Hi there, I would like to build a variable (preferably) pad in order to get signal from a mixers rec out ( mixer master audio MM1210 only available output) to a wireless microphone input, whose receiver would be on a dslr camera nearby. In this scenario I have to also sum the 2 channels to one. I was thinking an l pad in order to achieve near -40db attenuation and 2 1k resistors on each channel to sum them up. Will this work? Any advice is very welcome.
An schematic would make the question more easy to answer. How are u planning to implemment the pad (dif ways to do it)?. And yes u can sum both channels using resistors, u will be loosing some voltage. U could also try an easy op amp summer or adder to stay unity gain
Three resistors.
One 2k in series with each output, tied together at the far ends.
One more resistor to ground to attenuate from the common point,
could be a pot.
One 2k in series with each output, tied together at the far ends.
One more resistor to ground to attenuate from the common point,
could be a pot.
I think not, to be honest I have not look into it thoroughly. Also I would like to have my pads with me since I might meet other mixers too in different stadiums
Here what I have in mind. At the output I am thinking to connect the signal either to a Transmitter that has a lav input (mono signal Chinese made by the name fifine) or use the lav inputs on wireless go transmitters.
Attachments
Last edited:
40 dB is 1%. So I would use two 10K resistors and one 50 ohm resistor. Unless the mixer is transformer balanced out, I would not add 620 ohm load resistors. The MM1210 does not require them.
I would not make it adjustable as that should be controlled from the mixer.
I would not make it adjustable as that should be controlled from the mixer.
Last edited:
There appears to be a level control pot that is switchable between headphone/control room/rec out besides the main out which controlled by the main fader.
The original lav mic that connects to the transmitter is 850 Ohm. So I suppose (?) that this should be the output impentance (Correct?)
As far as the Input is concerned I dont know probably 100-150 ohm? ( I am guessing - any help would be welcome)
Sorry did not quite understand it. We are talking about the attenuator Correct. So We are going to use one 10k on each output and a 50 ohm (why not 100 or more so as to not crosstalk?) between line and ground. Correct?
I don seem to see it but I am certain that when used with other mixers this would not always be an option. That why I was thinking a variable attenuator.
I'm starting to understand better, i will work, to make it variable you should use those hard to figure out mutipole switches for the R's that are not shorted in this image: (sorry cant edit the image so it will go full as i'm on the run)( Also there is no need to use a double switch for each at desired, it could be something more like the image hand written) (Ria is your Zin) .
In that table i think all the values are for keeping Zin the same, same applies to the long hand writed page. The short hand writed one, also changes your Zin (raises it), but it could not be a "problem", since if its turned on, you are probably with High Z line level source. Many pads are done that way because its a cheap way to attenuate and raise the input impedance in comparisson to the mic in (no pad used). The only issue with changing the Zin (if the transference of voltage is OK for the application) i can think of if messing up with the noise figure of the input stage transistors, in this case the mic input if i got that right, but i dont think its critical at all in this situation.
This last one changes the Z, and Rb is your Zin, if i recall correctly
Regards!
In that table i think all the values are for keeping Zin the same, same applies to the long hand writed page. The short hand writed one, also changes your Zin (raises it), but it could not be a "problem", since if its turned on, you are probably with High Z line level source. Many pads are done that way because its a cheap way to attenuate and raise the input impedance in comparisson to the mic in (no pad used). The only issue with changing the Zin (if the transference of voltage is OK for the application) i can think of if messing up with the noise figure of the input stage transistors, in this case the mic input if i got that right, but i dont think its critical at all in this situation.
This last one changes the Z, and Rb is your Zin, if i recall correctly
Regards!
Don´t overthink it, keep it simple.
1) you are converting stereo to mono.
2) I guess starting with 40dB attenuation may be a bit too much, specially on some situations.
I would provide two possible levels, one somewhat high, another lower one, selectable by a simple switch.
Any fine adjusting needed comes from either mixer out volume or camera input adjustment, you don´t need a third voliume pot in the setup, at all.
Keep it simple 😉
I´d use two 2k2 mixing resistors, one from each channel (right, left), their output feeding series 100 ohm and 220 ohm resistors to ground, the 220 ohm one being shorted at will with a simple switch.
That will provide about 40dB attenuation with switch closed and about 30dB with switch open, will cover both "expected" levels, and a weak mixer output.
You can build it in a small metallic box, even a sardine or mints one, go figure.
Or a "fancy" Hammond box, such as used for Guitar pedals .
PS: you will NOT have cosstalk.
1) you are converting stereo to mono.
2) I guess starting with 40dB attenuation may be a bit too much, specially on some situations.
I would provide two possible levels, one somewhat high, another lower one, selectable by a simple switch.
Any fine adjusting needed comes from either mixer out volume or camera input adjustment, you don´t need a third voliume pot in the setup, at all.
Keep it simple 😉
I´d use two 2k2 mixing resistors, one from each channel (right, left), their output feeding series 100 ohm and 220 ohm resistors to ground, the 220 ohm one being shorted at will with a simple switch.
That will provide about 40dB attenuation with switch closed and about 30dB with switch open, will cover both "expected" levels, and a weak mixer output.
You can build it in a small metallic box, even a sardine or mints one, go figure.
Or a "fancy" Hammond box, such as used for Guitar pedals .
PS: you will NOT have cosstalk.
I see, so you need an L-pad for impedance of 850 ohms, because it will be sitting after the mic and before the transmitter.
What level of attenuation do you want?
Juan,
1,100 into 100 is -21.6 dB. Of course a simple switch is a good idea.
So I would still suggest 10,000 into 50, but with another 110 that could be shorted.
Of course this results in a lower impedance than the microphone, so should lower the noise floor.
1,100 into 100 is -21.6 dB. Of course a simple switch is a good idea.
So I would still suggest 10,000 into 50, but with another 110 that could be shorted.
Of course this results in a lower impedance than the microphone, so should lower the noise floor.
There will no be mic just the transmiter. I mean mixer output --->attenuator ---->mic transmitter (the line out will be on mics tramsmitter input)
My objective is to use mixer's line out to mics transmitter input (so I believe 30-40db attenuation??). Any idea if i use the wiress go wireless mics from rode what impendance they wait? At their page they appear as compatible 2 lav mics with resistance of 2k2 and 3k respectively. Does this means that the output impendance is those numbers?
Last edited: