[ARC5] BC-230 mic

[AKLDGUY .]

To run the filaments on 12.6 VDC (with 6AQ5's), I've decided the easiest
way is to use a discarded laptop or monitor power supply. These supplies
can even be bought brand new (about $55 here).

They usually supply 18 or 19 VDC at anything from a couple to quite a few
amps. I calculated that a series resistor of 7.8 ohms (2 x 3.9 @ 10W) will
drop the voltage to around 11 or 12, with fine setting done by fitting shunt
resistors across the 7.8 ohm resistor until the voltage reaches 12.6.

73 de Neil ZL1ANM

On Fri, Nov 7, 2014 at 3:16 PM, Ben Hall <kd5byb at gmail.com> wrote:

> Hi Neil and list,
>
> I plan to do something similar for my BC-230: Use a Motorola microphone
> with a built-in transistor pre-amp fed from the 12.6 VDC line as you note
> below.
>
> I've not tried it on the BC-230, but looked good on the scope with my
> 9-year old son singing into it...  ;)
>
> thanks much and 73,
> ben, kd5byb
>
>
> On 11/6/2014 7:25 PM, AKLDGUY . wrote:
>
>> I'd like to use an electret microphone from a taxi radio with the BC-230.
>> If the filaments were run on 12.6 VDC and the DC feed to the mic via
>> the primary of the mic transformer was retained, there should be enough
>> power for the electret mic plus a small preamp to develop a volt or two
>> of audio in the primary.
>>
>> It should be possible to use the same wire for the DC feed and audio by
>> using a dropper resistor to supply the mic and preamp. The audio would
>> be developed across the dropper resistor, which would need to be very
>> well decoupled on the mic/preamp supply side. Has anyone tried this?
>>
>
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