I have ordered a set of the 99 factory wiring manuals, I am hopeful they'll show the pinouts for the various connectors including the Nak system. I'm also hopeful that both male and female versions of the connectors, with pins, might be available on the aftermarket so I can build a T-harness. Or option B, just find the matching connector with pins so I don't have to bother with switching. Switching the audio signal itself (the 4 wires) without touching the control wires is basically what the manual splice/relay function does.

So long as the head unit is in a Ready state believing the changer is active, I would hope that's sufficient, but I expect there to be a line which is pulled either high or low when the changer cartridge is inserted and at least one disc is present.

If instead there's a digital signal indicating state and/or data separate from the audio signal itself (e.g. does the head unit track elapsed time in a track, or simply display a value sent by the changer?) then it's a lot more difficult.

 

I'll be watching your progress. So far, having the phone on the bezel is functional.

 

Never been a fan of the stock radio or the climate controller. Took a while to assess and select a double DIN unit (I preferred a”real” volume ****, too) and when the stock climate controller back ground lights went out was when the aftermarket Popformance controller was available. Below is a pic right after the install of the climate unit and later added a vent clip for the iPhone.

The Pioneer unit is a DVD/CD player and has the backup camera option as well (kind of cool for a ‘92). The setup is not for everyone; only sharing what I ended up with......

 

Here is how I have mine setup with the method I mentioned earlier. To me this is the best setup because its extremely seamless and unobtrusive

Bluetooth media control with mic for hands free talking with push to talk


Phone mounted

 

Yeah that's basically what I want too. That's the integration where you spliced into the changer wiring without a harness adapter, right?

The car I bought is low mileage and pristine so keeping it in that condition is important.

 

Not exactly. I'm gonna get a little technical here but this is the gist of it.
The charger/power to the bluetooth unit is just a cigarette lighter plug. There are 4 wires going from the cd changer to the head unit. Each wire carries a signal to each corner of the car, also called channels, so FR, RR, FL, RL. All 4 wires are white so you'll need a service manual (or the .pdf of one) to figure out which wire is which
You can simply cut those cables, cap off the side that leads to the cd changer and then redirect the others to a 3.5mm headphone jack and attach the bluetooth unit. The 3.5mm jack only has 2 channels though, left and right, so in order to have sound going to all the speakers, you need to join FL+RL on the left channel and FR+RR on the right channel. The base will also work in this configuration because the amp will redirect the correct frequencies to it (at least i think thats how it works, I didn't really question it lol)
The bluetooth unit has 3 ends. The puck that control the media, the cigarette adapter for power and a simple headphone jack for the audio signal.
If you want to keep the cd drive functional, then you'll need to wire in a relay that switches between the cd changer and aux. The relay I recommend using is a 4 pole 2 way 12v relay. The relay works by having 4 pins that can switch between 2 sets of 4 heads. It switches those sets when you run a current through an electromagnet. When there is a current running through it, the magnet pulls the pins to one set. When power is cut, a spring pulls the pins back to the first set. In order to run power to the relay, you need a simple on/off circuit that draws power from the back of the cigarette lighter.

So in simple terms,what you're doing is wiring a simple aux jack to your car in order to be able to connect your phone to the bluetooth kit and the kit to the radio.
I'll need to do a proper DIY of this at some point but that would require ripping out my dash again so I'll probably do it when something in there breaks...

 

Yeah, I get it, your understanding of the wiring is a little off though. A stereo aux connector requires two connectors -- a signal, and the corresponding signal ground -- for each side, left and right. The four wires you're describing are the two parts of each of the Left and Right channels coming out of the changer, which only deals with a stereo signal since that's all that is encoded on CDs. The distribution to the different speakers is processed by the amplifier, and can be modified by the balance and fade controls of the head unit.

This is why the changer interface is the preferred place to swap in an aux input. It is *before* all that other processing, where you're just dealing with a simple left and right signal.

Anyway I do understand all that part, as I've said my main issue is not the knowledge of the wiring, it's the intention to do it all without cutting anything so it's entirely reversible. I believe what I'll need are the matching male and female wiring plugs so that I can build a harness which pulls out the four signal wires you've described, but leaves the others in place so the head unit believes the changer is still operating. I'll then terminate the four wires to a stereo aux-in, and possibly a fifth wire for +12VDC if it's also in that connector, so I can connect up the necessary bluetooth puck.

What would be extra clever would be to recycle the Lexus factory hands-free mic that's in the little steering wheel control widget (my car has the factory optional phone in the center console), but that depends on the mic's electrical properties and gain characteristics matching my bluetooth adapter. I don't think I'll be quite that lucky.

Fun fun. Onwards to adventure!

 

Ok so my factory wiring guide finally showed up yesterday, and it does include breakouts for Nak vs Pioneer audio. It also has all the wiring for the factory-fit phone.

There are some interesting things revealed:

1) the mic input from the multifunction buttons on the steering wheel is a single wire plus ground. The 1/2/3 buttons and other inputs are handled separately
2) the phone "brain" takes the input for driver's door speakers from the amplifier and can obviously substitute phone audio, but only to that one speaker since it's downstream of the amp
3) the phone brain not only sends a mute signal to the audio head unit, it also sends a mute signal to the A/C system. My guess is this forces a reduced fan speed if it's high but I haven't traced that out yet

What I'm currently thinking about is something like this:

1) buy one of these: https://www.tinyosshop.com/tsa6016&filter_name=TSA6016
2) instead of using a typical visor mic, wire it into the outputs from the existing one. This is a big gamble as I don't know the electrical properties, impedance, etc of the factory mic at all -- highly probable it won't work
3) take the output from the bluetooth module and wire it into the CD changer line output, per the conventional aux-in approach
4) undo the driver's-door-only bypass from the existing phone brain

With such a setup, I'd still need to be in CD mode to get bluetooth audio. I could take it a step farther and use a latching output from the bluetooth module to trigger a set of relays for all the audio channels to all speakers but I'm already perilously close to (probably) breaking my rule of not cutting any wires. Inserting new connections doesn't help in that goal.

The module even lets you rename its bluetooth ID, so I could make it say something like "SC400 Bluetooth" when pairing a phone. But obviously if the steering wheel mic worked, the entire thing would be totally invisible and yet I'd get hands-free calling plus AptX streaming audio.

So we'll see. This will take some work and prototyping...

 

There's a guy /small company makes it real simple, you send your stock radio/cassette SC300/400, installs aux input or bluetooth on original face or install the extension cable and you decide where to install. Affordable too. The sweetness of his installation is everything still works including the stock CD changer. Don't think i'm allowed to include links.

 

Yeah I've seen references but so far haven't turned up the original contact info. I thought I found one old thread saying the service only worked for Pioneer, not Nakamichi, but I've not been able to confirm. Certainly I'd like to discuss that option if it's available.

 

I like this setup. Not a fan of aftermarket NAV units, especially now with my phone being ubiquitous. I can't tell from the picture - what is the phone mounted to? I bought a vent clip, but the vents are located in such a way that the phone won't fit. (I have an Iphone 12)

 

Actually the source that I know works more on Nakamichi then Pioneer since mine is Pioneer and wanted to make sure he could work on it ( I needed a repair on cassette side). PM me if you want to just checked out his website.

 

UPDATE

tl;dr: it works

I have a '99 SC400 w/Nakamichi. It is crazy low miles and pristine so I wanted to add Bluetooth capabilities to it without cutting a single wire or drilling any holes.

To accomplish this, I bought a few things:

1) this Bluetooth module: https://www.tinyosshop.com/tsa6016?filter_name=tsa6016
2) this 12V-5VDC isolated power supply: https://www.digikey.com/en/products/...mSeq=352055451
3) this 12-pin CD changer line-in adapter thing: 4) this external stereo microphone: 5) this 12VDC - USB adapter: 6) this 5VDC - Micro USB (male) solderless adapter: 7) this ProClip USA dash mount: https://www.proclipusa.com/vehicle/d...sc-series/1999

Plus a few misc USB and audio cables to connect all the bits.

My original plan was to drive USB female ports directly off the isolated power supply, but without the magic resistors and other USB 2.0+ tricks, I couldn't get enough current to charge a modern phone. It defaulted to 0.5A peak current.

I built a tiny power-splice harness to sit in between the feed line to the cigarette lighter, which is directly supported by a 15A fuse in the driver's kick panel. That plugs in and gives me a female 15A-capable feed, from which I power:

1) the isolated power supply
2) the SDSTOYO box
3) the 12V-USB adapter

The harness makes use of an old molex plug I had sitting around and also handles all the grounds, which are terminated under a bolt buried behind the stereo. Again, no wire taps, no cuts, no splices, no drilling.

Beyond that harness and figuring out where to store all the boxes and plugs, it was really just a matter of plug and play and tidying up the wiring. The SDSTOYO has a selector switch which I pulled back to the center console under the armrest, along with a second USB-A (female) plug coming off that 12V-USB adapter.

I chose the TSA6016 module because it supports the AptX bluetooth audio codec. Sound quality seems pretty good to my ears. Strictly speaking I ordered the TSA6017, which is a TSA6015 with a 3D-printed enclosure, but I asked the TinySine folks to insert the 6016 module instead. They happily obliged.

Wiring is clean and just about invisible. There is a thin microphone line which sneaks out in between the center console and the main part of the dash up to the ProClip mount, and the USB power line similarly peeks out, but that's it. All you see that's obvious is the phone in the ProClip mount.

Audio works perfectly. With the SDSTOYO selector switch on "1", and the Nak head unit set to CD, I get clear audio with no ground loop problems, no static, nothing. I can set the switch to "0" and the CD changer will happily play. I'm not using the second line input at this time but I could easily enough.

Sorry not to have pics of the dash torn apart, I can take a dash shot if folks are interested. I threw a CD in the changer so I wouldn't get "Err2" due to the empty magazine, but it plays Bluetooth happily in that state anyway so I may suck it up to avoid wear and tear on the changer.

Thanks to the various folks who shared ideas and experience. Hopefully this updated view on the Nak options will help some other people further down the line.

 

A bit more clarification on how my setup is wired up:

12V power from the car originates at the cigarette lighter connection. There is a male lug on the feed to the lighter and a matching female connector which attaches to it. I built a matching male/female adapter which goes in between those two points, and has a second hot 12ga wire which terminates at another female lug. Everything else that draws power gets it from that location and it's protected by the car's existing 15A fuse.

There are four powered items in total:

1) a 12VDC - 5VDC isoalted power supply. This is important for max audio quality.
2) the SDSTOYO adapter which sits in between the 12-pin plug from the car to the radio, using a T-harness adapter. This provides two switchable line-level audio inputs (using female RCA plugs) as well as the option to restore the signal from the CD changer
3) the 12VDC to (two) USB-A (female) connectors. I use these as charge points. One goes up to the ProClip mount on the dash, the other goes back to the center console under the armrest.
4) the TSA6016 bluetooth adapter. This is powered by the solderless micro-USB adapter which gets its 5VDC from the isolated power supply.

The isolated power supply is important because it eliminates the risk of ground loop noise. The easy way to do this is using inline line-level audio isolators, but these reduce signal quality fairly significantly. By moving it upstream, where more power is available, you can drive a clean 5V/3A output which is completely isolated from potential alternator noise or other issues. The power supply is about $22 delivered from Digi-Key and is absolutely worth the money.

These isolating supplies work by creating an inductive current from the source side to the output side. They draw a decent amount of power because the conversion is relatively inefficient, so to hit the output target levels (15W) you're pulling a lot more. The technical data sheet is here, but the bottom line is the unit runs at 68% efficiency. https://www.digikey.com/htmldatashee...datasheet.html

The reason you lose signal fidelity with the inline ground loop isolators is because the max power available to go in is so low on a line-level audio signal. You're using that to drive an inductive conversion and produce another line-level output at the same basic voltage on the other side. Something has to give. That's where the signal quality is lost.

Anyway once I get clean power into the Bluetooth adapter, I'm feeding its output into the RCA jacks on the SDSTOYO. When I select CD on the head unit, and have the SDSTOYO's selector set to the matching input, music flows. That TSA6016 device also has a connection for an external microphone, so it also works for phone calls. But the real value of it is that it has that separate line-level audio output, because that's the only option if I want to maintain the goal of no cuts, no holes. The various all-in-one bluetooth adapters which work with an existing aux-in could conceivably do the same thing, but I wanted the flexibility to hide everything but a tiny microphone. My car has the optional Motorola phone with the mic and buttons on the lower part of the steering wheel, so if I get brave one day I may pull the mic lines and see if I can use that one instead, that would be even better.

It all works as you would expect. Turn the key, the phone connects. You lose the audio-switching to bluetooth since the car has no notion of what it means; you have to press the CD button if it's not already on that mode, but it does remember it between ignition cycles.

The wiring diagrams do have an analog switching capability for the factory phone, where you trigger a mute signal and at the same time run the phone audio through the speakers in the driver's door. That would be OK just for phone calls but for music obviously you want the whole system to work. So I didn't bother to pursue that, but you certainly could, and have two separate bluetooth systems. One for phone, another for media.

Happy to answer other questions.

 

Hi! tegwj,
I saw your car yesterday on CARS & BIDS.
I have three SCs two 300s and one 400. The 400 is my wife's car and early in June it burned up under the hood and I am looking for a replacement.
Your car is beautiful and would make a great replacement.
Are you at all interested in selling it?