project help with toy IC boards

[audioguru2]

What do you think about this UTC KA8602 as an audio amplifier?

It is a Korean copy of Motorola's MC34119 that is used in telephones. It can't provide much power but is better (?) than an LM386 if you only have a 3V supply, and it doesn't need the pretty big output capacitor. I used one in my son's alarm clock.

With a 3V supply and an 8 ohm speaker, the LM386 provides only 38mW at clipping and about 0.2% distortion. The MC34119 provides 100mW at clipping and about 2% distortion.

Philips have a better one with more output power but I can't find its part number, maybe no longer made.

 

[CALAHAN]

Audioguru,

I have to give you guys credit that you can get any of this stuff to work. I have spent loads of money, buying electronic components, resisters that are of varying values, and having to guess as to what the wattage should be as none of the schematics I have seen either for the LM386 or the Motorola amp give a resistor watt rating. I bought all of the lower ones (1/4, 1/2, 1). I tried the LM 386 with this toy chip, got it to work one night, busted the little pot, and have never been able to reproduce the clear amplified sound I had again. I never bothered to try the 9 volt split you posted on the breadboard because I can't get anything else to work - so why bother?. I then went out and spent more money on more resistors, and more capacitors because every schematic one finds on the web for these chips have different component values. I tried this Motorola MC34119 headphone amplifier which is equivalent to a NJR NJM2113 (Mouser Part # 513-NJM2113D), and I can't get this thing to make any noise! I have looked for more schematics, and out of the three I found, all three are different. After all this is said and done, I should have just went to the local college, found an electrical engineer, gave him the chip from the toy, and paid the guy to solder a few working amplifier boards together for me.  The LM386 was disappointing, but this MC34119 really has me irked because it is supposed to run off a voltage as low as 2, and it doesn't do anything. I even searched and found this silly 39 ohm resistor to put in line with the output to power the 8 ohm speaker.

Bruce

 

[audioguru2]

Sorry to hear that it didn't work. :'(

Post the schematic of the MC34119 amplifier and we'll help you fix it.

 

[CALAHAN]

Here is the schematic I used. The next page of the text states "This first circuit ti the easiest. Just place a 10k resistor between your micro controller and the MC34119. If you want to drive a 8 ohm speaker watch out that you don't pull too much power from your power supply. If you do place 39 ohm resistor in series with the speaker."

Notice that he wasn't really telling the truth because there is also a second 10k resistor between pins 4 and 5?

In any case, I powered the breadboard with the 2 AA's, and ran both the toy chip and this thing off the bread board power, using the common ground etc... and it did nothing but sat there. I tested the chip to see if it was working, and it did by itself with the low volume sound effect that I always get (The one I want to amplify). I hooked the toy chip speaker wires (remember that I am running off of snipped speaker wires here from the toy chipboard - if it makes any difference) to the inputs marked "IO PORT" and the other to "VSS", The rest as it is shown on the schematic.



I had another MC34119 schematic off someone else's page, but it had completely different resistor values on it and even some capacitors, all of the values I do not have. Needless to say the Motorola reference sheet on these things, with it's illustrations of common schematics, is just as bad as the LM386 in way of extra capacitors and everything else under the sun. 


I don't have room for all of this stuff. I know it can be done with just a few small components because I have seen it done in other toys. I also do not want a volume or variable resistor. I don't have room for it. There must be a fixed resistor that can go in it's place.

Thanks,

Bruce

View attachment 39838

 

[audioguru2]

Hi Calahan,
With only 3V for its supply, an amplifier can't amplify much without producing severe clipping distortion. The MC34119 will produce only a little more volume than the original toy. If the supply voltage for the amplifier is doubled to 6V then the power to the speaker is quadrupled. But if the speaker is 8 ohms then the MC34119 or the speaker might blow up.

Your MC34119 amplifier is missing an important input coupling capacitor. So it was amplifying any DC from the toy chip and therefore its outputs were saturated.

It also had equal values for the resistors that set its gain, so it didn't have any gain.

You can select a different resistor value for R4 to change the gain to avoid clipping distortion. Don't forget that a 3V battery will drop to 2V over its life so don't have the gain too high.

View attachment 39839

 

[CALAHAN]

I'll try this tonight. Teh gain I assume is adjusted by the resistor you specified, becuse I have no pot of other device to to manually make this adjustment.

I also don't need much volume, just a touch. I will create this exactley as you have it here.

Bruce

 

[gogo2520]

Hi audioguru
    I am new to this stuff so I got a question
  vss means voltage source
  vdd means voltage drain
          I think
  So I think you got them on backwards in your schematic .
        I think like I said I am new to this stuff.
                      gogo

 

[audioguru2]

Hi GoGo,
People and manufacturers call the supply pins of ICs many things. You should always look at the datasheet of an IC before connecting it to make sure.

Motorola (now ON Semi) call the positive supply pin "VCC" and the negative supply pin "Gnd".

View attachment 39845

 

[gogo2520]

Hello audioguru
    Thank you for the reply
                              gogo

 

[Sukhbinder]

Hi guys, if u can do away with the LM386 i suggest the use of the TDA2822M. it is a 8 pin dip ic working from 1.8v to 15v and gives an output of 1W/channel ( its a sterao amp for low voltage devices). it uses minimal components and can be used in bridge mode also. here's the data sheet for it

TDA2822M.pdf

 

[audioguru2]

Hi Sukhbinder,
The TDA2822M is much better than the MC34119 at low voltages.
It gives an output of typically 220mW bridged into an 8 ohm speaker with a 3V supply and with very clipped 10% distortion. As the battery runs down the power will become less and the distortion will become higher.

 

[Sukhbinder]

i once read about the LM390 which is a low voltage high power amplifier. i have not myself used it but it may come in handy in this circuit. i've used the TDA2822M and it works well. i had made a small amp for my walkman using the TDA2822M driven from 4.5volts (3 AA batteries), well if u use small speakers then the quality is good and u won't find much distortion. i leave it up to the user and other senior members to decide which will be better.

 

[audioguru2]

Hi Sukhbinder,
I use LM390 audio amps in my clock radio and in a signal generator. It is too bad they have been discontinued for 10 years. They are like an LM386 but with a higher output current and bootstrapping of the driver transistor for a much higher voltage swing. Its minimum supply is 4.0V.

 

[CALAHAN]

I've had to take a break from these electronic projects for a bit for a couple of reasons. But, I did go into Radio Shack and buy one of these 741 Op Amps. There is no data on the back of the package, so I have no idea if it is even close to doing what I want. I have not pulled up the internet info on it yet either, and when I do, I'm sure there will be a completely different configuration of capacitors and resistors that will need to go with it from what is in any schematic I may find.

As for my 3v toy chip amplification project, I want to try this TDA2822M to see if it works with my 3 volt power supply feeding both the amp and the circuit board (it did not work with the MC34119 which was a waste of time and money). Of course though I have to order one of these things, and this takes time, then I have to get time to pull the bread board out and all of my alligator clips - again.


Once I get one of these amps down where it will work, then I can re-create more for my toy prototyping projects. I will try audioguru's schematic for splitting the 9 volt battery to feed the 3 volts for the toy chip, with the other voltage of the battery going into one of these amps.

I have tried about 3-4 different amp options and none of them have worked with my project yet. The only success I have had so far is when I powered a 386 off of a 9 volt separately from the toy IC which was fed off it's own 3 v supply.  This configuration takes up too much space of course, but I have not tried the 9 volt split to power both yet as time is a commodity I have little of. Perhaps this weekend I will attempt all the different configurations with fresh batteries.

The second project I was working on which was amplifiying the Radio Shack chip recorder, both off of one 9 volt battery, has also been put on hold until I can get this 3v toy IC chip amp working.

Is there any specifics I need to know, or a special schematic I need for this TDA2822M before I order a few of them?

Bruce (CALAHAN) 

 

[mvs sarma]

please download datasheet as sukhbider indexed in his message (reply#28)and you will find mono, stereo and even the tentative pcb layouts-- y-day iattended a mutimedia speakers using a similar version UTC2822 9V DC input) and is working fine -- you may rather GO AHEAD

sarma

 

[Sukhbinder]

Hi mvs sarma, your are right the TDA2822M is a very versatile IC and i've seen a number of computer multimedia speaker brands in INDIA which use the TDA2822M as the main power amp. although its rated as a  1W/ch IC the speakers show a rating like 220W PMPO (this PMPO thing is all rubbish, never go for the PMPO rating always check out the RMS ratings for amps, by the way PMPO ratings are not recognised as a standard by the electonics and electrical engineers). i had seen a 2.1 speaker system which uses a TDA2822M for the satellites and a TEA2025/KA2206 in bridge mode for the subwoofer. quite a small and cheap contraption but works well for low budget needs.

 

[audioguru2]

although its rated as a

 

[mvs sarma]

i am totally in line with audioguru's philosophy-- there were times when power was generally indicated (specified) as RMS watts. --over times the pmpo took over. in fact the transformer used in the multimedia speakers is too small( if not three small) it coud deliver few ma at 12V  finally the output power could not be greater than 400 to 800 mW per channel as the input DC power is 1 watt max

sarma