just built a lm3886 amp

[Jackdaniel]

The datasheet for the TDA2030A shows a circuit with an output of only 12W or 16W into 8 ohms and its distortion can be as high as a horrible 0.5%. It has enough power output to blast your house only if you have rice-paper walls. Most home stereos in North America have at least 100W per channel at very low distortion.

why is 100W? In my 5.1 system i get 5x18+35=125 watts and its enough for a horrible sound at my home! R u deaf? Lol

 

[dr.power]

Thanks a lot audioguru for all your helps. You are really so kind.

Regarding Power Dissipation, Plz take a look at the datasheet of LM3886 page NO18:
""Determining Maximum Power Dissipation"". the equations NO1,2 and 3.
What are saying and how to RELATE them to your post #6?

Thanks

P.s to be honest I even do not know why it use the term "2pi" while calculating power? It even used that term for calculating maximum power dissipation!

 

[audioguru]

Regarding Power Dissipation, Plz take a look at the datasheet of LM3886 page NO18:
""Determining Maximum Power Dissipation"". the equations NO1,2 and 3.
What are saying and how to RELATE them to your post #6?

You don't need to fiddle around with equations. The dissipation is shown on graphs on page 14. With a plus and minus 28V supply and a 4 ohm speaker the max heating is about 48W.
The thermal resistance of the package is 1 degree C per W and the mounting with thermal compound is 0.2 so the total thermal resistance is 1.2 degrees C per W. The max chip temperature is 150 degrees C but select 130 degrees to be safe and select a max ambient of 30 degrees C then select a heatsink that has a suitable thermal resistance producing a temperature rise of 100 degrees C or less with a power of 48W.

 

[dr.power]

You don't need to fiddle around with equations. The dissipation is shown on graphs on page 14. With a plus and minus 28V supply and a 4 ohm speaker the max heating is about 48W.
The thermal resistance of the package is 1 degree C per W and the mounting with thermal compound is 0.2 so the total thermal resistance is 1.2 degrees C per W. The max chip temperature is 150 degrees C but select 130 degrees to be safe and select a max ambient of 30 degrees C then select a heatsink that has a suitable thermal resistance producing a temperature rise of 100 degrees C or less with a power of 48W.

Thanks Audioguru,

What is the difference between power Dissipation and power of the op amp it self (68W for a 4 ohms load at 56V I mean?)

 

[carbonzit]

What is the difference between power Dissipation and power of the op amp it self (68W for a 4 ohms load at 56V I mean?)

Power dissipation is the total power drawn by the amplifier, including any power wasted as heat. The power output figure for the amp will, of course, be lower.

 

[audioguru]

Power dissipation is the total power drawn by the amplifier, including any power wasted as heat. The power output figure for the amp will, of course, be lower.

No.
Power dissipation is the heating of the IC. It heats because it is a linear amplifier.
The total power used from the power supply is the total of the output power plus the dissipation.

 

[carbonzit]

No.
Power dissipation is the heating of the IC. It heats because it is a linear amplifier.
The total power used from the power supply is the total of the output power plus the dissipation.

Yes. My bad.

 

[Jackdaniel]

what is the best IC for a subwoofer amp? I am Sorry if u think its a thread hijacking

 

[audioguru]

what is the best IC for a subwoofer amp?

Texas Instruments has a pretty good high power class-D amplifier IC which is good for a sub-woofer.
But you must select an amplifier with enough power for your speaker and it must be able to drive the impedance of the speaker.

 

[dr.power]

You don't need to fiddle around with equations. The dissipation is shown on graphs on page 14. With a plus and minus 28V supply and a 4 ohm speaker the max heating is about 48W.

Thanks audioguru,
regarding your above sentence which graphs at that page are you referring to?
Are you meaning the power dissipation by saiying heating?

The thermal resistance of the package is 1 degree C per W and the mounting with thermal compound is 0.2 so the total thermal resistance is 1.2 degrees C per W.

Sorry but what is the meaning of this ""The thermal resistance of the package is 1 degree C per W""? I do not know how to interpret it? For instance what should I say for 68W output power?

The max chip temperature is 150 degrees C but select 130 degrees to be safe and select a max ambient of 30 degrees C then select a heatsink that has a suitable thermal resistance producing a temperature rise of 100 degrees C or less with a power of 48W.

How to select the suitable heatsink by knowing those values?

Thanks again like always.

 

[audioguru]

Yes, the graph of Power Dissipation shows the amount of heating.

Thermal resistance and how to calculate for a heatsink are discussed in the datasheet, are taught in school and are in many articles in Google.

The package has a thermal resistance of 1 degree C per Watt. So with one Watt of heating then there is a difference of 1 degree C between the chip and the outside of the case. The mounting to a heatsink adds 0.2 degrees c per Watt. The heatsink is rated for a certain temperature rise with heat applied. So if the heatsink is rated at 2 degrees C per Watt then the combination with the IC at 1 degree C per W and the mounting at 0.2 degrees C per Watt results in a total thermal resistance of 3.2 degrees C per Watt. If the ambient temperature is 30 degrees C then a Power Dissipation of 48W results in a chip temperature of (48 x 3.2) + 30= 183.6 degrees C which is too high because the absolute max allowed temperature is 150 degrees C.
Now you calculate the chip temperature when the heatsink thermal resistance is rated at 1.3 degrees C per W.

 

[Jackdaniel]

Texas Instruments has a pretty good high power class-D amplifier IC which is good for a sub-woofer.
But you must select an amplifier with enough power for your speaker and it must be able to drive the impedance of the speaker.

thanx guru and what is the model number of that IC?

 

[audioguru]

Texas instruments make the TAS5631B power stage class-D amplifier (it has 4 channels that can be paralleled and bridged) with an output of 600 Whats into 2 ohms (at a horrible 10% distortion) with a clipped input signal or 480 Watts at 1% distortion into 2 ohms. It is driven from a TAS5518 PWM processor IC that converts audio to PWM.
They are in tiny packages with many pins.
Here is the datasheet: **broken link removed**

 

[Jackdaniel]

Texas instruments make the TAS5631B power stage class-D amplifier (it has 4 channels that can be paralleled and bridged) with an output of 600 Whats into 2 ohms (at a horrible 10% distortion) with a clipped input signal or 480 Watts at 1% distortion into 2 ohms. It is driven from a TAS5518 PWM processor IC that converts audio to PWM.
They are in tiny packages with many pins.
Here is the datasheet: **broken link removed**

What about LM4780 guru? National claims that it has 2 x 60W in stereo mode and 120W In mono (00.5% distortion)(bridged), i think 120W Is enough for a subby, what do u say guru?

 

[audioguru]

The 10" sub-woofer in my car is driven from a 188W RMS amplifier so I can feel the low frequencies. 120W for a sub-woofer is used in a home with rice-paper walls or in a trailer home.

 

[Jackdaniel]

are Mosfets good for that?

 

[Jackdaniel]

what ic is used by ur car amp guru?

 

[audioguru]

are Mosfets good for that?

The Texas Instruments high power class-D amplifier IC has built-in Mosfets for its outputs.

what ic is used by ur car amp guru?

I don't know. I ordered the deluxe stereo that came with the car. Most speakers are 2 ohms.

 

[Jackdaniel]

The Texas Instruments high power class-D amplifier IC has built-in Mosfets for its outputs.


I don't know. I ordered the deluxe stereo that came with the car. Most speakers are 2 ohms.

sorry but i must ask this as it is important.. WhaT is class-D,A,AB Guru?

 

[audioguru]

sorry but i must ask this as it is important.. WhaT is class-D,A,AB Guru?

Look at Amplifier Classes in Google.