[Elecraft] Fwd: D 104

[Sam Morgan]

ok since this thread has assumed the usual endless back and forth,
and before it is ended by the powers that be,
I'd like to repeat what I said when I first answered,

I now use an amplified D-104 on my K3
yes it does some impedance transformation magic,
that's not why I use it, it just has a prettier finish
than the un amplified one I have.

I have a local blind ham who has run an audio board
for recording studios and bans for the last 30 years
he has known me for the last 20 years,
so he knows my natural voice.

He helped me set up the K3's EQ and mike gain
for the amplified D-104 to where
it sounds exactly like I do in person

I then switched to the un amplified D-104,
the sound (frequency responses) were exactly the same!

I also have one of the ceramic heads,
nicknamed the D-104 Sideband Head.

I then swapped around the 3 different mikes and elements
others that listened were completely unable
to tell which mike and element I was using,
the all sounded good and identical in response.

So my vote is for the position that says
when the K3's EQ and mike gain are set up correctly
you can't tell a bloody bit of difference!

P.S. just to muddy the waters further
I also bought one of the Yamaha 400 headsets
and after adding the voltage required to the rear mike jack
again you can't tell the difference from the D-104's
all get glowing 'natural' audio reports

and that's my 2 cents
over

GB & 73
K5OAI
Sam Morgan

On 6/4/2011 8:42 PM, Paul Christensen wrote:
>> Then why not just put a 1 megohm or so resistor in series with the mic
>> element.  I believe the K3 mic input has adequate gain to compensate for
>> it, and it will keep the crystal (or ceramic) mic element happy.
>> The KISS principle applies - a resistor is much more simple than an FET
>> or a transformer.
>
> Plenty of folks have been doing that for decades with their D-104 mics.
> It's fine unless you want to optimize SNR as the source Z of the generator
> (D-104) increases by the amount of the added resistance .  I've tried it
> both ways, and a JFET configured either as a source-follower or
> common-source amp with a J201 JFET has always been noticeably quieter when
> compared to the addition of a single resistor after mic element.
>
> For the K3, it's easy to optimize the D-104 with a JFET by using exactly two
> parts: a pair of resistors.  That's just two more parts than one 1 meg-ohm
> resistor.  In  the K3 menu, one simply activates mic bias.  When using a
> JFET as a common-source amplifier, the drain resistor is supplied by the K3
> (R89 = 5.6K).  A 1uF cap also internal to the K3 (C28) isolates audio from
> the DC bias injection.  That leaves only a source resistor and gate leak
> resistor.  Sure, not quite as economical as a single 1 meg resistor after
> the mic element, but with only three total parts, I find that the added
> performance more than offsets the addition of a two more parts.  In one of
> my D-104 mics, the JFET and two resistors are mounted with adhesive tape
> right on the back of the D-104 element.  It doesn't get much simpler.
>
> The JFET is functioning only as an impedance transformation device -- it is
> not matching impedance, nor does it need to for the reasons cited by you and
> K9YC.
>
> Paul, W9AC