Both speaker and ground are isolated floating on the SSR so can be used on balanced amp.
Only ground on logic PSU input and that is optically isolated from speakers.
Only ground on logic PSU input and that is optically isolated from speakers.
Sorry for asking this question but I am playing it safe.
I have 2 wires from the transformer's secondaries- hot and neutral @ 15 AC and a small psu has 3 inputs.
Any chance someone can explain how to connect wires?
Thanks
I have 2 wires from the transformer's secondaries- hot and neutral @ 15 AC and a small psu has 3 inputs.
Any chance someone can explain how to connect wires?
Thanks
Hi Voxx,
It’s good that you ask. This is actually kind of tricky and it seems simple enough but I have had problems sometimes.
For your question:
Trafo secondaries are always “hot”. Do you mean the primaries that connect to mains are hot and neutral?
If there are 3 wires on secondaries it would mean that it is center tapped?
A photo or schematic diagram would be helpful.
In any case, if you can use a DMM and measure 15vac from one pair of the secondaries, (any two wires), connect those to the AC input of the small PSU board (pins 1 and 3 of J2) and connect the middle ground pin to the ground of your amp’s main PSU for reference only if using the same secondary from your main power transformer as the amp.
If a shared trafo is used for the SSR then connect pin 2 to one of the AC secondaries of the trafo to form a ground reference for the small PSU board.
Load D1 and D2 only if using separate dedicated trafo, else do not populate them if using common trafo secondary as main amp.
It’s good that you ask. This is actually kind of tricky and it seems simple enough but I have had problems sometimes.
For your question:
Trafo secondaries are always “hot”. Do you mean the primaries that connect to mains are hot and neutral?
If there are 3 wires on secondaries it would mean that it is center tapped?
A photo or schematic diagram would be helpful.
In any case, if you can use a DMM and measure 15vac from one pair of the secondaries, (any two wires), connect those to the AC input of the small PSU board (pins 1 and 3 of J2) and connect the middle ground pin to the ground of your amp’s main PSU for reference only if using the same secondary from your main power transformer as the amp.
If a shared trafo is used for the SSR then connect pin 2 to one of the AC secondaries of the trafo to form a ground reference for the small PSU board.
Load D1 and D2 only if using separate dedicated trafo, else do not populate them if using common trafo secondary as main amp.
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Thanks. Connect green and violet to pins 1 and 3 of J2. You can test the small PSU all by itself and see if it works if LED lights up and nothing blows up. 🙂
Edit: I think I may have this wrong, leave pin 2 disconnected if using dedicated secondaries.
Edit: I think I may have this wrong, leave pin 2 disconnected if using dedicated secondaries.
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4 since dedicated secondaries. But will work with only two if you want to save on diodes.
Clarification from Jhofland:
“If your AC source is 2 wire (a single secondary) then load D1 and D2 to get full wave rectification and don't connect COM input. If your AC source is a center tapped (3 wire) secondary then do not load D1 and D2.”
Clarification from Jhofland:
“If your AC source is 2 wire (a single secondary) then load D1 and D2 to get full wave rectification and don't connect COM input. If your AC source is a center tapped (3 wire) secondary then do not load D1 and D2.”
You are welcome. I’m glad you asked. It’s tricky as I have blown up some diodes when incorrectly connected.
When I last checked this thread for answers a few days ago I think the last post published was about #941. Since I'm pondering ways to power the SSR boards on another mosfet amp I'm building, I checked back late last night and there was the info I needed; power the low cap quick shutdown board from a single 15v raw AC secondary. This begs a question in my case though. 15v ac rectified is about 21vdc. Can I now use a 22uf 35v cap safely instead of a 50v rated cap? All I have is 4.7uf & 10uf at 50v.
Thanks for the clarifications, X!
Jim
Thanks for the clarifications, X!
Jim
The 22uF 35v cap can work fine but 10uF is enough and offers even faster shutdown when power is removed.
It has been a while since the last post, but maybe someone can answer my question about the TVS diode protecting the MOSFETs. Why do they have the same voltage rating as the MOSFET ? The BSC0402NSAT is rated for 150V, but a TVS like the SMAJ150CA with Vr=150V would not break down before 167V and clamping voltage is even 243V. So how can the diode protect the MOSFET ?
Hi Tojoko
I believe he sells them here:
Ready-to-Run (RTR) SSR DC Speaker Protection and Delay
Trigon
I believe he sells them here:
Ready-to-Run (RTR) SSR DC Speaker Protection and Delay
Trigon
This bothers me too.
The MOSFETs aren't really in series as each one has a parasitic diode that feeds the full voltage to the other. Maybe the TVSs should be chosen to be just above the rail voltage? You could also put one across the speaker if belt and brace is your thing.
I don't know if anyone's mentioned it (I think I've read the whole thread, but...) but using it in a bridged amp, it potentially sees twice the rail voltage, particularly with a class D amp. So +/-75V absolute max.
Has anyone simulated the back EMF from a speaker?
I’ll let @jhofland answer this one. But we have yet to see one fail in the field in this mode (or any mode). More thsn 400 units out there at present. It could be that no one’s amp has gotten close to the max rating of a 300W amp.
Back EMF of speaker will depend a lot on the crossover and driver used. Worst case would something like massive 40mH low pass inductor.
Back EMF of speaker will depend a lot on the crossover and driver used. Worst case would something like massive 40mH low pass inductor.