To Jimster : I think the explanations given by dw1narso are complete. Yes, there is NO DAC in the classical sense, and the transformation is a conversion from PCM to PWM ! In other words you're digital to the very end of the processing, there are no losses in the D to A chain !... Apogee was...

Hi Everybody, Please find enclosed 2 picts of the mods we made to the gain in order to adapt the amp to any Headphones, whatever its sensibility. Now the gain can be adjusted at three different levels. Even my AKG 240 Monitor (600 ohms) or the Fostex planar T50RP are perfectly usable with the...

To be honest, I must confess that one of my friends helped me to build this prototype... Anyway, there isn't any difficulty in this built, excepted the volume control through two interrupters here : one to raise and the other to lower the output level...

You're welcome !... Such FDA boards are only usable for "balanced" headphones. This is because the FDA doesn't share any reference/ground, in other words each output is totally independent from the other. Of course, it's possible to return to SE through an adapted circuit, but it's a pity...

As stated by dw1narso this is a voltage divider since the board is initially an amplifier for loudspeakers !... Then, as you probably know, such an amplifier is too powerfull to drive even the highest impedance headphones... Reducing the output power of the board in a balanced mode through a...

Hi Guys, After testing several FDA units (Topping, FX802, YJHiFi, etc...) most of them based on STA326 chips, I found a board based on the 333BW circuit, and the idea was to derive a high quality audio DAC-Amplifier for headphones with it... Here is the board ...

Please Inuponken can you tell us :   - the thickness and quality of the film you used for the membranes   - the total weight you apply to your jig for the tension of this film   I read the other interesting parameters in one of your posts (spacers and polarization).   Thanks for these...

Hi Inuponken,   Good job indeed !   I saw that you used Reztore : I still have somewhere one bottle for test purposes, but It seems that this product lasts unfortunately not enough in time ... Licron seems to be a much better candidate !    What is your opinion ?   OndesX

Or two wood squares with a serious weight on the upper one, the whole thing on a plane surface, this will do the job perfectly !...

  You're probably right, but anyway I guess it'll give an idea of how it'll work and delivers some numbers !   Thank you for your kind words.   OndesX

For those who are still interested in measurements and quantification, here is a simulation made with the simulator developed by Arend-Jan on his web site :   http://quadesl.nl/sim/     Don't worry about the yellow line : it is not meaningful.   You can see that for 500V of polarization...

  Unfortunately, there is no easy way to determine, from a theoretical point of view, the "best" tension of the diaphragm for a given polarization voltage. First of all, we have to define what we mean by "best". I think that we're looking for the tension of a given film, that allows the...

Hi BillG,   It's true that there are 2 perpendicular stretching directions for PET films, one direction is more difficult to stretch than the other : you might try to stretch manually a small piece of PET to convince yourself. But, this isn't a paramount point, as far as you make an...

  OK but do you remember your advice to somebody in this thread :   "If you can find a helping hand, I think the stretcher using clips and weights is better.  It's easier to repeat the process too."   Thus, I'll give a try to a 3µ Mylar with my jig since it's possible, this way, to...

  Yes I understand that I have to try and fail several times... But, my question was about the intensity : removing simply the ripples doesn't need 5 kg around the diaphragm...    Thus, with your more recent stretched membranes in which range are you ? around one kg or more than 5 kg for à 3...