[spritzer]

Ask away, plenty of information locked away in this head...

 
What film did you end up with, 3um?  Did you heat treat it at all?  That might help... I do have some ovens to play with. 

   I was also toying with the idea at work today to design a PCB driver and have it made at a fab house.  Those guys can do amazing tolerances and different materials.  I did do this once but the design was flawed.  Now it would be just one design for the stators and another one for the spacers. 
 
About the squeal, first attempt will be cleaning the diaphragm as they are dusty.  The copper oxidizing is an issue but I'll probably first try some polish liquid which forms a protective barrier that stops oxidation.  I used it on my KGSS back in the day and the bare aluminum is still nice and shiny. 
 
Edit, some pics:
 

 

 

[chinsettawong]

I sure will ask a lot of questions. 

 
The headphones look really good.  So, have you fixed the squeals?  Do you mean to clean the copper with polishing liquid and that would leave some protective shell on it?  That seems like a good idea. 

 
Today, I tried to put more tension on the diaphragm of my oval shape headphones.  The last time I had 9 x 600 ML of weight on the diaphragms, and they were not good enough. Today I used 12 x 600 ML, and it's a bit too much. 

  I'll try 10 x 600 ML next time and will report back.
 

 
 

 

[chinsettawong]

My Oval shape Orpheus clone is a lot bigger than the real one. 

 

 

 

[dude_500]

Quote:

My Oval shape Orpheus clone is a lot bigger than the real one. 

 
 
 
 

 
What is the active area of the actual Orpheus?

 

[chinsettawong]

Here are two more pictures comparing my Omega clone against my version of Orpheus.  

 

 
 

 

[chinsettawong]

Quote:

 
What is the active area of the actual Orpheus?

 
I don't really know, but I guess it's around 55 mm x 95 mm or 50 mm x 90 mm.  The ones I made for Spritzer are a bitt larger at 60 mm x 98 mm.
 
Wachara C.

 

[spritzer]

The HE90 is a bit smaller than these drivers so Wachara's estimate is about right.  It would be fun to build drivers like these and have them gold plated and put them together with black peek screws.  Almost impossible to tell them apart from the real thing... 
 
Quote:

I sure will ask a lot of questions. 

 
The headphones look really good.  So, have you fixed the squeals?  Do you mean to clean the copper with polishing liquid and that would leave some protective shell on it?  That seems like a good idea. 

 
Today, I tried to put more tension on the diaphragm of my oval shape headphones.  The last time I had 9 x 600 ML of weight on the diaphragms, and they were not good enough. Today I used 12 x 600 ML, and it's a bit too much. 

  I'll try 10 x 600 ML next time and will report back.
 
 

 
I took a nap instead of cleaning the diaphragms... 

 
I always use a larger piece of mylar when stretching so that might help.  It can take an incredible amount of tension but a small tear at the sides and all is lost.  Amazing material though... 

 

[Chazman]

If you want to know anything about DIY electrostatic amps just ask away.  Tubes, SS or crazy transformer hybrids... we've done it all.    I have one planned which has only two triodes in total for a fully balanced amp.  Not cheap and probably will sound quite... ehhh... special. .  

That's great thanks! So I have managed to source some lovely Cherry wood (only piece the entire timber yard had and is just big enough for the two cups with a little spare!

So in terms of the energiser I was thinking of making a nice basic one to get used to it and work out exactly what voltages I need then later on make something like a tube based amp.

- I saw a while ago (but been searching for hours with no luck!!) a very basic design for an energiser that had two step up transformers and a potential divider for the stator and a simple transformer with a bridge rectifier from the mains to get the bias voltage. Does anyone have a circuit diagram / parts list for one like this? Also I take it would be possible to make one where the bias voltage just comes from a rectified signal from one of the stator transformers (like I assume my Koss ESP-6a's do as there is no powered input)?

Any help on this one would be massively appreciated!

Chaz

P.s. lovely pics of the HE90 clones on here, I hope mine will at least half compare to you guys!

 

[spritzer]

What you want is the Stax SRD-7 Mk2 schematic.  You can find it online but basically it is just two transformers for the audio (1:25 in ratio or there about) and a basic bias supply.  The bias supply is just a 100V harmonic suppressor (100V zener diodes back to back) that limit the input voltage and then a six fold multiplier.  It's a neat circuit and easy to build. 
 
If you want to build a tube amp then the Egmont is a good choice.  It's dead simple but you need a transformer with two filament windings, one for each stage, or the amp won't behave and chew up tubes.  There is an alternative, this one I recently built:
 

 
Not high end by any means and the PSU voltages are a bit too hot but I just used the transformer I had at hand.  This one works with a single filament supply and can be built quite small.  Fully balanced too... 
 
My HE90 is the real thing... 

 

[dude_500]

After probably 20-30 hours of listening to both of my builds, there is no doubt the new ones just don't have enough bass (maybe due to the size, maybe due to the use of HD600 earpads, probably a bit of both). That said, I'd describe them as very fun to listen to, especially for classical music where bass isn't so important.
 
A few minutes ago while wasting time online reading about the SR007, I read about someone removing the cloth dampening built into the earpad. I didn't realize this was possible, and immediately tried it. Wow! What a difference. It really opens up the sound, dramatically increasing the sound stage and brightness. I guess not everyone would want it given that by default they come with those sheets in, but I'm really quite excited about the new sound without them.
 
 
I think I'm going to retire the new 'electrostatic HD600' headphones and put some effort into making my SR007 clones structurally better and more more aesthetically pleasing (replace some plastic with wood and improve headband).

 

[chinsettawong]

Hi dude_500,

The simple truth is the bigger, the better.

I don't like to do any damping on the drivers too.

Wachara C.

 

[Chazman]

Quote:

What you want is the Stax SRD-7 Mk2 schematic.  You can find it online but basically it is just two transformers for the audio (1:25 in ratio or there about) and a basic bias supply.  The bias supply is just a 100V harmonic suppressor (100V zener diodes back to back) that limit the input voltage and then a six fold multiplier.  It's a neat circuit and easy to build. 
 
If you want to build a tube amp then the Egmont is a good choice.  It's dead simple but you need a transformer with two filament windings, one for each stage, or the amp won't behave and chew up tubes.  There is an alternative, this one I recently built:
 

 
Not high end by any means and the PSU voltages are a bit too hot but I just used the transformer I had at hand.  This one works with a single filament supply and can be built quite small.  Fully balanced too... 
 
My HE90 is the real thing... 

 
Great stuff spritzer thanks, quite similar to a diagram I found previously.
 
In terms of Transformers found these: http://www.maplin.co.uk/miniature-250ma-transformers-3688 (if you look at the 9v application because with a bit of quick math 240v primary and a 9v secondary is a ratio of 1:26 ish), they take 250mA current, do you think that would be ok for the main transforer from the speakers? The next transformers up (double the cost) can take 18w of power so a loooot more beffy and dont think they are needed?
 
Possibly silly question about the SRD-7 diagram (I found on a previous post) it has 6 diode and capacitor for the multiplication system to get the bias voltage. The circuit diagram is for the japanese market so has an input voltage of 100v so does the 600v come from 6 x 100v (from the input) or because the diodes are 100v rating each and it will be limited to this across each regarless of input voltage? Reason I ask is that I am in the UK so input voltage will be 220-240v so would only need half the amount of diodes but higher voltage if it is mearly a product of multiplication.... Also I will put a coupld of taps off the diodes so I can play with different bias voltages.
 
Thanks,
 
Chaz

 

[spritzer]

That amp is just the Stax "A" model from 1968 with a new front end.  I'll probably draw up a PCB one of these days as it would be a good beginners amp, super cheap too. 
 
I would never use power transformers for audio unless it's just for testing or just some silly experimenting.  The cores are just supposed to run at 50Hz and you run into DCR issues.  Old tube output transformers are much better fit, just wire them backwards.  Just remember to divide the primary and secondary impedance and then take the square root of that to find the ratio. 
 
The Stax boxes are universal so any voltage higher than 100V is cut off via the two zener diodes and then multiplied.  It also calls for cheaper parts as the voltage rating is just 2*inputV.  If you are just going to use this at 230V then you can just leave out the limiter or use something like 200V.  I would recommend an isolation transformer though.  Stax or any of the others never used one but it helps with hum issues and safety. 

 

[Chazman]

I would never use power transformers for audio unless it's just for testing or just some silly experimenting.  The cores are just supposed to run at 50Hz and you run into DCR issues.  Old tube output transformers are much better fit, just wire them backwards.  Just remember to divide the primary and secondary impedance and then take the square root of that to find the ratio. 

Good advice, not especially easy things to just source so I have found so far. What is the actual difference between and Audio and power transformer (I know one is designed to carry decent current and one to match impedance but what makes them different)? Reason I ask is so I can spot which ones to use from other places and I could buy some cores and make my own transformers....

Chaz

 

[spritzer]

Very different winding techniques and core materials used.  Electrostatic step up transformers are an even further twist on this as they have their own requirements.