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emic text-to-speech module — Parallax Forums

emic text-to-speech module

blettieriblettieri Posts: 1
edited 2007-03-05 20:19 in BASIC Stamp
can somebody please tell me what is the best type of speaker to use for the text to speech module?
thanks
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Comments

  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-02-12 01:45
    A 25 or 32 ohm speaker will work best. If you try to use a lower ohm speaker, it will draw a lot of current and will distort. If you have an 8 ohm speaker, put a resistor in series with it to bring the total up to around 30 ohms. It won't be as loud. The Emic is actually pretty tolerant of what you put on the speaker output.

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    Tracy Allen
    www.emesystems.com
  • rrrr Posts: 63
    edited 2007-02-28 08:12
    whats the real deal???
    ·
    I just got a text to speech mod and I would like it to be as loud as possible. Currently I am using an 8 ohm speaker that is directly connected to the mod. The reason I am using an 8ohm speaker is because this is what the documentation calls for, but then I ran across this post and it seems like there is a contradiction. So what is the correct speaker to use?
    ·
    Also is it ok to hook up the emic mod to a powered speaker like the ones we use for desktop computers???
    ·
    ·
    Thanks for your help
    ·
    ·
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    rr
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  • Tracy AllenTracy Allen Posts: 6,664
    edited 2007-02-28 16:27
    The reason I suggested a higher ohm speaker was more an issue of distortion, not one of damage to the EMIC. On the scope, at the highest volume (volume = 7) I was seeing flat-topping of the output.

    You can drive an external amplifier either from the Aout pin, or from the speaker (+) pin. Either one is controlled by the volume setting.

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    Tracy Allen
    www.emesystems.com
  • latigerlillylatigerlilly Posts: 114
    edited 2007-02-28 18:44
    Hi,

    Can I use Radio Shack Mini Amplifier-Speaker 277-1008C ? Here are the specs; input sensitivity: 1mV, Input impedance: 5K ohm, Power Output(1 kHz): 200 mW (16 ohm load), distortion (1kHz): <2% THD @ 200 mW, Frequency Response: 100 Hz - 10 kHz, powersource: 9 VDC Adapter rated for 300 mA min. www.radioshack.com/product/index.jsp?productId=2062620&cp=&sr=1&origkw=mini+amplifier+speaker&kw=mini+amplifier+speaker&parentPage=search

    I am having the same problem. The volume is too soft with 8 ohm speakers. If I turn up the volume, there is distortion. I was wondering if the Radio Shack 277-1008 will be better, but since it is not 8 ohm, I am afraid it might fry my Emic. Please advise.

    Thanks,
    Lilly.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-02-28 19:06
    Either mini-amplifier should work. You'll need to attach them to the Aout pin since the Speaker pin probably puts out too much of a signal. The mini-amplifiers are designed for microphones and line-out signals like Aout. The fact that the 277-1008 speaker is 16 ohms doesn't matter since there's an amplifier between the speaker and the input jack.

    You can indeed run the Emic speaker output into an amplified speaker like those used with computers or MP3 players. Any amplified speaker designed to plug into a headphone/earphone jack should work fine since that's what the Emic speaker output is really designed for (earphones or a small speaker at close range).

    Tracy's comments about using a 32 ohm speaker·are correct.· It's a better match for the Emic speaker amplifier, but using an 8 or even 4 ohm speaker won't damage the Emic, it just may not sound as loud or as clear and at higher volume levels, the lower speaker impedance will result in more distortion.


    Post Edited (Mike Green) : 2/28/2007 7:11:21 PM GMT
  • latigerlillylatigerlilly Posts: 114
    edited 2007-03-05 07:30
    Hi,

    I am assuming that the other GND on the EMIC is for grounding the AOUT pin. Is the following schematic correct?

    pinktts3.gif

    Thanks,
    Lilly.
  • ZootZoot Posts: 2,227
    edited 2007-03-05 15:16
    Lilly -- you can also use an LM386 audio amp IC (only a few bucks) and a few external parts and wire up your own amplifier for Aout.

    I just did this two nights ago (thanks Dr. Allen). http://forums.parallax.com/showthread.php?p=632642

    It's LOUD -- and that's with a minimal enclosure on the speaker. I'm running the LM386 at 9v which gives somewhere around 650mw of power (nearly double that of the onboard Emic amp which is rated at 300mw).

    The two ground pins on the Emic appear to be tied together on the board. I've tied one or the other or both to ground without seeing -- uh, hearing -- a difference, but others perhaps know more about the true purpose of having both ground pins (I haven't seen documentation on why both ground pins are there).

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    When the going gets weird, the weird turn pro. -- HST

    Post Edited (Zoot) : 3/5/2007 3:20:43 PM GMT
  • Tim-MTim-M Posts: 522
    edited 2007-03-05 18:37
    I noticed that Future Electronics is selling a Mini LM386 board here:

    http://www.futurlec.com/Mini_Audio.shtml

    The cost is below $6,·much less than what you can purchase the parts alone·for... and you get a finished silk-screened board too!

    Tim
  • ZootZoot Posts: 2,227
    edited 2007-03-05 20:19
    Nice little board! I will add this though -- LM386's are cheap (coupla bucks) and all the other parts can be desoldered from techno-junk you may have laying around (even old volume controls and such for pots).

    In my case, my speakers are already mounted off-board on the chassis, and I had to experiment a bit with the input filtering to get noise-free sound, so a board would have worked against me.

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    When the going gets weird, the weird turn pro. -- HST
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