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How to build an attenuator Y-Cable (Splitter) for Ultrasync One?


Sound
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Until now I was using the Ultrasync One splitter cable to feed LTC audio timecode to one track of my camera plus the sound from a scratch mic via its minijack-input.

Heres the cable: https://www.timecodesystems.com/product/tcb-53-ultrasyncone-y-cable/

I realized that the LTC audio signal was way too loud and I cannot lower the volume on the USO, so there is audio bleeding to the audio track.

As I need to solder new cables anyway (the get torn apart sometimes and are very expensive) I would like to add an attenuator (pad) for the USO-signal.

I was thinking, maybe its possible to add just a small resistor inside the minijack, which is connected to the USO - is this possible?

 

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1 minute ago, Sound said:

Until now I was using the Ultrasync One splitter cable to feed LTC audio timecode to one track of my camera plus the sound from a scratch mic via its minijack-input.

Heres the cable: https://www.timecodesystems.com/product/tcb-53-ultrasyncone-y-cable/

I realized that the LTC audio signal was way too loud and I cannot lower the volume on the USO, so there is audio bleeding to the audio track.

As I need to solder new cables anyway (the get torn apart sometimes and are very expensive) I would like to add an attenuator (pad) for the USO-signal.

I was thinking, maybe its possible to add just a small resistor inside the minijack, which is connected to the USO - is this possible?

 

The ultra sync has two outputs which you can change level on use tc out for camera and sync out switched via menu to timecode out and set timecode level to level that suits for mini jack. 

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I know but unfortunately even the lowest level it too high, so there is still bleeding and I can hear the LTC signal on my audio track. USO was so kind to send me a small resistor to add it to the cable some time ago, but I was wondering if I could build a cable myself with a resistor included so I dont need to plug in an additional box.

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Thanks, I see, even for a mono signal there are two resistors required.

I must admit, I am absolutely new to all of this. I can estimate the attenuation, but whats the impedance in this case?

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5 hours ago, Sound said:

Until now I was using the Ultrasync One splitter cable to feed LTC audio timecode to one track of my camera plus the sound from a scratch mic via its minijack-input.

Heres the cable: https://www.timecodesystems.com/product/tcb-53-ultrasyncone-y-cable/

I realized that the LTC audio signal was way too loud and I cannot lower the volume on the USO, so there is audio bleeding to the audio track.

As I need to solder new cables anyway (the get torn apart sometimes and are very expensive) I would like to add an attenuator (pad) for the USO-signal.

I was thinking, maybe its possible to add just a small resistor inside the minijack, which is connected to the USO - is this possible?

 

There is almost always some timecode bleed between tracks on a mini jack sockets.. Any thing on the other track of mini jack should be considered guide audio, as an impedence the mini jack camera is probally about 2kohm, you could use impedence of 600ohm as well. 

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Thanks! With the custom built attenuator from TC-Systems it works perfectly fine - no bleed at all. I have a very cheap rode micro scratch mic on the other audio input and it sound ok given the price. I often used it and it saved me a lot of times when there have been sync issues or wireless audio issues. So I will try to build this.

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Sorry for all this stupid questions.

There are a lot of resistor-sets on amazon, they differ in the wattage and size. Is 1/8 watts enough for those audio needs?

That would be best to hide it in a cable.

 

And I will connect my Din 1.0/2.3 connector to the tip and the sleeve of the minijack, so its going to the left channel.

I will add a resistor to the connection of the tip of the minijack to the Din-connector.

And then I will connect the wires going to the tip and sleeve from the Din-connector to the minijack-connector with another resistor, is that right?

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An 1/8 Watt resistor is ok in any typical audio attenuator application in line level applications. For instance if you had a continuous 10 Volt audio signal (+20 or +22 dBm depending on reference) feeding a 1000 Ohm resistor, the resistor would only need to dissipate a 1/10 Watt max. (Power = Voltage squared divided by the resistance.) So 10 squared divided by 1000 is a tenth Watt. In short 1/8 or even 1/10 Watt resistors are fine.

Best Regards,

Larry Fisher

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