Adding a meter to a preamp

Discussion in 'Tech Talk - Electronic Repair Modifications DIY' started by DonnyThompson, Jun 26, 2015.

  1. DonnyThompson

    DonnyThompson Distinguished Member

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    Thanks for the explanation, Bos. :)
     
  2. Kurt Foster

    Kurt Foster Distinguished Member

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    Jul 2, 2002
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    77 Sunset Lane.
    i'm guessing the barrier strip is an adaptation for the shield for balanced in and outs ......
     
  3. eric labrie

    eric labrie Active Member

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    Mar 11, 2016
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    Quebec, Canada
    If you want to track the output with a vu, you have 2 option. One is to use a true vu meter, rated about 20micro amp IIRC, rated for 600ohm output with an external 3k6 serie resistor. You have tp use an rectified vu meter. Note this will add a little distortion due to the diodes. The other option is to use a driver board to implement the vu meyer. Thevsignal stay clean, you can somewhat adjst your 0 db, but you need something like 9 to 15v to drive it, which can be problematic sometimes when there is no rails in the psu for such voltage.
     
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  4. DonnyThompson

    DonnyThompson Distinguished Member

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    Thanks Eric.

    But I've kinda given up on the idea, and instead have taken note of the varying differences of XFO's and OpAmps, and that method seems to be working okay.

    I understand why the AP1 doesn't have metering; when Jon Erikson designed it - with the help of Justin Morse; and Larry Villella from ADK talked about the AP mic pres and priorities ( in his own words, "We spent so much money on the engine there was none left to put into a shiny paint-job and chrome bumpers...") they ended up spending a lot of money to hand-fabricate it, using top of the line standards, so costs had to be cut on "extras" - like a VU/LED, as well as on the cosmetics, which is understandable, as these things don't contribute to the quality of the sound.

    It's a very "sparse" looking preamp, but they put the money into where it truly counts - under the hood. Top quality components and wiring were used, and in the end, the quality was to the level that it couldn't compete with other cheaper mass produced preamps - it seems as though everyone wants "Made in The U.S.A." products, but they want them at Chinese prices. Personally speaking, if I found a pre that sounded great, I wouldn't care if it were mounted in a pine box with hand written magic marker lettering.

    ;)
     

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