I wish to wire up a Silver Eagle D-104 Mic to use with my Maestro C

KG5PTE

Hello, with the new Maestro C having a PTT 1/8 jack that requires Tip Sleeve (TS) and the HDST 1/8 jack that requires Tip Ring Ring Sleeve (TRRS) can I wire up a 1/8 jack for a old Silver Eagle D-104 mic and make it work ? This morning at our monthly radio club meeting I asked if it could be done. The question that I was told to ask the Flex experts is this. "Will the Flex 6400 and Flex Maestro C work with a high impedance mic" ?

Thank you.

Mike-VA3MW

Typically, the Mic impedance is pretty low for these connections, but I am checking with our engineers. Usually under 100 ohms.

For a high impedance Mic you'll like need to do some impedance matching which is pretty simple to do.

KG5PTE

Any word from the engineers about the D-104 Mic ?

Mike-VA3MW

The Mic Impedance on the Maestro is about 32 ohms. This is done to limit RFI issues.

KD0RC

Hi James, I would just give it a try. The Flex has a built in 20 dB pre-amp if you need it. If that isn't enough, then I think that there are little amps available that fit in the D-104 base.

johnn1jm

In using a D-104 with a low impedance input, it is best to use something to match the impedance such as a transformer or an FET source follower circuit. You may be able to drive the radio without impedance matching ok but the frequency response will not be great.

YMMV

KG5PTE

My Friend (NU5D) who is wiring up the D-104 mic for me told me this in response.

Good
info.  The cartridge itself is around 100 k ohm and needs maybe 1 Meg
ohm in series to bring up the low end of voice (otherwise the D104 is
very tinny)...   Trouble is 1 meg ohm in series will really really knock
down the output of the cartridge (called a swamping resistor)...  That
needs to be made up with a pre-amp stage.  The 20db in your radio might
just be enough - easy to try.  I just need to wire the plug to the
cable.  If there is not enough drive, then I might have to add a preamp -
these are little ready made boards that boost the loudness.