Sign in with
Sign up | Sign in
Your question

Sony C-48 condenser: know of anyone using it in radio

Last response: in Home Audio
Share
Anonymous
February 11, 2005 3:18:54 PM

Archived from groups: rec.audio.pro, (More info?)

A friend want to know if this Sony mic is used in radio by anyone.

Regards,

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

More about : sony condenser radio

Anonymous
February 11, 2005 9:27:47 PM

Archived from groups: rec.audio.pro, (More info?)

In article <XKednfpaIMGddJHfRVn-iA@comcast.com> tyreeford@comcast.net writes:

> A friend want to know if this Sony mic is used in radio by anyone.

I doubt that anyone would buy a new one for that purpose (wasn't it
recently re-introduced in the US?) but I suppose that old-but-good
ones are still in use, probably mostly for orchestral recording, if
radio stations still do that.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 11, 2005 10:17:08 PM

Archived from groups: rec.audio.pro (More info?)

The C48 is a dual diaphragm with electrical pattern switch the tube version
is the C800G. The C48 should work well for radio if you want the announcer
to sound natural... you will need a parametric eq for the typical radio
sound.

The head cage of the tube and fet versions are different...

It's the C38 that was just reissued.... a single diaphragm mic with a vent
valve to change from cardiod to omni.... the tube versions are C37a and
C800.

Rgds:
Eric

www.webermusic.com

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1108145481k@trad...
>
> In article <XKednfpaIMGddJHfRVn-iA@comcast.com> tyreeford@comcast.net
writes:
>
> > A friend want to know if this Sony mic is used in radio by anyone.
>
> I doubt that anyone would buy a new one for that purpose (wasn't it
> recently re-introduced in the US?) but I suppose that old-but-good
> ones are still in use, probably mostly for orchestral recording, if
> radio stations still do that.
>
> --
> I'm really Mike Rivers (mrivers@d-and-d.com)
> However, until the spam goes away or Hell freezes over,
> lots of IP addresses are blocked from this system. If
> you e-mail me and it bounces, use your secret decoder ring
> and reach me here: double-m-eleven-double-zero at yahoo
>
Related resources
Anonymous
February 11, 2005 10:35:33 PM

Archived from groups: rec.audio.pro (More info?)

Never used the C48 but back in the late '60's, or ealy '70's, we used
C37A's in the studios for talk and in the control rooms for the dj's.
This was at an AM station in Lethbridge, Alberta, Canada.
Wish I'd managed to save a couple when they were replaced by the next
big thing.




On Fri, 11 Feb 2005 12:18:54 -0500, Ty Ford <tyreeford@comcast.net>
wrote:

>A friend want to know if this Sony mic is used in radio by anyone.
>
>Regards,
>
>Ty Ford
>
>
>
>-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
>stuff are at www.tyford.com

Mike Cleaver Broadcast Services
Voice-overs, Newscaster, Engineering and Consulting
Vancouver, BC, Canada
radiovoiceone@hotmail.com
Anonymous
February 12, 2005 5:32:23 AM

Archived from groups: rec.audio.pro, (More info?)

In article <XKednfpaIMGddJHfRVn-iA@comcast.com>,
Ty Ford <tyreeford@comcast.net> wrote:

> A friend want to know if this Sony mic is used in radio by anyone.

Never seen it used in radio, but I have one that I still use and like
very much.

--
Jay Frigoletto
Mastersuite
www.promastering.com
Anonymous
February 12, 2005 9:26:53 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Cleaver" wrote ...
> Never used the C48 but back in the late '60's, or ealy '70's,
> we used C37A's in the studios for talk and in the control
> rooms for the dj's. This was at an AM station in Lethbridge,
> Alberta, Canada. Wish I'd managed to save a couple when
> they were replaced by the next big thing.

I did just that as a college student after the station manager
was shocked once too often by the ~300v bias that leaked out
of those lousy connectors! These were late 1950s vintage C37a
mics. I re-wired them with better cable and XLR connectors, etc.

I put new capsules in them because the old ones looked dirty
and I still have those old caps. Now that I know they can be
cleaned I want to make new electronics around them to have
another pair. Been thinking that the old original circuit with
a 6AU6 wired as a triode would be as good as any solid-
state alternative. Comments? Opinions?

Only component I can't reproduce is the output transformer.
Anybody have any experience/comment about the "Country
Boy's Capacitor Microphone" circuit/transformer as Jensen
has published here?...
http://www.jensentransformers.com/as/as076.pdf
Anonymous
February 12, 2005 12:37:08 PM

Archived from groups: rec.audio.pro (More info?)

The Country Boy's circuit has no bias on the capsule so it's for an electret
capsule.

The C38B is the fet version of the C37/C800 look here for information....
Review:
http://mixonline.com/mag/audio_sony_cb_microphone/
http://mixonline.com/online_extras/sony_c38b_specs/
Schematic
http://www.highvoltagerecording.com/Downloads/Sony_C38B...

If you wish to clone a C37 try getting the transformer from www.sescom.com
they made the transformers for the C800 and C800 G....

As mentioned previously the Sony C800 non G is the Sony clone of the C37....
although the headshell design is different, improvements include putting the
audio transformer on the microphone end and better shock mounting.

Rgds:
Eric

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:110s4he2njjfv2c@corp.supernews.com...
> I put new capsules in them because the old ones looked dirty
> and I still have those old caps. Now that I know they can be
> cleaned I want to make new electronics around them to have
> another pair. Been thinking that the old original circuit with
> a 6AU6 wired as a triode would be as good as any solid-
> state alternative. Comments? Opinions?
>
> Only component I can't reproduce is the output transformer.
> Anybody have any experience/comment about the "Country
> Boy's Capacitor Microphone" circuit/transformer as Jensen
> has published here?...
> http://www.jensentransformers.com/as/as076.pdf
>
Anonymous
February 12, 2005 2:33:12 PM

Archived from groups: rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
>
>I put new capsules in them because the old ones looked dirty
>and I still have those old caps. Now that I know they can be
>cleaned I want to make new electronics around them to have
>another pair. Been thinking that the old original circuit with
>a 6AU6 wired as a triode would be as good as any solid-
>state alternative. Comments? Opinions?

You'll have trouble finding 6AU6es that aren't noisy in that
application, but they do exist and they are cheap enough that you can
afford to buy a bag of pulls and select one or two that are quiet.

Also the pentodes tend to be more microphonic, even in triode mode,
because they have a lot of closely-spaced elements that can rattle
around.

If you want, I'll send you a submini or two that are reasonable
replacements for the ones used in the later Sony mikes, and which
will be a bit quieter than a 6AU6 or a 5899.

You can also, of course, buy my Shanghai mike retrofit board and use
it with those capsules, though your polarization voltage will be limited
to about 35V.

>Only component I can't reproduce is the output transformer.
>Anybody have any experience/comment about the "Country
>Boy's Capacitor Microphone" circuit/transformer as Jensen
>has published here?...
>http://www.jensentransformers.com/as/as076.pdf

I have no graphics today, but there's no reason not to use a Jensen or
Lundahl transformer. I bet, though, that if you want to emulate the original
Sony, that the current Tamura Microtran transformers are close if not
identical. I also bet the Jensen or Lundahl has better low end.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 12, 2005 2:33:13 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" wrote ...
> Richard Crowley wrote:
>>
>>I put new capsules in them because the old ones looked dirty
>>and I still have those old caps. Now that I know they can be
>>cleaned I want to make new electronics around them to have
>>another pair. Been thinking that the old original circuit with
>>a 6AU6 wired as a triode would be as good as any solid-
>>state alternative. Comments? Opinions?
>
> You'll have trouble finding 6AU6es that aren't noisy in that
> application, but they do exist and they are cheap enough that
> you can afford to buy a bag of pulls and select one or two that
> are quiet.
>
> Also the pentodes tend to be more microphonic, even in triode
> mode, because they have a lot of closely-spaced elements that
> can rattle around.
>
> If you want, I'll send you a submini or two that are reasonable
> replacements for the ones used in the later Sony mikes, and
> which will be a bit quieter than a 6AU6 or a 5899.

I would be honored. I suppose that I don't need much drive
current to produce mic level. :-)

> You can also, of course, buy my Shanghai mike retrofit board
> and use it with those capsules, though your polarization voltage
> will be limited to about 35V.

I understood that the low-voltage capsules have a closer
diaphram-backplate spacing than the ones designed for
high voltage? Will my C-37D capsules work at 35V?
I thought they were designed for 300V?

>>Only component I can't reproduce is the output transformer.
>>Anybody have any experience/comment about the "Country
>>Boy's Capacitor Microphone" circuit/transformer as Jensen
>>has published here?...
>>http://www.jensentransformers.com/as/as076.pdf
>
> I have no graphics today, but there's no reason not to use a
> Jensen or Lundahl transformer. I bet, though, that if you want
> to emulate the original Sony, that the current Tamura Microtran
> transformers are close if not identical. I also bet the Jensen or
> Lundahl has better low end.

The only Tamura/Microtran "Ultra Wideband Audio Transformers"
I found are little 1/4 inch cube things that claim 400Hz to 250KHz
band-width. I'll give them wideband at the top, but I hope Jensen
or Lundahl has a better low end. Else I'd have to limit myself
to recording piccolos. :-)

The power transformer in the originals is almost the size of a
cottage-cheese carton, and the output transformer is roughly the
size/shape of a coffee mug. Perhaps a lot of the bulk is magnetic
shielding(?) Back before the days of mu-metal, I'd assume.
Anonymous
February 12, 2005 4:02:47 PM

Archived from groups: rec.audio.pro (More info?)

On Fri, 11 Feb 2005 12:18:54 -0500, Ty Ford <tyreeford@comcast.net>
wrote:

>A friend want to know if this Sony mic is used in radio by anyone.
>

Yes, MOJO 640 News Radio in Toronto has a bunch of them in service.
There are also a number at the CBC Broadcast Centre in Toronto, but I
don't know how often they are in use.
--
Douglas S. Walker
Walker Microphones
Cambridge, ON, Canada
Tel: (519) 654-0070
Real E-mail: dsw(at)mgl(dot)ca
Anonymous
February 12, 2005 10:09:44 PM

Archived from groups: rec.audio.pro (More info?)

On Sat, 12 Feb 2005 09:37:08 -0600, "Eric K. Weber"
<eric-nospam@webermusic.com> wrote:

>The Country Boy's circuit has no bias on the capsule so it's for an electret
>capsule.

Although no resistor supplies capsule polarization, grid leak
will float the capsule up by at least many tens of volts. It
should be possible measure the cathode voltage and guesstimate
the grid to be a volt or two lower.

Chris Hornbeck
Anonymous
February 12, 2005 10:18:41 PM

Archived from groups: rec.audio.pro (More info?)

In article <110sga04l6pt545@corp.supernews.com> rcrowley7@xprt.net writes:

> The power transformer in the originals is almost the size of a
> cottage-cheese carton, and the output transformer is roughly the
> size/shape of a coffee mug. Perhaps a lot of the bulk is magnetic
> shielding(?) Back before the days of mu-metal, I'd assume.

That sounds like the good stuff - core and wire, probably minimal
shielding. And Mu Metal has been around for a mighty long time.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 13, 2005 1:55:39 AM

Archived from groups: rec.audio.pro (More info?)

Ty Ford wrote:
> A friend want to know if this Sony mic is used in radio by anyone.

Back in '93 when I lived in Lexington, my next door neighbor who worked for
Kentucky public radio said that's what they used.

I have one in mint condition that's spent most of its life in the case, and
I have no use for it. If anyone's interested...say... $750? Anyone???

Jeff Jasper
Jeff Jasper Productions, West Funroe, La.
Anonymous
February 13, 2005 1:03:10 PM

Archived from groups: rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
Scott Dorsey wrote:
>
>> If you want, I'll send you a submini or two that are reasonable
>> replacements for the ones used in the later Sony mikes, and
>> which will be a bit quieter than a 6AU6 or a 5899.
>
>I would be honored. I suppose that I don't need much drive
>current to produce mic level. :-)

That's the basic idea. You don't care about current, you care about noise
floor and to some extent gain.

>> You can also, of course, buy my Shanghai mike retrofit board
>> and use it with those capsules, though your polarization voltage
>> will be limited to about 35V.
>
>I understood that the low-voltage capsules have a closer
>diaphram-backplate spacing than the ones designed for
>high voltage? Will my C-37D capsules work at 35V?

Right. If you take a high voltage capsule and operate it at a lower voltage
than it is designed for, the output level will be correspondingly lower. Also
the frequency response _might_ change, because the electrostatic attraction
of the diaphragm to the backplate is reduced, reducing the resonant frequency
of the diaphragm.

Note that the Shanghai mikes use a capsule that was cloned from the U87,
which is supposed to have a much higher polarization voltage than they
use. This is where some of the problems in those mikes come in.

>I thought they were designed for 300V?

I don't think so... I think 300V goes into the mike input but the capsule
is polarized around 60V or so. You'll have to check the schematic and see.

>>>Only component I can't reproduce is the output transformer.
>>>Anybody have any experience/comment about the "Country
>>>Boy's Capacitor Microphone" circuit/transformer as Jensen
>>>has published here?...
>>>http://www.jensentransformers.com/as/as076.pdf
>>
>> I have no graphics today, but there's no reason not to use a
>> Jensen or Lundahl transformer. I bet, though, that if you want
>> to emulate the original Sony, that the current Tamura Microtran
>> transformers are close if not identical. I also bet the Jensen or
>> Lundahl has better low end.
>
>The only Tamura/Microtran "Ultra Wideband Audio Transformers"
>I found are little 1/4 inch cube things that claim 400Hz to 250KHz
>band-width. I'll give them wideband at the top, but I hope Jensen
>or Lundahl has a better low end. Else I'd have to limit myself
>to recording piccolos. :-)

No, Tamura makes a whole line of nice little audio transformers. Digi-Key
only carries the mil-spec communications things, though. It might be worth
looking for the Tamura web site. They made, for instance, all of the input
transformers for the Yamaha PM-1000.

>The power transformer in the originals is almost the size of a
>cottage-cheese carton, and the output transformer is roughly the
>size/shape of a coffee mug. Perhaps a lot of the bulk is magnetic
>shielding(?) Back before the days of mu-metal, I'd assume.

Is the design such that there is DC on the transformer primary? If that
is the case, such a large transformer might be required to get decent low
end. I am not a fan of such designs, but you see them around.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 13, 2005 1:03:11 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" wrote ...
> Richard Crowley wrote:
>>I thought they were designed for 300V?
>
> I don't think so... I think 300V goes into the mike input but the
> capsule is polarized around 60V or so. You'll have to check
> the schematic and see.

Original, 50s-era "blueprint" manual is online at my website.
Schematic http://www.rcrowley.com/SonyC37/images/diag.gif

It is such a high impedance, I don't know any way of measuring
the actual voltage across the capsule. My scope probes are only
10M and that is the highest-impedance measuring device I have
here. Maybe I can find something at the the office.

> Is the design such that there is DC on the transformer primary?
> If that is the case, such a large transformer might be required
> to get decent low end. I am not a fan of such designs, but you
> see them around.

It appears that there are blocking capacitor(s) to prevent DC
current through the output transformer.
.....
> No, Tamura makes a whole line of nice little audio transformers.
> Digi-Key only carries the mil-spec communications things, though.
> It might be worth looking for the Tamura web site. They made, for
> instance, all of the input transformers for the Yamaha PM-1000.

I'll look for them. Thanks for the lead.
Anonymous
February 13, 2005 2:02:02 PM

Archived from groups: rec.audio.pro (More info?)

Ty Ford Wrote:
> A friend want to know if this Sony mic is used in radio by anyone.[/url]

Yep. There are several stations that still use them on a regular
basis... there are still some stations that still use U-47 FET's too.

The C-48 is a great mic for that application.


--
Fletcher
Anonymous
February 13, 2005 2:32:12 PM

Archived from groups: rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
>"Scott Dorsey" wrote ...
>> I don't think so... I think 300V goes into the mike input but the
>> capsule is polarized around 60V or so. You'll have to check
>> the schematic and see.
>
>Original, 50s-era "blueprint" manual is online at my website.
>Schematic http://www.rcrowley.com/SonyC37/images/diag.gif
>
>It is such a high impedance, I don't know any way of measuring
>the actual voltage across the capsule. My scope probes are only
>10M and that is the highest-impedance measuring device I have
>here. Maybe I can find something at the the office.

You can't, but you CAN measure the voltage between that 3K and 100K
resistor. Since the capsule resistance and grid resistance are more
or less infinite, the voltage at that tap point is going to be the
same as the voltage on the capsule.

You could also get the 6AU6 curves in the tube handbook and see what
the voltages would be with algebra, but it's probably easier to measure
it if it's out on the bench.

>> Is the design such that there is DC on the transformer primary?
>> If that is the case, such a large transformer might be required
>> to get decent low end. I am not a fan of such designs, but you
>> see them around.
>
>It appears that there are blocking capacitor(s) to prevent DC
>current through the output transformer.

Yup, looks like a simple step-down. I don't know why they used so much
iron, but I bet the bottom end is nice!

>> No, Tamura makes a whole line of nice little audio transformers.
>> Digi-Key only carries the mil-spec communications things, though.
>> It might be worth looking for the Tamura web site. They made, for
>> instance, all of the input transformers for the Yamaha PM-1000.
>
>I'll look for them. Thanks for the lead.

They aren't Jensen or Lundahl, but they OEMed for a lot of Japanese
companies over the years.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 13, 2005 2:32:13 PM

Archived from groups: rec.audio.pro (More info?)

"Scott Dorsey" wrote...
> Richard Crowley wrote:
>>"Scott Dorsey" wrote ...
>>> I don't think so... I think 300V goes into the mike input but the
>>> capsule is polarized around 60V or so. You'll have to check
>>> the schematic and see.
>>
>>Original, 50s-era "blueprint" manual is online at my website.
>>Schematic http://www.rcrowley.com/SonyC37/images/diag.gif
>>
>>It is such a high impedance, I don't know any way of measuring
>>the actual voltage across the capsule. My scope probes are only
>>10M and that is the highest-impedance measuring device I have
>>here. Maybe I can find something at the the office.
>
> You can't, but you CAN measure the voltage between that 3K and 100K
> resistor. Since the capsule resistance and grid resistance are more
> or less infinite, the voltage at that tap point is going to be the
> same as the voltage on the capsule.

Bzzzt! Of course! <hand slapping forehead> Dunno why I
thought some (all?) of the excitation charge may be "leaking"
out of the tube grid. I've pretty much avoided dealing with
firebottles in the rest of my life, but in this particular appliction,
it seems compelling.
Anonymous
February 13, 2005 2:32:14 PM

Archived from groups: rec.audio.pro (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:110v1n1kaqnoaa6@corp.supernews.com...
> "Scott Dorsey" wrote...
>> Richard Crowley wrote:
>>>"Scott Dorsey" wrote ...
>>>> I don't think so... I think 300V goes into the mike input but the
>>>> capsule is polarized around 60V or so. You'll have to check the
>>>> schematic and see.
>>>
>>>Original, 50s-era "blueprint" manual is online at my website.
>>>Schematic http://www.rcrowley.com/SonyC37/images/diag.gif
>>>It is such a high impedance, I don't know any way of measuring
>>>the actual voltage across the capsule. My scope probes are only
>>>10M and that is the highest-impedance measuring device I have
>>>here. Maybe I can find something at the the office.
>>
>> You can't, but you CAN measure the voltage between that 3K and 100K
>> resistor. Since the capsule resistance and grid resistance are more
>> or less infinite, the voltage at that tap point is going to be the
>> same as the voltage on the capsule.
>
> Bzzzt! Of course! <hand slapping forehead> Dunno why I thought some
> (all?) of the excitation charge may be "leaking"
> out of the tube grid. I've pretty much avoided dealing with
> firebottles in the rest of my life, but in this particular appliction,
> it seems compelling.

Now I'm wondering how that circuit really works. It seems to
me that while the cathode has quite a bit of DC voltage on it
(because of the 103K to ground), it also has the full AC signal
which is ultimately conducted to the output transformer. Doesn't
97% of the AC output signal make it through the 100M resitor and
into the tube input (grid)? Or does the capacitance of the capsule
with the 100M resistor form some sort of a "filter"? Why
would that "filter" not also affect the audio signal we are trying
to produce from the transducer? It seemed deceptively simple
at first glance.
Anonymous
February 13, 2005 3:25:18 PM

Archived from groups: rec.audio.pro (More info?)

It should be noted that they changed the 3K resistor to a 1K in the late
60's version... I'll have to dig out the drawing for the current C800 and
see what they went with.

http://www.users.uswest.net/~ecweber/c37apg9.html
http://www.users.uswest.net/~ecweber/c37apg9.html

Rgds:
Eric

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:110v1n1kaqnoaa6@corp.supernews.com...
> "Scott Dorsey" wrote...
> > Richard Crowley wrote:
> >>"Scott Dorsey" wrote ...
> >>> I don't think so... I think 300V goes into the mike input but the
> >>> capsule is polarized around 60V or so. You'll have to check
> >>> the schematic and see.
> >>
> >>Original, 50s-era "blueprint" manual is online at my website.
> >>Schematic http://www.rcrowley.com/SonyC37/images/diag.gif
> >>
> >>It is such a high impedance, I don't know any way of measuring
> >>the actual voltage across the capsule. My scope probes are only
> >>10M and that is the highest-impedance measuring device I have
> >>here. Maybe I can find something at the the office.
> >
> > You can't, but you CAN measure the voltage between that 3K and 100K
> > resistor. Since the capsule resistance and grid resistance are more
> > or less infinite, the voltage at that tap point is going to be the
> > same as the voltage on the capsule.
>
> Bzzzt! Of course! <hand slapping forehead> Dunno why I
> thought some (all?) of the excitation charge may be "leaking"
> out of the tube grid. I've pretty much avoided dealing with
> firebottles in the rest of my life, but in this particular appliction,
> it seems compelling.
Anonymous
February 13, 2005 3:52:18 PM

Archived from groups: rec.audio.pro (More info?)

Richard Crowley <rcrowley7@xprt.net> wrote:
>Now I'm wondering how that circuit really works. It seems to
>me that while the cathode has quite a bit of DC voltage on it
>(because of the 103K to ground), it also has the full AC signal
>which is ultimately conducted to the output transformer. Doesn't
>97% of the AC output signal make it through the 100M resitor and
>into the tube input (grid)? Or does the capacitance of the capsule
>with the 100M resistor form some sort of a "filter"? Why
>would that "filter" not also affect the audio signal we are trying
>to produce from the transducer? It seemed deceptively simple
>at first glance.

This circuit uses the same resistor to charge the capsule up as it does
to set the bias on the input grid. This means that when the circuit is
completely stable and there is no signal, there is no current flowing
through the 1G resistor.

Now, when there is modulation and there is AC going through, there is
a filter formed by the capsule capacitance, the Miller capacitance of the
tube, and that resistor. And that is what restricts the total system
response. This is why using higher and higher value resistors on the
front end becomes important.

It's easier to think about the standard circuit with a pull-up 1G resistor
from the capsule to a regulated supply, a blocking cap between the capsule
and the tube grid, and a 1G from the tube grid to ground. BUT such a
circuit has a lower input impedance!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
!