Adding an amp: too many watts? Antenna lead always on?

garypear · Feb 22, 2005

What's the largest size amp (watts) one should consider adding to an 04/05 Prius given it uses a smaller than normal 12v battery?

I'm assuming the amp will be powered only when both the ACC and radio are on, hooking up the amp to the radio's antenna on lead.

Regarding that, I've read that some head units only supply power to that antenna lead when the radio is on (that the power is cut when a CD is played). Is that the case with the Prius standard radio?

flareak · Feb 22, 2005

does anyone konw if you can replace the 12v battery with a larger capacity?

naterprius · Feb 22, 2005

You can use the pin next to the antenna lead on the standard radio for the Amp signal. You'll have to buy an extra pin from Toyota to go in that slot.

Nate

DanMan32 · Feb 23, 2005

If you are talking about the antenna amp signal, someone posted that it is on only with AM/FM radio, not with CD or tape.

The battery has been said to be 35AH, and the DC/DC converter is rated at 80A. Now realize that there are other 12V devices on the car, so you can't just use up all that 80A continuously. The battery can handle short term loads over 80A if the accessory is connected directly to the battery, but again, it is only a 35AH battery. You be the judge on what current load you will allow, based on how long you want to run it in ACC.
Watts is V*A, so a 120 total watt output amp would draw at least 10A in a perfect world. Probably would be closer to 15A at full volume in real world.

Also note that the signal coming out of the header on a JBL system is fixed line level. The JBL amp adjusts the volume, fade, balance, and 3 band EQ.

DanMan32 · Feb 23, 2005

does anyone konw if you can replace the 12v battery with a larger capacity?
Click to expand...

You can, under the following conditions:
It must not ever produce harmful gas, or else it must have a means to vent the gas outside the car.
It must be resistant to spills of harmful fluids, such as acids or alkalines. In other words, sealed.
You may have to adapt the terminals to fit.
You will have to adapt a way to secure it to the car.
It must be 12V.
It needs to have a capacity exceeding 35AH to be considered bigger electrically.
It must be able to handle large charge currents unless you isolate it and provide its own charging cirucuit. But then you wouldn't be replacing the original battery, but adding to it.

garypear · Feb 23, 2005

Thanks for the replies but I'm still unclear on the feasibility of connecting the head unit's antenna wire to an external amp's 12v on wire.

There is a pin I should use instead on the radio that's NEXT to the antenna "lead"? Please elaborate! What does each do?

Re: head unit's amp turn on leads (none on the Prius), my understanding is that they simply send a signal alerting the amp that it's time to start (or stop) drawing power from it's source (different wire) so as to be in use only with the radio. Re: a head unit's antenna lead. same story or more to it since the result is the antenna lowers or raises? Re: both: I'm unsure of the exact nature of those signal(s) the head unit sends: momentary or constant?

Whether momentary (sent briefly both when the radio is turned on and again when turned off) or constant, if it gets changes when the radio is switched to CD then I'd expect that'd be problematic in regards to it's use connected to an external amp's 12v on and I'd like to know more about it before I have my audio system upgraded. As popular at the Prius is, not many have been worked on at the several audio shops I've visited.

Seems unlikely it'd be designed with the result that a power antenna is lowered just because the user decided he/she wanted to play a CD for a while. And although I'm glad it's there, not sure why it is - did the designers anticipate a desire for owners to upgrade to a power antenna?

The above info is requested to help answer what I really want to know about: can the head unit's antenna wire (or the pin next to it) be used to make an external amp power on and off along with the radio and stay on even when I switch to a CD?

If no (or yes but not perfectly), what are other/better solutions for hooking up the amp's 12v on wire? Thanks.

naterprius · Feb 23, 2005

Okay, Toyota has used the same connector on their base radios since 1987. And, since 1987, the pin next to antenna lead in the back of the radio has been empty, but I located documentation form fujitsu ten (the manufacturer of most Toyota radios) that this pin is for an external Amp connection.

Take a look at this diagram:
http://www.installdr.com/Harnesses/Toyota-Wiring.pdf

Note that pins H and I are both labeled "power antenna" wires and you are instructed to tie them together. This is NOT correct. Pin H is the power antenna, and pin I is the Amp wire. The Amp wire will be empty. Part number 82998-12340 (from your local dealership) fits in that hole and can be connected to your Amp for remote power on.
--WARNING! It's possible that this pin is dead. This may not work at all, but probably will.--

By the way, the easiest way to do this is buy one of these:

http://www.crutchfield.com/S-fRcvNuaIxTZ/c...&display=XL#Tab

Double check the wiring for pin H and I so that they are not tied together. You'll want pin H to pass through and pin I to be broken out into the long harness. Cut the end off that goes to the bazooka and wire that to your high-level input on the Amp. You may need to break out a few more wires for all the speakers; I don't know if everything is there, but it sure is an easy way to start this project.

Nate

DanMan32 · Feb 24, 2005

First off, we haven't established if we are talking about the JBL system or not. The radio connectors are vastly different between them; the JBL amp also controls volume/fade/balance/EQ through the AVC and cannot be replaced. The header in the JBL system has fixed line level. The amp turns on when the car turns on, whether you are using the radio/CD/Tape or not.

But that was not your question, so I will AGAIN answer your question.

I will assume you do not have JBL system.
There is one 'antenna' signal lead that turns on the antenna amplifier. From a previous post, this is only live whey you are playing the radio, not when playing CDs.
Looking at the wiring diagram, again for the radio with built-in amp, there are 3 connectors to the radio. The 3rd connector contains the steering control, and AVC network connection (for MFD mostly). The amp is on pin 8, which may correspond with pin H on installdr diagram. If unused pin I is always on with the header, then use it. If you have a voltmeter, that is easy to check. Otherwise, turn the amp on with ACC.

garypear · Feb 25, 2005

Ok thanks. You assumed correctly - I was referring to the non-JBL system (what I called the "Prius standard radio".) By the way, a prior reply referred to it as a "Toyota" radio and something gave me the impression that even the non-JBL header was made by an audio electronics company?

I didn't realize "antenna lead" was referring to a power on for an antenna AMPLIFIER - that makes much more sense (than cutting power to a "raise/lower" power type antenna.)

What kind of antennas use amps? Do "amplified antennas" (a less ambiguous description IMHO) do anything to improve the tonal quality of a signal already strong enough to be received without static or do they just help pull in weak signals? Do XM antennas have amps?

Also, my research has determined a 3rd solution: not as good as what we hope will work above but probably better than using ACC: connecting the amp's 12v on to a device that will turn on the amp when it senses a voltage change in the speaker wire. That way the amp won't stay on when not needed (because the radio/CD is off.)

XravenX · Feb 25, 2005

Could you splice into the 12v ignition wire (Pin 3 or C) and use that as your lead wire?

DanMan32 · Feb 25, 2005

That won't help him turn the amp off if the radio is off. Don't think there's a solution for that if the unused amp pin is dead.

Guess you could engineer a current sensor for the radio power. don't think sensing speaker output would work well.

garypear · Feb 25, 2005

The "2nd best" solution device I was referring to is the LVT2 made by Peripheral Electonics. It's apparently a dual function device that can be used to either (or both?) upgrade a too weak (speaker/12v-on?) signal and/or create a 12v on signal merely by sensing current (like what comes through a speaker wire when a car radio is on.)

Since the description of the install (for an earlier version, the LVT), did not seem to have separate output wire for the two different functions described above, it occurred to me that the device could only be used when speaker wires weren't needed for sound (because the head unit had RCA outputs) and thus could not be used on a Prius.

Nevertheless, I was assured in two separate phone conversations (one with Shaun (CarDomain.com's tech guy) and tech support guy at Peripheral Electronics) that the LVT2 could be hooked up to a speaker wire to sense its current (and send a turn on signal to an amp accordingly) in conjunction with and without interfering with actual audio signals traveling through the speaker wires to the speakers in the car.

Device is briefly described at the manufacturer's website here:

http://peripheralelectronics.com/2002/triggers.asp

Described (even better) and onsale at cardomain.com here:

http://www.cardomain.com/item/PERLVT2

Installation instructions for the earlier version, the LVT, are here:

http://peripheralelectronics.com/periph_pr...uctions/lvt.pdf

garypear · Mar 4, 2005

RE: supplying amp with 12v on

Possible problem with my suggested 2nd best solution (using a 3rd party device that provides amp with 12v on upon sensing current coming through speaker wires). Would that device misinterpret the MFD beeps that apparently travel through those speaker wires (even when the radio is off) and send a turn on signal to the amp every time the touchscreen is used?

Better solution posted by bobc: tap in to the line that sends the radio a signal to turn on when the radio power button is pushed. Will post here if I get more info regarding where to find/identify that wire.

Anyone know if that's as good as using the pin in back of the radio if that is in fact a 12v amp on? Am I correct that head unit 12v ons might be better? Do some provide a slight delay (also a feature on some higher end amps) so that radio turns on slightly before amp to protect speakers?

Even though was hoping to do my upgrade without pulling radio out, maybe I'll have the install guy do it get a definitive answer regarding whether that unused pin is a 12v amp on.

naterprius · Mar 4, 2005

Gary, here is a diagram of where to get the Amp 12V turn on.

By the way, would you be interested in buying custom built plug in harness that goes to an Amp for $100? It would accomplish this function.

Nate

DanMan32 · Mar 4, 2005

have we verified that the Prius radio still puts out on pin 9, and that it is not NC?

There is no signal that tells the radio to turn on. The actual button is on the radio itself, and the mode switch is connected to a third connector on the radio. The MFD sends its instructions through the AVC network also sent to the radio through that third connector. The ACC tells the radio the car is on and so it can turn on.

finman · Mar 4, 2005

I've tapped into the ACC wire at the back of the radio (base radio, non-jbl), then run that into a relay at the 12 V battery to trigger my amp. That way, all the ACC wire at the back of the radio is doing is turning a relay on/off and the 12 V battery is being used to 'truly' trigger the amp. I normally have the radio on whenever the car is on, so I am not too worried about turning the amp on/off using the radio power button. And when I do turn the radio off while the car is running (mostly in parking lots in stealth mode to get people to turn their heads and wonder "how so quiet"), I don't hear ANY amplifier pop or hiss. Not sure of the draw on the 12 V battery. I fused the main amp power wire at 30 amps...Love the added bass, nice solid sound. Gives the factory speakers a break from bass distortion.

DanMan32 · Mar 4, 2005

I don't think you needed that relay, that is what the amp trigger wire does: turn on the built-in relay in the amp, even if the 'relay' is solid state.

garypear · Mar 4, 2005

Thanks for the back of the radio diagram post, Nate.

I compared it the corresponding plug diagram found at this link you also provided in one of your earlier posts on this same thread

http://www.installdr.com/Harnesses/Toyota-Wiring.pdf

I think the following mostly reiterates what you already stated in that same earlier post:

1. Location 8 on the back of the head unit ("Power Supply Ant +") corresponds to pin H on the plug ("Power Antenna Wire 1")

2. Location 9 on the back of the head unit ("Power Supply Amp +") corresponds to pin I on the plug ("Power Antenna Wire 2")

3. Location 10 on the back of the head unit ("Power Supply Ill +") corresponds to pin J on the plug ("Do Not Use")

Of course in comparing the two diagrams, the locations are reversed, like a mirror.

Regarding #1 above (8 and H), is that the Antenna 12v that IS on only when radio is on and off when CD is in use and that that's because it's meant to power an AMPLIFIED amp?

Regarding #2 above (9 and I), assuming it IS live, would that be an always on 12v on (still on even after switching the radio to CD) designed for use either to an amp or to an antenna's power up / down which I still say most consumers would NOT want to be activated whenever the user switches back and forth between CD and Radio.

Regarding #3 above (10 and J), what is "Power Supply Ill +"?

Regarding your harness suggestion, let's refer to your thread devoted exclusively to that idea:

http://priuschat.com/forums/feeling-out-in...ess-vt7025.html

DanMan32 · Mar 6, 2005

If 9(I) is live, it is labeled as an amp rather than antenna so that should work. A voltmeter should easily tell you.

Power supply ill+ is illumination. It is so the dash illumination circuit can control the lights in the radio.

garypear · Mar 6, 2005

So I take it then that it IS being used?

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