2N3055 heat sink

[gophert]

Remove the 100 ohm resistor between pin3 and the speaker. You can either replace it with a 1000uF capacitor or wire pin 3 directly to the speaker if you have a good old fashion NE555.

 

[ronsimpson]

Driving a transistor like that usually does not work. Cap C5 will charge up and not do what you want.
Add a B-E diode. And reduce the size of the cap. (maybe much smaller) You might want a base resistor also.

 

[audioguru]

Why did you add a capacitor between the 555 and the 2N3055? Then the 555 #2 and the 2N3055 will not work properly. A capacitor is used if the output of the amplifier is push-pull and there is a single polarity supply (the 2N3055 is not push-pull). Also the capacitor you added might have destroyed the output of 555 #2. Maybe you did this before and that is why 555 #2 does not work properly?

Since your 555 #2 was marked "AC NE555" and it could not drive the 100 ohms resistor in series with an 8 ohms speaker then I suspect it is not a good or normal 555. Swap 555 #1 and 555 #2. If the 555 #2 cannot activate the relay then it is bad.

An NE555 can easily produce 10.5V into the 100 ohms in series with the base of the 2N3055 to produce a base current of 103mA. Then the 2N3055 can produce a collector current of 1A to 1.6A in the speaker. The AC power in the speaker will be 4W to 10.3W which will blow up your little speaker.

 

[audioguru]

Remove the 100 ohm resistor between pin3 and the speaker. You can either replace it with a 1000uF capacitor or wire pin 3 directly to the speaker if you have a good old fashion NE555.

Why do you think the output of a NE555 will survive being shorted with an 8 ohm speaker?

 

[gary350]

Why did you add a capacitor between the 555 and the 2N3055?

You told me to put a 470uf cap there look at post #32.

 

[gary350]

Remove the 100 ohm resistor between pin3 and the speaker. You can either replace it with a 1000uF capacitor or wire pin 3 directly to the speaker if you have a good old fashion NE555.

I tried lower resistor values and nothing at all none of them worked.

 

[gary350]

Why did you add a capacitor between the 555 and the 2N3055? Then the 555 #2 and the 2N3055 will not work properly. A capacitor is used if the output of the amplifier is push-pull and there is a single polarity supply (the 2N3055 is not push-pull). Also the capacitor you added might have destroyed the output of 555 #2. Maybe you did this before and that is why 555 #2 does not work properly?

Since your 555 #2 was marked "AC NE555" and it could not drive the 100 ohms resistor in series with an 8 ohms speaker then I suspect it is not a good or normal 555. Swap 555 #1 and 555 #2. If the 555 #2 cannot activate the relay then it is bad.

An NE555 can easily produce 10.5V into the 100 ohms in series with the base of the 2N3055 to produce a base current of 103mA. Then the 2N3055 can produce a collector current of 1A to 1.6A in the speaker. The AC power in the speaker will be 4W to 10.3W which will blow up your little speaker.

I have a 10" 20w 8 ohm speaker waiting to be used. Actually I have 2 10" 20w 8 ohm speakers i can use. I tried what your said it did not work. I tried smaller resistors to and no resistor. Only thing I did not try is .1 uf which is what I would have tried if no one had made suggestions. If a 2N3055 will make 10w I want to see it happen.

 

[audioguru]

Post #31 shows the 555 driving a 39 ohms resistor in series with an 8 ohm speaker to ground. Then the output of the 555 is overloaded when it goes high and it is not loaded when its output goes low (it Is Push-Pull unlike a single 2N3055!).

In post #32 I recommended adding a coupling capacitor between the 555 and the resistor in series with the speaker. Then with a series coupling capacitor like with every push-pull amplifier that uses a single supply, its output current is balanced going high and going low.

Lower resistor values will simply destroy the output of the 555.

 

[audioguru]

10W from the 2N3055?
When a 2N3055 is turned on hard, its collector to emitter voltage produces a max saturation voltage loss of about 0.4V when its collector current is about 1A and its base current is 100mA. Then with a 13.2V supply, an 8 ohm speaker gets (13.2V - 0.4V)/8 ohms= 1.6A and its power for half the time is (1.6A squared x 8 ohms)/ 2= 10.2W. If 555 #2 is good then it can produce about 103mA into the 100 ohms resistor in series with the base of a 2N3055 and the output of the 2N3055 into the speaker might be only 1A instead of 1.6A so the power in the speaker will be only 4W.

Guess what? The 1kHz and 1.5kHz is a squarewave that produces only 2W to 5W. The high frequency harmonics produce the other 2W to 5W that maybe the speaker or your hearing cannot produce.

The output of the 2N3055 is not push-pull so DO NOT USE A SERIES CAPACITOR FROM THE 2N3055 TO THE SPEAKER!

If you used a push-pull audio amplifier and it produces sinewaves, not badly distorted squarewaves like a 555 does, then a coupling capacitor blocks DC and low frequencies and is needed when there is a single polarity supply. The speaker voltage swings positive and negative because the coupling capacitor stays charged at half the supply voltage.
But the capacitor feeding the speaker is a highpass filter that cuts off low frequencies. There is a simple formula to calculate the cutoff frequency of a coupling capacitor feeding a certain load impedance.

A 470uF capacitor feeding an 8 ohm speaker cuts 43Hz to half the power (-3dB) of much higher frequencies and the 0.1uF capacitor you guessed about cuts radio frequencies higher than the AM broadcast band and less. The middle of the AM band would be at 1/5th the max power, ultrasonic squeaks from bats would be at a fairly low level and audio sounds would have levels lower than you can hear.

 

[gary350]

10W from the 2N3055?
When a 2N3055 is turned on hard, its collector to emitter voltage produces a max saturation voltage loss of about 0.4V when its collector current is about 1A and its base current is 100mA. Then with a 13.2V supply, an 8 ohm speaker gets (13.2V - 0.4V)/8 ohms= 1.6A and its power for half the time is (1.6A squared x 8 ohms)/ 2= 10.2W. If 555 #2 is good then it can produce about 103mA into the 100 ohms resistor in series with the base of a 2N3055 and the output of the 2N3055 into the speaker might be only 1A instead of 1.6A so the power in the speaker will be only 4W.

Guess what? The 1kHz and 1.5kHz is a squarewave that produces only 2W to 5W. The high frequency harmonics produce the other 2W to 5W that maybe the speaker or your hearing cannot produce.

The output of the 2N3055 is not push-pull so DO NOT USE A SERIES CAPACITOR FROM THE 2N3055 TO THE SPEAKER!

If you used a push-pull audio amplifier and it produces sinewaves, not badly distorted squarewaves like a 555 does, then a coupling capacitor blocks DC and low frequencies and is needed when there is a single polarity supply. The speaker voltage swings positive and negative because the coupling capacitor stays charged at half the supply voltage.
But the capacitor feeding the speaker is a highpass filter that cuts off low frequencies. There is a simple formula to calculate the cutoff frequency of a coupling capacitor feeding a certain load impedance.

A 470uF capacitor feeding an 8 ohm speaker cuts 43Hz to half the power (-3dB) of much higher frequencies and the 0.1uF capacitor you guessed about cuts radio frequencies higher than the AM broadcast band and less. The middle of the AM band would be at 1/5th the max power, ultrasonic squeaks from bats would be at a fairly low level and audio sounds would have levels lower than you can hear.

This morning I did some experiments for my own learning experience. See drawing. 47uf sounds best. 39 ohms prevents 555 from getting hot. Diode seems to do nothing. I looked online for push pull circuits only one that uses two 2N3055s requires 2 transformers. Push pull with no transformers required 1 NPN and 1 PNP transistor. There must be a PNP = to 2N3055 I have no clue what is it.

I replaced 2N3055 with 2N3904 sound is only slightly less.

 

[audioguru]

Gary, you seem to be making random circuits that are usually wrong. Instead, you should learn the basics of the electronics parts you are using.
1) Your 39 ohms is overloading the output of the 555.
2) Your capacitor polarity is (are) backwards which causes it to act like a piece of wire. If the polarity is corrected then it charges then discharges negatively into the base of the transistor damaging the transistor (that is why others added a diode).

You showed a push-pull amplifier that must be 59 years old. Transistor amplifiers have not used audio transformers for at least 50 years.

 

[shortbus=]

It is time for a new forum heading -Morphing. Every one of Gary's threads do it, start out being about the subject in the heading and end up somewhere else.

 

[gary350]

Gary, you seem to be making random circuits that are usually wrong. Instead, you should learn the basics of the electronics parts you are using.
1) Your 39 ohms is overloading the output of the 555.
2) Your capacitor polarity is (are) backwards which causes it to act like a piece of wire. If the polarity is corrected then it charges then discharges negatively into the base of the transistor damaging the transistor (that is why others added a diode).

You showed a push-pull amplifier that must be 59 years old. Transistor amplifiers have not used audio transformers for at least 50 years.

+ side of caps to B+ if I turn cap around that puts - on B+. I tried what you said and reversed the cap the circuit does not work no sound. I changed cap the way it was now it works again. Is B on the transistor more or less positive than pin 3 of 555? Meter shows pin 3 = +6.22v

Changing resistor to 100 ohms seems to make no difference to sound output if 100 is better I leave it.

Look at post #62 I experimented reducing value to the best sounding cap. I tried the diode it does not seem to help it sounds exactly the same.

2N3055 needs no heat sink at all. If output could be higher than 1w it might need a heat sink. Connected to 100a car battery 2N3055 still does only 1w.

 

[audioguru]

The With a 13.2V supply, the datasheet of the NE555 shows its output high with a 100mA load is +11.5V. Yours is overloaded to only +6.22V which might be the average voltage of its AC. The datasheet of the 2N3055 shows that its base is about +0.8V.
The un-needed coupling capacitor is between them. Which end of the coupling capacitor is more positive? the +11.5V end of course.

With the capacitor polarity corrected, when power is applied the capacitor charges immediately causing a POP. But there is nothing to discharge the capacitor so there is no sound after the POP.
Adding the diode allows the capacitor to discharge into it during each half cycle so there will be sound. But the capacitor and diode are not needed.

If the capacitors are good with very low resistance then changing the capacitance of the coupling capacitor should not change the sound, it should only change the output level because your squarewaves have no bass.

The 2N3055 is not producing a smooth sinewave tone, instead it is a buzzer producing a squarewave. When it turns on its collector current is 1.6A into the 8 ohm speaker and its Vce voltage is about 0.15V. Then the transistor heats with 1.6A x 0.15V= 0.24W for half the time.
When the 2N3055 turns off then it has no current so it does not produce any heat for half the time.
It will need a heatsink if it heats with more than about 2W.

 

[audioguru]

I think you are using an expensive monster old 2N3055 because you have some. Its massive heatsinked 15A of current and 115W is not needed in your 1.6A/10W circuit. A smaller TIP31 transistor would work fine at 1/10th the cost.

 

[gary350]

I think you are using an expensive monster old 2N3055 because you have some. Its massive heatsinked 15A of current and 115W is not needed in your 1.6A/10W circuit. A smaller TIP31 transistor would work fine at 1/10th the cost.

I did have a 40 year old American made 2N3055 on this circuit but 2 days ago I swapped it for a brand new Chinese made 2N3055 there is no difference how the circuit works.

I decided to do all the things you said and take notes.

With 47uf cap connected from pin 3 of 555 to B of 2N3055 + on B circuit works. Turn cap around with - on B circuit works but volume is 99% lower. I have to listen close to hear it osc.

Add the 100 ohm resistor with cap still connected - to B no change circuit works volume is so low it is hard to hear.

With 100 ohm resistor and 47uf cap in series + on B circuit works good.

Remove 47uf cap leave the 100 ohm resistor between pin 3 and B volume has gone up very noticeable louder. 1w is now 1.1w of sound.

Remove 100 ohm resistor pin 3 connected directly to B, 555 is stuck on 1KHz it will not osc.

Put 100 ohm resistor between pin 3 and B again circuit works good, louder than before about 1.1w.

Looks like output of 555 needs to be stronger to get more power from 2N3055.

My 8 yrs old camera is acting up, time to go camera shopping.

 

[audioguru]

With 47uf cap connected from pin 3 of 555 to B of 2N3055 + on B circuit works. Turn cap around with - on B circuit works but volume is 99% lower. I have to listen close to hear it osc.
Add the 100 ohm resistor with cap still connected - to B no change circuit works volume is so low it is hard to hear.

Of course, the backwards polarity is a piece of wire that works but the correct polarity capacitor charges quickly on the first positive half-cycle of the audio then has nothing to discharge it from then on.

With 100 ohm resistor and 47uf cap in series + on B circuit works good.

Because the backwards capacitor is a piece of wire.

Remove 47uf cap leave the 100 ohm resistor between pin 3 and B volume has gone up very noticeable louder.

Because that is how the circuit should be without a capacitor.

volume has gone up very noticeable louder, 1w is now 1.1w of sound.

No. Twice the power sounds only a little louder. 10 times the power sounds twice as loud. The power went from 0.5W to 5W.

Remove 100 ohm resistor pin 3 connected directly to B, 555 is stuck on 1KHz it will not osc.

Because the output of the 555 is severely overloaded.

Looks like output of 555 needs to be stronger to get more power from 2N3055.

No. When the supply is only 13.2V and the speaker is 8 ohms then a perfect output transistor fed with enough base current will produce an output of (13.2V squared)/8 ohms= 21.8W for half the time which is 10.9W. Like all transistors, the 2N3055 has a small saturation voltage loss so when the 555 provides it with a base current of 160mA through a 62 ohms resistor then the power in the 8 ohm speaker is 20.5W for half the time= 10.2W.
More power? Then double the supply voltage and double the base current and the power in the speaker will be 35.7W. Or use a 4 ohm speaker and double the base current and the power in the speaker will be about 18W. Double the supply voltage AND use a 4 ohm speaker with much more base current then the power will be massive.

 

[audioguru]

The power numbers I mentioned are with half the power in the distortion harmonics since the waveform is a squarewave. The speaker and your hearing might not sense the harmonics then you hear only half the power.

 

[gary350]

I checked pin 3 with volt meter it reads 4.7v

I checked B through the 100 ohm resistor volt meter reads .44v

I wonder if I change the square wave from 50% duty cycle to 20% will output voltage go up? I was getting 11v on the other circuit board at pin 3.

I was joking about 1w increasing to 1.1w removing cap makes it sound 2 times louder. I'm not sure if an increase from 1w to 2w will sound 2 times louder or not especially to me? I can remember when a 1N34 radio was easy to hear now I hear nothing. I remember when 10w music amp was loud now it seems like not very loud.

I can make a voltage double 13v to 26v for the 2N3055 but how to increase current at B of the 2N3055? What about a preamp between 555 and 2n3055 to get B current up? I don't see anyway to get 26v out of the 555 but might be about to get 26v our of a preamp using voltage double on the preamp and 2n3055?

But wait, I know how to build voltage double from sine wave AC power supply but not from 13.2v DC car battery?

 

[audioguru]

Pin 3 of the 555 produces 1kHz AC, not DC. If you measured DC then your measurement is the average voltage but it still might be wrong. For measuring AC, your meter probably is accurate only at 50Hz or 60Hz. Its measurement of 1khz will probably be low.
The base of the 2N3055 goes high to about 1V and low to about almost 0V, alternating up and down at your 1kHz and 1.5kHz.

If you change the duty cycle then the power output will be less. 50% is the loudest.

When I turned 69 years old I got a free hearing test. The results were normal for my age, I was officially deaf. Men start to become deaf at age 25 or 30. They programmed demo hearing aids for my mainly high frequencies loss and I was amazed at how clear sounds became. I bought them with a nice discount and a government grant.

A preamp amplifies signal voltage that has very low current. A high power car amplifier uses a DC to AC converter then rectifies and smooths it into higher voltage DC to power the high power amplifier. Usually a car audio amplifier (even in an ordinary car radio) has two amplifiers per channel in a bridge which doubles the voltage and doubles the current to a speaker. Many amplifier ICs use this "bridged" type of amplifier per channel.