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ke5gnz
Audio Head


Joined: 23 Nov 2012
Posts: 3
Location: south texas

PostPosted: Fri Nov 23, 2012 8:09 pm    Post subject: Hello, New to the Forum Reply with quote

hello my name is Ray call is KE5GNZ down in south Texas. My rig is a Kenwood TS 950 SD (wish it was an SDX but have what i got) I feed the audio in the back from a Marshal MXL 2010 with a Beringer tube preamp and a Beringer 15 band eq works great have had excellent reports but can get better i am sure. I am out for audio the is easy to listen to. I also have a Yaesu FT 2000 but i enjoy my Kenwood more. thank you
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BillPaul
Digital Voodoo Guru


Joined: 19 Jan 2011
Posts: 66

PostPosted: Tue Nov 27, 2012 11:55 am    Post subject: Reply with quote

There's one thing to bear in mind here: Kenwood intended the audio input on the ACC2 port to be used for data (packet radio), not voice. This is true of pretty much all the Kenwood HF rigs, going as far back as the TS-440. As a result, the ACC2 inputfrequency response is actually worse compared to the front panel mic jack audio input: the low end roll-off occurs at a higher frequency (i.e. you get less bass). The audio sounds clean, but it really is missing a lot of bass. Like the front panel mic input, the ACC2 audio input also goes through a small pre-amp circuit, but some of the component values on that circuit are different than the front panel mic pre-amp.

Over in the "Modification Madness" section, there's a thread called "TS-950sdx - Line Level ACC2 Audio Mod" that talks about this. The TS-950S/SD has the same pre-amp circuit on the ACC2 input as the TS-950SDX. You can modify it as follows to improve the low-end response:

On the IF unit (X48-3060-00):

1) Change C154 from .1uF to 4.7uF
2) Change C158 from .1uF to 4.7uF
3) Change C161 from 1uF to 4.7uF
4) Change C159 from 10uF to 470uF

Note that this is only part of the story, however. On the TS-950SDX, the audio signal from the ACC2 pre-amp is fed to the input of the DSP unit. There is one additional cap to change on the signal unit right before the DSP, and then you're done. However the TS-950S/SD design is different: my understanding is that the DSP unit isn't used for TX on that rig. This means the signal from the ACC2 pre-amp probably feeds into a balanced modulator circuit instead. (Kenwood's typical design uses an AN612 balanced modulator chip for both SSB and AM. This is what my TS-430 and TS-850 use at any rate. The TS-950S/SD is probably very similar.) I haven't looked too closely at the TS-950S/SD schematics though so I'm not sure if there's any other places where caps need to be changed. If there is a balanced modulator, then you may need to change out an emitter shunt cap in the modulation drive amplifier right before it. That seems to be a common theme in Kenwood's design as well.

In the end though, all this will do is improve the bass response on the rig. You won't be able to improve the high end response because that's limited by the crystal filters. Because the TS-950S/SD doesn't use the DSP unit for TX, you can't bypass the filters for SSB: if you do, you'll be transmitting in double-sideband mode. Improving the bass response may give you a richer tone though, so it may not be a total waste of effort.

That said, you _can_ disengage the filters for AM transmission, and the result then should be some very nice AM audio. I've done this with my TS-850 and the results are wonderful -- I just wish I could run some more power with it. (I live in an apartment building: running anything more than barefoot would aggravate the neighbors.)

-Bill, N1GPT
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ke5gnz
Audio Head


Joined: 23 Nov 2012
Posts: 3
Location: south texas

PostPosted: Tue Nov 27, 2012 12:09 pm    Post subject: Reply with quote

Hello thank you for you responce i know that if i unhook the dsp the rig double sidebands for some reason(found out by accident bad connector) but i will look into changing the caps as any help to improve the tx audio will help on the other end. any other info will always be helpfull. thank you KE5GNZ
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BillPaul
Digital Voodoo Guru


Joined: 19 Jan 2011
Posts: 66

PostPosted: Tue Nov 27, 2012 12:29 pm    Post subject: Reply with quote

For the SDX, there is a special configuration menu option that lets you configure the rig so that the '8.83' and '455' filter selection buttons work in TX mode as well as RX. The 950-S/SD may have the same trick. If so, you may have enabled it and set the rig to have all the filters off during TX. That could be why it was transmitting in double-sideband mode when you unhooked the DSP.

BTW, I have a copy of the TS-950S/SD service manual here:

http://people.freebsd.org/~wpau/ts-950sdx/TS-950S-SD_Service_manual.pdf

This may help you figure out what other components may need changing.

-Bill, N1GPT
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ke5gnz
Audio Head


Joined: 23 Nov 2012
Posts: 3
Location: south texas

PostPosted: Tue Nov 27, 2012 3:19 pm    Post subject: Reply with quote

You are right there is a power on mod that allows the filters to be selected in Tx mode and only the 8.83 can be turned off. At the time it was double side banding I dont recall if the filter was off or in the 6kc position(where it usually stays) on tx. I dont know how wide it is really transmitting and as per your info earlier probabily not much as i feed the rig from accy 2 mainly just to keep the front of the desk clean. i will order the caps from mouser in the next couple of days. that way i can get a good list. if you can think of any thing else that might help please feel free to let me know. it all helps. thank you
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