Does anyone have a design for a FET preamplifier for a
D-104 that will work off the K3 mic bias (rather than the
separate +8V line) and the typical 3.3V mic bias in the
current crop of laptops?
I'd like to avoid providing separate preamp power when
the mic is connected to a computer soundcard ..
> Does anyone have a design for a FET preamplifier for a
> D-104 that will work off the K3 mic bias (rather than the
> separate +8V line) and the typical 3.3V mic bias in the
> current crop of laptops?
Joe,
I would try the circuit shown in the link below.
http://72.52.250.47/images/ECM.png
Refe
I have used the following circuit on a D104 to my K2:
http://members.cox.net/n4jk/d104.htm
Works great and you wire it for power through the mic connector.
Mark
W5EZY
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Sent from the Elecr
> I have used the following circuit on a D104 to my K2:
>
> http://members.cox.net/n4jk/d104.htm
>
> Works great and you wire it for power through the mic connector.
That circuit won't work with the K3's bias on mic pin (Joe's intended use).
To work that way with mic bias, power and audio must be
Joe,
If you aren't married to the original element you could change it out to an
electret element wired directly to the K3 input with the bias turned on. I
did that than trying to find a replacement crystal element.
The electret element is available from many sources (including your local
Radio
George,
> If you aren't married to the original element you could change it out
> to an electret element wired directly to the K3 input with the bias
> turned on. I did that than trying to find a replacement crystal
> element.
If I were going to change the element I would change it to a Hei
I said it once, and I'll say it again.
My 1956 crystal-element D-104 works great with my K3. I plugged it in and
did an on-the-air check with K9YC. Jim reported outstanding audio. Before
modifying your D-104 or building a preamp, try the bare-bones D-104.
K9YC: If you don’t have a problem, don
> I suspect the solution lies in an MPF-102 as a common source amplifier
> with a 470 Ohm resistor in the source lead, 680K to 1M as a gate leak
> to set the low frequency roll of at around 150 Hz (my preference -
> since I see absolutely no benefit in reproducing unnecessary and power
> wasting lo
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