Speaker Fuse

[ziloo]

hello folks,

Looking at the following circuit:




They say the low resistance R8 is used as a fuse to protect the speaker against high current;
whenever the speaker draws too much current, R8 would burn up to save the day!
I somehow don't understand why removing R8 (same as frying it) would save the speaker?

ziloo

 

[djg]

Datasheet says its for frequency stability of the amplifier. It has slightly different component values.

https://media.digikey.com/pdf/Data Sheets/ST Microelectronics PDFS/TDA2030A.pdf

 

[ziloo]

Datasheet says its for frequency stability of the amplifier.......

Thank you djg...... that was my grok as well!
Mebe the people who were telling me about the fuse for speaker
were referring to a different circuit and I somehow misunderstood!
I /they stand corrected...

ziloo

 

[jlang]

The network c6 r8 is there to provide a low impedance load at high frequency.
The speaker voice coil is an inductor. Impedance goes up as the frequency goes up.
The RC network does the opposite.

 

[ziloo]

An electronic repairman was explaining to me over the phone about
my faulty amplifier and he mentioned that I should be checking some
very low resistances right before the speaker. He said that these
low resistances act like a fuse and once they get burnt up, there would be
no sound coming from the speaker! I found the schematics for my
amplifier and the only low Resistance I found had no resemblance to
a fuse !!

Anyways.......There could be other models (specially high power ones)
that could employ a low resistance in series with the power signal to
act as a fuse.

ziloo

 

[Chuck(G)]

If this were a high-fidelity application, I wouldn't be in favor of a high-pass filter terminated in a resistor to protect the speaker. The reason is that the arrangement would impart a high-frequency rolloff in the response that might sacrifice fidelity. I'd be more in favor of a couple of high-wattage zeners to clip things above a certain level.