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Sony amplifier -speaker relay delay circuit modify??

Midhunhere

Jun 28, 2017
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Jun 28, 2017
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Dear brothers,
I have a Sony amplifier (hifi music system)board and transformer from scrap yard . I took power amplifier section and it's working now. and want to add delay in relay section to protect speaker when it's power on... the diagram is attached below... waiting for your reply.... thank you.best regards..
 

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Kabelsalat

Jul 5, 2011
182
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Ok schematic.
Can you give an idea in specific what you want to protect the speakers from? DC voltage? Voltage spikes? Too high current out? What's the speccs of the speakers you intend to use?
 

Midhunhere

Jun 28, 2017
11
Joined
Jun 28, 2017
Messages
11
Dear brothers,
I have a Sony amplifier (hifi music system)board and transformer from scrap yard . I took power amplifier section and it's working now. and want to add delay in relay section to protect speaker when it's power on... the diagram is attached below... waiting for your reply.... thank you.best regards..View attachment 49428
Ok schematic.
Can you give an idea in specific what you want to protect the speakers from? DC voltage? Voltage spikes? Too high current out? What's the speccs of the speakers you intend to use?
Ok schematic.
Can you give an idea in specific what you want to protect the speakers from? DC voltage? Voltage spikes? Too high current out? What's the speccs of the speakers you intend to use?
Sir.
Wanna protect from all above...short circuit, switch on -off noise, overload...etc... speaker spec (150w ,8ohm?) please check attached image. thank you.
 

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Kabelsalat

Jul 5, 2011
182
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Ok, I see. The issue is mainly - you don't know excactly how much it takes to destroy the speakers. You need to work this out before making a plan how to protect and how much protection you're willing to put into this - and if it's worth the effort at all.

However - there is a couple of things you may do to prevent damage:
  • Avoid clipping. That's probably no #1 thing known to destroy speakers. If you're to make a protection device, you must work out the maximum voltage out from the amplifier (need to see the audio IC datasheet for that) and still you should have some safety margin. Then you need a comparator and set up a fixed voltage, then a latching circuit that triggers a relay and the relay contacts connected to speaker ouputs.
  • However - it doesn't protect if the input signal is already clipped. For this, you may opt for an opamp derivator circuit. From that you just follows the same steps as above.
  • If electric effect over time also should take into account, you may opt for a current transformer between main transformer and rectifier. Then feed into a opamp based integrator circuit (must rectify this current first). But - first you must work out the power losses in the amplifier and also a sort of power over time curve that the speakers are guaranteed to withstand.
So - it is doable. The question are : Does the speaker cost so much that it is worth spend a lot of time and effort (and cost) to build this extra protection devices? And - is there enough space inside the amplifier cabinet to put another PCB, relays and current transformers?
 

Midhunhere

Jun 28, 2017
11
Joined
Jun 28, 2017
Messages
11
Ok, I see. The issue is mainly - you don't know excactly how much it takes to destroy the speakers. You need to work this out before making a plan how to protect and how much protection you're willing to put into this - and if it's worth the effort at all.

However - there is a couple of things you may do to prevent damage:
  • Avoid clipping. That's probably no #1 thing known to destroy speakers. If you're to make a protection device, you must work out the maximum voltage out from the amplifier (need to see the audio IC datasheet for that) and still you should have some safety margin. Then you need a comparator and set up a fixed voltage, then a latching circuit that triggers a relay and the relay contacts connected to speaker ouputs.
  • However - it doesn't protect if the input signal is already clipped. For this, you may opt for an opamp derivator circuit. From that you just follows the same steps as above.
  • If electric effect over time also should take into account, you may opt for a current transformer between main transformer and rectifier. Then feed into a opamp based integrator circuit (must rectify this current first). But - first you must work out the power losses in the amplifier and also a sort of power over time curve that the speakers are guaranteed to withstand.
So - it is doable. The question are : Does the speaker cost so much that it is worth spend a lot of time and effort (and cost) to build this extra protection devices? And - is there enough space inside the amplifier cabinet to put another PCB, relays and current transformers?
Thank you sir....Can you please give the step by step procedure....I will do as it as... formula and related things....I am zero in electronics...it's hobby only... thank you for your reply....
 
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