McIntosh PF-2824I and PF-4113I first glance

2015-03-27I now have on hand a Clarion/McIntosh PF-2824I and PF-4113I head units. These are fitted to higher end Subaru Legacy vehicles produced between 2005-2008. It includes MP3 and WMA support (why they didn’t support AAC instead of WMA beats me), a dual row VFD display and a more integrated look than the previous version (PF-2551I).

The PF-4113I is the Japanese version of the PF-2824I with a different tuner and a MiniDisc player. They are built around the same hardware platform (most components are the same including the PCB), however unfortunately run slightly different firmware. Unlike the previous model of McIntosh head unit in 2003-2005 Legacys, there is no easy way to convert the PF-4113I to European or American FM bands without hacking or replacing the firmware. There does appear to be a Micom firmware upgrade port on the side of the main board in the unit, however it appears that the microprocessor is of a mask ROM type and therefore cannot be flashed with new firmware.

It does use the same FM tuner module as many older McIntosh units, so if the firmware were to be sorted the necessary tuner mods are very simple.

Under the left hand seat is the EF-1259I amplifier. Unlike the old EF-1080I, this amplifier does not contain any EQ or crossover components as all this is now done in the head unit.

McIntosh Secret Key Combinations

After a bit of reading I’ve found that many Subaru head units have hidden options for changing settings. I couldn’t find much information on this unit so I spent a few moments trying various combinations to see what happens. Here’s the list I’ve discovered so far. If you discover any more please let everybody know by posting it in the comments!

To use these key combinations, switch the ignition to ACC and make sure the head unit is powered off.

Radio Location

Press the following to change the radio tuner region.

2 + AM is EXPORT (North America)
5 + AM is AUS & EXP

Here are the differences between these modes:

Location AM Range AM Step FM Range FM Step
Australia 531–1620 kHz 9 kHz 87.5 – 108 MHz 100 kHz
Export 540–1610 kHz 5 kHz 87.5 – 107.9 MHz 100 kHz
Aus & Exp Same as Australia

Note that switching locations will erase the radio presets.

5 + AM is JAPAN

Display firmware version

Press 5 + 6 + FM


PF-2824I (Japanese manufactured):
M 4.20

M 5.60
G37.00 0.37

Disc 1 on the display lights in both cases too. If anyone has details for Chinese-manufactured versions of the radios please let me know.

Button and Display Test

5 + 6 + press RPT twice

Button test that displays the name of any button you push as well as the tuning up/ down.
Use the volume knob to toggle the display test feature which illuminates every display element and LED. When in display test you can use the tune knob to toggle a checker board pattern to more easily view display state. This will make any phosphor burn very obvious!

To exit this mode switch the ignition off.


In previous McIntosh models this was an analogue circuit built into the amp or head unit. It’s now all software controlled so can be changed between a number of presets or bypassed completely. This is very useful if you buy a replacement unit, so you can have it sound like the original if it needs to be replaced.

Press the following buttons and T/B:
2 + 5 + T/B THROUGH MODE (bypass)

I haven’t investigated the frequency response of each setting, however after a very quick listen the sedan options appear to have more bass than the wagon (quick bass boost option if you have a wagon!) and the cloth seat options appear to have a little treble boost. While it’s intended to compensate for the acoustics of the vehicle interior, purists might prefer to bypass the EQ altogether.

Loudness Control

Unlike the other settings, this must changed while the unit is powered on.

To toggle loudness, press 5 + 6 + T/B.

The default setting is on.


Press 1 + 4 + CD to enter some sort of diagnostics mode. This displays the following:

H01 A1 256

Use tune to scroll through various options. As far as I can it seems to be read only. It also plays the current CD and the volume control works normally while in this mode.

Clarion and McIntosh parts

I recently had somebody refer me to PacParts who turn out to be an excellent source of spares for Clarion and McIntosh car audio. Parts include laser pickups, spindle motors, tuner modules, LCD/VFD displays, knobs and more.

Unfortunately they only ship to the US, however there are many companies around who offer international parcel forwarding such as Shipito.

Clarion CeNET – a first glance

I’m keen on reverse engineering at least some aspects of the Clarion CeNET bus in order to hook other gadgets to my car stereo. CeNET is a proprietary interconnect used by Clarion on many of their car audio products over the last ten years.

It uses a proprietary 13-pin square DIN style connector that is not available off the shelf. The pinout is shown below (this was taken from a Clarion service manual).

Electrically, CeNET appears to be a form of asymmetric serial bus. There is some discussion online that suggests a 38400 baud rate. The same person also says that it appears to use some form of encryption which may make it difficult to hack.

My experience with CeNET stereos is that the display will flash SYS or SYSTEM if the battery is disconnected or a CeNET device is inserted or removed. They do this until the stereo is powered on. Perhaps an encryption key is negotiated during that period?

On the hardware side, closer inspection reveals the bus consists of a transceiver IC (CA0008AM) connected to one of UARTs in the host devices microprocessor as shown in the simplified diagram below. Note that there are also some pull-down resistors on the Tx and Rx pins, as well as a 68 Ohm termination resistor across the Bus+ and Bus- pins. I’m unable to find data on the bus transceiver but I guess it’s possible that other generic ICs could be used here. The bus itself floats at 2.5v and swings +/- 200mV during signalling.

I have capture some data samples from a stereo connected to a EA-1251B iPod adapter that emulates a 6 disc changer. I haven’t yet studied them in detail but you can download the capture files below.

You will need to download Saleae Logic to view the capture files (it’s free). The cables were connected according to the colours in the diagram below:

In all captures I powered on the stereo from cold (no battery) immediately, then switched the unit on after about 3 flashes on the display (4-5 seconds). With the EA-1251 samples I switched from radio to the CD changer at about 7-9 seconds. From here the stereo waits for the iPod to wake up (it thinks the CD changer is loading) before it starts playing the first track of the first ‘disc’ (playlist) at about 14-15 seconds. The song then continues to play until the end of the capture.

Update: I’ve also grabbed a couple of samples of a TV tuner and display.

When the TV tuner is selected via the TV display it places the head unit into aux mode (it displays Aux on the screen). This could be a very useful hack; to make a ‘proper’ CeNet aux input. In the samples above, all units were powered up from cold (no battery) immediately after beginning the capture. The head unit is switched on at about 4 seconds, then there is a bit of wait for the display unit to boot up. Once this is done I’ve switched to the TV tuner at about 27 seconds. Shortly after (about 35 seconds) I switch back to the head unit’s internal FM radio.

It turns out trying to capture the bus pins was a waste of time as they normally float at 2.5V. I haven’t been able to look into that side of things any further as my only oscilliscope died before I could check it.

Hopefully somebody else finds this useful. I’ll keep working on it as I get time, and post any updates to the site if i come up with anything.

McIntosh EF-1080I Information

I’ve had quite a few requests for more information about the McIntosh EF-1080I amplifier (often but incorrectly referred to as the EF-10801). This unit is actually made by Clarion and is supplied as stock equipment with many Subaru Legacy and Outback cars manufactured between 1998-2003. Read more of this post

McIntosh PF-2520I-A

I recently acquired this lovely McIntosh PF-2510I-A 6-disc in-dash CD changer. This model was available as an option in the North American market Subaru Legacy and Outback. It is often but incorrectly referred to as the PF-25201 or PF-25201-A.


McIntosh PF-2520I-A. Yes those are solid aluminium knobs!


Fortunately it shares the same connectors and pinout as the Japanese and Austrailasian market Legacys so can be fitted in cars destined for other markets with very little effort. Having said that there are a couple of gotchas. Read on… Read more of this post

Subaru Legacy McIntosh subwoofer hack

Here’s a quickie on adjusting the gain of the OEM-supplied McIntosh subwoofer in many BE and BH series (MY 1998-2003) Subaru Legacy’s. The subwoofer gain and crossover frequency is non-adjustable, at least until now. : ) If you have such a car and want to get a little more punch from the sub, read on!

The amplifier is bolted to the floor under the drivers seat and has two connectors on the end closest to the door. Disconnect and unbolt the amplifier and take it apart. Make a careful note of where each screw goes as they are not interchangeable; you can permanently damage the amp by shorting things out of you replace the screws incorrectly.

Find R519 on the underside of the PCB near the power and speaker connector. In station wagons this is rated at 10k  and in sedans 4.7k, labeled as either 103 or 472 respectively. This resistor sets the negative feedback in the final stage of the subwoofer crossover.

Identifying R519

Replace this resistor with a higher value to increase the gain. Don’t leave it out of the circuit or it may overdrive the sub and do damage. If you short it you will mute the sub entirely.

R519 replaced

After some experimenting I feel 33k delivers quite a nice bit of punch in a station wagon, which should boost the sub by about 5.2dB. Feel free to choose any value you want between 10-100k. Be careful using high values as it becomes quite easy to inadvertently overdrive the sub.

You might want to use a potentiometer instead so you can adjust the sub gain as you please. If you do this, I suggest a 50k linear (type B) pot in series with a 10k resistor. Make sure you use shielded cable and keep the cable very short to help prevent any instability in the amp. Connect the cable shield to a suitable ground point in the amp and (ideally) a 100nF or similar capacitor between the cable shield and the pot casing to prevent possible ground loops.


Japanese import FM tuner conversion

This post describes how to modify a McIntosh PF-2142I (often but incorrectly referred to as PF-21421) JDM car radio to natively tune from 87.5-108MHz as used in most countries around the world. This model of radio is fitted as standard equipment in many JDM Subaru Legacy and Outback cars manufactured between 1998 and 2003. Read more of this post