With my current setup, I've got the external amp trigger by the remote amp output of the headunit. As my speakerphone is wired between the output of the headunit and inputs to the amp, I have to have the headunit on in order for the speakerphone to generate audio.

I'd like to wire the amp to trigger on either the remote-amp output of the headunit *or* the mute line of the speakerphone unit.

First off: does the remote-amp line from a headunit or empeg trigger by providing +12V or by grounding? I presume +12V, similar to the "ignition" wire into a headunit. If so, it gets complicated.

The speakerphone itself triggers mute by asserting ground (or 0V) on the mute sense. So, I figure I need to get funky with some relays in order to have either line do the work.

Recommendations? This is what I have so far:

I figure at a minimum: 2 bosch relays, one wired "normally" on the remote line (+=remote, -=ground), one wired "reverse" on the mute line (+ side ignition, - side mute), with the output side of both wired +=ignition,-=remote-amp-sense and in parallel.

I don't know how many of these paths would also require a current limiting resistor and if so, what specification. For example, would I need to put a resistor in the output path, or do amps typically have a high resistance/impedance on their remote-amp-sense input? Would I need to put a resistor on any of the input paths as well?

running out of room behind the dash...
-brendan

I'd like to wire the amp to trigger on either the remote-amp output of the headunit *or* the mute line of the speakerphone unit.

Should be solveable with a couple of diode and/or possibly a relay...

First off: does the remote-amp line from a headunit or empeg trigger by providing +12V or by grounding? I presume +12V, similar to the "ignition" wire into a headunit. If so, it gets complicated.

Correct. It provides +12V when active.

The speakerphone itself triggers mute by asserting ground (or 0V) on the mute sense. So, I figure I need to get funky with some relays in order to have either line do the work.

Recommendations? This is what I have so far:

I figure at a minimum: 2 bosch relays, one wired "normally" on the remote line (+=remote, -=ground), one wired "reverse" on the mute line (+ side ignition, - side mute), with the output side of both wired +=ignition,-=remote-amp-sense and in parallel.

I don't know how many of these paths would also require a current limiting resistor and if so, what specification. For example, would I need to put a resistor in the output path, or do amps typically have a high resistance/impedance on their remote-amp-sense input? Would I need to put a resistor on any of the input paths as well?


Unless you're running lots of gadgets off the remote wire (in which case you should already have a relay in place and would have known that it provides +12V to tell the amp to turn on) I'd do it like this:

1 standard bosch relay (SPST)
2 diodes, 1N400x

Run +12V (fused, 2-5A, could borrow for instance from the amps +12V wire) to pins 30 and 85 on the relay, run the phone kit mute wire to pin 86.

From pin 87 run a wire with a diode inline (positive, (anode) end towards the relay pin 87).
This makes the phone kit also provide a +12V signal instead of a ground,
Add the other diode the same way to the remote wire from the empeg (positive, (anode) end towards the empeg).

Then tie the negative ends (kathodes, striped end) of the diodes together and to the amps remote turn on port. This makes a logical OR function of the two inputs. The amp will see +12V when either of, or both, the phone kit and empeg are active.

No current limiting resistors required - all the items are designed to run off/handle +12V without problems. When tapping into a +12V source with a failry small wire, put a fuse close to the point where you take +12V, this is to protect the wire from overheating (and in the end the car from going up in flames should the overheated wire set anything on fire) should it short out to ground.

If you intend to run lots of gadgets controlled by the remote, instead wire the diode to pin 85 of a second bosch relay, ground pin 86, run a fused +12V wire (fuse size depending on what stuff you're running) to pin 30 and hook your amps remote + your other gear up to pin 87

Edit: Oh yeah, if you're running out of space behind the dash, put the relay(s) and diodes (the latter should effectively take no extra space as you can run them inline in the wire (cut wire, solder in diode and cover with heatshrink tubing)) by the amp (assuming you having stuffed that into the dash as well...)

/Michael

Wow, thanks Michael, that's immensely useful. Another project for this week then.

I already have piles of bosche (and bosche type) relays/sockets.

I picked up 4 1N4001s, 2 1N4004s and 3 "silicon rectifier" diodes that seem to have similar specs (no standard part number like the 1N400x series even though they just look like bigger ones), but even higher current handling and lower voltage drop (1V vs. 1.6V).

Got the last ones because I'm not sure how well the amp remote-sense might handle 1.6V off the top. I'll keep 'em around just in case.

This was all a handful of bucks at radio shack, and would have been pennies bought in bulk.

-brendan

Hi,

IIRC the 1N400x series all can handle about 1A forward current - not a problem since the relays draw well below that, likewise for the amp turn on input.
The difference between the various 'x' models of the 1N400x series is, again IIRC, the max reverse voltage they can handle. I'm suprised at your number of 1.7V for voltage drop over a 1N400x -- IIRC they're more like 0.7V (starts to conduct) and about 1V when running ~1A through then...

Another diode point, you may want to put a diode in the reverse direction across any relay coils (if teh relay doesn't already have such a diode internally). When the relay turns off, the coil can generate a fairly large kickback voltage, possibly large enough to harm any delicate output that is controlling the relay (ie your phone kit). Wire the striped end of the diode to pin 85 (if you connect the positive side there) and the other end to pin 86. This limits the induced kickback voltage to about 0.7-1 volt.

/Michael

Yeah, I was surprised at 1.7V too. Perhaps that's worse case, as your experience shows otherwise.

Thanks for the advice on the relay coil issue. All of my relays are diode-less. In this case of this kit, the speakerphone mute line grounds on active, so I'll be energizing the coil by connecting the coil's ground connection, essentially.

When mute is de-asserted, then the ground will be cut. Well, that is, I assume the speakerphone just N/Cs the connection...would it do something else?

I also assume the coil will be trying to discharge it's stored EMF back into the 12V system (ignition wire). Not sure if that's bad or not. Perhaps it'll take slightly longer to turn the amp off than expected after the mute is no longer asserted and the stereo is off?

used the word "assume" too much, I think...
-brendan

PS - both the battery and ignition lines are fused, just in case you were worried.

When mute is de-asserted, then the ground will be cut. Well, that is, I assume the speakerphone just N/Cs the connection...would it do something else?

If it cuts it with a relay of its own - no problem at that end, but if it uses a transistor to create the connection to ground you might run into problems. Adding the diode is a low cost insurance. If they're actually Bosch brand, you should be able to pop off the top and solder on the diodes on the inside (just remember in which orientation between 85 & 86 you wired the diode [the relays actually don't care which way you wire +12 and ground across 85 & 86, so if you wire it up "the other way" with a diode inside, you'll then first pop the diode, then have a functioning relay, but w/o diode protection ])

I also assume the coil will be trying to discharge it's stored EMF back into the 12V system (ignition wire). Not sure if that's bad or not. Perhaps it'll take slightly longer to turn the amp off than expected after the mute is no longer asserted and the stereo is off?


Nah, it produces very little current, so it shouldn't affect times anything, but if you take the +12V feed from the amps feed, you might get a pop...

both the battery and ignition lines are fused, just in case you were worried.

Me worry? Nah, after all, it's not my car...

/Michael

I take the 12V feed from the same empeg/headunit/speakerphone feed, not the amp.

I can certainly hear at least one relay in the ck3000 when mute engages or disengages, but it's also cutting off 8 speaker wires and inserting 4 of it's own at the same time, so the relay sound might take care of all of them, or just the speaker level signals. I'll use the diode.

Again, thanks.

-brendan