C131 Mod and iBox for 870

XLAXX · Post by **XLAXX** » Fri Jul 09, 2010 11:59 am

Howdy Do-
Newcomer here.
If I mod the 870 with the C131 cap, so as to use the ACC2 port for the audio feed,... do I need to use the iBox still? Just curious as most references to the iBox have been made when using the front mic jack.

XLAXX

Post by **Voodoo Guru** » Sat Jul 10, 2010 6:28 am

Howdy XLAXX,
Welcome to the Forum!!!

The main reason for using the I-Box is for Level reduction. The Level coming from the Rack Equipment is at Line Level, and the Level that goes into the front mic jack is Mic Level. The I-Box can attenuate the level so that you do not overload the Mic circuits with too much audio.

The I-Box also gives you a way to transform the Balanced Line output of the Rack Equipment to the Unbalanced Audio input of the rig.

The next thing it does is Isolate between the Rack Equipment and the Radio. This is done by using an isolation transformer inside the I-Box. This can help if you are having hum or RFI issues.

Doing the C131 mod and imputing the Line Level Audio into the ACC2 jack is by far the best way to feed the TS-870. You can still use the I-Box for level control and isolation, but there are many people that do not use anything at all. They adjust the input audio using the output fader on the last piece of equipment.

One last note, the I-Box uses a Stancor Telephone Modem isolation transformer that is Iffy at best. The quality control on the production of these transformers is not very good and sometimes you will get one that does not pass the low frequencies very well.

Hope this helps,
Take Care,

XLAXX · Post by **XLAXX** » Sat Jul 10, 2010 6:48 pm

OK,... thanks for the help on that one. The iBox is helpful to have and seems to have many uses for sure.

Got another question for you though...

What is the wiring hookup for the 5 pin DIN from the iBox to the 13 pin DIN of the 870? I'm using XLR starquad cabling 4 wires with a shield. I guess I need to make the connection from balanced to unbalanced entering the 870? Everything in the chain has been XLR. I used a stereo plug to enter the iBox.

Thanks for the help and looking forward to making some VOODOO.

XLAXX

Post by **Voodoo Guru** » Sat Jul 10, 2010 6:56 pm

Howdy XLAXX,

You will have to look on the manual for the I-Box for their hook up pin out.
You can download that from the W2IHY site.

Check this thread for the Pin out on the ACC2 and the Menu Settings.
http://www.wz5q.net/talkvoodoo/viewtopic.php?t=39

Have Fun!!

XLAXX · Post by **XLAXX** » Sat Jul 10, 2010 7:08 pm

Maybe this will help you with what my wiring problem (no voodoo at dis time),...

From output of iBox (5pin DIN)/solder side to connecting wire with 13pin DIN:

pin 1 - + mic
pin 4 - (-) mic
pin 5 - n/c
pin 3 - GND (shield of XLR)
pin 2 - n/c

I am running PTT through the front mic jack so there is no connection at pin 5.

Connection to 13pin DIN to Kenwood ACC2 is as follows:

pin 11 - (+) mic
pin 12 - (-) mic
pin 8 - GND (shield of XLR)

This is a Balanced system but you mentioned that the 870 is Unbalanced, so I guess I need to make a different connection somewhere because I am getting NO audio to the 870 and hear nothing through the moni. Also, do you suggest connecting any other wires to the 13pin DIN for monitoring purposes?

Thanks for da help in making the voodoo happen.

XLAXX

XLAXX · Post by **XLAXX** » Sat Jul 10, 2010 9:48 pm

Thank you for the link to the wiring.

A bit confusing though.

I used pins 11 and 12 on the 870 and also switched to the PTT on the back too, using pins 8 & 9. The radio keys now but still no audio.

Am I only to use these two pins for audio?... 11 being (+) mic and 12 being (-) mic,...where is the shield (GND) going from the iBox?

Should I put the (+) and (-) together on pin 11 and the shield (GND) on pin 12? The explanation in the link is unclear. I am voodoo-less.

THanks!
XLAXX

XLAXX · Post by **XLAXX** » Sat Jul 10, 2010 10:10 pm

Maybe I should just leave the iBox out of the chain? Can you recommend a decent output fader to level things out?

Chain:

preamp
DEQ2496
2024P
MX882

XLAXX

Post by **Voodoo Guru** » Sun Jul 11, 2010 4:33 am

Howdy,

You figured out the PTT problem already. You have to key the ACC2 connector in order for the 870 to use the ACC2 Mic Audio input. If you try and use the front mic jack PTT, it will override the ACC2. They do this in order to choose the mic audio input as the ACC2 is actually meant for Packet Audio, they wanted the front mic jack to override the Mic audio input for voice. So...only key the ACC2 PTT line.

The I-Box is a Balanced Input with the 1/4" TRS (Tip, Ring, Shield) Stereo Plug to an Unbalanced output with the DIN. Make sure you have the XLR to 1/4" TRS wired correctly...Pin 2 of the XLR goes to the Tip of the 1/4", Pin 3 of the XLR to the Ring of the 1/4", and Pin 1 of the XLR to the Shield of the 1/4".

On the DIN side, Try connecting Pin 1 of the DIN to Pin 11 of the ACC2 for Mic Audio +, and Pin 4 of the DIN to Pin 12 of the ACC2 for mic audio -. You can connect the shield ground Pin 3 of the DIN to the chassis ground of the ACC2 but it should work either way.

BE SURE you have the right pins on the DIN as it is confusing. They are usually marked on it.

Make sure Menu20 in the radio is set correctly.

If all of that doesn't work, maybe you made an error in the C131 modification?.

Good Luck,

XLAXX · Post by **XLAXX** » Sun Jul 11, 2010 9:24 am

Thank you Voodoo master for the email. Man,... you're a night owl or an early riser!

OK,... I checked all the connections and re-wired the DINS to what you suggested. Also, re-checked the 1/4" plug. No audio! Aaaargh!

Guess I will be pulling the radio apart to re-check the cap. No joy here.

XLAXX

XLAXX · Post by **XLAXX** » Sun Jul 11, 2010 9:25 am

Oh ya,... the PTT is working in the back too,... just no audio getting to the rig.

XLAXX

XLAXX · Post by **XLAXX** » Mon Jul 19, 2010 8:57 am

Well,...

I have some voodoo in the monitors now.
There is 'tearing' when I announciate a word that starts with 'SSSS'. Sounds like some distortion and crackling.

Could I adjust the DEQ 2496 to clean this up (the SSSS distortion) at all or is this inherent in the 870?

Also,... if I place an Ultrafex EX3200 into the chain, would it go after the 2496 and before the the 2024P? Would the 3200 add something to the lows given the flatness of the 870?

My vocal charateristics are fairly low, so I was thinking about giving the 3200 a try.

Thanks for the help. Time will tell if I get some RF into the chain as I have been running everything into the D/L for testing.

XLAXX

Post by **Voodoo Guru** » Mon Jul 19, 2010 9:21 am

Great!
Glad you got the audio flowing.
No that is not inherent in the 870, well it is when going into the front mic jack, but that's one of the reasons you are going into the ACC2.

What your hearing is what they call 'Tearing' and this is usually caused from trying to boost to many high frequencies. You need the set up the DEQ (compressor) of the DEQ2496 to fix this. Try the settings that John, NU9N has on his site first and see if that helps.

http://www.nu9n.com/deq2496.html

The best place for the EX3200 is after the EQ and before the compressor.
This can be done by using the Left Channel of the DEQ2496 for the EQ then going to the EX3200, then back to the Right Channel of the DEQ2496 and using the DEQ (compressor).

Have Fun!