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questions about diy a 12V trigger output

MCH

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hi,
i have the intention to transform my two SVS SB 1000 subwoofers to passive subs, bypassing the electronics and using an external amp connected directly to the driver. After some time doubting and reading about the cheap amps this forum loves, i think i have finally found a good candidate, the new Fosi Audio ZA3:
1698696617838.png

- it can operate in both stereo and mono mode
- has balanced inputs (my dac is balanced)
- 240W in mono mode (vs 300 of the original SVS plate amp. I plan to use 1 fosi for each sub)
- has 12V trigger input
These are basically all the features i need, and i have not seen any other amp with all of them at this price point (i can get it for 115 euros).

Now, as so far all my amps had audio sense, this will be my fist time dealing with trigger inputs/outputs and i am not sure if my plan is feasible or not. I would like to know your opinions and suggestions:

All the devices and audio signals in my system are managed by a raspberry pi 4b and a raspberry pi pico, so 3.3V and 5V is what i can get from them. However, i also have a 12VDC source, that is the PSU of my minidsp 2x4 HD. I thought that i could use this 12V source to be able to use the 12V trigger of the Fosi. I am thinking of two possibilities:

1. easy but not ideal: run a connection from the minidsp DC input to the trigger input of the fosi = whenever the minidsp is on, the fosi will be on. Concern: will this do any bad to the minidsp? i understand these trigger inputs don't draw any current, it is just like a signal sense. is this correct?

2. ideal solution: the raspberry pi knows when there is an actual audio signal -> from the GPIO, activate an optocoupler that switches a connection from the minidsp DC input to the Fosi trigger -> when the minidsp is on AND there is an audio signal, the Fosi will be on. Of course, i will leave a few minutes delay before the optocoupler switches off upon no audio signal is going on. Concerns: 1. same as previous. 2. in this case, the fosi will be switched on and off a few times a day, maybe several times a day, say 20-30 times. Is this something to worry about? (note: all the software and hardware to make this work is sorted out, i only seek answers to my concerns)

Thank you for any answers and suggestions.
 
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mcdn

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You should ask @Fosi Audio what voltage is actually needed. They are called "12V triggers" for historical reasons, but many will be triggered just fine by 5V as they rarely operate a relay directly these days.
 
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7Tiger

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Why would one want to use external amps for SB-1000s unless the built-in ones are broken and there is no way to get replacement(s) ?! :rolleyes:
 
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MCH

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You should ask @Fosi Audio what voltage is actually needed. They are called "12V triggers" for historical reasons, but many will be triggered just fine by 5V as they rarely operate a relay directly these days.
Ah, didn't know that. Will certainly ask Fosi, 5V would simplify things. 3.3V even more. Thanks!

Why would one want to use external amps for SB-1000s unless the built-in ones are broken and there is no way to get replacement(s) ?! :rolleyes:
Because of this:
 

7Tiger

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Because of this:
I see... But why not just use a proven working solution like some Behringer or Crown amp ? It seems to me that Fosi is not quite up to the task.
 
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MCH

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I see... But why not just use a proven working solution like some Behringer or Crown amp ? It seems to me that Fosi is not quite up to the task.
Crown; size, price + I don't need the DSP features.
Behringer: don't know, which ones you mean.
Why do you think the fosi is not a good choice? I know nothing about passive subs. Appreciate your input. Thanks.
 
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MCH

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You should ask @Fosi Audio what voltage is actually needed. They are called "12V triggers" for historical reasons, but many will be triggered just fine by 5V as they rarely operate a relay directly these days.
Fosi answered:

"The minimum voltage that will activate the trigger input is 12V.
5V and 3.3V do not work.
If you have any problems please feel free to contact us.
Thanks for your continued support."


Bold is theirs. So I guess I will have to use the 12V of the minidsp and find out. Not a big deal, I am 80% confident it will work.
 

7Tiger

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Fosi is not designed for heavy lifting i.e. driving a subwoofer, professional grade amplifiers are more suitable for this use case.
Not all Crown amps have DSP, XLS series don't. XLS1002 will do the job nicely - a friend of mine runs a couple of sealed subs based on Peerless 835017 drivers (same as used in SB/PB-2000) off an XLS1502 and is absolutely satisfied with its performance.
 
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MCH

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Fosi is not designed for heavy lifting i.e. driving a subwoofer, professional grade amplifiers are more suitable for this use case.
Not all Crown amps have DSP, XLS series don't. XLS1002 will do the job nicely - a friend of mine runs a couple of sealed subs based on Peerless 835017 drivers (same as used in SB/PB-2000) off an XLS1502 and is absolutely satisfied with its performance.
That is a serious amp and makes me have second thoughts indeed. The problem is that it is just the opposite of what I was trying to achieve here (cheap, small, silent) but I know is a much better option.

Btw, while checking it at thomann the website suggested this 12 kg monster instead: 2x500W at 0.1% THD and audio sense 188 eur shipping and taxes included (!!) Wth, does it come stuffed up with stones??? If I had the space and knew the fans wouldn't bother me (I am going through all this because of background noise)...

 
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7Tiger

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That is a serious amp and makes me have second thoughts indeed. The problem is that it is just the opposite of what I was trying to achieve here (cheap, small, silent) but I know is a much better option.

Btw, while checking it at thomann the website suggested this 12 kg monster instead: 2x500W at 0.1% THD and audio sense 188 eur shipping and taxes included (!!) Wth, does it come stuffed up with stones??? If I had the space and knew the fans wouldn't bother me (I am going through all this because of background noise)...

Fans in Crown amps aren't too noisy in general but if you find them too audible just replace with some Noctua or other quiet ones from some other manufacturer.

T.amp you linked to is class H which uses linear power supply with big chunky transformer(s), hence the weight. Unfortunately, I don't have any experience with these amps so can't comment on their performance.
 
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