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Ready-to-Run (RTR) SSR DC Speaker Protection and Delay GB

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randytsuch

Member
Joined 2003
randytsuch-audio.blogspot.com/2005/10/my-system.html
My board arrived in the mail yesterday, now have a question.
Going to use in a class A Sissysit amp, but to drive very power hungry headphones.

Wondering if and how to adjust the DC offset trip point to something lower than 1.5V?
Was thinking something around 0.5 or 1.0 VDC. Probably closer to 0.5.

I can change out SM resistors, figure that will be required. Need to place a Mouser order, so I can buy whatever I need with the order.

TIA
Randy
 
xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
I have a SSR headphone protection circuit made just for headphones. It’s pretty easy to assemble if you can do basic SMT parts.

https://www.etsy.com/listing/971912371/ssr-headphone-protection-pcbs?click_key=01201391821312372668eff65fb7242f997d9a97:971912371&click_sum=159bf2c4&ref=shop_home_active_12

For the speaker SSR threshold level to be set to a lower value - will require some calculations. Let me ask Jhofland if he has suggested values. What would you like the threshold to be? 1.5v should not destroy a headphone. You might want to keep it to allow deep transient bass kick drums.

The threshold is controlled by an RC circuit R102 and C102. When DC charges this up there is a time constant and this powers an LED in an optoisolator. The output of the optoisolator feeds a comparator. R104 is a 200k resistor that sets the trip point of the comparator. One could make this value larger to force the reference voltage divider to a lower value. Something like 200k to 300k might make it trip at a lower voltage. Depends on where you want it. Changing R102 to a smaller value will let the RC charge up faster for a quicker response.

1663702450561.jpeg
 
Last edited:
R

randytsuch

Member
Joined 2003
randytsuch-audio.blogspot.com/2005/10/my-system.html
xrk971 said:
I have a SSR headphone protection circuit made just for headphones. It’s pretty easy to assemble if you can do basic SMT parts.

https://www.etsy.com/listing/971912371/ssr-headphone-protection-pcbs?click_key=01201391821312372668eff65fb7242f997d9a97:971912371&click_sum=159bf2c4&ref=shop_home_active_12

For the speaker SSR threshold level to be set to a lower value - will require some calculations. Let me ask Jhofland if he has suggested values. What would you like the threshold to be? 1.5v should not destroy a headphone. You might want to keep it to allow deep transient bass kick drums.

The threshold is controlled by an RC circuit R102 and C102. When DC charges this up there is a time constant and this powers an LED in an optoisolator. The output of the optoisolator feeds a comparator. R104 is a 200k resistor that sets the trip point of the comparator. One could make this value larger to force the reference voltage divider to a lower value. Something like 200k to 300k might make it trip at a lower voltage. Depends on where you want it. Changing R102 to a smaller value will let the RC charge up faster for a quicker response.
Click to expand...
Thanks. I have one of you headphone protection boards too, but it has a common ground and I didn't want to tie the output lows together at your board (even if they are ground).

1.5V seems high to me for headphones, maybe its just me being overly cautious.

Randy
 
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