Speaker protection product

[sonosphere]

Hi everybody,
I am on lookout for used amps. Reading on web, I note that such amps can be temperamental at times, releasing a surge of DC suddenly and frying your speaker. This can happen even with the amps that have speaker protection.

I searched further and found a product that protects speaker here >> Velleman Speaker Protection Circuit Kit | Parts-Express.com

I am looking for a similar product in India. If anybody knows of a similar product available in India, please convey where I can purchase it. I am open to DIY kits too.

Thanks in advance,
Sonosphere

 

[captrajesh]

The kit disconnects the speaker if DC current is found?

Then what is that it allows to go through? I thought it is DC current (carrying the amplified audio signal) that goes through the speaker cable connecting the amp with the speaker. Am I wrong?

 

[borg]

The kit disconnects the speaker if DC current is found?

Then what is that it allows to go through? I thought it is DC current (carrying the amplified audio signal) that goes through the speaker cable connecting the amp with the speaker. Am I wrong?

The speaker will see a dc current only if there is a fault in the amp(like a short to the dc supply rail) otherwise during normal operation the speaker cables will be carrying audio frequency ac current

i meant continous dc,dc surge will be there during swith on / off

 

[sonosphere]

Hi Captain,
I suppose Borg has cleared your query. BTW apart from switching on /off stage, you may have something called "DC offset current" that is present at amp outputs even as the speakers are playing music. Too large value of DC offset can also damage speakers. I may be having a little misunderstanding here... audio gurus please correct me if I am wrong.

If you are curious, try searching the web for DC offset problem of audio amplifiers.

Regds,

The speaker will see a dc current only if there is a fault in the amp(like a short to the dc supply rail) otherwise during normal operation the speaker cables will be carrying audio frequency ac current

i meant continous dc,dc surge will be there during swith on / off

 

[venkatcr]

Though it is safe to be cautious, the chances of this happening is very rare - IF you protect the amp with a stabiliser. The chances of an amplifier (well built) generating a DC surge by itself is very near impossible. If it happens the amplifier's power unit has been designed and built badly. Actually the chances of an amplifier passing on AC current that is used to boost the audio signal is more possible. That is the reason a stabiliser is recommended.

Most speaker manufacturer have protection circuit built into the crossover. In a worst case scenario, the crossover will fry and can be replaced.

Cheers

 

[borg]

Hi Captain,
I suppose Borg has cleared your query. BTW apart from switching on /off stage, you may have something called "DC offset current" that is present at amp outputs even as the speakers are playing music. Too large value of DC offset can also damage speakers. I may be having a little misunderstanding here... audio gurus please correct me if I am wrong.

If you are curious, try searching the web for DC offset problem of audio amplifiers.

Regds,

yes you are right ofcourse there is the issue of dc offset as well

 

[captrajesh]

As per my understanding, AC current from the wall outlet is firstly fed to a transformer to reduce the voltage, then sent to a bridge rectifier to make it DC and fed to a capacitor Bank to take care of transient loads and from there, is supplied to transistors/tubes where the music signal is also fed through another grid. There the electric current is used to amplify the music signal and this goes to the speakers where the current moving through the coil interacts with the speaker magnet which in turn results in vibration of the attached speaker cone and the sound signal is regenerated for us to listen.

Now in this entire process, where is the DC current is reconverted to AC current?

 

[borg]

As per my understanding, AC current from the wall outlet is firstly fed to a transformer to reduce the voltage, then sent to a bridge rectifier to make it DC and fed to a capacitor Bank to take care of transient loads and from there, is supplied to transistors/tubes where the music signal is also fed through another grid. There the electric current is used to amplify the music signal and this goes to the speakers where the current moving through the coil interacts with the speaker magnet which in turn results in vibration of the attached speaker cone and the sound signal is regenerated for us to listen.

Now in this entire process, where is the DC current is reconverted to AC current?

the dc is for powersupply and biasing,ac signal(music) is fed to the input terminal of the amplifying device(base/gate/ or grid), output of amp gives proportional amplified ac signal based on input.

You can find a more detailed explanation on basics of electronic amps onnet (wiki etc)

 

[borg]

@Capt
Amplifier

here is a nice animation which shows the input and output waveforms,

 

[captrajesh]

@Capt
Amplifier

here is a nice animation which shows the input and output waveforms,

Thank you Borg but that was like Greek & Latin to me. You see, I was weak in mathematics

 

[sonosphere]

Dear VenkatCR,
I guess I am getting scared by reading only the failure reports on web. Just one example out of many >> See this opinion below regarding DC servo protection built-in some amps:

Originally Posted by xxxx
dose the dc servo act as a protection for the speaker outputs?
Response:
Nope. If the amp blows up, it'll take your speakers with it and the servo can't do a thing about it.

So what does a layman do after reading above? ... he gets prepared to spend 10-15% addtional cost of spkrs, on additional protection, as insurance to cater to rare case of falure, and of course for peace of mind (which is priceless)

?? And what if addtional protection fails ?? me getting paranoid... need to see a shrink first, spkrs can come later :lol:

On a serious note:
I am getting cautious, only regarding case of old amp purchase. Semiconductors can act temperamental after 7-10 yrs, and worst case consequence is you favourite spkrs up in smoke (<< a common experience posted on forums by many)

So guys, help me out with a Indian spkr protect solution, so I can peacefully own a "economical" vintage classic (NAD /Bryston /Krell /Adcom etc) !!!
Regds,

Though it is safe to be cautious, the chances of this happening is very rare - IF you protect the amp with a stabiliser. The chances of an amplifier (well built) generating a DC surge by itself is very near impossible. If it happens the amplifier's power unit has been designed and built badly. Actually the chances of an amplifier passing on AC current that is used to boost the audio signal is more possible. That is the reason a stabiliser is recommended.

Most speaker manufacturer have protection circuit built into the crossover. In a worst case scenario, the crossover will fry and can be replaced.

Cheers

 

[borg]

i found this, could easily be assembled in a common pcb
DC detect speaker protection - Quasi's DIY Audio Site

 

[sonosphere]

Big thanks borg!!!

i found this, could easily be assembled in a common pcb
dc detect speaker protection - quasi's diy audio site