Elementary questions about electronics

Car radio/CD in a motorcycle tank bag

I was told the outputs from the rear of car radios are unamplified and
don’t have enough power to drive headphone speakers mounted in a helmet.
Yet you can go right from the radio to the speakers in the car. I don’t
understand.

So what’s a simple way to get the signal amplified enough to drive the
helmet speakers, yet add as little volume to the package as possible?

I know J&M has an AudioPak. I don’t like their design.

If you’ve got any experience with this kind of experimentation or
installation, please e-mail me. I need some help.

Thanks


douglas_par…@ccmail.orl.mmc.com

posted by admin in Uncategorized and have Comments (19)

19 Responses to “Car radio/CD in a motorcycle tank bag”

  1. admin says:

    - Hide quoted text — Show quoted text -

    douglas parker wrote:

    > I was told the outputs from the rear of car radios are unamplified and
    > don’t have enough power to drive headphone speakers mounted in a helmet.
    > Yet you can go right from the radio to the speakers in the car. I don’t
    > understand.

    > So what’s a simple way to get the signal amplified enough to drive the
    > helmet speakers, yet add as little volume to the package as possible?

    > I know J&M has an AudioPak. I don’t like their design.

    > If you’ve got any experience with this kind of experimentation or
    > installation, please e-mail me. I need some help.

    > Thanks

    > —
    > douglas_par…@ccmail.orl.mmc.com

    If you can drive car stereo speakers from this unit, then you can drive
    headphone speakers.  Further amplification is unnecessary.  I’ve done
    this myself.  The only problem is in the selection of your helmet
    speakers.  I used some of the smaller ear plug style speakers and had
    some difficulty getting the helmet on 8)

  2. admin says:

    douglas parker <douglas_par…@ccmail.orl.mmc.com> wrote:
    >I was told the outputs from the rear of car radios are unamplified and
    >don’t have enough power to drive headphone speakers mounted in a helmet.
    >Yet you can go right from the radio to the speakers in the car. I don’t
    >understand.

    Was this the same guy who told you not to jump a motorcycle from a
    car because of the voltage overload?

    >So what’s a simple way to get the signal amplified enough to drive the
    >helmet speakers, yet add as little volume to the package as possible?

    If you are going to drive helmet speakers from a car stereo output, you
    must limit the output so as to not accidentally fry you brains when
    someone cranks the volume control.

  3. admin says:

    Most car stereos now have on-board amplifiers, so you should
    have no problem at all.  Just ask a reputible salesperson to
    point you to one

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      _/      _/  _/    _/        _/  _/  _/    _/    _/  _/        _/

  4. admin says:

    In article <DtK62o….@moraga.ness.com>,

    Reverend Tweek <tw…@netcom.com> wrote:
    >douglas parker <douglas_par…@ccmail.orl.mmc.com> wrote:
    >>I was told the outputs from the rear of car radios are unamplified and
    >>don’t have enough power to drive headphone speakers mounted in a helmet.
    >>Yet you can go right from the radio to the speakers in the car. I don’t
    >>understand.

    He’s probably thinking of a pre-amp-only unit, and you’re probably thinking
    of a radio with a pre-amp *and* a main amp. In other words, apples
    and oranges.

    >>So what’s a simple way to get the signal amplified enough to drive the
    >>helmet speakers, yet add as little volume to the package as possible?

    >If you are going to drive helmet speakers from a car stereo output, you
    >must limit the output so as to not accidentally fry you brains when
    >someone cranks the volume control.

    Why don’t we do this on home stereos, then?


    Griff Miller                         "Keep my mind on higher things; keep my
    Systems Administrator   ’95 Z-28      mind on truth."
    Positron Corporation    ’85 VF1100S
    griff.mil…@positron.com            My opinions are mine, not Positron’s.

  5. admin says:

    douglas parker (douglas_par…@ccmail.orl.mmc.com) wrote:

    : I was told the outputs from the rear of car radios are unamplified and
    : don’t have enough power to drive headphone speakers mounted in a helmet.
    : Yet you can go right from the radio to the speakers in the car. I don’t
    : understand.

    Who ever told you this bs needs to have their head examined :)

    Actually, the better high end unit (kenwood, alpine, etc) only have preamp
    outputs – after all, you’re investing in such a good unit, 95% of the people
    will run separate amps for ‘em, and don’t need the measly 10 or 15watts (rms)
    that the head unit can offer – these types of unit require an amp to get any
    sound out of, although I’m pretty sure there’s enough juice in ‘em to drive a
    small set of ear phones (like the ones by sony that go into your ear).  I know
    on my kenwood, the voltage output is up to I believe 1 volt (or such).

    The ‘el cheapo units have an amp built in, and as such can power small
    speakers rather well.. So that should answer your last and second to last
    question.


            jdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdjds
            jds                  <j…@ripco.com>              jds
            jds 1988 Kawasaki Ninja 600R  <—   Deceased     jds
            jds 1995 Kawasaki Gpz 1100  <—– My new ride    jds
            jdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdsjdjds

  6. admin says:

    Griff Miller <griff.mil…@positron.com> wrote:
    >Reverend Tweek <tw…@netcom.com> wrote:
    >>douglas parker <douglas_par…@ccmail.orl.mmc.com> wrote:
    >>>I was told the outputs from the rear of car radios are unamplified and
    >>>don’t have enough power to drive headphone speakers mounted in a helmet.
    >>>Yet you can go right from the radio to the speakers in the car. I don’t

       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    >>>understand.

    >He’s probably thinking of a pre-amp-only unit, and you’re probably thinking
    >of a radio with a pre-amp *and* a main amp. In other words, apples
    >and oranges.

    No, "He" isn’t, but his "friend" might be.

    >>If you are going to drive helmet speakers from a car stereo output, you
    >>must limit the output so as to not accidentally fry you brains when
    >>someone cranks the volume control.

    >Why don’t we do this on home stereos, then?

    You do… but you don’t know it.  Sometimes there is a limiting resistor
    in the headphone circuit prior to the headphone plug.  

  7. admin says:

    In article <4qpet9$…@aslan.positron.com>
               griff.mil…@positron.com "Griff Miller" writes:

    > In article <DtK62o….@moraga.ness.com>,
    > Reverend Tweek <tw…@netcom.com> wrote:
    > >douglas parker <douglas_par…@ccmail.orl.mmc.com> wrote:

    > >>So what’s a simple way to get the signal amplified enough to drive the
    > >>helmet speakers, yet add as little volume to the package as possible?

    > >If you are going to drive helmet speakers from a car stereo output, you
    > >must limit the output so as to not accidentally fry you brains when
    > >someone cranks the volume control.

    > Why don’t we do this on home stereos, then?

    The phones socket on home stereos is driven by an earlier stage
    of the amplifier circuitry, at lower power than the main speaker
    outputs.

    I’d be inclined to use a Walkman instead of a car stereo.


    Mike (DF) Fleming  MAG #79794  DoD #4446  Opinionated Twat #3  UKMC #9
      Save the slug, save the slug, save the slug, save the slug
      They’re not cute and sexy, they’re covered in slime
      But so many species have run out of time

  8. admin says:

    douglas parker wrote:

    > I was told the outputs from the rear of car radios are unamplified and
    > don’t have enough power to drive headphone speakers mounted in a helmet.
    > Yet you can go right from the radio to the speakers in the car. I don’t
    > understand.

    > So what’s a simple way to get the signal amplified enough to drive the
    > helmet speakers, yet add as little volume to the package as possible?snip
    > If you’ve got any experience with this kind of experimentation or
    > installation, please e-mail me. I need some help.

    Most head units with front amp channels will also have rear amp channels.

    I tried using the Audiovox head in the Goldwing’s Cycle Sound unit to drive a set
    of small "earbud" type headphones, and also a pair of Collett Electronics
    Mega-Blasters (don’t laugh… the just licensed their 2-way radio design to HJC, a
    helmet manufacturer, and are themselves laughing all the way to the bank)

    The problem was, I think, that the earphones were too high an impedance load for
    the ic-based amp channels.  With a matching transformer I think it would have
    worked just fine.  


    CP Tomes    1982 300SD "Hans"    1981 GL1100 "Bertha"    1984 VF500F "Hamster"
    Any opinions I espouse are certainly not those of my Internet Service Provider
    (ie my employer)

  9. admin says:

    In article <douglas_parker-2506960108260…@pm15-04.magicnet.net>, douglas_par…@ccmail.orl.mmc.com (douglas parker) wrote:

    >I know J&M has an AudioPak. I don’t like their design.

    Not to mention it’s damn expensive, and I don’t see where the antena goes on
    their tank bag ads (perhaps I should look again).

    I was thinking of making my own also, but I wanted to find some remote
    controls that would mount on the handle bars, or some easy to use location.
    And where would I put an antena? Or are the headphone lines doubling as the
    antena?

    What if I used the chromed harley style speakers, then what would I do about
    an antena?

    Matthew
    ’96 ACE

  10. admin says:

    - Hide quoted text — Show quoted text -

    In article <DtKo49….@rci.ripco.com>, Macrotech <j…@ripco.com> wrote:
    >douglas parker (douglas_par…@ccmail.orl.mmc.com) wrote:
    >: I was told the outputs from the rear of car radios are unamplified and
    >: don’t have enough power to drive headphone speakers mounted in a helmet.
    >: Yet you can go right from the radio to the speakers in the car. I don’t
    >: understand.

    >Who ever told you this bs needs to have their head examined :)

    >Actually, the better high end unit (kenwood, alpine, etc) only have preamp
    >outputs – after all, you’re investing in such a good unit, 95% of the people
    >will run separate amps for ‘em, and don’t need the measly 10 or 15watts (rms)
    >that the head unit can offer – these types of unit require an amp to get any
    >sound out of, although I’m pretty sure there’s enough juice in ‘em to drive a
    >small set of ear phones (like the ones by sony that go into your ear).  I know
    >on my kenwood, the voltage output is up to I believe 1 volt (or such).

    >The ‘el cheapo units have an amp built in, and as such can power small
    >speakers rather well.. So that should answer your last and second to last
    >question.

    ————————————————-
    Yeah, some idiot thought he meant the interface DIN plug that is used
    to go to eQ’s and/or bigger linear amps slung beneath or in the trunk.
    He clearly meant the actual DIRECT drive speaker wires. Answer, no the
    DIN plug isn’t "loud" enough, but the speakers sure are!! Just don’t
    get caught DRIVING with headphones on, as it is a ticket and a fine!!
    And actually MOST non-SUPER EXPENSIVE AM-FM-Cassette units DO have
    both interfaces on them anymore!! Some folks demand a cute little eQ
    for the crap speakers and crap acoustics inside a car!!
    -Steve Walz


    -Steve Walz  rste…@armory.com  ftp://ftp.armory.com:/pub/user/rstevew
    mirrored: ftp://ieee.cas.uc.edu:/pub/electronics/faqs/ftp.armory.com
    and Europe: ftp://ftp.cised.unina.it:/pub/electronics/ftp.armory.com
    and Oz: ftp://ftp.peninsula.apana.org.au:/pub/electronics/ftp.armory.com

  11. admin says:

    When we were in 25 Jun 1996 14:32:57 -0500, there came Griff Miller and
    stated on mil…@positron.com that…

    >In article <DtK62o….@moraga.ness.com>,
    >Reverend Tweek <tw…@netcom.com> wrote:
    >>douglas parker <douglas_par…@ccmail.orl.mmc.com> wrote:
    >>If you are going to drive helmet speakers from a car stereo output, you
    >>must limit the output so as to not accidentally fry you brains when
    >>someone cranks the volume control.

    >Why don’t we do this on home stereos, then?

    >–
    >Griff Miller


    The reason is that home stereo speakers usualy have a very low resistance
    (impedance, in this case as we are talking non continous signals eg.
    sound is an alternate signal, a vibration) and the current drain from the
    stereo is "big". this results from the OHM law I=V/R. If R is low, I, for
    a given V, is high.
    Typical values for the speaker "resistance" are 4 to 16 OHM(usualy 8
    OHM).
    In the case of the headphones, the internal resistance is aprox. and
    typicaly of 32 OHM. This by itself limits the current drain for that same
    V previously mentioned.
    All this means that we can just conect the speaker outputs of a regular
    car stereo directly to the headphones.
    note:
    There are two kinds of outputs a car stereos can give.
    One has the aplified audio signal at the terminals. These are the ones
    that we connect directly to the speakers.
    the other is the line-level output type. they need one external amplifier
    to drive the speakers. If you have one of this type and connect it to the
    headphones, the sound will be very low, almos unhearable.
    In this case you must build the external amplifier. If you are
    interested, i can post the schematic for a very simple one.
    sorry for the long post. Hope that this helped.

    Third_galaxy_after_black_hole#9999. Via_lactea. solar_system @ Earth.
    north_hemisphere.
    europe. *Portugal*. Lisbon. by_the_river. person waving.
    My spelling gets better everyday. If you found some errors in my typing,
    please be patient…
    Have a good life.
    Aramis.

  12. admin says:

    In article <4qt7gt$…@eccdb1.pms.ford.com> usfmd…@ibmmail.com "Aramis" writes:
    > The reason is that home stereo speakers usualy have a very low resistance
    > (impedance, in this case as we are talking non continous signals eg.
    > sound is an alternate signal, a vibration) and the current drain from the
    > stereo is "big". this results from the OHM law I=V/R. If R is low, I, for
    > a given V, is high.
    > Typical values for the speaker "resistance" are 4 to 16 OHM(usualy 8
    > OHM).
    > In the case of the headphones, the internal resistance is aprox. and
    > typicaly of 32 OHM. This by itself limits the current drain for that same
    > V previously mentioned.
    > All this means that we can just conect the speaker outputs of a regular
    > car stereo directly to the headphones.

    No, no, no, no, no!

    If you have a car stereo delivering 12.5W ‘music power’ into 8
    ohms, it’s running at 10V peak-to-peak. Connect this to a pair
    of 32 ohm headphones, and you’ll be trying to put about 3W
    through them. Headphones typically have power ratings of 50 to
    60 mW, so you’re overloading them by 50 to 60 times! And that’s
    with a fairly low power stereo – a 100W stereo will be pushing
    25W through 32 ohms. (Music power = RMS power * 1.414)


    Mike (DF) Fleming  MAG #79794  DoD #4446  Opinionated Twat #3  UKMC #9
      Save the slug, save the slug, save the slug, save the slug
      They’re not cute and sexy, they’re covered in slime
      But so many species have run out of time

  13. admin says:

    <clip>

    - Hide quoted text — Show quoted text -

    > > stereo is "big". this results from the OHM law I=V/R. If R is low, I, for
    > > a given V, is high.
    > > Typical values for the speaker "resistance" are 4 to 16 OHM(usualy 8
    > > OHM).
    > > In the case of the headphones, the internal resistance is aprox. and
    > > typicaly of 32 OHM. This by itself limits the current drain for that same
    > > V previously mentioned.
    > > All this means that we can just conect the speaker outputs of a regular
    > > car stereo directly to the headphones.

    > No, no, no, no, no!

    > If you have a car stereo delivering 12.5W ‘music power’ into 8
    > ohms, it’s running at 10V peak-to-peak. Connect this to a pair
    > of 32 ohm headphones, and you’ll be trying to put about 3W
    > through them. Headphones typically have power ratings of 50 to
    > 60 mW, so you’re overloading them by 50 to 60 times! And that’s
    > with a fairly low power stereo – a 100W stereo will be pushing
    > 25W through 32 ohms. (Music power = RMS power * 1.414)

    > —
    > Mike (DF) Fleming  MAG #79794  DoD #4446  Opinionated Twat #3  UKMC #9
    >   Save the slug, save the slug, save the slug, save the slug
    >   They’re not cute and sexy, they’re covered in slime
    >   But so many species have run out of time

    If you plan on using the walkman type headphones, that may or may not be
    accurrate… for regular headphone speakers that he can fit into the ear
    openeings of the helmet… it is defintely inaacurate.  They are 8ohm
    nominal impedance.  So much for the emphatic "no no no no…"
    In any event, you’ll notice that the origianl poster was told there
    would be INsufficient power to drive the headphones… either way, he
    was misinformed.


    "Nobody ever went broke underestimating
     the intelligence of the American public."

    Richard G. Mainar       Digit…@serv.net

  14. admin says:

    In article <4qt7gt$…@eccdb1.pms.ford.com>, usfmd…@ibmmail.com (Aramis)
    wrote:

    (HUGE snippage)

    > Third_galaxy_after_black_hole#9999. Via_lactea. solar_system @ Earth.
    > north_hemisphere.
    > europe. *Portugal*. Lisbon. by_the_river. person waving.
    > My spelling gets better everyday. If you found some errors in my typing,
    > please be patient…
    > Have a good life.
    > Aramis.

    how utterly charming


    ’83 Honda V45 Sabre , ’76 Yamaha XS 650 (D)
    yet to be nominated as an ‘Olde Phart <tm> ‘

  15. admin says:

    perhaps one of you has some real help to offer in terms of mounting
    chassis electrical provisions, experience with _particular_ brands of
    speakers or dash units??????????????

    as opposed to techno geek rambling thinly disguised as a flame over what
    again must have been an innocent typo or some such?

    Thanks  Bryan


    ’83 Honda V45 Sabre , ’76 Yamaha XS 650 (D)
    yet to be nominated as an ‘Olde Phart <tm> ‘

  16. admin says:

    In article <bpr-3006960745540…@bpr.clark.net>,
       b…@clark.net (Bryan in Baltimore) wrote:

    >perhaps one of you has some real help to offer in terms of mounting
    >chassis electrical provisions, experience with _particular_ brands of
    >speakers or dash units??????????????

    >as opposed to techno geek rambling thinly disguised as a flame over
    what
    >again must have been an innocent typo or some such?

    Been there, done that.

    I mounted a walkman with a digital tuner on a tank bag. I put a power
    amp inside the bag and made appropriate modifications for cableing. I
    attached a set of small speakers that I had from years gone by
    intended to attach to the mirror mounts, only I attached then to the
    tank bag. It sounded great on the bench, but was about useless on the
    bike. Those little 2 1/2 inch speakers don’t cut it and the walkman
    controls are too small/ackward.

    The fix would be to use much larger speakers and a more normal car
    radio.

    I now have the same walkman on my belt and a very small set of
    headphone speakers inside my helmet liner. It is working out fine, but
    I suspect it borders on illegal in some states.


    Cal 1100 Guzzi  Bumble Bee     |
    XL600R ——– Thumper        |
    ZG1200 ——– Land Yacht     | KotFMGO
    Mazda Miata — Toy Cage       |

           wayne.or…@atlantaga.ncr.com
       As always, my opinions are just that, mine!

  17. admin says:

    Wayne Orwig wrote:
    > [snip]

    > I mounted a walkman with a digital tuner on a tank bag.

    Maybe the digital tuner is the answer?  I’ve tried both a small GE radio
    and an analog-tuner Sony, and they pick up so much ignition static as to
    be less than useful.

    I’ve noticed digital Sonys for around $49, so they’re certainly
    affordable enough.  If that solves the interference problem, it would be
    worth it to buy one for biking.

    I did find that the small in-your-ear stereo earphones are a good answer
    for listening with a helmet on.  They’re relatively comfortable, and if
    you put a good signal into them, they sound pretty good.  At least, good
    enough to listen to the morning talk show while I drive to work.

  18. admin says:

    Gentlemen,

    A word of warning – this applies to all audio kit, not just car hi-fi.

    The term "Music Power" is _extremely_ poorly defined. Whilst it did (once) tend
    to mean peak power (as opposed to RMS – the only useful quantity), it has now
    become a kind of subjective "how loud does this sound to me" kind of thing.

    I have seen a stereo marked as "50W Music Power", even though the output
    devices were LM381s.

    As most tekkies who are not "audiophiles" will know, subjective volume normally
    equates to distortion – i.e. the less powerful your output stages, the greater
    will be the rated "music power".

    It’s mindless bollocks for mindless people.

    Vic.

  19. admin says:

    Vic Watson <vicw> wrote:
    > The term "Music Power" is _extremely_ poorly defined. Whilst it did (once) tend
    > to mean peak power (as opposed to RMS – the only useful quantity), it has now
    > become a kind of subjective "how loud does this sound to me" kind of thing.
    > I have seen a stereo marked as "50W Music Power", even though the output
    > devices were LM381s.

    Yeah. I used to have an old bass guitar amp, rated 200W, but it would
    give more ‘music power’ than a cheapo 350W rated amp I last tried at a
    music shop. Maybe it depends on total speaker surface, too.

    > As most tekkies who are not "audiophiles" will know, subjective volume normally
    > equates to distortion – i.e. the less powerful your output stages, the greater
    > will be the rated "music power".

    It seems to me that the ‘audiophile tekkies’ will sooner realize this
    than the ‘non-audiophile’ techies, but…

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