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Posts posted by nanopoylos

  1. hello guys
    i wanted to make an active filter for my car
    nothing special

    no need to be adjustable , no need to have more gain , my car r/cd is 4 volts preout

    i found some very interesting chips in maxim
    active filters with programmable q,f0,anything
    i bought some ic's from maxim max262,264,265,274,275,278
    i have the documentation but its very complicated to me

    i am ascing if someone has a site with ready projects for this chips or with other chips
    i do not want to use op-amps nad calculate anything on the paper , i just cant , i do not know how to do that

    i think the project with maxim is much more easy but i cant make it work

    please help me anyways
    thank you

  2. my digital multimeter is a true rms meter
    when i am measuring a signal 1khz 1Vpp , it does not show me the peak value , but the rms value
    is there any way to read the peak value?

    (even with the max feature on , it shows me the max RMS value , not the peak value)

    another problem is that with my osciloscope i do not see that the rms value is correct , it has a +/- 5% up or down
    why is this happening?

    when i see 1 volt Vp on osciloscope Vp (not Vpp) in the multimeter i should read 0,707 ? right or wrong .Because i read 0.667 .
    where is the problem ?

  3. thank you for replying

    actualy i think tha t you both are right

    GPG is right cause what i saw was on a mixing deck , and not a power amp

    Audioguru is right too for the problems he said that tis project has

    anyway , what can we do to make the project?
    i think the solution of the 3 leds was pretty good

    maybe i will try the project from westhost , ive seen many projects from there and they are all good

    what about the LM? wich should i use?
    i am interested on a output indicator for the ffinal amp
    the inputs to the final amp are beeing set by an osciloscope , so they do not clip .They outpts maybe will clip

    i am waiting for a new reply !

  4. Thank you for replying
    as for the project i cant understand the diference between a project for an power amp and a project for a mixing console

    as you say they are not the same

    well , i set the gains for my amp with an osciloscope , so the inputs are not clipping for sure
    but what about the output of the final amp?
    That is what i want to monitor , the outputs

    I think GPG is right , a mixing console is not an power amp
    But i think that audioguru is also right for the problems with the output of an power amp

    so what can we do?
    the project audioguru posted is very nice , but complicated , i think i will try it :) . i know the sound.westhost , and the projects are very good , and the explanations are too :)

    my idea was not to use an IC , but i think this cant be done , i dont know , you know !

  5. I was on a studio , and i saw a 32 channels console for recording.
    I noticed on EACH channel 3 leds

    A yellow , that showed PRESENT of signal (guess -20dB)
    A green that showed 0 dB signal
    A red (non adjustable !?) that showed distorsion , clipping

    So , i think , if this console has 32 circuits like this , they must not be very complicated

    Imagine how usefull circuit can it be , on the car amp , on the home amp , on everething !!!
    For us who construct usefull projects , i think this is a MUST HAVE

    I think even only red and yellow leds are fine , forget the green led !!

    But there must me some adjustment because each one will use this project on diferent purposes (amps with diferent amps , etc)

    the clipping means present of dc , negative or positive , so that time the led flashes
    the yellow led should have some transistor that can find low signals
    for the green led i can not imagine the circuit

    the whole circuit its impossible for me to find (i am a newbee in advanced electronics,IC's etc), but a electronic i think can make it !!

    So i say lets start building this , and put it on every audio source we have (calm down :P)
    More than that we make it even better if forum's readers have anything else to suggest

    Go GO GO electronic maniacs!
    i am dying to see a diagram ;D

  6. Thanks for replying
    Actually it is a function generatos with max frequency 2MHz

    I tied the TTl output in my osciloscope and i found a +4Volt signal (the dc offset doesent work in TTL output)
    I really cant understand where to use this signal
    If someone knows please tell me

    Now ,about the dc offset you were right
    I thought that the +/- dc offset was something like a clipping signal (like when an amp is clipping its output)
    In my osciloscope when i was in ac mode and i was checking the output i found a signal like a clipping output of an amp when i adjusted the dc offset knob
    But in DC mode , i found that the dc offset is what the reply was talking about .

    I cant still understand what the sweep in is .
    I really want to use sweep signal , and i dont know how it works!!

    As for the coaxial cable i have some questions.Why should i use coaxial cable?
    When i want to drive an external amp with the generator i shouldT use a coaxial? The end of the cable should be RCA !!!!

    And final question :
    Can i drive for example a speaker direct from the generator?
    Or should i drive an amp for example and then a speaker?

  7. Hi friends
    a very simple problem.
    i use a acoustic generator and i do not have the manual
    My generator has 1 input and 2 outputs in BNC

    The one output is called TTL out .WHAT IS THIS??? How does it works?
    The second output is the 50Ohm output. 50 ohms is its internal resistance?
    The input is called Sweep in. What is this and how does it works?

    Another problem is the DC offset button and the +/- offset trimmer .What are they and how do they work ? when do we need them?

    I know many things about acoustic,electronics , but it is my first time with an acoustic generator


  8. ok
    so i must measure the thd% of the amplified output with 4 ohms load .
    How should i do this??
    i mean , if i connect to the output the load , where should i connect the measuring cables and where the attenuator circiut?
    Do i still need the attenuator circuit?

    What about the preouts?
    do they need load so i can measure the thd? and if yes , what load should i connect to them . The preouts are for connecting the input stage of an amp , not a speaker...

    Another question :
    if i am using an acoustic generator and an osciloscope (not to the pc) , the things are easier?
    Can an osciloscope measure the harmonic distorsion?Or i only see when the graphic starts to clip?
    With an osciloscope i do not need an attenuator?

  9. HI

    I would like to construct a device wich will have a motor,20 inputs of fluids and an output.

    The pc will have a programm to tell to the device wich fluid must be connected to the output each time and for how long.

    The selector will be in circle shape , on the one side the inputs , in the center the motor , and to the other side the output.

    The pc must know the position of the selector any time , and the pc must know when the selector is beeing "locked " to each output .
    The pc must be able to tell the selector where to go toconnect the correct fluid to the output.

    So, how should i do this?
    Do i need a step motor?a servo?
    How will the pc able to know the position of the selector?
    What programm should i use? What language?
    Some people told me about plc's , others for pic's , others for just rele's .

  10. Thnx for repluing
    i do not something strange to attenuate the signal .
    My car cd player has amplified outputs and preouts.
    The outputs are 5volts maximum , with no amplification
    The amplified outputs deliver 17 watts rms at 4 ohms

    So, i guessed that this ratings are to much for my sound card to handle!
    So i user a voltage divider (20db) , simply a resistor in series 1000 ohms and a resistor in parallel 100 ohms .
    Thats all i used to attenuate the output voltage in order not to "burn" my sound card .

    My second question is :
    There MUST be some way to measure thd% at high volts and high watts .For example how do we measure thd to an amp with 1000 watts rms ??? Do we attenuate the output? And if the answer is yes , then how much lower ratings do we get?

    So when i attenuated my output to the cd-layer the measure was right or wrong?

  11. HI
    I would like to measure thd% on my pc. I use spectra plus software .
    If i use a low watt device, there is no problem .
    When i use my car cd-player , the output is 17 watts rms.
    So i guessed , i should protect my sound car from frying, and i used an attenuator 20db .
    Now the question is, when i use an attenuator , i get lower reading of thd%???
    If yes , how can i measure an audio device with enough wattage without using an attenuator??
    please help me.

  12. Hi
    I would like to construct a device that will be connected to the parallel port of my pc , and i would be able to control RELE's .
    I dont know if i can find something like that ready or i should construct it from scratch .
    The device must be controlled by a windows programm, that i must construct .This programm would control the device as i want , for example , to enable the rele's as i want , for as long that i want .It should be able to accept schedule for seconds , minutes , or hours .
    I dont know wich language should i use to build the program .
    If someone knows what should i do at all , please reply, i must construct it since it is part of a medical machine i like to construct.
    ThANK U

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