Small pad for 3.5mm lav mic

[samchurchill]

Hi,

 

I’ve got a lav mic that plugs directly into a smartphone but occasionally it distorts slightly if someone with a loud voice uses it. Does anyone know iof a small adapter or cable I can use to pad the signal slightly?

 

Not sure if https://www.amazon.co.uk/Xcaliber-XGA-11-Stereo-Socket-Resistors/dp/B000T9NLNU will do the trick.

 

Thanks,

 

Sam

[Mixermend]

Rather poorly described in the Amazon advert - but I think the resistors are for L+R combining to give a mono signal from a laptop or similar 3.5mm TRS output.

 

Out of stock anyway - and not suitable for your requirement!

 

Have a search for L pad attenuators - it is possible to fit the 2 resistors needed into a standard 0.25 inch jack plug - you probably need about 10dB, this is an experiment, but that will be a good starting point.

[sandall]

Presumably any adaptor needs to be TRRS 3.5mm socket - 3.5mm plug, so it might be easier to cut your existing lead near the plug-end to add the resistors. Alternatively I wonder whether a disposable foam ear-protector over the mic would provide any useful attenuation. Suggesting that people don't shout is presumably not an option?

 

 

Edited May 10, 2020 by sandall

[bigclive]

I've added a series resistor with a similar microphone. I initially added a small resistor substitution box in line, and then recorded me saying each selected resistor value as I incremented it to find the optimum result.

[sunray]

I've added a series resistor with a similar microphone. I initially added a small resistor substitution box in line, and then recorded me saying each selected resistor value as I incremented it to find the optimum result.

I'm glad it's not only me who does that sort of thing.

[samchurchill]

Thanks all, that’s really useful.

 

Yes, I think I knew that link want the right thing for the job, but just wanted to narrow my search. And yes, you’re right about it needing to be TRRS.

 

I’m tempted to make a small adapter with a project box and a fly lead, or, as you say, just chop the end off and solder a resistor in-line. Will see if I can work out an appropriate resistor value.

[MrBoomal]

If you're making a project box, why not use a potentiometer instead.

That way you could adjust it depending on how shouty the person is.

[kgallen]

This link any use to you for working out the resistors for say a 3dB or 6dB attenuation:

 

http://www.nu9n.com/tpad-calculator.html

[samchurchill]

If you're making a project box, why not use a potentiometer instead.

That way you could adjust it depending on how shouty the person is.

 

Good, errr, shout! May see if I can get the parts next week.

 

Just need to google which TRRS part is used for what now. Cheers all.

[sandall]

Just need to google which TRRS part is used for what now.

Mic audio is furthest from the tip (so no metal-bodied plugs!!), screen is 2nd ring (headphone audio on tip & 1st ring).

[samchurchill]

Just need to google which TRRS part is used for what now.

Mic audio is furthest from the tip (so no metal-bodied plugs!!), screen is 2nd ring (headphone audio on tip & 1st ring).

 

Thank you!

Edited May 17, 2020 by samchurchill

[samchurchill]

Sorry for being a bit clueless on this one, but could I just check I’ve got the right idea before I order some resistors (or a potentiometer if I can find one)?

 

The spec on the mic says “output impedance 1000 ohm or less”, so am I getting the right resistor values of I put in, say, 600 ohms and a starting value of 10dB attenuation at http://www.sengpielaudio.com/calculator-Lpad.htm?

[sandall]

I think I would be inclined to put a 4.7k trim-pot between phone-audio & screen, with the wiper going to the mic output, & see what happens. With the wiper at one end there should be no change; with the wiper at the other end you will get no output. A lower value pot (say 3.3k) would drop the bias-voltage less, but might not give enough gain-reduction. Lots of scope for experimentation before you commit to resistor values :).

[david.elsbury]

10dB seems a lot to me?

Remembering that 3dB is a doubling or halving of audio... I might try for 6 as a start?

[leopheard]

On 5/19/2020 at 12:10 AM, samchurchill said:

Sorry for being a bit clueless on this one, but could I just check I’ve got the right idea before I order some resistors (or a potentiometer if I can find one)?

 

The spec on the mic says “output impedance 1000 ohm or less”, so am I getting the right resistor values of I put in, say, 600 ohms and a starting value of 10dB attenuation at http://www.sengpielaudio.com/calculator-Lpad.htm?

What solution did you come up with for this in the end @samchurchill? I have the exact same situation I need to solve - need to reduce the input form a great 3.5mm lapel mic into a digital audio recorder by around 20%.