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tone control on your d104-m

Discussion in 'CB Radio Modifications' started by bob85, Aug 5, 2005.

  1. bob85

    bob85 Supporting Member

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    have you ever wished you could change the tone on your d104 like you can with the 575, I did and its easy,
    the late d104 and the 575 use same amplifier and same cartridge but the 104 uses a fixed load resister and the 575 uses a 100k in series with a 2meg potentiometer, if you want lots of bass then clipping the load resister will do the trick but i dont recommend that even though some have done it and are happy with the sound, a better way is to use a 2meg potentiometer in series with the 270k fixed resister thats in the mic already, unsolder the end of the 270k thats connected to ground and either insert a 2meg/2.5meg pot, middle wiper leg goes to the lifted 270k resister and one of the remaining legs goes to ground this will give you a good range of tone adjustment, or if you want to be stingy you could just use a fixed resister around 500k to 1 meg to get a bass boost without going ott, heres a pic to help you locate the resister
    [​IMG] if you just want to remove some trebble for ssb use then a small value cap in series with a 500k resister connected from the wire end of the 270k load to ground will do it, I would start with a .0022uf cap and see how it sounds if its removed too much then go smaller on the cap.


     
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  2. Switch Kit

    Switch Kit Active Member

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    I ran a 575-M6 for damned near 15 years in my motor cars / and even tried it on the base a few times ,my experiance with those and the tone control slider on the side of the mic is that it always sounded best in the middle ,it was kind of strange though ? up or down on the slider would almost give what sounded like a off frequancy sound ,very strange ? I have since retired my 575-M6 in my motor car /RK-56 all the way these days/ I still don't know what in the hell I was thinking all those years with that power mic in my ride ? I was never much for road noise or back ground modulation coming in ,tuned up radios I would only have to crack the volume control sliders on those anyway (it was the same with the D-104 hand helds) I suppose depending on how the radio was tuned ? I never really needed a power mic / IM very pleased with the RK-56 being a NC mic along with not being amplified/I suppose it just dependings on how ones radio has been tuned in many cases ? I notice the 575-M6's are going for a very good price these days on Ebay ,saw one go for 100 bucks the other day !! Remarkable !!
     
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  3. bob85

    bob85 Supporting Member

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    i hear you on the price, i see them going for £50+ used which is more than they ever cost new, even the d104's are £48 plus shipping and people here pay it which is crazy, i just bought a brand new d104 from ebay usa which cost me £26 and thats including shipping from the seller to my buddy and his shipping costs to me.
     
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  4. fatdude1

    fatdude1 Active Member

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    Thanks bob for the info
    I have a D104 that sound's like poop going to try what you posted and see
     
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  5. mackmobile43

    mackmobile43 Jock Supporter

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    It works great.
     
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  6. loosecannon

    loosecannon break on through

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    i will second that it works great.

    i am very happy with mine.
    not so tinny sounding anymore.
    LC
     
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  7. mackmobile43

    mackmobile43 Jock Supporter

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    [​IMG]
    [​IMG]
    [​IMG]
     
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  8. bob85

    bob85 Supporting Member

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    (y)
     
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  9. Robalo

    Robalo Active Member

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    [​IMG]

    [​IMG]



    i couldn't lift the pc board so i couldn't figure out the ground side of the resistor, so i did it this way and I wonder if this is the right way because i dont have a microphone tester.
     
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  10. bob85

    bob85 Supporting Member

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    that should work fine from what i can see robalo;)
     
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  11. fnkycoldmedina

    fnkycoldmedina Well-Known Member

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    i would like to try this too.....i actually have a m6b thats a little bassy on my rig.how can i add treble?can someone donate me a pot to do this mod with ?or does radio shack have them?
     
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  12. bob85

    bob85 Supporting Member

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    fnky the only d104's i ever heared that were too bassy are the old original large cartridge versions with the 2 stage amplifiers like the 555 truckers,
    you could reduce bass by reducing the value of the load resistor across the input to the amplifier to reduce the cartridges ability to make bass,
    just a reverse of what i do with the newer ones that sound tinny,
    you are restricted in how much trebble you can actually add while leaving the bass response where it is because the mics dont have enough capacitance to ground that you could alter to make a significant boost in trebble,
    i never managed to get the old style sounding as sweet as the tone modded new ones but big improvements can be made on just about any microphone or radio.
     
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  13. KC2OST

    KC2OST BANNED

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    im screwing with one now.. would rather have a fixed resistor than a adjustable pot..

    anyone try it the hard way yet?
     
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  14. bob85

    bob85 Supporting Member

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    whats the hard way?
    i tried fixed resistor clipped resistor and tiny surface mount pot, the pot was the most tricky to solder by far but it works perfect, fixed resistor works just as well its just more messing about finding the one that suites your voice and the radio you use, clipping the resistor gives too much bass for my ears,
    astatic never changed the case front when they changed to the smaller cartridge, putting foam or a baffle around the cartridge to seal it against the case front helps remove coloration from reflections within the case,
    a bit of work and you can almost make a silk purse out of a sows ear.
     
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  15. KC2OST

    KC2OST BANNED

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    has anyone "stabbed" the points on the back of the board to see
    what value they come up with after they get the mic set right?

    oh.. hard way = fixed resistor..
     
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