12v Trigger

This post is both a complaint and a fix.

I'm not sure why Outlaw chose to not include a switched outlet on the 990 but it would have made my setup considerably easier. I needed a switched outlet to control both a 120v component and a 12V wall wart (AC/DC transformer). I ended up using a relay (DPDT) from Radio Shack. One side was used to control the 120V circuit and the other was used to control the 12V circuit and I used the 12v trigger on the 990 to activate the relay. The second problem I had was finding a relay big enough to control the output that I needed but could still be activated by the measly 50mA output of the 12v trigger. Anyhow, if anyone finds themselves with the same problem (and doesn't have some type of electronics background) email me and I can give you the Radio Shack number for the relay and explain how to correctly hook it up so everything works.

There's actually a pretty sound reason behind the omission of a switched outlet. Outlaw (and many other manufacturers) avoid putting switched outlets on receivers and processors because they don't want to give users the opportunity to plug high-current devices into the outlets - the power side of a surround processor is not up to passing the kind of current that a power amp, subwoofer amp, or large TV needs to operate. A 12v trigger, on the other hand, can easily turn on amps (which almost always come with a trigger input these days) or trigger on switched outlets in surge protectors and power conditioners made by companies like Panamax and Monster.

There are some power strips around that support a 12V trigger - they essentially do the same thing as the rig that you built. I'll see if I can track down a link when I get a chance...

Gonk and Theproletariat, there are plenty of power strips that take a 12v trigger, but you have to read the specs carefully to make sure the one you're looking at is sensitive enough for the 990's 50ma trigger output. The Master strip that was praised a few years back in The Absolute Sound isn't that sensitive. The label on the back of the 990 says 100ma - or at least mine did; maybe the newer ones have been corrected - and that sure didn't help. I ended up using a Panamax 4300, not fancy but adequate. Maybe the other Panamax stuff will be OK but I'd still check the specs in the owner's manual before buying.

I looked into the switched surge protectors that you were talking about (Monster, Panamax etc) but $250+ is a little step just to turn on my amps and a 120V component. If the Outlaws really wanted to make the 12v switch useful then it needs a lot more output than 50mA (of current. Thats only enough current to turn on two, or maybe three, amps (I have 13). Which would preclude it from being used with a system comprised of the Model 2200's. Even the Xantech AC-1 switch cost $100, which is kind of step considering I paid about five bucks for the relay to do the same thing.

My Panamax MAX5100 works just fine with the 990's trigger. It also worked with my Model 950 and 1050 before. I suspect they've kept the current involved low to avoid potentially overloading some other brand's trigger input, but that's just a guess - I'm not sufficiently up on the lower and upper thresholds for most amps' triggers.

How do you handle switching your thirteen amps on and off, theproletariat? That's quite a stack to leave on all the time, but it's also a significant number to try to trigger from any processor's 12v trigger.

To switch the amps on I wired a 500mA wall wart thru a relay to turn on 10 of the amps via the DCV input on the back of the M200's (these ten amps run my front two main speakers), they are triggered by the #1 12V relay on the 990. The other three amps are turned on by a second wall wart that is controlled by a second relay and is triggered by the #2 12V relay on the 990. This was done since the last three amps control the center and back surround speakers so they only need to be on when the source requires surround sound, otherwise they remain off when I am listening in stereo mode. The amps all run through one of two brick wall surge protectors and the amps are split evenly among two seperate 20A circuits, so turning all of them on at once is not a problem. Your last question, Gonk, was what I had the most difficulty trying to find. A relay that could handle the output I needed and still be triggered by only a 50mA 12V source.

Not to insult anyones intelligence but for those who don't know a relay keeps the activation cicuit electrically isolated from the output circuit. Essentially it uses a small voltage to control a significantly larger voltage (or amperage).

Five amps to drive each front speaker... Woah. I started to ask why you're not using the M200's auto-sense feature, but under the circumstances I can see why - presumably you've got an active crossover upstream of the amps, and you'd likely have each amp triggering on randomly as you start the system and start putting out a signal. Very interesting stuff.

Actually I do have an active crossover for the woofers, but only to adjust the input sensitivity (since the M200's don't have an adjustment built in, which would be very nice. Hint, Hint Outlaw). It was the only way I could get the five amps balanced. The midranges and tweeters have their own built in passive crossover network so they do not use an active network. BTW the active crossover was the 120V device that I needed to be powered by a switched outlet on the 990, but instead had to wire it through the other side of the relay.

Hey all:

Another way to handle this is to use a NPN BJT transisitor as the switch (i.e relay). You can use this either to source the trigger current downstream (you will need a wall wart or something similar) or to a relay.

The reason this works is that the input impedance looking into the base of the transistor is quite high (probably at least 100 k Ohm and probably even higher); the collector is tied off to the + of the wall wart and the emitter goes to the 12 V trigger inputs downstream (or the relay if you are switching that).

Since (looking into the base) the impedance is high, very little current is required of the 990's trigger outputs (using this approach it almost seems to the 990's trigger output that it is sourcing no current at all, which is a good thing). In short, the current flowing into the base of the NPN will be on the order of 120 microamps - at least three orders of magnitude less than what the 990's triggers are rated to source (50 mA). This is a good thing.

So, once the base is turned on, the operating current (current flowing into the downstream components' triggers) is sourced by the wall wart. The only potential issue that I can see is that the wall wart should be at least 700 mV above 12 V due to forward bias voltage drop in the transistor. I suspect that using a 13-15 VDC wall wart would be just fine.

The only caveat is that the wall wart must be able to source the operating current required by the triggers on the amplifiers. Keep in mind that the more devices you tie to the emitter, the more current the wall wart will have to source. Still, if you found one that would source 500 mA that would be more than you would ever need.

Additionally, if you want to adapt this circuit, you can have the emitter drive a relay - this is a nice way of switching AC mains while providing low current draw on the trigger output of the 990 as well as making relay selection (those capable of being switched by a source limited to 50 mA max) a bit broader.

A friend of mine used this approach (Darlinton transistor only) to get his projector to switch on - he did not have a 990, but had the same issue, namely, the trigger input impedance was low enough to pull the trigger voltage down to nearly zero (i.e. it looked for all purposes like a dead short). Anyway, the Darlington transistor (he found it at Radio Shack) approached worked like gangbusters for him. Inexpensive and effective... two of my favorite things.

Mark

What kind of speakers require 5 M200's? Just curious.

Hand built speakers (They took me two years to build and I am a fairly accomplished woodworker). The lower cabinets house one 15" woofer and one 12" woofer. The upper cabinets house two 6.5" mid/woofers, one 5.25" midrange and three tweeters. Everything is hooked up in a four ohm impedence. Needless to say the speakers are extremely power hungry. These speakers do a pretty good job at testing the ability of the M200's (both from a sound quality point and from a load point). I can vibrate things in the house all the way down to about 15Hz and the highs are crystal clear (no hiss, static, crackle or anything normally associated with tweeters). Of course you have to spend a good bit of money on high end tweeters and crossover components (NPE capacitors and iron core inductors aren't going to cut it).

Sounds like we need some pictures.
I love it when someone breaks with the status quo and, like Frank Sinatra says, "I did it my way".

Lonster

Here is a link to a few pictures of the speakers being built and the finished products.

http://groups.msn.com/SpeakerPage/shoebox.msnw

Cool pictures, theproletariat - looks like some nice, solid cabinets. I can see why it took you so long to get them built. I also liked the gaggle of binding posts .

Not to mention that the orientation is a welcome change, kudos on that one. I'm always b*tching about plugging/unplugging my banana-term cables from the recessed boxes, being down low and recessed, and one of the leads always kinks from the bend in the cable.

Very nice!

Wow, those look like awesome speakers, so... when are we invited over for a demo?