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#335907 - 09/08/2010 00:24 Turn on car's amplifiers by applying voltage to the amp remote wire?
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
If, when the Empeg wasn't present, I wanted to turn on my car's amplifiers by applying voltage directly to the amp remote wire, what would be the best way to go about that without hurting anything?

Would it be a problem to just wire the ignition power, through a switch of course, directly to the blue wire?

If the Empeg were present and I accidentally left the switch "on", would that hurt the Empeg?

I'm thinking of doing a stunt whereby I have a secondary input for ipods and such that will work when the Empeg is not present. I'd send the ipod output through a stereo volume potentiometer and into a resistance mixer circuit into the front/rear lines to the amps.

I'm just investigating the idea for now, wondering what sorts of troubles I'd run into.
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Tony Fabris

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#335908 - 09/08/2010 00:31 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
Thinking that whatever volume control I use, it could be one of the ones with a built-in on-off switch. You know, the old kind where you turn the volume all the way down, and at the bottom of the volume knob's travel, there's a little CLICK that turns off the radio. I could run the amp remote through *that* switch. But most of those kinds of switches are only rated for a certain amount of amperage... If I ran the ignition power directly through that to the amp remote, wouldn't it be too much?
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Tony Fabris

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#335909 - 09/08/2010 00:42 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
Although those seem to be hard to find.
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Tony Fabris

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#335910 - 09/08/2010 03:10 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
Shonky
pooh-bah

Registered: 12/01/2002
Posts: 1938
Loc: Brisbane, Australia
To protect the empeg, I'd suggest a SPDT switch with the common going to the amplifier. One side of the switch goes to the empeg remote and one goes to the ignition +12V (I'd recommend adding a 1A or so fuse - depends where you tap it from - if from the empeg harness after the fuse that's probably good enough).

That way the empeg will never see the ignition +12V on its amp line. If you want the amp off, switch to empeg (if the empeg's missing it will turn off, if the empeg's there it will do whatever the empeg wants).
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)

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#335924 - 09/08/2010 15:02 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: Shonky]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
What about the amps? If I simply direct-connect the ignition wire to the amps' blue wires (even if it's through a switch) then would I be sending too much juice to the amps' blue wires?


Edited by tfabris (09/08/2010 15:02)
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Tony Fabris

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#335940 - 09/08/2010 22:57 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
Shonky
pooh-bah

Registered: 12/01/2002
Posts: 1938
Loc: Brisbane, Australia
Nope. That's not how electricity works. Using the term "juice" is kind of where it falls down smile Technically juice probably should be power (V x I)

Current flow is determined by voltage and impedance (resistance for a linear circuit). V=IR. Increase the voltage into a fixed load and current increases proportionally.

The amps present only a very small load (impedance) on their remote lines (which is the whole point of having them so they don't excessively load the head unit). The amplifiers will draw only enough current on their amp remote lines to power up the amp. Internally they'll have some form of switch that turns the rest of the amp on (which then draw most of their power from the +12V battery connection). Typically this would be of the order of mA or maybe 10s of mA.

To put it another way, the power (juice) supplied to the load is as much dependent on the load itself (the impedance) as it is the supply (the voltage).

So the only way you'll supply too much "juice" to amps would be by increasing the voltage significantly, in which case the rest of the car would probably blow up too smile
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)

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#335941 - 09/08/2010 23:00 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: Shonky]
Shonky
pooh-bah

Registered: 12/01/2002
Posts: 1938
Loc: Brisbane, Australia
Hmmm.. One thing I didn't consider here would be that if the empeg were in the dock AND the switch was set to ignition, it would be possible to have the amps on without the empeg itself actually on.

That might cause some thump issues with the empeg if it was turned on and off - I don't fully remember the problem there.

I'd still try it that way initially. Otherwise the switching could probably be made a little more elaborate to prevent it.


Edited by Shonky (09/08/2010 23:01)
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)

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#336078 - 13/08/2010 07:34 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: Shonky]
boxer
pooh-bah

Registered: 16/04/2002
Posts: 2011
Loc: Yorkshire UK
I did something like this some years ago, but instead of connecting an ipod, I was connecting a standard car radio: My wife only listens to the radio (and occasional CD), but I only listen to the Empeg, and also use it, in another dock, in my other car.

Take the amp switching line of the Empeg to a 12v reed relay, that relay admits power from the battery through a fuse to either a 2 or 4 (one for each channel) pole relay, connecting the amp outputs of the radio and Empeg to the amp's input. A further relay switches off the radio when the Empeg is in use

Thus when the Empeg is absent the relays are off, connecting the amp outlet of the car radio (or in this case the volume control from the ipod) to the amp inputs.

When you insert, and switch on, the Empeg, its amp output is automatically connected to the amp input.

That's not 100% clear to me, if you're interested, I'll draw a circuit diagram, I think I posted one before, but I cn't locate it!
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Politics and Ideology: Not my bag

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#336097 - 13/08/2010 16:58 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: boxer]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
I know the sort of thing you're talking about and I think I understand your description. I had considered that sort of thing as well. I've got a few options to try. Thanks!
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Tony Fabris

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#336112 - 13/08/2010 20:28 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
JBjorgen
carpal tunnel

Registered: 19/01/2002
Posts: 3426
Loc: Guadalajara, MX
Russmeister did this a few years back with a fake "pocket" that could be inserted into the sled. Has the added value of being an anti-theft device.

More info here.

Sorry...pictures are no longer there.
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~ John

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#336115 - 13/08/2010 21:20 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: JBjorgen]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
That's exactly the sort of thing I'm going for now. That's why I was asking about the player-side dock connector in another thread (and which I've ordered and am awaiting it to arrive). Thanks for the link to Russmeister's project info, I shall read it with enthusiasm.
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Tony Fabris

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#337284 - 17/09/2010 14:29 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
tman
carpal tunnel

Registered: 24/12/2001
Posts: 5528
Bit late to this conversation but I vaguely remember something about it being not a good idea to supply voltage to the amp remote line. I believe the display PSU is actually connected to the same high side driver that controls the amp remote line.

The TL;DR version is don't put 12V into the amp remote line if the empeg is actually installed.

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#337287 - 17/09/2010 14:50 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tman]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
Originally Posted By: tman
Bit late to this conversation but I vaguely remember something about it being not a good idea to supply voltage to the amp remote line. I believe the display PSU is actually connected to the same high side driver that controls the amp remote line.

The TL;DR version is don't put 12V into the amp remote line if the empeg is actually installed.


Thanks for that reminder, TMan. Fortunately, I ended up making a loopback connector that was only inserted when the Empeg wasn't inserted. So that problem didn't affect me, but it's always good to note here just in case someone else comes along reading this thread later.

So far, the project is going well. The loopback connector works well, even when I connect the iginition pin directly to the amp remote pin. No giant amplifier pop noises when I turn the ignition on and off. So that's good.

The real problem, which I hadn't thought of when I started the project, is that the loopback connector idea doesn't benefit from the Empeg's fantastic equalizer. So I get a flat-sounding connection for any device that I plug into the aux when the empeg isn't installed. Ick.

So I've bought a small line-level EQ unit in hopes that I can make it work as part of the loopback connector system. It just came in the mail and I haven't opened the box yet. Not quite sure how I'm going to mount it and such, but I'll come up with something, I've got some options.


Edited by tfabris (17/09/2010 14:58)
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Tony Fabris

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#337292 - 17/09/2010 15:28 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
tman
carpal tunnel

Registered: 24/12/2001
Posts: 5528
Depending on how much work you want to do with this, you should be able to do something similar to what boxer did so it'll all be hidden inside the dash and automatic.

If amp remote line is on then the empeg is there so disconnect everything else. If the amp remote line is off then wire in the EQ unit and also turn on the amp remote line.

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#337295 - 17/09/2010 17:19 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tman]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30784
Loc: Seattle, WA
Yup, that was definitely an option I considered in detail. I chose to go the simpler, more physical route of something that plugs into the sled.
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Tony Fabris

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#337313 - 18/09/2010 08:09 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tfabris]
Crapaddict
new poster

Registered: 24/03/2002
Posts: 21
Loc: The Netherlands
I would suggest to put LED's in the leads to the blue wires.
As LED's are Light Emitting Diodes, a diode's feature is that it allows the current to flow only in one direction. (towards the amp, in this case)
This way the empeg will have no knowledge of power on the blue wire if the ipod is up, and vice versa.
And as a bonus, you can mount the led's somewhere visible to see which device is powering up the amp. (or even both) grin
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#337722 - 29/09/2010 16:02 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: Crapaddict]
siberia37
old hand

Registered: 09/01/2002
Posts: 702
Loc: Tacoma,WA
Originally Posted By: Crapaddict
I would suggest to put LED's in the leads to the blue wires.
As LED's are Light Emitting Diodes, a diode's feature is that it allows the current to flow only in one direction. (towards the amp, in this case)
This way the empeg will have no knowledge of power on the blue wire if the ipod is up, and vice versa.
And as a bonus, you can mount the led's somewhere visible to see which device is powering up the amp. (or even both) grin


No LED will work at 12V without blowing up so you would need a resistor. If you wire it with resistors then you have to wire it in parallel so you don't resist the main turn-on voltage which means the Diode feature actually wouldn't work.

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#337723 - 29/09/2010 16:42 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: siberia37]
tman
carpal tunnel

Registered: 24/12/2001
Posts: 5528
Originally Posted By: siberia37
No LED will work at 12V without blowing up so you would need a resistor. If you wire it with resistors then you have to wire it in parallel so you don't resist the main turn-on voltage which means the Diode feature actually wouldn't work.

What siberia37 said. Any 12V LED you find will either have multiple LED dies within the package in series or have power regulation circuitry built into it. In both cases it'll drop the voltage significantly.

Use a diode :P

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#337732 - 30/09/2010 04:32 Re: Turn on car's amplifiers by applying voltage to the amp remote wire? [Re: tman]
StigOE
addict

Registered: 27/10/2002
Posts: 567
The LED wouldn't have 12 volts across it in normal use for turning on the amp. When the empeg was powered on, it would still only have it's normal forward voltage across. The rest would be used to raise the sense-line on the amp, assuming the sense-line only draws a few mA. But it still wouldn't work, because if the empeg is turned off and the sense-line brought high by a switch, it would have 12 V across as reverse voltage and it looks like LEDs normally don't like more than 5V reverse voltage.

Stig

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