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Julie KC0TMD
Julie KC0TMD Member ✭✭
edited June 2020 in Third-Party Software

I have a FLEX-6600M. I just picked up a new PreSonus TubePre V2 Single-Channel Tube Preamplifier/DI Box from Guitar Center today. I got it home with and it hooked it up, and nothing is working and it won't even drive to the VU Meter in the V2 Mic Pre Amp VU.

I notice that when I remove the PreSonus TubePre V2 Single-Channel Tube Preamplifier/DI from between the my Mic, Flex-6600M and PALSTAR LA-1K AMP, eveything is working as it should with+20db in the radio setup and Bias off.

After getting confused and putting the mic in the output and the Radio
in the Input. I then had to find the correct cables that I did have on
hand. I finely was able to get the Mic in to the Input and the Radio to the output of the Mic Pre Amp.

According to the user manual of the PreSonus TubePre V2 Single-Channel Tube Preamplifier/DI, the first thing is to hook your balanced mic up to the Mic input and adjust the Drive.

Set the input level on your audio interface or mixer, using the recommended level-setting procedure for that device.

Speak into the microphone while monitoring the TubePre V2 (again, following the monitoring instructions for your audio interface or mixer), and turn the Drive knob clockwise until the desired effect  is is achieved.

Speak into the microphone while watching the VU meter on the front panel and slowly turning the TubePre V2 Gain knob clockwise.

The entire user manual can be found at,


I notice that if I keep the drive down to 0, and toy around with the Mic Gain, I can get my LA-1K Amp to have spikes from 150 to 300 watts for a few sec, but no SSB carrier. I notice to even get it to the spikes I have to set select the the BIAS and the +20 DB.

I don't get this, but I seen photos of Flax Radios users with that same Mic Pre Amp. What I not doing or failing to do!

Once again with the  PreSonus TubePre V2 Single-Channel Tube Preamplifier/DI removed, my PR40, FLEX-6600M and PALSTAR LA-1K works with no issues.

Any Help would be greatly appreciated in this matter.

My Phone Number is 636-578-1990.

Thank You,

Julie K0CTMD.


  • Paul - K6HR
    Paul - K6HR Member ✭✭
    edited May 2020
    Hello Julie,
    Which input on the radio are you connecting the output of the preamp to?
    It should be connected to the LINE input, and LINE should be selected as the input on the "P/CW" tab. HTH.
  • Rick N0VT
    Rick N0VT Member ✭✭
    edited May 2020
    Hi Julie--Unlike FM, AM or CW, there's no power output with SSB until you have audio.   That's why you see the output spikes.  It sounds like It's working the way it should.

    Rick WR0H
  • David Decoons, wo2x
    David Decoons, wo2x Member, Super Elmer Moderator
    edited June 2020
    Another thing, make sure phantom power is disabled on the tube pre. The PR40 is a dynamic mic and the 48 volts can damage the mic.. What input are you using on the Flex? Mic, line, or balanced? Make sure your selection on SmartSDR matches the input you are using. If you are not seeing any audio on the level indicator on the mic pre then that is where you need to start looking. I am not familiar with that equipment so cannot offer any additional advice. Dave wo2x
  • Bob Needleman
    Bob Needleman Member ✭✭
    edited May 2020
    Dynamic mikes, like the Heil PR-40 and all Bob's  other mikes designed for amateur use, do NOT need any preamps. Mike preamps are generally reserved for use with condenser mikes, which require phantom power and amplification. So that is not the right mike to be using with a mike preamp. 

    Bob K3AC. 
  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator
    edited May 2020
    Julie, what are you trying to accomplish with the preamp?  It sounds like it was working without it.
    Len, KD0RC
  • Bob Needleman
    Bob Needleman Member ✭✭
    edited May 2020
    Julie - if you're trying to do external EQ with a PR-40, I'd return the tube preamp, and pick up a mixer board (eg. Behringer Xenyx) or W2IHY EQ Plus box. That will allow you to connect your PR-40 and have external audio control over several parameters, such as parametric EQ, echo effect, background noise reduction (eg. amp blower noise), etc. I use a W2IHY EQ Plus with my RE-27 dynamic mike feeding the audio into the rear mike jack with very good results. It has a built in pre-amp circuit if you need it, but with a PR-40 you won't  need it. 
    Bob K3AC
  • Brian Denley  KB1VBF
    Brian Denley KB1VBF Member ✭✭
    edited May 2020
    But it’s the right mic for the Flex.  Keep the mic and dump the preamp

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