Thank you for the links. After reading some of the links, one problem is on my mind. What is the different between use a conventional amplifier(stereo amplifier) parallel the both channel together, and built a parallel poweramp, such as the schematic in the AN-1192?
Oi, sorry its 28V into 4ohms, ta for the link PA.
"The other way to determine IC power dissipation capabilities
is to analyze the output power specification in the datasheet.
In the case of the LM3886T, there are two output power
specification guarantees: 60W (min) into a 4Ù load using
±28V supplies and 50W(typ) into an 8Ù load from ±35V
supplies....
....the IC can handle a maximum of ±40W of continuous power dissipation without SPiKe Protection being turned on under continuous sinusoidal input with proper heat sinking. The same theory applies to other Overture ICs as well, like the LM3876T, which is capable of dissipating 31W with proper heat sinking."
P.A. can you just confirm my understanding that this basicaly means that even if the chip is guaranteed to reach 60W, everything exceeding the initial 40W, will incur a big hit on THD due to Spike?
"The other way to determine IC power dissipation capabilities
is to analyze the output power specification in the datasheet.
In the case of the LM3886T, there are two output power
specification guarantees: 60W (min) into a 4Ù load using
±28V supplies and 50W(typ) into an 8Ù load from ±35V
supplies....
....the IC can handle a maximum of ±40W of continuous power dissipation without SPiKe Protection being turned on under continuous sinusoidal input with proper heat sinking. The same theory applies to other Overture ICs as well, like the LM3876T, which is capable of dissipating 31W with proper heat sinking."
P.A. can you just confirm my understanding that this basicaly means that even if the chip is guaranteed to reach 60W, everything exceeding the initial 40W, will incur a big hit on THD due to Spike?
so do you all think that bridge the LM3886 is an ideal way to have more output power or this is a very bad ideal? If this is not the good way, do you all have any ideal to get a more output power chip amp?
If bridging was a bad idea (or parallel, for that matter), it wouldn't be in one of their app notes...
I still have problem to understand in between bridging and parallel. What's the different in between bridging and parallel?
Bridging = Double output voltage, load not connected to ground (not suitable for 4 ohms load)
Parallel = Double output current, load connected to ground
Parallel = Double output current, load connected to ground
And which one is better? Bridging will have louder output and parallel is still the same right? In terms of perfomance and output quality, which one is better?
This dependent of your load and your power supply voltage.
I'll recommend that you check the Excel file above.
I'll recommend that you check the Excel file above.
Can I parallel more than 2 ICs in a time, such as 4 ICs parallel together? Before this never I never do any of these electronic thing, so I really have no idea what it is all about. Hope you all can help me.
You can connect as many you like in parallel but I'll that you'll need more than two for a 4 ohms load.
Have you checked the design guide (the excel file)? If not, do that!
Have you checked the design guide (the excel file)? If not, do that!
You don't need any zobel networks for LM3886.
Hum may be because of poorly designed schematic diagram , or incorrect connection of components.
You only need a carefully designed schematic , as stated in its datasheet.Its layout is critical for IC amps.
It is important that all ground points are connected to one ground point.Otherwise , noises may pass to input , as only tiny amounts of current are required.
All connections should be as short, as possible.
Hum may be because of poorly designed schematic diagram , or incorrect connection of components.
You only need a carefully designed schematic , as stated in its datasheet.Its layout is critical for IC amps.
It is important that all ground points are connected to one ground point.Otherwise , noises may pass to input , as only tiny amounts of current are required.
All connections should be as short, as possible.
I really want to show you the schematic that I followed, but I can't find it in my PC, don't know where it is gone. It has little bit different to the National one. So you are meaning following the schematic that given by National will be better? If you are saying that LM3886 no need zobel network, then maybe my poweramp has distorted output when I turn the volume to 11 o'clock because I added the zobel network to my poweramp already. Will it be? Regarding to the parallel the ICs, when I parallel the IC, it won't get louder than single IC, am I right?
I don't know your schematic diagram. What is the purpose of zobel network ?
If you want to parralell your ICs , you need :
1) Very well matched feedback components(0.1 % tolerance preffered)
2) Some resistors on output (like 0.5 ohm or so , 5 W).
By paralelling ICs you can get a bit more output if you rise power supply voltage(Remember , LM3886 can handle AT MOST +/-42 V no load!).Power output will not double , though.
Also , you can google "BPA 200". It is a schematic of amp , based on 4 LM 3886 chips , delivering 300W RMS.
LM3886 must be absolutely quet even at max volume .I made an amp without a volume control very succesfully, by using National's preferred schematic.
Did you read Lm3886 datasheet carefully ? It has lots of explanations.
If you want to parralell your ICs , you need :
1) Very well matched feedback components(0.1 % tolerance preffered)
2) Some resistors on output (like 0.5 ohm or so , 5 W).
By paralelling ICs you can get a bit more output if you rise power supply voltage(Remember , LM3886 can handle AT MOST +/-42 V no load!).Power output will not double , though.
Also , you can google "BPA 200". It is a schematic of amp , based on 4 LM 3886 chips , delivering 300W RMS.
LM3886 must be absolutely quet even at max volume .I made an amp without a volume control very succesfully, by using National's preferred schematic.
Did you read Lm3886 datasheet carefully ? It has lots of explanations.
The voltage, possibility to more current out.Matthewong said:
Seriously, you must set up the specifications of you project, then choose topology. Put those specs in the Excel file I mentioned and from it get facts. Much of you questions are based on that you don't have tried the Excel file nor read the AN-1192 anf the datasheet.
Matthewong said:
Hi,
Are you still suffering from the hum?
Almost every hum problem is caused by incorrect ground loops, not only within an amp but it can also exist between an amp an a pre-amp.
You can also measure the voltage potential between the (not connected) RCA-ground of the amp and pre-amp: does it have any ac component?
About your other question, bridging is only advisable when you need more output power.
Connecting 2 (or more) amps in parallel is desired when you need to drive low impedance loads.
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