12v trigger question - Electrical issues?

[nightflier]

I have a pre/pro that has a single 12v. trigger output to power on an external device. It uses the standard 2.5mm cable. However, I want to power up a two amps, a 2-channel & a 5-channel. Can I buy a simple cable splitter at RS, or will that change the voltage, i.e. the ability to power them both up?

[ToddL]

You would need a parallel electrical split, which a 2.5mm split may do. I will try it out with what I've got here for curiosity sake

Just wondering. Does your 5-channel amp also have a 12V. you can chain them if you do.

[ToddL]

Okay my experiment was inconclusive. The main thing is that all cables including the splitter are going to need to be 3.5mm mono and not stereo. I can not find a mono 3.5mm splitter anywhere, on-line or through distributers.
So if you can find a 3.5mm mono parallel splitter then it should work, but good luck finding one.

[nightflier]

Interesting, I used a stereo splitter and it did not work either. I thought it was because of some voltage issue, but if it's because of the stereo part, it seems rather strange since there should be no overlap in the connector inside the splitter right? I always thought that a stereo splitter would just split the signal evenly.

Any electrical engineers out there who can confirm this is not because of voltage?

[ToddL]

I am an electronics technician (in diploma anyway). The way I figure it the 12V signal is essentially a 12V pulse that travels, when it is put into stereo it is getting split into L/R which is nice for audio but not for electrical. Technically it would be dividing the voltage probably into a 6V-left and 6V-right and then splitting that is going to whack it even more. That is why a mono cord is necessary so the 12V pulse is there with positive and negative and not L/R. The stereo splitter does diminish the voltage level so it is the voltage level caused by the stereo split.

[nightflier]

Todd,

Thanks for the expertise. So if I were to just splice the cable and match + and - into two cables, then I should be fine, right?

[ToddL]

I would assume so as long as they are wired in parallel and there are no impedance issues.
This really shows how unprepared college grads are these days.

[nightflier]

Hey Todd, thanks for the info, but you don't have to be insulting about it. Next time you need a programmer to tweak your CAD results, keep walking.

[ToddL]

Hey Todd, thanks for the info, but you don't have to be insulting about it. Next time you need a programmer to tweak your CAD results, keep walking.

That wasn't what I meant at all. I was refering to myself and how I should know this problem because of my schooling, but I don't know for sure.

[nightflier]

My apologies. I thought this was a swipe at me.

[Glen B]

Okay my experiment was inconclusive. The main thing is that all cables including the splitter are going to need to be 3.5mm mono and not stereo. I can not find a mono 3.5mm splitter anywhere, on-line or through distributers.
So if you can find a 3.5mm mono parallel splitter then it should work, but good luck finding one.

I have seen it recommended that each positive half of the split should be fed through a diode (e.g. 1N4148).

[nightflier]

GlenB,

I don't speak EE, can you explain what the diode does and how I would add that to my DIY cable.

(I was just about to start with the rasor blade, when I read your post.)

[Glen B]

GlenB,

I don't speak EE, can you explain what the diode does and how I would add that to my DIY cable.

(I was just about to start with the razor blade, when I read your post.)

A diode allows current to flow in one direction only (from anode to cathode - positive to negative) and blocks the flow in the opposite direction. This process is called rectification. Diodes are used in A/V equipment power supplies for example, to change the household alternating current (AC) to direct current (DC) for use by the equipment's circuitry. In the case of your trigger circuit, the diodes are used to isolate and prevent interaction between the two triggers. In the image I provided, the arrow-point represents the anode or positive side of the diode. The bar represents the cathode or negative side. On the diode, the cathode is usuallly identified by a band. The triggers should be wired in series with the diodes. The + conductors of the two trigger cables going to the amps should be connected to the anode side of each diode. The cathode side should go to the center terminal of your 3.5mm phone plugs going to the amps.

[nightflier]

Glen,

Allright, I'll give that a try this weekend. I presume that wiring this wrong won't do any damage to the amps(?).

I also was wondering about a different solution. My old B&K amp actually used RCA connectors for the 12v trigger. Back then, I used a simple RCA-to-3.5mm mono adapter to connect my preamp to it. Now, I should be able to pick up another two of these adapters and then use a standard RCA splitter (like a subwoofer cable Y-splitter) to split the signal, correct?

[Glen B]

Glen,

Allright, I'll give that a try this weekend. I presume that wiring this wrong won't do any damage to the amps(?).

I also was wondering about a different solution. My old B&K amp actually used RCA connectors for the 12v trigger. Back then, I used a simple RCA-to-3.5mm mono adapter to connect my preamp to it. Now, I should be able to pick up another two of these adapters and then use a standard RCA splitter (like a subwoofer cable Y-splitter) to split the signal, correct?

Here is a hookup diagram for your trigger cable. The "+" wire (red) goes to the tip of the plug and the "-" wire (blue) to the barrel. Connect the diodes in the proper orientation, i.e., anode to the controlling unit and the cathode side to the amps. BTW, the diodes are available at Radio Shack for $1.39. When you're done, some heat-shrink over the connections should finish your cable off nicely and make it more secure. With regard to your old B&K amp, as long as the connector matches what is on the amp, no problem.

http://www.radioshack.com/product/in...entPage=search

[Kursun]

The 12V output at your pre is simple DC. At the power amp side there is a miniature 12VDC relay inside. It consumes very little current. So using a splitter you can connect this 12VDC output to as many devices as you wish.

In my opinion diodes are NOT necessary. Diodes are required when there are more than one energy sources, as in connecting two car batteries in parallel. In that case, if there are no diodes, each battery will try to charge the other. But this case is entirely different. There are no reverse currents, as there is only one energy source (12VDC from pre).

[nightflier]

Glen,

Is what Kursun says correct? I dont really mind buying a pair of $2 diodes (if I can stil find a RS store), although it does complicate the whole thing a bit.

[Glen B]

Glen,

Is what Kursun says correct? I dont really mind buying a pair of $2 diodes (if I can stil find a RS store), although it does complicate the whole thing a bit.

Yes, Kursun is right. I went back and took a second look at the source of this information on using diodes. The suggested use of diodes were for turning on a single device from from two DIFFERENT triggering sources - not that this would have done any harm to your equipment to incorporate the diodes. Just make up your cable without them.