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I recently ran across a microphone capsule that appears to keep its
fet a few inches outside of the capsule.

If there is no downside to that design I could see modifications of
the inexpensive capsules to have higher output and maybe less noise
with trial and error.

Also my RF condenser mics have all the electronics away from the
capsule as well, but that would be more expected.

Anybody know of any downside to having a seperation between the
capsule and the electronics?

Rich Peet

Rich Peet wrote:

Anybody know of any downside to having a seperation between the capsule and the electronics?

EMI shielding effect in capsule for noisy environments? FET inputs
are extremely sensitive.

Indrek

--
Indrek Rebane | Borthwick-Pignon
Electronics Engineer | Tartu Science Park
Phone: (+372) 7 302 641 | Riia 185, 51014 Tartu
Fax: (+372) 7 383 041 | Estonia
indrek@... | www.bps.co.ee

This is true, however I have customers that have been specifing that I make them
ECM's with no FET's for years. In my customer's applications they are operating in
strong RF fields (radar) and they just use good spiral shield coax, run a few inches,
then hit their input device.

We make many kinds of ECM's It's time the WM-60/61 had some competition. If
everyone can agree on what such a device ought to be, I'll run some, pass them out
and you guys can see what you think.

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some competition. If
everyone can agree on what such a device ought to be, I'll run some, pass them out
and you guys can see what you think.

What an interesting offer! Personally I'd be interested in
some with larger diaphragms, say 1/2", to increase the SNR
above the molecular shot noise and in directional models of
the same, particularly a cardiod and a figure 8.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

certainly. i too would be interested in half a dozen half inch cardioids to build some directional mikes.

umashankar

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some

competition. If

everyone can agree on what such a device ought to be, I'll run some,

pass them out

and you guys can see what you think.

What an interesting offer! Personally I'd be interested in
some with larger diaphragms, say 1/2", to increase the SNR
above the molecular shot noise and in directional models of
the same, particularly a cardiod and a figure 8.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

_________________________________________________________________
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mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some competition. If
everyone can agree on what such a device ought to be, I'll run some, pass them out
and you guys can see what you think.

Further thoughts: while the default configuration probably
should remain common source, it would be nice if the design
had the modification to two wire source follower topography
in mind. That implies an easily located single trace to cut
and another to bridge that is easier to solder to than the
little tab on the WM-60/61 is.

A collaborative design would be a great inauguration of the
new group.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

i would like to see a capsule without the fet. that should make it possible for many more design ideas - a low noise fet opamp for instance, bootstrapped, might work.

umashankar

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some

competition. If

everyone can agree on what such a device ought to be, I'll run some,

pass them out

and you guys can see what you think.

Further thoughts: while the default configuration probably
should remain common source, it would be nice if the design
had the modification to two wire source follower topography
in mind. That implies an easily located single trace to cut
and another to bridge that is easier to solder to than the
little tab on the WM-60/61 is.

A collaborative design would be a great inauguration of the
new group.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

_________________________________________________________________
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For my applications I agree a larger diaphragm of 1/2" would be great
and going much larger one starts to worry about condensation and
humidity in outdoor recordings.

There is a growing number of people that are recording "faint field"
and it is the omni's that don't have the proximity effect and it is
the figure 8's that are most hard to find.

No one is really marketing a product for this area of recording and
what I see dominating the "faint field" right now is the Senn ME 62
condenser, and the MKH 20-P48 which is an RF.

I don't consider my uses to be in the majority but with more people
looking at the new digital recorders there is more of a demand for
lower noise and higher s/n numbers.

I am off traveling to record the great white north tomorrow sometime.
Will return sunday nite. Recording White Pines, Streams, and winter
birds in woodland new snow is true "faint field".

Rich Peet

--- In micbuilders@..., Bob Cain <arcane@a...> wrote:

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some

competition. If

everyone can agree on what such a device ought to be, I'll run

some, pass them out

and you guys can see what you think.

What an interesting offer! Personally I'd be interested in
some with larger diaphragms, say 1/2", to increase the SNR
above the molecular shot noise and in directional models of
the same, particularly a cardiod and a figure 8.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

umashankar mantravadi wrote:

certainly. i too would be interested in half a dozen half inch cardioids to
build some directional mikes.

Yeah, I'd like them for a DSP based DIY Ambisonic mic and
the fig 8 for a M/S mic. For the M/S I could live with back
to back cardiods for S but its more circuitry. The WM55A's
are just too noisy but the price is sure right.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

12.7mm is 1/2". We can look at that. We can make anything makeable,
HOWEVER 6mm or 9.7mm is what we run all day, every day. That is where it
is realtively easy to slip in something special or different, like no FET, a
different FET, different membranes, spacers, tensions, etc.

What you have to realize here is that there are maybe 1,000 of you guys
doing very interesting and creative things with SMALL quantities of ECM's

Personally, I'm fascinated with this. It's my hobby as well as my day job. My
wife says I have no life outside of those little f-in silver cans ;-)

I can't make a dozen of this and a dozen of that. I need to make a minimum of
10,000 of something and know that eventually they will be consumed.

So we need to go for the highest usage DIY capsules and those are the 60/
61. We need to narrow down what is wanted in an off the shelf replacement
for them.



--- In micbuilders@..., Bob Cain <arcane@a...> wrote:

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some

competition. If

everyone can agree on what such a device ought to be, I'll run some, pass

them out

and you guys can see what you think.

What an interesting offer! Personally I'd be interested in
some with larger diaphragms, say 1/2", to increase the SNR
above the molecular shot noise and in directional models of
the same, particularly a cardiod and a figure 8.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

Bob,

I couldn't agree with you more about "A collaborative design would be a great
inauguration of the new group."

I was here a long time ago and dropped out. I am constantly pestered by
steath mic makers and hobbyists to make DAT head type stuff. It's been way
on the back burner for a long time.

Finally I come back to look at doing this and find the group has starrted a
migration to a new group within days, maybe hours... PERFECT timing, or
what?

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is simply
bypassing the internal FET?

How about we make a batch of something a bit better than 60 or 61 with NO
FET in it in the first place ?

--- In micbuilders@..., Bob Cain <arcane@a...> wrote:

mstrong82 wrote:

We make many kinds of ECM's It's time the WM-60/61 had some

competition. If

everyone can agree on what such a device ought to be, I'll run some, pass

them out

and you guys can see what you think.

Further thoughts: while the default configuration probably
should remain common source, it would be nice if the design
had the modification to two wire source follower topography
in mind. That implies an easily located single trace to cut
and another to bridge that is easier to solder to than the
little tab on the WM-60/61 is.

A collaborative design would be a great inauguration of the
new group.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

OK - the whole point for me is to help people play wih microphone stuff and
make their own inexpensive, probably better versions of stupidly expensive
microphone products, besides I'm so bored making cargo container after
cargo container of telephone microphones and having no fellow mic nerds to
play with.

Later on, if it's needed, we can run small batches of odd ball parts, blank
PCB's, SMD PCB's, foam, metal, cables... whatever enough people would be
interested in and can agree on.

I'm looking to learn more about acoustics and microphone applications from
you guys and what I have to bring to the table is manufacturing capabilities.

Anybody here have serious microphone testing capabilities ?

At 12:00 PM 12/6/03 +0000, you wrote:

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is simply
bypassing the internal FET?

How about we make a batch of something a bit better than 60 or 61 with NO
FET in it in the first place ?

Remember that for 6mm range diameter capsules, the FET is not the predominant noise source, and the modification to allow source-follower operation does a pretty good job at linearizing the internal FET.

Having been through a design recently that I had to provide the FET and balanced amplifier for an electret capsule, I would suggest that capsules without FET's would be much more troublesome than with.

My suggestion is to build capsules with three solder pads, one tied to the metal shell, one to the source and one to the drain. Users who want two-wire operation can provide an external resistor source-to-shell.

-----------------------

Glad to be rid of the old group -- are safeguards in place to prevent SPAM from this one? Is there some specific action that users should do to prevent it?

Dick Campbell


Bang-Campbell Associates
3 Water Street PO Box 47
Woods Hole, MA 02543-0047
(T) 508-540-1309 (F) 508-540-8347
(C) 508-989-3771 (world wide)
(E) rhcamp@...
(W)

mstrong82 wrote:

Finally I come back to look at doing this and find the group has starrted a
migration to a new group within days, maybe hours... PERFECT timing, or
what?

That's just what I thought. :-)

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is simply
bypassing the internal FET?

No, it is changing the configuration of the internal FET to
source follower from the as-shipped common source mode.
This involves cutting a trace on the little PC board and
making another connection to the can. The problem is that
the solderable tab that allows connection to the tab is a
tiny little thing and so well heat-sunk to the can that
soldering to it can be difficult or even destructive. I use
silver ink to make a low temp connection but others have
objected to the durability of the solution (which I haven't
really found to be a problem.)

How about we make a batch of something a bit better than 60 or 61 with NO
FET in it in the first place ?

I think that managing the high impedence issues over a
longer connection from diaphragm to an amplifier would be
more than challenging and has strong impact on the noise and
high frequency performance of the result. If there is such
a thing, a better FET might be more appropriate. By
encapsulating it within the near Faraday cage of the can,
induced noise is also minimized.

Frankly, short of better noise performance which seems to be
limited by the small size of the diaphragm I am not sure how
much real improvement is attainable in a device of the size
of the WM-60/61.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

mstrong82 wrote:

What you have to realize here is that there are maybe 1,000 of you guys
doing very interesting and creative things with SMALL quantities of ECM's

Personally, I'm fascinated with this. It's my hobby as well as my day job. My
wife says I have no life outside of those little f-in silver cans ;-)

I can't make a dozen of this and a dozen of that. I need to make a minimum of
10,000 of something and know that eventually they will be consumed.

Yes, I understand that the larger you make it, the more
specialized the market becomes. It's just that my interest
has moved beyond tiny but noisy omni's toward much quieter
first order mics that are suitable for coincident stereo or
surround recording. I fully understand that the market size
for such devices is relatively small, as evideneced by the
lack of inexpensive parts for it, but nonetheless I wish to
speak to this type of application and open the door wider to
experimentation in the area.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

mstrong82 wrote:

Anybody here have serious microphone testing capabilities ?

As Jerry Avins in comp.dsp is so fond of saying,
"Engineering is the art of making what you want from what
you have." To that end I have worked out testing and
characterization methods that seem to be repeatable and
accurate. I do my work out of doors, when I can find calm
days, to get a good hemi-anechoic space, use a calibrated
reference mic and fairly sophisticated DSP methods for
compensation of parts of the stimulus and measurement chain
that are less than ideal. I haven't yet taken on the
problem of directional measurement but have given it some
thought.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

only about the last point: the sony ecm 907 and others like it have more than an inch of wire from the capsule to the fet; the nakamichi cm 300 i have sitting in front of me has a one and half inch cylinder between the fet and the capsule; it includes a switchable capacity which servers as a 10 db pad. an inch of wire i think we can live with.

umashankar

mstrong82 wrote:

Finally I come back to look at doing this and find the group has

starrted a

migration to a new group within days, maybe hours... PERFECT timing, or
what?

That's just what I thought. :-)

AS FAR AS MAKING THE LINKWITZ MOD Easy, what could be easier than
having it already done? If I recall the capsule part of the mod is

simply

bypassing the internal FET?

No, it is changing the configuration of the internal FET to
source follower from the as-shipped common source mode.
This involves cutting a trace on the little PC board and
making another connection to the can. The problem is that
the solderable tab that allows connection to the tab is a
tiny little thing and so well heat-sunk to the can that
soldering to it can be difficult or even destructive. I use
silver ink to make a low temp connection but others have
objected to the durability of the solution (which I haven't
really found to be a problem.)

How about we make a batch of something a bit better than 60 or 61 with

NO

FET in it in the first place ?

I think that managing the high impedence issues over a
longer connection from diaphragm to an amplifier would be
more than challenging and has strong impact on the noise and
high frequency performance of the result. If there is such
a thing, a better FET might be more appropriate. By
encapsulating it within the near Faraday cage of the can,
induced noise is also minimized.

Frankly, short of better noise performance which seems to be
limited by the small size of the diaphragm I am not sure how
much real improvement is attainable in a device of the size
of the WM-60/61.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

_________________________________________________________________
Marriage? Join BharatMatrimony.com for free.

--- mstrong82 <mstrong@...> wrote:

12.7mm is 1/2". We can look at that. We can make anything makeable,

I think something that would be really great would be a capsule that
ran off of 48v, so it could easily be run off phantom power.

I know a lot of people on this list wouldn't have any problems putting
together a circuit to do that, but at least some of us would have
problems.

My thinking is that it would be great to have a handy source of
"utility" mics. Just wire it up to an XLR and plug it into the mixer.

Bob Rogers

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