When Nokia announced their music player capable phones they neglected to mention the lack of support for external headphones. Since the release of the 6230 and its related family with mp3/aac playback support, many disgruntled users have made their own home-brew cables to plug in headphones. Today we will show one such mod for the Nokia HDS-3 cable. Our mod includes an analog volume dial integrated into the push to talk unit. The HDS-3 cable ships with the 6230 and other Nokia phones capable of stereo playback.

by Fabienne Serriere

Before starting, a quick rundown of some other Nokia models of pop port headphones and adapters include:

Nokia HS-3 “Nokia Stereo Fashion Headset” white or black,
smaller push to talk unit than the HDS-3, headphones are still of an inferior audio quality

Nokia HS-8 “Nokia Activity Headset” ugly and bad audio
quality headphones

Nokia HS-6 “Display Headset” lcd display and controls for
audio and calls, but yet again no port to plug in your own headphones

Nokia HS-23 “Nokia Stereo Headset” includes volume control,
lesser quality headphones

Nokia AD-15 “Nokia Audio Adapter” allows you to plug in your
own headphones, unfortunately this is achieved with a big box on the end of the cable, there is no mic, and as far as
we can tell no button to switch tracks.

Even headset models that are not available on the market yet don’t allow for the consumer to plug in their own
headphones. Why Nokia? Why! For a few weeks we assumed that the audio quality coming out of our 6230 was just as dismal
as the headphones in the HDS-3 headset led us to believe. The astonishing part is that no, the audio quality of the
6230 is comparable to most mp3 players on the market once you manufacture your own adapter cable.

The second mistake by Nokia is the misinformation as to how much memory can be recognized on the mmc cards. The
manual for the 6230 states the mmc card can be up to 128 mb.
In reality the phone can recognize mmc cards up to 1 gig. To see if your phone’s firmware is up to date enough to work
with that much memory, in the 6230 type: *#0000#. On the screen you should see something similar to:

Nokia 6230

V 05.24

25-11-04

etc.

The important information in this is of course the firmware version on the second line, in this case 5.24. If your
phone is not up to date you can have the firmware flashed at most cell phone provider stores. Note that firmware
upgrades will wipe the memory of the phone, so be sure to save important info before upgrading. The firmware of the
6230 starting with version 4.44 should correctly recognize 1 gig of memory on the mmc, but may not search the
subdirectories on the card for music files to include in the playlist. Before loading audio on the mmc card, we suggest
you format it in a card reader on your computer rather than on the phone. Format the card, re-name the card, then fill
that 1 gig of happiness with a playlist of mp3/aac and/or mp4 if you have a Nokia model that supports it.

You will need for this how-to: a soldering iron, a knife of some sort, a multimeter, a round file, hot glue gun,
electrical tape, a Nokia stereo headset (we will be using the HDS-3, but you should be able to extrapolate to another
on the list above), a cheap pair of headphones with integrated volume control, a cable with a female mini jack (3.5 mm)
connector on one end, or if you have only a cable with a male mini jack connector you will also require a mini jack
female to mini jack female adapter (see the second to last picture at the end of this article). You may also need a
small philips screwdriver depending on the model and make of your Nokia headset.

The Nokia HDS-3 (ships with many Nokia models including the 6230):

The HDS-3 has several flavors: the older models have four screws on the back of the push to talk module. If you have
this model, first remove the screws. Now for both models, we are ready to pop open the connector. We use a knife to
carefully separate the front from the back of the push to talk unit in the middle of the cable:

Once the unit is open, check to see if the speaker is on the front or the back of the unit. Chances are if you have
a model with screws, your solder points for the headphones are already visible. If you have the newer model without
screws on the outside, you must now carefully pry up the circuit board and flip it over.

If you have the newer model your circuit board should resemble this:

Note the connections on the circuit board. The headphones Nokia supplies are attached to (from left to right) L-,
L+, R+, R-. These are the points which we are now going to de-solder:

Your de-soldered circuit board will now look something like this:

Prepare the housing for the volume control knob by filing a rectangular notch out of one edge of the push to talk
unit. Ideally you would do this before adding the volume control unit shown in this picture:

Now cut off the volume control from the cheap pair of headphones (ours cost about six bucks at our circuit
city-esque store). We used the Proline IE-500, but any no-name cheap in-ear headphones with volume control on the cable
will do. Pop open the volume control module. The circuit will look something like this:

Note the direction of the audio with respect to the circuit. Our audio comes in on the left side of the circuit and
exits on the right hand side. The board may even be labeled as ours was:

G (ground)

R (right)

L (left)

We will be inserting this volume control where the Nokia headphones were originally attached on the push to talk
unit. Our female mini jack port will then be connected to the output of this volume controller. De-solder the cables
from the volume controller and if needed, file down the circuit board to fit it under the circuit board in the push to
talk unit.

Now tin (prepare them with a bit of solder) and solder jumper cables (you can salvage these from a piece of the
cable you cannibalized for the female mini jack connector) from the push to talk unit’s output (labeled L-, L+, R+, R-)
to the input side of the volume control circuit. Both L- and R- are soldered to ground on the volume control
circuit:

                                 
L- ___    G

push to talk output     R- /                    
volume control circuit input      

                                 
R+ == R

                                 
L+ == L

This image shows the volume circuit partially soldered to the push to talk circuit and the mini jack cable soldered,
which will be covered in the next step:

Since we filed down the volume control circuit where the input ground and output ground were connected by a trace in
the circuit board, we also added a jumper cable from input ground to output ground on the volume control circuit.

Next prepare your female mini jack cable by cutting it to the desired length (we chose a length of about 3
centimeters). This length will be how long the mini jack cable extends out from the push to talk unit. Denude the
cables leaving a half centimeter of shielding over the two audio cables. Do not split the grounding wires as they are
in this photo, but instead twist them into one bundle:

Determining which is right and left in the mini jack cable is easy if the colors of the cables are red and white.
Red is right and white is left. If, like us, you found yourself with a creatively colored cable, notably orange and
yellow, bust out your multimeter and a male mini jack connector on a cable that has been similarly denuded. Test the
male mini jack connector with a multimeter and note the wiring, for example our male mini jack connector was (where tip
is the tip of the connector, ring is the middle, and sleeve is the base):

TIP orange

RING yellow

SLEEVE ground

This meant that our mini jack female connector would have the same pin-out because the female and male mini jack in
this case were cut from the same cable. Let us assume for a moment that your male mini jack connector came from a
different cable and had this pin-out:

TIP white

RING red

SLEEVE ground

We would then simply plug the male mini jack into the female mini jack and test the cable with a multimeter to
determine the pin-out. In the example noted above:

TIP white === orange male

RING red === yellow female

SLEEVE ground === ground

Now we can extrapolate from the fact that on a tip-ring-sleeve style connector the pin-out for L/R/ground is:

TIP left

RING red

SLEEVE ground

This leaves us with the wiring to the volume circuit board as follows:

TIP left orange

RING right yellow

SLEEVE ground ground

So to solder to the output of our volume control board we will have:

G ground

L orange

R yellow

Your diagram may be a bit different depending on the colors of your female mini jack cable. A common example would
be:

G ground

L white

R red

Next tin your cables (prepare them with a bit of solder on them) and trim them down. Solder them onto the points on
the output of the volume control circuit following the diagram you have made yourself with the tip-ring-sleeve
explanation above:

Note that the volume control unit is face down. This allows the volume control dial to spin freely against the
smooth plastic underneath it. Also note that it is facing towards the rectangular notch we filed earlier.

Underside of the completed soldering:

Now file a rounded notch to let the cable exit out of the top center of the push to talk unit. You only need to file
the round notch into the backside of the unit (the side without the button):

Stick a piece of electrical tape between the volume control unit and the push to talk circuit. Push the volume knob
to the edge of the rectangular notch. At this point, plug your phone in and your headphones and play some music to test
your wiring skillz.

Now add a blob of hot glue on the inside edge of the volume controller circuit to force it to the edge of the
plastic housing. Take care to not glue the volume potentiometer in place. We want to be able to change our
volume!

Now gently fold the original circuit on top of the volume controller knob and test once again with audio to make
sure you don’t have any connections shorting or breaking.

Now replace the top cover and test the push to talk unit. Now carefully put hot glue all around the outside edge of
the push to talk unit, taking care to not glue the volume knob.

If you wish to change the fugly beige color of the unit, you can do so now. Tape off the button and the base cable.
Bust out that black nail polish from your goth phase or some black hobby model paint from that black hawk helicopter
you never finished. Alternatively you can pick a more vibrant color to match your colorware computer. Give the unit two
coats of paint, leaving time for it to dry between coats. If you don’t dig paint, you can also go for the ghetto black
electrical tape look.

Version 01 with ghetto black electrical tape, without the volume controller, a male mini jack connector and a female
to female mini jack adapter and some not-so-stellar sony in-ear headphones:

Here is the completed unit with volume control (unpainted) with a Nokia 6230:

And finally a painted version of the completed unit in use on a messenger bag:

If you are feeling less adventurous or don’t want the analog volume control on the push to talk unit, hop over to
Engadget to read the basic How-To. Nokia, if you are
listening, please include ports for standard headphones on the phone itself and if not, at least in the cables that are
provided with the phone.