matguy

Yeah, I wouldn't have understood why they'd multiplex it, either. I mean, it takes one more wire to discretely send signal for the sub; and it turns out they seem to have used 2. Interesting. I wonder why the Metra kit doesn't add this wire. I know it'd mean adding the isolation transformer inline, but they could have done that (or do two kits, one with, one without.) Unless it's a different signal level, too.

I'd have to look back at the diagrams I was looking at, but I think it made it seem like the RU+ and RU- might have been part of the phone option or something. It was about a year ago when I was doing mine.

pogoism9

iTrader: (1)

Ru+ and - are in the pioneer setup. The only wires that feed into the sub portion of the nak amp is sub + and -, a power, and a ground (both of which are shared with the main amp plug)

The nak amp has the filters. If you are using the metra harness, cut off the RCAs, take the jackets off the lines and cut the ground crap out. This will give you 4 very thin wires color coded to your aftermarket HU speaker outs. Connect the radio harness and the ends of the metra harness, and snip the common ground (the one that the 4 sets of rca grounds are going to) as you won't need it. The Nak amp only uses the + for the signal. I did mine this way and after I tweaked some filter stuff in the headunit, I have nice sound out of the sub...it bumps as good as the factory head unit.

pogoism9

iTrader: (1)

The sub out on my HU was bumping the hell out of the sub but the rear speakers were suffering too. That's how I knew all facets of the amp was working.

tsmith1315

On the Nak diagram I posted, the sub + and - are labeled as RU+ and RU-. Are these the same as the sub + and - you're referring to?

So, you're using only the positive center conductors from the 4 Metra full range and sub RCA inputs? I'm not doubting you, just trying to be sure I'm clear on your method.

And now that we've successfully hijacked the thread, has the OP had any luck resolving his issue?
That indeed sound like a shorted speaker, speaker wire, or component inside the amp. I would disconnect the speaker wires at the speaker and check by listening, one speaker at a time, starting in the back where they are easiest to reach. If you have a reliable multimeter, you can check the from the amp output plug more quickly & easily.

Hopefully I'll be able to work on my own system one of these days!

MackOnDeez

you CAN use a Pioneer AMP w/ a nakamichi system. im currently using it in my 1998 SC400 Nakamichi system. you wont have an operating deck sub as the pioneer amp wont have the extra slot for your subwoofer.

the con's to using this amp. (bass-mid-treble) you will need to adjust because depending on your speakers it will sound way too sharp but just turn it down. L-R balance & fade work just fine.

i just attached a better wiring diagram to the nakamichi system. it has codes and everything nak and a complete breakdown of each plug and numbered wire.

pogoism9

iTrader: (1)

No the ru+ and - are internal to the nak amp. The sub +/- are the cables running to the sub itself. The pioneer amp has the ru+/- running from the amp to the sub amp but the nak handles it all internally.

That is correct. The Nak amp does not get a +/- signal from the HU, just the line signal, which is from the center core of the RCA. The grounds from the RCA will just be snipped off and not connected to anything. This will give your nak amp the signal it is looking for and allow the amp to send what it needs over to the sub amp correctly.

I am attaching the PDF of the radio/amp setup from the 95 sc4 EWD. It's pretty much the same for all years. Toyota set up the schematic to show both pioneer and nak wiring.

LexusNubus

Ok, thank you guys so much for all of the support and information. Not gonna lie, a lot of it is going over my head especially with all the wiring diagrams. I havent had time to even touch my car yet. As soon as I do I will pull the amp and open it up and see if there are any visible burned spots or shorts. To be honest I dont care for the sub or anything crazy sound wise I just want to be able to listed to the radio from time to time haha. Regardless I will try to find a solution to this amp thing and I will keep you guys updated. Thank you guys so much!

LexusNubus

What was the part number? I am ok with the sub not working, just as long as I can get some sort of sound. Is this plug and play? Im thinking of trying it with a freind of mine's amp before I buy one just to check how it would work