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Discussion Starter #1
(UPDATE: JohnM_10 found what looks to be much cheaper and easier solutions. See his links in post 7 below. Thanks John!) :cool:


I don't know about the rest of you, but the "auto-on" feature of my subwoofer amp doesn't work very well. It's supposed to turn on my subwoofer whenever it sees a signal from my receiver. It's not sensitive enough though, so the volume from the reciever needs to be really high. I'm not *always* watching Led Zep DVDs, so this isn't always the case.


Simple solution if my subwoofer amp had a 12v trigger and my receiver did too. But they don't.


Well, I found a couple of solutions that will allow me to turn on my subwoofer and any other equipment when my reciever turns on. These solutions assume your reciever has an auxillary power jack that turns on when your reciever turns on. (I've never seen one that doesn't) Unfortunately these jacks can't support the power requirements of an amp or TV. They are basically for DVD players, as far as I can tell.


The first and cheapest solution (requires a little bit of basic electric work)

Get a Furman MP-20Q and put it in a square electric box (you can find these at any hardware store). You will also have to hook it up to power somehow. Use an extension cord or romex (whatever is legal in your situation)


Now you have your nifty little box. You just need a way to trigger it with a 12v input. Find a small transformer. (you know the ones that are used to power modems, hubs, etc. and seem to multiply like mice.... everyone has a couple old ones lying around. ) Make sure it puts out 8-15volts and at least 10mA. Cut the plug off the end. Strip the two wires and attach them to the MP-20Q's positive and negative trigger screws. Then plug the transformer into your amp. Plug your sub into the MP-20Q. Now, when you turn on your reciever, your sub (and anything else attached to the MP-20Q) will turn on. This totals about $80-$90 worth of parts.


For those who want a cleaner, premade solution with more features and don't mind paying a little more, get a Furman PS-REL relay in place of the small transformer, and get a MP-15 in place of the MP-20Q. This setup will cost around $150, but gives you more options and is pretty much plug and play.


These are the best solutions I was able to find for my setup. If any of you guys know of better and/or cheaper solutions, post it here.


Until 12v triggers are put on all home gear, we will need to be creative. :)
 

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Or just leave it on, or turn it on manually when you use it, assuming there is an ON switch aside from off/auto-on.


That's a lot of work and money for a sub that might cost the same or less.
 

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I didn't know such a thing existed from the OP so I started a DIY one.


If you've worked on electrical projects before and know what you're doing, it's not difficult to use a relay for this. I'm waiting on one now.


If you haven't worked with 120vac before, I don't recommend this be your first project. Do this at your own risk or hire an electrician to do this for you.


Items needed

1 Relay (120v 15amp or larger) ($15 shipped)

1 plastic Electrical box from home depot with cover and 3 tension release clasps ($2?)

1 Power strip ($5)

1 simple extension cord (I'm gonna use a cheap brown one) ($2)

1 wire cap for 14-10 gage wire. (pennies)


Total = +/- $24


1. Cut the power strip wire somewhere between 1/4 and 3/4 and push both ends you just cut into opposite sides of the electrical box.


2. Strip and twist the green ground wires together and attach them with a wire cap.


3. Solder the black and white wires of the plug side of the wire you just cut onto the "common" contacts on the relay.


4. Solder the black and white wires of the power strip side onto the "normally open" contacts on the relay. Make sure to get the polarity correct.


5. Cut the female plug off of the cheap extension cord and throw it away, strip the wires and put them through a 3rd side of the box and solder them to the relay "switch" contacts.


6. Mount the relay inside the box. I haven't received one yet so I'm not sure the best way to do this, I will probably drill small holes in the box and mount it with small bolts/nuts or I might use epoxy or both.


7. Check for shorts with a continuity tester first, then cover the box with it's plate or a blank plate you buy separately ($.75 or something).


8. To test this first I'll plug it into a safety plug in the kitchen or bathroom just to make sure it doesn't have any problems. (The ones with the little test/reset switches)


9. Make sure it turns something on and off correctly when you plug in/unplug the 3rd cord (the brown one).


10. Plug the brown cord into your amp, plug whatever you want switched into the power strip and the power strip cord into the wall, or for extra safety, plug it into another power strip that has load protection (fuse/circuit breaker).


11. Enjoy


Upon retrospect, I like the OP's idea of using the transformer so that you're not running a 120v wire out of your amp and around the house, I'm only running it 5 feet so I don't care. 12v Relays are also available.
 

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I've never had a problem with my auto on feature. If the sub is connected properly and you have your mains balanced right, as long as you set the LFE output to the proper level, you should have enough juice to turn it on. If not, you need to fix the sub. What your suggesting is a band-aid approach, rather then getting to the source of the problem



Ian
 

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If there is silence during a quiet scene and your amp isn't outputting anything to the sub it might switch off, then take a moment to switch back on.


Many people have some hum or small levels of power even during silence which will keep their sub on, but others don't. I think this way is alot more solid for turning the sub amp on and off appropriately. It's also good if you use a 2400watt pro amp like me :)
 

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Discussion Starter #8
Some people on this forum are WAY to critical. The solutions above can be used for many things. Stop dissing stuff just to watch yourself type. :rolleyes:
 

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Discussion Starter #10
Quote:
Originally Posted by Bachelor
Why not make your sub line level stronger and turn down your gain on the sub amp? Just a suggestion.
In many cases, that doesn't work. Sometimes people listen to things at a volume that is just enough to trip a line-level sensor on and off, unfortunately.


To the poster who put up the plans with a relay... are you sure that will work? That 7 dollar relay sounds awful cheap for something that can trigger with 120volts. The cheapest ones I found were $60.... if you know what you're doing, and can vouch for that, that's fantastic. One that tripped with a smaller voltage input would be even better (and safer) as you pointed out. :cool:
 

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Discussion Starter #11
Quote:
Originally Posted by cyberbri
Or just leave it on, or turn it on manually when you use it, assuming there is an ON switch aside from off/auto-on.


That's a lot of work and money for a sub that might cost the same or less.


I think of it as a system. A system that doesn't sound that great without the sub. $80 or even $150 to improve a $1500-$2000 system isn't bad, IMHO, especially when it can be used to turn on other stuff.
 

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My sub is an older unit without auto on circuitry. I use a simple X-10 appliance module and chair-side remote which works well since I run my receiver for more than home theater use. My setup is quite likely much cheaper than has been proposed and certainly simpler to impliment.


YMMV
 

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Quote:
Originally Posted by cyberbri
Or just leave it on, or turn it on manually when you use it, assuming there is an ON switch aside from off/auto-on.


That's a lot of work and money for a sub that might cost the same or less.
I vote for just leaving it on. Many subs with an "auto-on" in reality merely have an "auto-mute". Your amp is actually on all the time. All the auto-mute does is what its name implies: it mutes the sound until it receives a strong enough signal.
 

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Quote:
Originally Posted by S_rangeBrew
Those are just glorified power strips, from what I can tell.
No, they both auto-sense when your receiver is on and will turn on the other outlets appropriately.


For the price, they can't be beat.
 

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Quote:
Originally Posted by S_rangeBrew
To the poster who put up the plans with a relay... are you sure that will work? That 7 dollar relay sounds awful cheap for something that can trigger with 120volts. The cheapest ones I found were $60.... if you know what you're doing, and can vouch for that, that's fantastic. One that tripped with a smaller voltage input would be even better (and safer) as you pointed out. :cool:
That relay works great. I received it last week and put my box together just as I planned. Cost was about right too, $23 for everything.


Those auto sensing power strips are a much easier option though.
 

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Quote:
Originally Posted by petergaryr
I vote for just leaving it on. Many subs with an "auto-on" in reality merely have an "auto-mute". Your amp is actually on all the time. All the auto-mute does is what its name implies: it mutes the sound until it receives a strong enough signal.
Or just turn it on when you use it like the rest of the equipment (TV, receiver, DVD player, etc.).
 

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Quote:
Originally Posted by cyberbri
Or just turn it on when you use it like the rest of the equipment (TV, receiver, DVD player, etc.).
...or that too! :)
 

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Quote:
Originally Posted by cyberbri
Or just turn it on when you use it like the rest of the equipment (TV, receiver, DVD player, etc.).
That would mean getting up. You can't be serious!
 

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Quote:
Or just turn it on when you use it like the rest of the equipment (TV, receiver, DVD player, etc.).
That is probably the best advise I've read on this topic yet. :D


To S_rangeBrew:Unless your planning to hyjack this thread , you really don't need to start a new post every time you write a comment with a quote. ;)



Ian
 

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Discussion Starter #20
Quote:
Originally Posted by mailiang
That is probably the best advise I've read on this topic yet. :D


To S_rangeBrew:Unless your planning to hyjack this thread , you really don't need to start a new post every time you write a comment with a quote. ;)



Ian
My sub is 2 ft. away from my chair. Much to far away. Effort is verboten. Why must everything make sense? We are talking about *leisure* time people. ;)


I'm not sure how I can hijack my own thread, but I'll make a best effort. :D
 
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