Added some preamp outputs to the brz

[rmjjensen]

So it really bothers me to have to use a line level converter on my stereo so I decided to hack open the unit and add some preamp outputs.

The mosfet ic is a Toshiba TB2956HQ. Using the datasheet I tagged the input pins and used a USB cable to feed the signal (works good since its shielded and four conductor).

The sound quality is better but to be honest it wasn't worth the time.

In the pic:

Right front = black
Left front = white
Left rear = red
Right rear = green

[jpit]

I made some preamp outputs by cutting into the wires going to the amp (supplying power to the door speakers) located in the trunk area.

[rmjjensen]

Originally Posted by jpit

I made some preamp outputs by cutting into the wires going to the amp (supplying power to the door speakers) located in the trunk area.

The amplifier in the trunk takes speaker level inputs - those aren't preamp. Did those work for you to simply plug into your aftermarket amp?

[jpit]

The amp in the back gets a right and left low level input signal from the HU. It then amplifies the signal and sends it to the door speakers. I cut into the low level signal and added some RCA connectors. I used a T to route the signal to a new Alpine amp to control the front speakers and to a Infinity Basslink (10") sub-woofer. Works perfectly.

[Nissanfan]

Originally Posted by rmjjensen

So it really bothers me to have to use a line level converter on my stereo so I decided to hack open the unit and add some preamp outputs.

The mosfet ic is a Toshiba TB2956HQ. Using the datasheet I tagged the input pins and used a USB cable to feed the signal (works good since its shielded and four conductor).

The sound quality is better but to be honest it wasn't worth the time.

In the pic:

Right front = black
Left front = white
Left rear = red
Right rear = green

Where did you tap for the (-) or have you used a common ground for all of them? Thanks

[P3tras]

Originally Posted by jpit

The amp in the back gets a right and left low level input signal from the HU. It then amplifies the signal and sends it to the door speakers. I cut into the low level signal and added some RCA connectors. I used a T to route the signal to a new Alpine amp to control the front speakers and to a Infinity Basslink (10") sub-woofer. Works perfectly.

rmjjensen is correct. Amplifier in the trunk takes high level input. 100% checked. Output from head-unit splits into amp and speakers on dash (mids and tweeters) that have caps to filter low frequencies. There are separate outputs for rear speakers.

[Nissanfan]

Originally Posted by P3tras

rmjjensen is correct. Amplifier in the trunk takes high level input. 100% checked. Output from head-unit splits into amp and speakers on dash (mids and tweeters) that have caps to filter low frequencies. There are separate outputs for rear speakers.

Correct, Radio sends speaker level signal to the oem amplifier.

FYI.

Pin on IC processor, between Left Front and Right rear (op's picture) is for Preout GND.

I suggest adding 1uf capacitors and then speaker wires to filter out the noise.

Needlessly to say for me, this Headunit still doesn't do the job in comparison to the aftermarket deck. To be fair, I did solder some crappy RCAs, so i'll give it another shot with better cables and see if that works better.

[Mr.ac]

Well. That's another way I guess. Maybe just me but that too much work for same result.
The typical inline converter does a good job.

[sly]

Looking at the service manual, the factory head unit puts out:

• 16 watts per channel

• THD 1% at 1kHz

• channel separation >55dB

• signal to noise S/N >70dB

All of this is with the signal running though the head unit's onboard amp. Needless to say these specs suck. If you use a line level converter then you are looking at even worse specs. A 70dB S/N is barely better than a tape deck and certainly not 90dB that is typical of CD players.

If you can bypass the onboard amp and run low level RCA cables to an aftermarket amp then this receiver might stand a chance of having good sound quality.

It may seem like it's more trouble than it's worth but for a 2016 what other option is there? As of now there are no aftermarket radio bezels that will fit and accommodate a standard double DIN unit. So either you keep the factory unit and try to install RCA cables before the internal amp or you install an aftermarket double DIN and either live with the gap around the stereo or try to hunt down a 2015 trim piece and live with a different carbon fiber piece that doesn't match the rest of the car.

So for now I'm going to look at installing RCA cables and keep the 2016 head unit. FYI, simply soldering on cables is probably not going to work. Most of these have an internal DC offset. Hooking up cables without removing the offset with capacitors can damage your amp long term and your speakers.

[Nissanfan]

Originally Posted by Mr.ac

Well. That's another way I guess. Maybe just me but that too much work for same result.
The typical inline converter does a good job.

That depends who you ask. I see it as taking low level signals, amplifying those by onboard radio amplifier only to put those signals down into low levels again. You lose some at the end of the process. Is it a huge difference? Not really. Whether it is worth extra work? Probably Not for the most. I had a head unit apart anyway, so it wasn't that much of extra work.

Originally Posted by sly

Looking at the service manual, the factory head unit puts out:

• 16 watts per channel

• THD 1% at 1kHz

• channel separation >55dB

• signal to noise S/N >70dB

All of this is with the signal running though the head unit's onboard amp. Needless to say these specs suck. If you use a line level converter then you are looking at even worse specs. A 70dB S/N is barely better than a tape deck and certainly not 90dB that is typical of CD players.

If you can bypass the onboard amp and run low level RCA cables to an aftermarket amp then this receiver might stand a chance of having good sound quality.

It may seem like it's more trouble than it's worth but for a 2016 what other option is there? As of now there are no aftermarket radio bezels that will fit and accommodate a standard double DIN unit. So either you keep the factory unit and try to install RCA cables before the internal amp or you install an aftermarket double DIN and either live with the gap around the stereo or try to hunt down a 2015 trim piece and live with a different carbon fiber piece that doesn't match the rest of the car.

So for now I'm going to look at installing RCA cables and keep the 2016 head unit. FYI, simply soldering on cables is probably not going to work. Most of these have an internal DC offset. Hooking up cables without removing the offset with capacitors can damage your amp long term and your speakers.

I agree there aren't many options out there. I was never a fan of those aftermarket bezels in any car, so I might be biased on that part. It's not the greatest head unit, but it has all the functions (HD MP3 etc).

[Nissanfan]

Just an FYI

I didn't have time to play around with this radio recently, but I do believe it was designed with line level outs in mind and its missing a DAC semiconductor in the space labeled with red "Xs" in the picture attached. I can't find a service manual for any subaru Fujitsu ten Radio or Eclipse AVN827GA (Subaru Fujitsu ten unit is a watered down version of Eclipse AVN827GA). I searched to see what other Toyota/Subaru fujitsu ten units might use 64 LQFP IC for audio and found:

RENESAS R5F35MCEJFF but those radios also have AK4358VQ (IC DAC 24BIT SERIAL) on their boards.

Picture of Fujitsu Ten lower radio board: