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Archive :: DriveRack PA [PA+] help/schematic
Teeroy
Posts: 13
The below is a very, very old thread I found in the "archive" section I wanted to resuscitate. Perhaps the original posters are still lurking about. There is some incomplete data and mis-information I'd like to correct...
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CalPoly
(unregistered)
Subject:
DriveRack PA help/schematic
05/08/2003
looking for a schematic, want to convert the piece for 12v operation. a professor of mine said to search for a photofact manual. anyone have info? thank you
Robert Boatright (dbx)
(unregistered)
Subject:
DriveRack PA help/schematic
05/09/2003
I think your best bet would be to run an inverter off of 12VDC and then power the PA from the inverter. The PA would take unkindly to being powered from +12V for several reasons. One of the most significant, however, is the fact that the audio path is powered by +/-15VDC rails... There's just not enough headroom/dynamic range available from 12V.
lee patzius
(unregistered)
Subject:
DriveRack PA help/schematic
05/10/2003
Great Idea! I was extremely surprized to find inverters for sale "off the shelf" at Walgreens here in St. Louis. Walmart has them too, and the QT truck stop centers also have them, including the high powered ones that require the use of battery clamps. But walgreens sells 12vdc to 120vac 400 watt/800 watt peak inverters with cigarette lighter plug connectors for something like $40 to $60 or so. I can't remember the exact price, but it seemed very reasonable.
Lee
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CalPoly
(unregistered)
Subject:
DriveRack PA help/schematic
05/08/2003
looking for a schematic, want to convert the piece for 12v operation. a professor of mine said to search for a photofact manual. anyone have info? thank you
Robert Boatright (dbx)
(unregistered)
Subject:
DriveRack PA help/schematic
05/09/2003
I think your best bet would be to run an inverter off of 12VDC and then power the PA from the inverter. The PA would take unkindly to being powered from +12V for several reasons. One of the most significant, however, is the fact that the audio path is powered by +/-15VDC rails... There's just not enough headroom/dynamic range available from 12V.
lee patzius
(unregistered)
Subject:
DriveRack PA help/schematic
05/10/2003
Great Idea! I was extremely surprized to find inverters for sale "off the shelf" at Walgreens here in St. Louis. Walmart has them too, and the QT truck stop centers also have them, including the high powered ones that require the use of battery clamps. But walgreens sells 12vdc to 120vac 400 watt/800 watt peak inverters with cigarette lighter plug connectors for something like $40 to $60 or so. I can't remember the exact price, but it seemed very reasonable.
Lee
0
Comments
Now, if you connect a DriveRack to your inverter in a vehicle how are you going to power up and power down the processor and/or the inverter gracefully with the ignition? Do you really want to turn off your car and then remember to make a trip to the trunk to switch off the DRPA and inverter? Even without a load on the inverter, it is sitting there idling making AC and as such slowly draining you battery. There are of course mechanisms to account for this but adds cost and complexity. One option is to add an automotive 12VDC DPST relay to chassis ground side of the inverters DC input--only supplying ground when the ignition is on and the relay's coil is energized. Now here again, you get what you pay for. Everytime you hit the ignition switch, the relay engages and your cheap, bargin basement, poorly filtered inverter is gonna send a nasty AC voltage spike straight into your expensive processor, that your DriveRack's P/S is gonna have to compensate for. So, now you wanna look for an inverter that has a "soft-start" feature. Still, just more cost. Meatloaf said it best, "...there ain't no Coupe de Ville at the bottom of a Cracker Jack box."
If you are still convinced to go the inverter route, look at something like the, MorningStar SureSine: http://www.morningstarcorp.com/en/sure-sine. What I like about this one is it has remote terminals that when shorted turn on the unit. You can then tie these to a relay, energized by the ignition, to turn the inverter on an off. The specs say nothing of a soft-start feature though.
Now, the *best* solution is to convert your rig for true 12VDC operation. This however is not for the faint of heart. I don't know what, "Robert Boatright (dbx)" is talking about above? Not enough voltage, really? Now if your car's 12 volts can create 115 volts of AC with an inverter, it sure as heck can make another ~5 or so volts of DC! Going back to the inverters for a moment, over simplifying, the power supply in these inverters have two main sections. A DC to DC Converter section and a Switching section. The DC to DC Converter section takes the car's 12 volts of DC and boosts it to ~130VDC !! Then the Switching section turns this voltage on and off at periodic rate that makes it look like an AC Sine Wave. Getting back to converting you processor. While it is true, the DRPA's Analog Signal voltage rails works on +15 AND -15 VDC, it also uses +5VDC for Digital Signal, AND again, a rock solid, steady, +3.3VDC (no more, no less) for the DSPs...
Taking a page from the inverter's play-book, you just need a couple of DC to DC Converters. But instead of a DC voltage that is north of 100+ volts, you just need converters with an output of 18VDC or so. You may be able to find *isolated* Converters outputting ~18V but most, with the kinda voltage you need, are spec'd for 24. At 24V out you'll need to regulate or "trim" it down to 18 before entering the DR's power supply. There are even dual output DC to DC converters that will give you both the plus (+) and minus (-) rails on one converter module.
I have used (2) single output 24 volt modules before to convert a Rane AC23B Crossover and a Yamaha YDG-2030 EQ for use in my Sound Quality competition vehicle. The DC converters I used were the single output, Vicor VI-J00 Series: http://www.vicorpower.com/cms/home/prod ... converters. In this arrangement we, (EE friend and me), tied the (+) output of module "A" to the (-) output of module "B". These being tied together provides the Common Reference of the DR's +/-15 voltage rails. Then, the (-) output of module "A" is -15 volts to Reference. The (+) output of module "B" is +15 volts to Reference. Vicor provides a great Applications Manual to get you started. You can also purchase the Vicor prototype/modeling board and ape their design. Also, have a look at the, muRata UQQ Series of DC to DC Converter: http://www.murata-ps.com/en/products/dc ... s/uqq.html.
These are all overkill in the application of powering the DriveRack alone and are also as expensive as the high quality inverters. There is a fella, Douglas/Doug Winker, that lurks about on the DIYMobileAudio forum that has designed a 12VDC power supply for the DR 260. He too may be able to help ya (if you can get ahold of him)...
Cheers!
Although it's obvious that this circuit doesn't have a place to provide a single DC source (like a 12V battery), it should still be possible, if DC sources of varying voltages are available, to bypass the AC circuit.
Here's what I do know: the toroidal xformer puts out one secondary voltage at 10V (pair of red wires) and one secondary voltage at +/-17V (blue/white/blue). These are connected to the circuit board by a 5-pin connector at P7.
Presumably these are then run through bridge rectifiers to convert to DC voltages.
So question one would be: where are the connections "downstream" of these rectifiers, so that the appropriate DC voltage could be connected at that point.
A second question would be if the rectifier circuit is adequately rated to have DC voltage applied to the AC side of the rectifier (which should still pass through the circuit, but essentially the full load would be handled by only half the diodes). This would make for far simpler connections, as the wires to the P7 plug could be used.
Now, I know that dbx will not be caught giving their blessing to such outrageous modifications, but if they'd be willing to talk in hypotheticals, or at least simply address the ratings of their components and give information to their loyal customers, they can still claim to be innocent of aiding and abetting...