Connect with us

3 dB bandwidth

Discussion in 'Electronic Design' started by [email protected], Jun 21, 2005.

Scroll to continue with content
  1. Pooh Bear

    Pooh Bear Guest

    At that kind of SPL - I'm sure you're mainly right !

    Try 90-100 and it gets interesting.

    Graham
     
  2. Pooh Bear

    Pooh Bear Guest

    It's excellent at relative nevertheless.

    I once performed a blind test to 'line up' a multitrack audio tape recorder by ear though -
    lol !.

    I managed to match the track one calibrated test tape playback levels to 0.3dB. This
    potentially explains a lot of the golden ears stuff. You have to *educate* your ear to work
    that well.

    Graham
     
  3. Pooh Bear

    Pooh Bear Guest

    Actually, ( basically you're right ) 1dB is the volume change discernable
    by the supposed 'average' listener in average situations.

    A 'trained ear' has little trouble trebling that accuracy.


    Graham
     
  4. Pooh Bear

    Pooh Bear Guest

    You're right and few ppl know it or understand it.

    I guess few ppl care to imagine why we call them *deci* Bels.

    Simple answer.

    It's 1/10 th of a Bel ! A Bel being the ratio that sounds to the ear like a
    doubling of intensity. Named after Alexander Graham Bell of telephony fame.

    Graham
     
  5. Pooh Bear

    Pooh Bear Guest

    In valve amps ? Erk !

    Essentially you're right. Pro-audio has always tried to make the passband as
    flat as possible. You won't find me arguing over that one for sure !

    Graham
     
  6. Pooh Bear

    Pooh Bear Guest

    No it isn't ! See Ohms Law !

    You really mean transistors ?

    I studied them when I was 12 !
    That's why toobs are only used by nitwits these days.........

    < plonk >

    Graham
     
  7. Pooh Bear

    Pooh Bear Guest

    I forgot to mention. Not in audio. RF I expect.

    You can voltage match toobs in audio perfectly well. I have done so myself.
    I can design discrete vacuum tube, bipolar or fet ( junction or MOS )
    circuitry and any amount of of IC circuitry inclusing DSP and its
    micrcontroller host requirements..

    I trust that explains !

    Graham
     
  8. Well it would certainly do by back a service by not being such a nitwit.
    My Fender Twin Combo is just about impossible to carry single handed up
    the stairs.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  9. Dont forget the valve telephone SSB amps. Flat from 60Khz to 120Khz at
    0.01% thd. They needed to be as they had 100s in a chain.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  10. You havent the slightest idea of what your talking about. You have
    learnt a phrases from somewhere with no idea as to how and when they are
    used.

    The maximum power transfer theorem is useless and irrelevant for
    many/most power amp situations.

    Loads for most power amps, if not all are determined from the maximum
    voltage and current ratings of the devices used. Period. For example, if
    a tube has a max voltage of 400V and a max current of 100ma, it wants to
    see a load of 4k, other wise one or the other aspect of the tube ratings
    will be wasted, hence a bigger more expensive device is being used. This
    is also true for RF power amplifiers. A transistor with an 15V max V
    rating and 1A max current will want to see a load of 15 ohms. That's
    what one does when one "matches".

    Matched power means that one will waste 1/2 the power in the driving
    source. This is about the daftest thing one can do for a power amp.

    Hands up those that actually know when impedance matching actually has a
    use?

    Hint: "Singing" return loss on a 4 to 2 wire converter.
    Hint: Switching fast signals.

    {snip more drivel}


    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  11. Pooh Bear

    Pooh Bear Guest

    Sorry mate, they sound *great* on guitar !

    I had the audiophool fraternity more in mind when I said that.

    A bit of colouration / soft-compression and THD makes guitar sound wicked !
    You pay the price in iron though.

    Graham
     
  12. Guy Macon

    Guy Macon Guest

    Sigh. Another ineducable newsgroup participant.

    The formula for calculating power decibels is:

    Po
    G = 10 log10 ----
    Pi

    Where
    G = Gain in dB
    Po = Power output from the device
    Pi = Power input to the device


    The formula for calculating voltage decibels is:

    Vo
    G = 20 log10 ----
    Vi

    Where
    G = Gain in dB
    Vo = Voltage output from the device
    Vi = Voltage input to the device


    Or. if you don't believe me, you can read this tutorial:

    [ http://home.comcast.net/~zcomco/decibel_1.htm ]

    or this one:

    [ http://et.nmsu.edu/~etti/fall96/communications/db/db.html ]
    You can join Aylward in my killfile. Assuming that he still posts to
    sci.electronics.design, the two of you can have your own little flame
    war without bothering me with the personal attacks that you think are
    an acceptable alternative to having a civil discussion on the topic
    at hand. Maybe later in life, after you have learned to read, write,
    spell, and count, you will have more success. True, these are rudimentary
    skills that many of us "normal" people take for granted that everyone
    has an easy time of mastering. But we sometimes forget that there are
    "challenged" persons in this world who find these things to be difficult.
    If I had known that this was true in your case then I would have never
    have exposed myself to what you wrote. It just wouldn't have been
    "right." Sort of like parking in a handicap space. I wish you the
    best of luck in the emotional, and social struggles that seem to be
    placing such a demand on you.

    *plonk*
     
  13. Don Bowey

    Don Bowey Guest

    So put 3 dB in each hand.

    Don
     
  14. Pooh Bear

    Pooh Bear Guest

    Guy Macon wrote:

    I note that you redirected my reply to alt.dev.null !

    I think that speaks for itself ! You're a usenet troll and clearly know
    nothing about electronics whatever.

    Here's my original reply that you attempted to censor !


    .............................................................................................................



    Yes.

    So when Zin = Zload ; Vo/Vi = 0.5

    Log10 ( 0.5 ) = -0.301.....

    G = -6.02.....

    Shame you didn't bother to check the math wasn't it ?

    Killfile ? I'd be pleased to be in the killfile of someone who doesn't even
    understand basic dB calcs !

    Sorry to anyone else I have may offended. I loathe incompetence when it's
    stuffed up your nose by a half-arse who erroneously and elaborately wants to
    make a cheap point of correcting your supposed 'error' without even bothering
    to check his own sums first !

    Graham
     
  15. Pooh Bear

    Pooh Bear Guest

    Once again you misdirected my reply to
    alt.dev.null.................................................

    My reply is below

    ...............................................................................................................................

    Don't waste my time on formulas I already know.

    In audio 600 ohm working the source Z is 600 ohms and the load Z is also 600
    ohms.

    That forms a potential divider with a value of 0.5.

    Thats -6dB !

    Don't play semantics with your 10 log, 20 log stuff. I eat ppl like you for
    breakfast ! After which I'm employed to sort out their ****-ups.

    Graham
     
  16. Don Bowey

    Don Bowey Guest

    Where do you obtain the 0.5 value and what is the "potential" divider?

    When an amplifier's input and output impedances are the same (for example
    600 Ohms), and it's gain is adjusted with a 600 Ohm 0 dBm input signal, to
    provide a 0 dBm output into a 600 Ohm meter, There is neither gain nor loss.
    Only an impedance mismatch or an uncalibrated oscillator or meter will
    provide a different "view."

    Don
     
  17. Ro/(Ro + Rl)...dah...
    Sure, if you "adjust the gain", i.e. increase it. That is beside the
    point.

    The point is that given that one has an output from a *low* impedance
    source (i.e *the* typical case) that has an output matching resister,
    there will be a loss of 0.5 when there is that same valued resister
    connected to ground at the tap point, when referenced to the raw low
    impedance output.

    People rarely design an amp with an inherent non resister resistance to
    match some standard load impedance. However, Marshal do that on some of
    their transistor guitar amps to simulate tube amp characteristics.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  18. I did realise you were not referring to guitar amps graham.


    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  19. Well, I will quible on "a lot".
    Yes. The ear is quite sensitive under the right conditions, especially
    when trained. There is no doubt that pretty much all non musical minded
    individuals simply do not recognise what parts belong to what
    instruments in a finished piece of music. Ask them if the bass is too
    loud or soft, and they will have no idea. One has to learn to correlate
    prior knowledge of expected sounds with new sounds.

    I do find it quite fascinating how I can pick out the individual
    intrument parts of music, and then sequence them. Most of the
    information is in the same bandwidth at similar levels, so how does the
    brain do it? Try and get a computer to do that and your nacked. It
    clearly uses come sort of correlation technique, but the details are
    still pretty amazing.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  20. My most-hated electronic calculator is also my best one. I bought
    it about 15 years ago; it is programmable and whatnot.

    Ten years ago, when I turned it on, it told me, in clean
    black-on-white alphanumeric characters, that its battery was low
    and I had to change it. Nothing else worked any more.

    The way an electronic pocket calculator is supposed to work when
    the battery goes out is to get progressively fainter until, after
    at least a decade of usage, you have to squint at the LCD from a
    certain angle to make out the numbers. Then you buy a new one.

    Having lost interest in the fancy calculator, I quickly misplaced
    and forgot all about it. Recently, I found it again at the bottom
    of a junk drawer and turned on. "Battery low", still in full
    contrast.

    All my LCD calculators now have PV cells.

    robert
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-