Any suggestion for an amplifier for EMIC Text-to-Speech module

CoolDad

Hello,

I am new to BASIC Stamps and have a basic understanding of electronics.

I am working with the EMIC text-to-speech module with a 8-ohm speaker (from RadioShack) and I find that the volume of sound is very low. I want to amplify the sound and drive a bigger speaker or get better sound with the existing speaker.

Any suggestions for an amplifier circuit that will help me out will be greatly appreciated.

Thanks in anticipation.

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Thank you,
CoolDad

rixter

If you would like to use a circuit that Parallax uses on it's Professional Development Board, the schematic is here:
http://www.parallax.com/dl/docs/prod/boards/PDB-RevC-Schematic.pdf

This is based on the LM386 amplifier chip, available everywhere, e.g. Radio Shack, and a collection of cheap capacitors, resistors and one POT. The LM386 chip documentation also has several examples of how to construct amplifiers with various levels of gain, the most basic of which is quite simpler than the circuit used in the Parallax link above. I've constructed a few of them.

Good luck.

Rick

CoolDad

Thanks Rick. That was very helpful.

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Thank you,
CoolDad

LoopyByteloose

The LM386 is a 0.3watt output. The nice thing about it is that it can easily use +5volt supply or much higher. If you really want more, there are other audio chips. Much depends on if you want it on a mobile BOEbot or at a desk. Alternatively, you can further boost the LM386 by adding another output stage to it that drives one or two small transistor [noparse][[/noparse]like the 2n2222] at a higher voltage. How you do it really depends on the extent of your desires for audio perfection.

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"Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

osull

hi,
try using an operational amplifier (e.g 741 chip). Set it up as a buffer with a gain of 1. The advantage of this circuit is that is supplies the same voltage to the speaker but the op-amp enables you to supply the speaker with a lot more current which will enable you to drive a larger speaker. The disadvantage is the op-amp must be supplied with a positive and negative voltage e.g. +15V and -15V

hope it works

CoolDad

Kramer,

The amplifier is for a RFID-based authentication application. I am looking to use it for a speaker mounted on the wall to greet & usher in authenticated users.

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Thank you,
CoolDad

Sing America

Hi I am trying to find an easy to use and program speech board to use with the basic stamp. Any interesting new speech tech boards.

Thanks Mark

LoopyByteloose

Well, if it is a wall mounted application for public use, you may want more watts output. Much depends on the enviroment - noisy or quiet. Als, you may want volume control easily available. Treble/Bass adjustment are attractive features.

Basically there are three ways to go. 1] building from discrete components - transistors; 2] a fully packaged audio chip; or 3] interfacing with a ready made mono amp and speaker enclosure. Of course, you can additionally consider a combination of the above, but I don't see a reason to discuss the complexities of that.

While using an OP Amp is an interesting alternative, it presents additional obstacles. The ready made audio chips have dealt with all the issues of fidelity and harmonic distortion of the whole range. And you need merely one polarity of power supply.

The LM386 is just one of a series of available audio chips by the same vendor. The problems with the other audio chps is that they come in packages that are not DIP. I believe they are ball soldered and I have never tried to hand fabricate such chips. Also, as the audio output power increases, the DC oiwer supply voltage requirements go higher and higher as the additional stages of amplification require greater and greater voltage. So you may be needing a 30-50 volt power supply.

The increased voltage requirement is also a problem with discrete components, but this option may be more fun to build. You certainly get to review your fundamentals of amplifiers, transistors, and feedback.

The easiest is prepackaged audio amps and or prepackaged audio amp with speaker enclosure. For example, I recently bought a ready made 12v audio amp board for merely $3 new at the local supply house. All I have to provide is an enclosure with speaker and a wall wart.

The LM358 is an excellent alternative for using on the BOEbot, with a small bench speaker, or an 8 ohm earphone as it will tolerate a 5 volt supply. but you could just about do the same thing with a 2n2222 transistor configured at a Class A amp.

So, you begin to see that the trade offs are between learning more or having a finished product that looks well made and works well at low cost.· Incidentally, there are a similar set of issues with motor controllers and H-bridges.· At the end of the day, there are always some of us that want to build from scratch just to observe the fundamentals of electronics in use or because we believe that we can save a lot of money, though·it is getting harder to save money this way.

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"Everything in the world is purchased by labour; and our passions are the only causes of labor." -- David·Hume (1711-76)········

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 10/19/2007 9:02:16 AM GMT

CoolDad

Kramer,

Thanks for your detailed response.

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Thank you,
CoolDad

CoolDad

Mark "Sing America",

You can get the Emic TTS module from Parallax. It was not available with them for a long time. Today I see that it is backordered and will be available only in Feb, 2008. If you want it quicker, you can get one from the HVWTech. http://www.hvwtech.com/products_view.asp?ProductID=352

I am not associated with them. I just happened to find them when searching for my TTS module.

Good luck

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Thank you,
CoolDad

Jonathan

George,

You forgot method 3) Tubes! Get a 12AU7, a 250 volt power supply, a 12V filiment supply, and then spend hours shocking yourself and tracking down 60hZ hum and biasing tubes. At least, that's what I'd do.

Just kidding, just kidding.

Jonathan

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

Dgswaner

how about one of these guitar amps..... no not a 12" speaker amp. www.generalguitargadgets.com/pdf/ggg_ruby.pdf you can build one for about $5.00 I've seen one in action they would be plenty loud.

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A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster

CoolDad

Thanks Dgswaner. I like the circuit with the volume control.

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Thank you,
CoolDad