Condenser Element Project

Hello
Yesterday I began work on a condenser element following the paper written by R.Williamson. I am an Acoustic Engineer but in the field of underwater acoustics and use gold deposition on stretched membranes in a variety of our underwater sensors. With this in mind I read the R.Williamson paper with great interest and began machining the backplate & shell and golded the required material ready for use as the membrane. I am expecting to have the element finished by the end of the week (I am only doing this when I have time at work)
My problem is the circuit given with the R.Williamson paper. I am not an electronic engineer and began the project with in an interest in the effect of the backplate, hole positions and sizes and also materials used.
I was hoping somebody could help me with a simpler circuit to use with my completed element, I was hoping for something without a tube that I can just use with phantom power.
I really hope you can help.
Regards
Adam

Hi Adam,

Welcome to the forum. There are a lot of people here, myself included, who would love to see how you get on with this project. Capsules are a bit of challenge, and it's always nice to see when someone takes the plunge.

In terms of simple circuits, I would point you to this discussion. A lot of people have built something like this circuit.

http://www.groupdiy.com/index.php?topic=2357.0

The 'schoeps' circuit mentioned is here
http://www.xaudia.com/xaudia/Schematics/Pages/Schoeps_Sony_files/Media/Schoeps/Schoeps.jpg

and a version by MXL is here

and
This one from Neumann is also worth a look...

That should get you started. Might also be worth joining the mic builders group at Yahoo.

If you don't want to go totally DIY, you could buy a cheap chinese mic and put your own capsule inside it. Some of the guys here will have good suggestions for which of the current mics is better.

Stewart

Let me also welcome you. I have designed air ultrasonic transducers for the past few years, but have been working on studio condensors for the past 6 months or so.

As you know, both the acoustic and electronic elements are a pretty mature technology. Lots of AES and IEEE papers.

Zuckerwar has a very good model.

Are you in Micbuilders Yahoo group? It has a wealth of information as does this site. I invite you to join.

Tell us about your capsule. Resistance controlled pressure gradient? Compliance controlled omni?

And tell us about gold coating too. Sputtered? Evaporated? Adhesion promoters?

As stewart mentioned, the Schoeps circuit is very common. A fet phase splitter and two bipolar emitter followers.

Les
L M Watts Technology

Thank you very much to both of you for your warm welcome, and thank you Stewart for those links as they are exactly what I was looking for.

In regards to Les' questions, the gold is sputtered and we currently use a layer of chrome to assist in adhesion. Whether the capsule is Resistance controlled pressure gradient or Compliance controlled omni I have no idea, but I shall do some research along those lines today.

I can tell that there is a lot of knowledge to be gained from this project and a large amount of information for which I am still to get a grasp of, but I am sure that will make the project far more rewarding and hopefully allow for me to expand the project into some experimental research into changes I can make.

For the time being my focus is on completing the capsule in the R.Williamson paper and then making a circuit to go with it from one of the schematics in the post from Stewart. I shall continue this thread with progress reports and pictures.

Thank you very much once again to both of you for your assistance and warm welcome.

Kind regards

Hi Adam,

We'd love to see pictures as you go along.

Where are you, geographically speaking?

Stewart

I am in Dorset, England.

Thanks again for the help, shall post some pictures when the capsule is finished (hopefully this week)

Regards

Another thread for you:

http://www.groupdiy.com/index.php?topic=6790&highlight=

Les
L M Watts Technology

Pounder said:

I am in Dorset, England.

Click to expand...

I was guessing UK from the time of the post. Anyway, I have lots of microphone spare parts kicking about, so if you need anything, shout and I'll see if I can help.

Adam,

Welcome, sorry to hijack your thread.

Stewart,

You don't happen to have any capsule mounts that would suit one of Dales M7 type capsules in your "loads of mic parts kicking around" ?

Hi Rob,

Not sure - I'll have a look.

I didn't get any of Dales M7s, just the C37 style capsules, which were difficult to mount because of the lack of screw holes. I ended up soldering the back of one onto a brass rod.....  Scary, but it survived!

Rob - what I was trying to say before I got sidetracked is that I don't know the dimensions of Dale's capsule, so not sure if I have anything to fit.

Welcome to the forum Adam!
Keep in mind that the Williamson design expect about 75V of polarization voltage. Building yourself a separate PSU for this would save you some headache and allows for experimentation to find the perfect polarization for your capsule and taste...

@ Rob & Stewart: The dale M7 capsule I had has the same dimensions as a regular Neumann/Gefell/Thiersch M7...

Axel

Stewart

The dale m7 has a diameter of 31.75mm on the outside of the lip.

mad.ax said:

The dale M7 capsule I had has the same dimensions as a regular Neumann/Gefell/Thiersch M7...

Click to expand...

Rob, I think your best bet would be a brass ring style mount, either from thiersch, or one of the ones that lewilson sells.

http://www.groupdiy.com/index.php?topic=37112.0

Cheers!

mad.ax said:

Keep in mind that the Williamson design expect about 75V of polarization voltage.

Click to expand...

Axel, you might just have accidentally solved a problem for me! I have very poor signal from an old DIY capsule - i may have it polarised way too low.

http://www.groupdiy.com/index.php?topic=40152.0

Back to the bench...

@ Rob : I used a Thiersch STS7 holder with my Dale's M7 and it fitted perfectly

@ Stewart : In a attempt to keep this forum better organized than my summer bench, I answered you in the other thread!

Highjack mode : off.

Axel

Stewart thanks for the tip !

I have finally finished the machining on the capsule, I shall post some pics of it if anybody is interested (?) on Monday.
I am starting to source the parts I need for the circuit now and was wondering if anybody would be interested in a trade for a working circuit?
As I have a gold deposition machine which I use at work everyday I could quite happily swap some golded film for a working circuit if anybody has a spare one knocking about?
Just an idea, but it would save me a lot of time as I have limited experience with electronics and am mostly interested in the acoustic effects of the changes which can be made to the capsule. 
I hope you can help

Adam

Hi Adam,

I can probably help - I sent you a pm.

We'd love to see pictures!

Stewart

If you are more interested in the capsule part you might want to use a transformerless solid state circuit.