[Elecraft] D 104

[Paul Christensen]

If an active transformer/buffer is really desired, I recommend staying away 
from an op-amp circuit.  A single-stage JFET transistor uses fewer parts, is 
generally less susceptible to RF, and there's no voltage-divider bias needed 
** -- and still have the benefit of a high-Z input and low-Z output.  See my 
QRZ.com page for D-104 alternatives with the K3.

Beware of Google searches on this topic.  Most active transformer D-104 
circuits I've seen on the web are incorrectly designed and several use 
superfluous components, the exception being W8JI's design which is similar 
to the one shown on my QRZ.com page.

Paul, W9AC

**  Most op-amps are designed for use with bi-polar power supplies.  When 
used with a single-supply rail, the op-amp input must be biased such that 
the output is 1/2 the supply rail with no input signal present.

----- Original Message ----- 
From: "Lou Kolb" <loukolb at gmail.com>
To: "elecraft" <elecraft at mailman.qth.net>
Sent: Saturday, June 04, 2011 2:45 PM
Subject: Re: [Elecraft] D 104


> You'd also be well advised, if its an unamplified D-104, to add one of the
> op-amp matching circuits which can be powered from the K3.  It'll make the
> D-104 look into the 10 megohms or so that it likes and it will sound much
> more natural. a Quic google search should yield a few of these circuits.
> Lou WA3MIX
> ----- Original Message ----- 
> From: "Sam Morgan" <k5oai.sam at gmail.com>
> To: <elecraft at mailman.qth.net>
> Sent: Saturday, June 04, 2011 1:30 PM
> Subject: Re: [Elecraft] D 104
>
>
>>I use an amplified D-104 with my K3, excellent audio reports.
>> I have also used an un amplified D-104, with equally good reports.
>>
>> Try your local radio shack for the 8 pin jack.
>>
>> 8-Pin Ham Microphone Plug
>> Model: 274-025  | Catalog #: 274-025
>> $4.19
>>
>> http://www.radioshack.com/product/index.jsp?productId=2062445
>>
>> GB & 73
>> K5OAI
>> Sam Morgan
>>
>> On 6/4/2011 12:22 PM, CHARLES WHITE wrote:
>>> I would like to connect a D 104 mike to the K3 but the D 104 is a 4 pin
>>> jack and the K3 is 8 pins.
>>>
>>> I have not been able to find a 8 pin jack for the mike at either MOUSER
>>> or DIGIKEY suppliers.
>>>
>>> Does any one use the D104 with the K3?
>>>
>>> Any advise?
>>>
>>> Thanks
>>>
>>> Charlie White
>>> K6TBB
>>> San Diego
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