6 x lm3886

[FlexQ]

Well it's OK to hand match, and cheaper, but what if someone, not so experienced, finds your schematic and decides to use it, not reading this tread? Than he will have a amp that most likely going to oscillate.

It's always good to write the correct values, if not for your own sake then for somebody else's.

I would have edited the post, but it is not possible, why, i do not know.

But here i have written down some safety precautions.

http://img510.imageshack.us/my.php?image=nr2uq6.png

 

[AndrewT]

Where did that input switching relay come from?
What is the gain of the amp when the relay creates an open circuit on the input?
What is the effect at the output when the input goes open circuit?

 

[FlexQ]

Where did that input switching relay come from?
What is the gain of the amp when the relay creates an open circuit on the input?
What is the effect at the output when the input goes open circuit?

I changed it a second after i posted it, it was just a designing thought, not finished yet.

It was to ensure that when powering up, i will not have any signal at the output. It will be driven by a soft start circuit, but i am just calculating right now.
havent been making a soft start before, so it is not easy , but i hope it will come, reading this guide:

http://sound.westhost.com/project39.htm

A good idea?

 

[AndrewT]

an input mute is a good idea for start up and during fault detection.
An open circuit is a bad idea and even worse when using inverting topology.

 

[FlexQ]

an input mute is a good idea for start up and during fault detection.
An open circuit is a bad idea and even worse when using inverting topology.

I can see your point, but it is not easy to work around the problem with the open circuit.

 

[pacificblue]

Remember the LM3886s mute input from post #9

 

[FlexQ]

Remember the LM3886s mute input from post #9

Just as reading my mind ;P

http://img186.imageshack.us/my.php?image=nr3rp6.png

This is the last change for this week, now i am going to visit my parents, if you have any comments or questions, feel free to say it, i am open to almost anything.

have a nice weekend, and thanks for the help so far guys.

Caught this in the datasheet:

Under-Voltage Protection: Upon system power-up the
under-voltage protection circuitry allows the power supplies
and their corresponding caps to come up close to their full
values before turning on the LM3886 such that no DC output
spikes occur. Upon turn-off, the output of the LM3886 is
brought to ground before the power supplies such that no
transients occur at power-down.

 

[pacificblue]

Under-Voltage Protection: Upon system power-up the
under-voltage protection circuitry allows the power supplies
and their corresponding caps to come up close to their full
values before turning on the LM3886 such that no DC output
spikes occur. Upon turn-off, the output of the LM3886 is
brought to ground before the power supplies such that no
transients occur at power-down.

Yes, and some people still report about pops and clicks during power up and down. Many say that only faint sounds ocurr, so they live with it.

For power up the muting circuit from the datasheet works fine even without a separate switch. And you can always try an RC circuit across the main switch to get rid of pops when switching off.

By the way, you can connect all mute pins together and use one Rm, Cm and switch for all ICs. Rm must be smaller then.

 

[FlexQ]

Yes, and some people still report about pops and clicks during power up and down. Many say that only faint sounds ocurr, so they live with it.

I think i might make the layout so it is possible to wire it over, if it is not possible to hear, then it will only be a thing more which can break.

For power up the muting circuit from the datasheet works fine even without a separate switch. And you can always try an RC circuit across the main switch to get rid of pops when switching off.

Sounds like a good idea.

By the way, you can connect all mute pins together and use one Rm, Cm and switch for all ICs. Rm must be smaller then.

I am doing that right now =)