I'm pretty sure Crasher is talking about using the ACC2 port for audio _input_, not output.
The pinout for the ACC2 port is in the TS-440S owner's manual. You can get a good copy of it here (warning: big file):
http://www.kenwoodusa.com/UserFiles/File/UnitedStates/Communications/AMA/Manuals/TS-440.pdf
The diagram is on page 11. Audio in (Data input) is pin 11, and ground is pin 12. You need a 13-pin DIN connector and will need to make your own cable. You can get a 13-pin DIN plug from here if you don't have one:
CONN CIRCULAR DIN 13POS MALE - SD-130
That said, you should be aware that if you just plug your mic/EQ setup into ACC2 port, the resulting TX audio may not be "better" than what you'd get with the mic jack. Because the ACC2 port is designed for data use, Kenwood usually designs the data pre-amp with even more of a low-end rolloff than the mic pre-amp. That is, it has less bass response. For data use you don't need the added bass, so it doesn't matter, but for regular mic audio you may not like the missing low-end.
I say this because most people want to" bypass the mic-preamp" in the first place because they've heard the pre-amp circuit has limitations on frequency response. Using the ACC2 audio input instead does indeed bypass the mic-preamp, but you end up going through a different pre-amp instead which may have even worse response.
Furthermore, your TX bandwidth will be limited at the RF level by the IF filters in the radio. For AM, there are hardware mods to bypass some of the filters during transmit which can improve this. For SSB, you can't really bypass the IF filters because they're used to filter out the opposite sideband. Turn them off, and you'll be transmitting in double-sideband mode instead of single-sideband, which you don't want.
So, if your goal is better TX fidelity, I would take a look at the service manual for the TS-440 and see where the ACC2 data input pin goes. The designs vary a bit from rig to rig, but my money says there's a separate data input pre-amp that may need some small modifications. With my radios (TS-950SDX, TS-850), I had to change a handful of capacitors to get things where I wanted them.
Also, I use one of these to connect my audio gear to the rig:
Radial Engineering J-ISO Jensen Transformer Equipped Stereo Isolator +4dB to -10dB Converter | Musician's Friend
It provides impedance matching from the low impedance audio gear to the line level input on the rig, and it also provides isolation between the rig and audio gear to help prevent ground loops and RF feedback. That particular one is a bit expensive due to the Jensen transformers. There's also this one which is a bit cheaper:
Radial Engineering PRO ISO Stereo Line Isolator +4dB to -10dB with Radial Transformer | Musician's Friend
The cheaper one should be more than good enough.
Oh and as for keying the rig up, I generally use my Kenwood hand mic plugged into the front panel as a hand switch. Note that pin 9 in the ACC2 port can be grounded to mute the mic input to prevent getting any pickup from the hand mic while the ACC2 connection is plugged in. Pin 13 of the ACC2 plug is the SS (standby) line which you can ground to key up the radio. You can use this rig up a separate hand or foot switch.
-Bill