Seperate Amp Question

ChrisBoyde · 09-17-2003, 07:38 PM

I was wondering if there was anyway to use a sperate amp for the 2 front speakers for example the HK PA2000 with a receiver that doesn't have pre-out's (JVC RX6010V)?
Thanks

Wayne A. Pflughaupt · 09-18-2003, 11:39 AM

You can probably find a gizmo in the car audio department of Radio Shack that will convert speaker level to line level. Better make sure any amp you get has gain controls, though.

Regards,
Wayne A. Pflughaupt

John Garcia · 09-18-2003, 12:53 PM

Many external amps will accept speaker level input. Just check to see if the H/K does. If not, then what Wayne said.

ChrisBoyde · 09-18-2003, 03:19 PM

Well I was looking at the PA2000 because they seem to be a good deal. Basically I have to get something to convert the speaker wire output to a rca style output correct? What exactlly are gain controls?

Wayne A. Pflughaupt · 09-18-2003, 07:16 PM

Gain controls are akin to volume knobs. The pad the incoming signal. Your amp will need them because even after the speaker-line level conversion you will probably still be pushing a pretty strong signal into the amp. Gain controls will insure that you can match levels with your other speakers.

Actually, the more I think about it the more I doubt the car audio converter will work. Those things are made for very low powered head units that usually put out something like 5-10 watts. It’s possible the power you’ll be pushing from your receiver will either give a very distorted signal, or perhaps even fry the converter.

There are other ways to accomplish this, but you will have to be handy with wiring and soldering.

Regards,
Wayne A. Pflughaupt

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ChrisBoyde · 09-18-2003, 09:08 PM

I've done some soldering before as long as your not talking small pcb connections.

Wayne A. Pflughaupt · 09-20-2003, 02:48 PM

Chris,

The process involves not only getting the speaker-level signal to the outboard amp you want to use, but to also “fool” those two amplifier channels of the receiver into thinking they have a load.

For the first item, we need to make a couple of patch cables that will connect between the receiver’s amp (i.e. speaker terminals) and the outboard amp’s RCA input. You can use two pairs of small-gauge wire (one pair each for left and right channels) or something like 20ga. zip cord. Solder an RCA jack on one end of the wires and strip back the insulation of the other end. Make sure the tip connection of the RCA jack connects to the speaker (+) of the amp.

As I noted in an earlier post, the problem here will be that this will give too hot a signal to the outboard amp. So you will have to pad the signal down by adding a resistor to the cables we made. It will go in-line on the wire we connected between the receiver’s amp (+) terminal and the RCA jack’s center. I don’t recall the value of the resistor, but I think it will be in the mega-ohm range, probably something between 10 - 100M. A ¼-watt resistor will do the trick.

Alternately - most receivers only have level controls for the center and rear speakers, but if your receiver also has level controls for the main L/R speakers, you won’t need to add the in-line resistor. Just turn the L/R mains way down and you should be okay.

Okay, we have signal to the outboard amplifier. The next thing we have to do is make the receiver’s amp think it is driving a load. Otherwise the only load it will see is the input of the outboard amp – not good.

This is accomplished with a couple of heavy-duty resistors that will mimic a speaker’s load. A pair of 100 watt 8-ohm resistors will do the job nicely (one for each amp channel), or perhaps 50-watt 16-ohm resistors. The resistors will connect to the same speaker terminals of the receiver that the cables we made did.

Hope this makes sense. If not let me know and I’ll e-mail you a wiring diagram.

Regards,
Wayne A. Pflughaupt