• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

TS440S question

Crasher

Member
Apr 25, 2012
49
6
18
44
Norwalk, OH
Can someone tell me exactly how to use my pre-amplified microphone bypassing the audio section. I believe I need to use the Data input, however I am not exactly sure. Thanks for the help!
 

Kenwood TS-440 Yahoo users group, join it, great info there.

The TS440 has a pretty decent mic amp in it all ready.
 
  • Like
Reactions: 1 person
Thanks, I have a pretty nice mic setup with EQ I was trying to use with the 440s. I know the audio in and such, just not sure how to key the radio using the acc2 jack.

Joined the yahoo group, i'll be sure to check there.
 
the accy2 port has a FIXED output level designed primuarly for DATA modes, but it will also work for fone


go here and look around ts440


There are three ways to get a clean signal from and to, the TS-440. When I say clean signal, I mean a signal that is at a steady level, and not affected by user settings. They are from the FSK jacks, the ACC-2 13 pin connector and the remote connector. FSK jacks were meant to be connected to dedicated terminals for teletype style communications. The FSK connectors are the easiest to use, because they require standard RCA style jacks. The remote connector was meant for use with a linear amplifier, and the ACC-2 was designed for data connection. The remote is suitable only for reception, and it's receiver in pin was set up to permit a reception path that did not pass through the amplifier.
ACC-2, even though it will require purchase of construction of a special cable and connector. It has two great advantages over the FSK connectors. Though both have a clean 300 mv signal on output, untouched by AF gain, cw sidetone, feeper, or voice response unit, input is a bit different. On input AFSK and microphone signals both go through the mike preamp and speech processor. On data they do not
 
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
 
I'm pretty sure Crasher is talking about using the ACC2 port for audio _input_, not output.
-Bill
I understand that..... thay why I BOLDED the last paragraph:

Though both have a clean 300 mv signal on output, untouched by AF gain, cw sidetone, feeper, or voice response unit, input is a bit different. On input AFSK and microphone signals both go through the mike preamp and speech processor. On data they do not
 
It was my understanding that the ACC2 plug was the direct input to the balanced modulator. Void of any equalization. At least, that is what I have been explained so far. It is the mic preamp and the headphone amp that have the tone filtered. Often unfavorably too.

The filtering section is ultimately going to determine the TX width . . .
 
Well then, I do appreciate all the replies. I may just leave it as-is as I do get great audio reports the way I have it setup now, mainly used on AM but find myself more often on SSB DXing!

Thanks again!
 
Robb: like I said, it varies from rig to rig.

I got curious so I looked at the TS-440 service manual schematics. It looks like the ACC2 data input line goes to J25 on the IF unit, which does bypass the mic pre-amp. (This is different from the TS-850 and TS-950SDX that I have: both have additional pre-amp circuits on the data input line.) From there, it looks like it goes to the front panel mic gain control pot via and back to the IF unit via J23. And from there it goes the modulation drive amp Q44 (2SC2459) before being fed into the balanced modulator chip, IC5 (AN612).

I see the following components that would limit low-end response a bit:

C132 -- 1uF coupling cap feeding into pin 3 of J23 (not sure if this matters)
C133 -- 1uF coupling cap feeding audio to base of Q44
C135 -- .1uF coupling cap to pin 1 of balanced modulator
C136 -- 47uF emitter shunt cap on the modulation drive amp

Probably the biggest limiting factor is C135, the .1uF cap between the collector of Q44 and pin 1 of the balanced modulator. Just changing this should make a noticeable difference. But I would do the following:

Change C132, C133 and C135 to at least 4.7uF (maybe even 10uF)
Change C136 to 470uF

This will avoid quite a bit of low-end roll-off.

But the crystal filters still limit the overall bandwidth. If you can bypass the AM filters during TX though, you might get some nice HiFi sound out of it. :)

-Bill
 
Last edited:
  • Like
Reactions: 1 person

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Tucker442 has left the room.
  • @ BJ radionut:
    LIVE 10:00 AM EST :cool:
  • @ Charles Edwards:
    I'm looking for factory settings 1 through 59 for a AT 5555 n2 or AT500 M2 I only wrote down half the values feel like a idiot I need help will be appreciated