Meter project

Discussion in 'General Audio Discussion' started by ducati2, Jun 11, 2018.

  1. ducati2

    ducati2 Well-Known Member

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  2. WaynerN

    WaynerN AK Subscriber Subscriber

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    I have built a couple of VU meters. The driver boards are 12 volt, so they usually need a 120v to 12vdc wall wart. The meters are powered by the board which in turn, gets it signal from record outs found on almost all receivers and preamps.
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    Wayner
     
    Last edited: Jun 11, 2018
  3. Justgotohm

    Justgotohm AK Subscriber Subscriber

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    Those are cool. If your using the record outs are they variable? Interesting enough I have a couple of these NOS Denon DSV-1’s coming to play with. They were originally used in car audio, 12v, variable RCA in and outs for signal.
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    I originally was on the hunt for the Mac MPM 4000 which was also used in car audio. It is an accurate meter and calibrated for 4ohm speakers. It requires speaker lead in and outs from the amplifier. The Denon has adjustable signal pots but is cheap in comparison. I’ve always wanted to build some meters after seeing the parts available relatively inexpensive.
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  4. WaynerN

    WaynerN AK Subscriber Subscriber

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    Why would you want them variable? They are calibrated.
     
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  5. Lavane

    Lavane AK Subscriber Subscriber

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    Variable would be good if used at line level. Say plugged in to a tape out. Being able to switch from say, 1 watt, 10 watt, 100 watt, etc. might be a good idea. I have a watt meter that is a B&W CRT with the screen split for left and right channel. Kind of cool. It has a switch for power input.
     
  6. Justgotohm

    Justgotohm AK Subscriber Subscriber

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    I may not understand how the meters work. I was assuming if it is record out it is a constant signal at a certain voltage. Using pre outs the voltage would rise resulting in the meters going up higher as you turn up the volume. I may be confused with the difference between signal meters and power meters or not understanding the design and function at all?
     

     

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  7. woodj

    woodj Super Member

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    Same thing except the numbers on the dials.
     
  8. ducati2

    ducati2 Well-Known Member

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    I know just enough to be dangerous, but you may have just answered why one set of meters I have that I hooked to the tape out jacks do not respond to volume settings. If I move to the pre-out ports maybe they will work as I want? Just don’t want to burn up my meters ..
     
  9. twiiii

    twiiii Addicted Member

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    All VU meters lie. Macs meters less than 2% up to 2000 HZ. Some of the older owners manuals show a chart of the error versus frequency and level of modulation. professional VU meters using needles in the past could have up to 18 db errors of peak versus continuous signal levels. The mechanics and ballistics of the needle are the problem. Electronic displays using LED's or those using visual displays on OLED screens or CRT tubes are much more accurate. The response time can be so fast the human eye and brain can't perceive the energy displayed. I grew with the old Prof. VU meter and got a feel as to what was actually happening. I was never comfortable with peak meters like Nakamichi used on their early machines. My later machines with LED read outs were more accurate. I have Mac amps with three different types of meter and display options. The original on my 2505 Which I much prefer though the range is much smaller 20 db . And the latest 60 db scale. The older meter shows more small details which I prefer but the newer is more accurate and can display digital recordings with a much wider dynamic range when called for. So unless you are usig Mac meters or meters by Accuphase, I would be preprepared for at least 10 db inaccuracy and most likely much higher. During the disco craze there were horizontal displays mounted in 1 space rack plates that we used to try to keep a lid on the DJ's. Thank God for Power Gard and Urei Compressors and limiters.
     
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  10. ducati2

    ducati2 Well-Known Member

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    twiii - great lesson in meters, but as the OP, I was really just interested in a cool way to 'see' my music. I am not measuring anything. Maybe a disco setup is what I truly seek. ha.
     
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  11. motorstereo

    motorstereo AK Subscriber Subscriber

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    My Mitsubishi meter box has switchable sensitivity and also has adjustable gains. It's a necessary function if it's being used on the pre-outs (like mine is) to keep from pegging the meters and damaging something.
     
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  12. Justgotohm

    Justgotohm AK Subscriber Subscriber

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    The jumpy needles are fun, I did actually find a flaw in some interconnects using meters. It was slight but enough for the music to (not be right). I watched for peaks then switched the sides and saw the same drop in the meter. I would say 90 percent of the time meters are just jewelry but they are fun. If the little Mac unit wasn’t $400 used I would definitely have one in my vehicle.
     
  13. WaynerN

    WaynerN AK Subscriber Subscriber

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    No. A preamplifier does not affect the record outputs at all. Those signals do not even pass thru the preamp's main section if they are going to the record outs. In fact, they would work with the preamp off.
     
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  14. Justgotohm

    Justgotohm AK Subscriber Subscriber

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    Thanks, I understand that. I was confused with using record outs the meters would not raise as the volume is increased given record out is not variable as in it is not effected by volume. I’m assuming in this design the meters are for the signal not the relative volume or wattage the amp is seemingly producing. I guess like the meters on a reel to reel and not like the meters on an amplifier. I maybe reading to much into this.
     
  15. ducati2

    ducati2 Well-Known Member

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    In same boat w justgotohm,, I was trying to get my Coleman mb2 meters to respond to the volume setting on my kenwood kr6160 receiver, sounds like it can not be done...?
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  16. WaynerN

    WaynerN AK Subscriber Subscriber

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    Now you got it.
    You want power meters that will respond to power output from your amp in relationship to your preamp's volume control. That is a different animal then VU meters. There are power amplifiers with meters that are labeled VU and it is confusing what they are actually measuring.

    At any rate, I use my VU meters to check left/right balances, and if things are working as they should. It's a handy tool that has found problems a time or 2.
     
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  17. gdmoore28

    gdmoore28 Super Member

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    I just ordered the kit your referenced - and for no reason other than to watch them jump. :dunno:

    If I can get them to work properly, I intend to mount them on an aluminum equipment rack spacer and build a mahogany box around them. Just for fun - nothing else.

    GeeDeeEmm
     
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  18. ducati2

    ducati2 Well-Known Member

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    Post your finished product so I can see how you brought power to it. I mean — does the wall 120v ac to 12v dc unit plug right into this kit?
     
  19. gdmoore28

    gdmoore28 Super Member

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    Hmm. I'm a little confused as to how this driver should be powered. There are two 12V inputs (+ & - on each) and two "VU" inputs (again, + & - on each). How should this be wired. (I know there might be instructions included, but you know how the Chinese translations are . . . :crazy:)
    [​IMG]



    Another question: the line/signal input on this driver has terminals for "L," "R," and "G." (Left, right, and ground.) Which output on a preamp is likely to have a common ground for both signals? My old Dynaco PAT-IV preamp has three outputs to choose from: L/R Output 1; L/R Output 2; and Tape Output. I guess I just need to grab the schematic and see if these have common grounds. If not . . . . . ????? :dunno:

    GeeDeeEmm
     
    Last edited: Jun 13, 2018 at 9:00 AM
  20. ducati2

    ducati2 Well-Known Member

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    it is also advertised as VU meters, which I think means they will not respond to our volume adjustments. If they are true VU meters... I think I would like the kit better if they were power meters and the size of the meters were 2x.
     

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