Lewitt MTP 840 DM Dynamic Vocal Microphone

Unusual usage case: I bought this to feed into an amateur radio transmitter (an Icom 9100, which comes supplied with an 8V fed condenser mic and has a very low 680Ω input impedance) and I used an Art Pro phantom feed to both power the mic and isolate it from the transmitters internal 8V phantom feed. Enabling the 6dB gain option got the level within range of the mic gain control and it all sounded very nice indeed.

A few days later, I added a dbx 286s to add a touch of compression and with that device, I just used the Lewitt mic in passive mode and it all sounded excellent. Pondering the mic activator situation, I then tried it in active mode (both +6dB and +12dB) with the dbx 286s providing phantom power and it didn't make much difference (if anything, I thought passive was better) but remember that we’re talking about a radio with noisy internal circuitry, so the mic activator trick would be pretty pointless.

So, I reverted to passive, had a listen, then just out of sheer curiosity, I again tried the Lewitt active, but this time with its internal preamp set to 0dB. I expected to hear little difference, but to my great surprise there was noticeably more detail and it added a vibrancy to my voice; it made a fabulous sound! I reverted back to passive and by comparison it all sounded 'closed in' and the voice sounded rather lifeless, so active and set to 0dB gain is how it will now remain.

Okay, the amateur radio is a very bandwidth restricted system and for anyone who’s curious, I was using FM mode for the tests (and a separate local receiver – a FT-817 – feeding my Beyerdynamic DT-131 headphones) and even given the system limitations, the difference was really quite obvious and the resultant audio is now first class.

As to speculating on why it made a difference (I’m only using 3m of Mogami Starquad to the dbx) perhaps the dbx has an input impedance of 4.2kΩ and Lewitt's internal preamp has a higher impedance and thus better suits its capsule? I have no idea, but hey, whatever the reason, the results are very good indeed.

It seems a shame to use such a lovely microhone for ham radio, but my goodness it sounds good and with the preamp enabled (and set to 0dB gain) it sounds even better when feeding the dbx. I'd love to hear it in a studio and with someone 'proper' singing into it (not me; I can’t even sing) as I'd expect it would sound pretty amazing.

Briain