Need help! Preamp or amp circuit

audioguru said:

You can use one TDA2822M IC and connect it bridged to one speaker for an output of 1.1W.
Then you can use a multi-pole switch to change it to stereo for headphones.

It is easier to use a second TDA2822M and use one channel for one channel for headphones and an output coupling capacitor on the output of the bridged TDA2822M for the other channel for headphones.

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Enclosed circuit

If i have the circuit setup for the one Speaker which can only be mono with one speaker. correct!
Now...How do I use the multi-pole switch, and a Headphone switch jack to made the headphnoes in stereo. Please advise.


How do i setup set for two tda2822 chip as stated in the last paragraph. Don't understand.

I'm choosing on which way i want to use either the one chip or two. So i need help with both.

It is your project, not mine so you need to think about how many things need to be switched to convert a mono bridged TDA2822M into a stereo one.

I know its my project. And not yours. Right!

I'm new to audio circuits with no experience with amps. I told you this in post #1 and post #6 I'm trying my best in understanding all this.

If i new how to connect the two circuits together. I wouldn't need to ask for help.

OK. By me using only one speaker and one TDA2822M chip in a bridge circuit in figure 2, the speaker sound will be mono and not stereo. For a stereo sound though a speaker, you need two speakers.

By connectinig the two circuits in post #42 with a multi-switch the sound through the Headphones will be stereo only.

And what multi-pole switch are you referring to. SPDT, DPDT, 3PDT, 4PDT, Toogle. slide. rocker switch.

This is how i like it to work.
1.For the headphone circuit i want to use an audio jack switch so when the headphones are used the speaker is disconnected and when the speaker is used the headphones are disconnected.

2.On the input of the bridge circuit i want to add a plug with leads connect to a switch so i can switch from the plug to connect to a radio output ear jack Or back to the Mics Preamp.

I still can't figure out how to connect the bridge circuits output to the headphones circuit in post 42. I'm tryin. I need HELP!

Look at the two circuits I posted in post #42 and write down the differences. A switch must cause all the differences. I think the switch will have many poles, too many. The switch inside a headphones jack is not complicated enough to do it.

The mic preamp can be connected to a switched jack so that it works when the radio is not plugged into the jack. When the radio is plugged into the jack then the mic preamp is switched off it and the stereo radio connects to the jack.

audioguru said:

Look at the two circuits I posted in post #42 and write down the differences. A switch must cause all the differences. I think the switch will have many poles, too many. The switch inside a headphones jack is not complicated enough to do it.

The mic preamp can be connected to a switched jack so that it works when the radio is not plugged into the jack. When the radio is plugged into the jack then the mic preamp is switched off it and the stereo radio connects to the jack.

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Are you talking about a type of cmos flip flop switch IC to connect between the bridge amp circuit output to the headphones input.And if you are how would i connect this switch between the two.

Don't know what the differenes are..Don't know about audio amps to write down the differences between the two.

I throught I had something going with the LM386 amp.

This is more complicated then I throught. you're going to have to explain this further so i could understand what you mean.

It is not complicated, it is very simple to see the differences of the bridged amplifier feeding a speaker and the stereo amplifier feeding headphones. Write down the differences and add a switch to do them.

I noticed that you posted a bridged amplifier that has its input pin 7 floating without being connected to ground.

Enclosed is edit bridge circuit. kept 100k vol control pot but now resistor is directly tied to ground. Is this right!


What i think the differences are between the two circuits in post #42.

In the bridge circuit.

1. The two inverting inputs pin 8 and 5 are tie together with two 10uf caps to ground.
2. Pin 6 is tie to gound.
3. speaker added to its outputs to pins 1 and 3 . With cap on pin 1.

In the headphone circuit.

1. The to inverting inputs pin 8 is ground with 100mf cap and tie to ground the same for pin 5, But they are not tie together.
2. Pin 6 and pin 7 are your inputs. with 10k resistors.
3. pins 1 and 3 are your output this the headphones get connect to.with two 470mf caps.


I might be wrong on the differences away. but i tryed.

Even if i know the differences. How is this going to help me connect the two circuits together with a multi switch if i don't know how to connect them together. And what multi -switch are you referring to. You never mentioned what knid of switch this is.How would i know what switch to use.

cyberquest said:

Enclosed is edit bridge circuit. kept 100k vol control pot but now resistor is directly tied to ground. Is this right!

Click to expand...

No.
It is wrong because you added a capacitor at the output to the speaker that you added before (and I copied without seeing the error).

What i think the differences are between the two circuits in post #42.

In the bridge circuit.

1. The two inverting inputs pin 8 and 5 are tie together with two 10uf caps to ground.

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No.
Pin 8 is not tied to pin 5. It has a 10uF capacitor to pin 5.
Pin 5 does not have a 10uF capacitor to ground, it is 10nF.

2. Pin 6 is tie to gound.

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Yes.

3. speaker added to its outputs to pins 1 and 3 . With cap on pin 1.

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No.
You made a mistake before when you added the capacitor that is not shown on the datasheet.

In the headphone circuit.

1. The two inverting inputs pin 8 is ground with 100mf cap and tie to ground the same for pin 5, But they are not tie together.

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No.
They have 100uF to ground, not 100mF.

2. Pin 6 and pin 7 are your inputs. with 10k resistors.

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No.
Pins 7 and 6 are the inputs.

3. pins 1 and 3 are your output this the headphones get connect to.with two 470mf caps.

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Yes.

Even if i know the differences. How is this going to help me connect the two circuits together with a multi switch if i don't know how to connect them together. And what multi -switch are you referring to. You never mentioned what knid of switch this is.How would i know what switch to use.

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Use a switch with enough poles. It might not be available.

audioguru.

I Revised circuits enclosed.

Will the two circuits work now, as is.

All I did was delete the two caps on the input and output on the amp, so pretty much, its the same circuit as in the datasheet in figure 2.

As for the Headphone amp I just add the 100k volume pot and headphone Jack.

Can I use 9V on the tda2822m for the Power supply for both of these circuits,will the amp get HOT if i use 9V because the amp is rated from 1.8 to 18 volts VS . Becuase I'm using 9Vs for the mic's preamp and for the TL071 op amp and all other ICs on 5V supply.

I think I figured out how to connect both circuits with the preamp by using a multi-switch.

Now.As for the multi-switch you mention i think i would need a 4PDT type I may not find one as you stated, but some places do have them. But I must Order a minmum of 100 like at digikey. So I'll use two DPDT switches. I may need to use one SPDT switch for the Plug to switch back & fourth between the radios ear jack output and the preamps output.

cyberquest said:

Can I use 9V on the tda2822m for the Power supply for both of these circuits, will the amp get HOT if i use 9V because the amp is rated from 1.8 to 18 volts VS?

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The datasheet shows a max supply of 6V when the TDA2822M is bridged, has an 8 ohm load and shows how hot it gets. It does not get as hot when its load is 32 ohms so it can have a higher supply voltage.

I.The vol control pots for both circuits that I have are rated at 1/4W,will they be eough wattage in both circuits, or would i need to go with a 1/2W or 1W rated Pots.

2.Will the headpone amplifier circuit drive my 8ohm pair headpones with decent sound or will the sound be low at maximum volume.
Or should i use a 16ohm or 32ohm headphones. Which pair would give me the best or decent sound quality,but at low cost i don't want to spend more then $25 bucks for headphones. And could get them at best buy or Radio shack.

3.I couldn't fine where it states the temperture in a bridge circuit at 8ohm load how hot the IC would get, do you know the page number where its at.

In post #49.
4.Also. Where would be the apporpriate placement to connect the plug to the switch back and fourth between the mics preamp output and to the radios output jack... Between the PreAmp and the headphone input then to the input of the speaker amp. OR between the PreAmp and the speakers amps input, then to the input of the headphones. Or dose it matter how its connected either way.

cyberquest said:

1. The vol control pots for both circuits that I have are rated at 1/4W,will they be enough wattage in both circuits?

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Simply calculate the power in the pots. The TDA2822m has a max output of 1.4V RMS and a gain of 95. Then its max input is 1.4V/95= 15mV. The dissipation in each pot is 15mV squared/10k or 100k= almost nothing.

2. Will the headpone amplifier circuit drive my 8ohm pair headphones with decent sound or will the sound be low at maximum volume.

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It will be very clear and very loud at max volume.

3. I couldn't fine where it states the temperture in a bridge circuit at 8ohm load how hot the IC would get, do you know the page number where its at?

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The "Total Power Dissipation versus Output Power (Bridge)" graph on page 6 of the datasheet shows a dissipation of almost 1W when the supply is 6V and the output power is 1.1W into 8 ohms.
The second page says that the max allowed dissipation is 1.4W when the case is 50 degrees C. The thermal resistance is shown so you can calculate the exact chip temperature.

4. Where would be the apporpriate placement to connect the plug to the switch back and fourth between the mics preamp output and to the radios output jack... Between the PreAmp and the headphone input then to the input of the speaker amp. OR between the PreAmp and the speakers amps input, then to the input of the headphones. Or dose it matter how its connected either way.

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The toggle of the switch connects to the input of the volume control.

The switch is a On-off-On. So your saying the toggle is the off position the center lug the volume control input gets connect to that center lug so i could switch to On for premp circuit and in the opposite On position would be connected to the speaker circuit. Is this Right!


Because if I was to connect to one Of the On lugs it would always be in the On position. correct!

I think the connections will be confusing abit but I'll work on it.

The switch should have only two positions and not have a 3rd position in the middle when it is off.

1.Why can't I use a On-Off -On position type of switch, to switch between the two circuits and between the preamp and the radio plug.

2.So your saying, all's i need is a On-On position type of switch. I don't need center off position on the switch to switch back and fourth between the circuits

3.Only the power switch will have two positions On/Off


4.Also> I forgot to mention.
In the two circuits the TDa2822M bridge circuit and the headphone circuit what is the total current draw for both circuits. operating current drawn from the battery.100mA,200mA or more.

cyberquest said:

1.Why can't I use a On-Off -On position type of switch, to switch between the two circuits and between the preamp and the radio plug.

2.So your saying, all's i need is a On-On position type of switch. I don't need center off position on the switch to switch back and fourth between the circuits

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Only two positions: 1) The radio or MP3 player. 2) The microphone preamp.

In the two circuits the TDa2822M bridge circuit and the headphone circuit what is the total current draw for both circuits. operating current drawn from the battery.100mA,200mA or more.

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It is easy to calculate since the datasheet shows the efficiency in figure 14:
If the output is 1.1W into 8 ohms then the heating is shown to be about 0.95W so the total power from the battery is 2.05W. The total current is 2.05W/6V= 342mA for momentary peaks. The average power for music (not acid rock) is 1/10th so the average current is 0.205W/6V= 34mA.

If you are the guy who wants to blast telephone touch-tones (DTMF) as far as possible then the 6V battery will not last long with a continuous drain of 342mA.

The headphones use low power so the battery current will be low.

Good think i asked. I was going to use a 9V battery but the current capacity is low 500mA so i will use AA cells to increase the capacity.

The decoder. Mic preamp, speaker amp, and Hp amp in one case. It will receive the tones. The speaker in the circuit is for listen to music from a radio or Mp3 are hear the tones from the Generator when switch to that option.

The generator . Tthe circuit in post 1 plus the speaker amp posted in 42 in its own case. This will only generate the tones or emitt them.

audioguru

So. Will the circuits work (as is) in post #49, and in post #42 that you posted and will the cut-off frequencies from low to high for the DTMF tones and for radio sound co-insde with the bass frequencies for my project as discussed in this thread.


Also. I need to know in post #49 do i I connect to one side of the Headphones amp output or both of the outputs to connect to the input of the decoder circuit in post # 6

The same gos for the outputs of the speaker in post #49 to the decoders input in post #6. Also, would i need to add a extra capacitor to both of the outputs before connecting them to the decoders input and what vulues would i need. Or no additional capacitors are needed.

cyberquest said:

audioguru

So. Will the circuits work (as is) in post #49, and in post #42 that you posted and will the cut-off frequencies from low to high for the DTMF tones and for radio sound co-insde with the bass frequencies for my project as discussed in this thread.

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The circuits in post #42 have two capacitors that you added by mistake. The circuits in post #49 are correct and have good low frequency response.

Also. I need to know in post #49 do i I connect to one side of the Headphones amp output or both of the outputs to connect to the input of the decoder circuit in post # 6

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Each ear of the headphones connects to the output of its amplifier and the common wire of each ear connects to ground as shown in the schematic with a headphones jack.

The same gos for the outputs of the speaker in post #49 to the decoders input in post #6. Also, would i need to add a extra capacitor to both of the outputs before connecting them to the decoders input and what vulues would i need. Or no additional capacitors are needed.

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The TDA2822M power amplifiers drive a speaker and headphones. The mic preamp drives the amplifiers and the decoder. Your decoder schematic already has an input coupling capacitor.

The obsolete touch-tone generator needs an emitter resistor to ground and a coupling capacitor at its output.
The TDA2822M power amplifiers need a coupling capacitor to their volume controls if the sound source has DC on it.

In post #49, How would i connect the headphones amps outputs to the decoders INPUT. Do I connect both of its outputs or ONE ouput to the decoders INPUT.

The same gos for the speaker outputs to the input of the decoder.