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

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J

jhofland

Member
Joined 2009
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.

View attachment 1092733
Click to expand...
Regarding trying to drop the threshold, it's really dictated by the voltage drop across the input diodes of the optoisolator. It won't trip unless the offset exceeds what's across this input. Off the top of my head I don't recall what that minimum is. I do know that it is greater than 1V. Trying to modify this circuit for input offsets less than that just plain doesn't work.
 
xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
Just use 0.250 Faston tabs. You can use AMP brand (nice) or basic knock offs. You can also use a Molex MiniFit Jr locking 4pin connector. But those are really not necessary for this basic application.

1679960927180.jpeg
 
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xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
Picture is Gen 1. Yours is the latest Gen 2.3 which has several improvements.

1. Isolated GND on power supply input so that it can be used on bridged amps with floating outputs.

2. Added external logic control to allow remote mute/graceful startup and shutdown with an open collector logic from an MCU.

3. Higher voltage MOSFETs so can handle amps up to 300w.

4. Comes with bonus blank PSU PCB to allow connection to secondary trafo windings to make a low capacitance PSU to provide instant off when power to trafo is cut. This prevents turn off thump.

But speaker and amp connectors are still the same.
 
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xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
Last edited:
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voxxonline

voxxonline

Member
Joined 2012
I am trying to use parts I have for the low-capacitance psu.
My transformer secondary is 15 V AC , this gives 21 DC, right?
Caps I have at hand are:
4.7 uF 50 V
10 uF 25 V
47 uF 35 V
Is any of these 3 good?

In case I don't need a led and resistor- just put jumpers instead?
Thanks
 
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