "Headphone Systems".
The high-voltage DC supply for the membrane need not be a problem at all. Normally these are high-voltage cascades with quite low short-circuit current. To further reduce the risk and to minimize distortion, you can indeed put a couple of large resistors in series with the supply (making quite sure the voltage ratings of the resistors are high enough). (I assume you make a balanced transducer with a high-ohmic membrane charged to a high DC voltage between two stators driven in antiphase.)
By the way, if I were you I'd ask a moderator to move this to the "Planars & Exotics" or the "Headphone Systems".
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They look quite small, so you probably won't get much bass. When you put the 8 ohm sides in parallel and the 1300 ohm sides in series, the step-up ratio of a pair is 2*sqrt(1300 ohm/8 ohm) ~= 25.5.
Thanks a lot Marcel, Yeah they are pretty small. I will look into a diy toroidal transformer once I see that this is working. I have Ferrite core and iron powder core with me. I think iron powder core would be good as it is a power transformer core and does not saturate. But I have no idea of its frequency response.
All this work makes a direct drive amplifier sound more and more good. But I have no idea how to make one for headphones. I do not want to get in to ESL Loudspeakers yet so do not want to spend a lot on just amplifiers.
Also thanks again for transformation ratio calculation..
Also, Yes I am going with balanced transducer with a high-ohmic membrane charged to a high DC voltage between two stators driven in antiphase (guess push-pull).
I am following "chinsettawong's" design and will iterate more if its successful.
Will see if this thread can be moved to Planars & Exotics. Going to use 3d printer to design all the hardware and use a 1 mm FR4 board for the driver design.
All this work makes a direct drive amplifier sound more and more good. But I have no idea how to make one for headphones. I do not want to get in to ESL Loudspeakers yet so do not want to spend a lot on just amplifiers.
Also thanks again for transformation ratio calculation..
Also, Yes I am going with balanced transducer with a high-ohmic membrane charged to a high DC voltage between two stators driven in antiphase (guess push-pull).
I am following "chinsettawong's" design and will iterate more if its successful.
Will see if this thread can be moved to Planars & Exotics. Going to use 3d printer to design all the hardware and use a 1 mm FR4 board for the driver design.
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