HELP - Mic Mute Pedal - Phantom Power and LED

[Whoops]

Hi,
I built a Mic Mute pedal for Condenser microphones, and I used this circuit:



It works great, there's no pops or clicks when switching.

But as I use it in live sound on a stage I would like to have 2 LEDs, one red to indicate MUTE position and a Green one to indicate ON. I would like to draw power for the LEDs using the phantom power supply so that no battery or external supply is needed.

Whats are your advices on how to add the LEDs supplied by the Phantom Power without introducing Pops/Clicks when switching
the ON and OFF/MUTE?

Thank you so much for your help

 

[Whoops]

As far as I can see, I can only find one product in the Market that does this, it's the Orchid Electronics Mic Mute:

http://orchid-electronics.co.uk/Mic_Mute_lite.htm

 

[Whoops]

Hello,
I made a drawing of something to try out, could the LEDs be implemented this way?
What do you guys think?

thank you so much

 

[PRR]

That may work.

It is a fairly high current drain if it also has to power a Phantom mike.

With modern LEDs on stage you may not need high current.

The 3-R network can be reduced to 2-R.

The switching need only shunt the Red LED across the Green LED. The lower Vf of Red will steal 95% of current away from Green. This also makes no "open" period as the switch contact travels one to the other, so current is 98% constant instead of a big click to no-current and back to full current at each switch action.

I have no idea what your 10k+0.1 network is for.

 

[Whoops]

Thank you so much PRR,
I will try that out, it's a great idea to shunt the Red LED across the Green LED, thanks.
I tried to do the Mute pedal with LEDs in the past but I always got terrible Pops/Clicks when switching.

As for the 10k+0.1 network, I noticed there's a mistake in the schematic,
this is a circuit from Crown website that I used a lot in the past, and it always provided Clickless switching with condenser microphones (although no LEDs involved), I couldnt find the Crown webpage any longer, and the schematic I found on the web had for some reason the connection between the 10k+0.1 network and the 1000uf cap removed.

This was the actual original circuit by Bob Stadtherr published in the Crown website, that I used before with good results:

Explanation from Bob Stadtherr
"This is essentially a lowpass filter, with a cutoff frequency around 1 Hz (assuming a 150 ohm mic impedance). The 10K resistor allows the capacitor to charge to the DC voltage between the lines, so when the switch is closed, no change to the DC levels occurs.

Pin 2 might be positive relative to pin 3, or vice versa. So the capacitors should be non-polarized. To create the 1000 uF capacitor, you could use two 470 uF polarized capacitors in parallel, wired in opposite polarity."

https://web.archive.org/web/20120510065956/www.crownaudio.com/mic_web/popless.htm

 

[Bo Deadly]

It's not crystal clear to me why you need capacitors at all. I would just use the 10k and the switch to bypass it. If pins 2 and 3 are not already within a few millivolts, something is very wrong with the phantom supply.

Also phantom is only good up to ~14mA which is about what an LED uses so you cannot power a mic and an LED at the same time. Ditch the green one and just use red to indicate mute. Logically it is equivalent. The mic doesn't need power if it's muted so you can use a red one.

Just wire a two pole switch with one pole for mute and the other to power the LED. The LED series resistor can be very small since it's already got 3.4K in series at phantom supply. So maybe a few hundred ohms just to prevent robbing the mic of supply too much. Otherwise, if it's a little slow to charge up, the mic might not come out of mute as quickly as you might like.

 

[Whoops]

Thanks,
I prefer to have both LEDs, Green and Red.
I can use low consumption ultrabright LEDs, so the current draw is lower

"Otherwise, if it's a little slow to charge up, the mic might not come out of mute as quickly as you might like."

No problem at all if there's a slow charge, being it in the MIC or the LEDs as this is to be used between songs, so slow charge works perfectly fine,

 

[Bo Deadly]

I can use low consumption ultrabright LEDs, so the current draw is lower

Won't work. Phantom supply has 3.4K source resistance. So even with two 22K in parallel the phantom voltage will drop by ~11V already. And that's only like 4mA which is going to make for a super dim LED.

 

[Whoops]

Thanks,
with most condenser mics I will use the current draw of the Mics is around 2mA, 5mA max, so I think there's margin to work around the limitations and have the 2 LEDs.  Thats my goal and what I'm trying to achieve with this thread and your help.
I'm more concerned of possible Pops/Clicks when switching, but I will try PRR suggestion next time I go to the shop.
thank you so much

here is a list of condenser mics and their current draw:
https://www.sounddevices.com/phantom-powering-basics/

 

[Whoops]

Won't work. Phantom supply has 3.4K source resistance. So even with two 22K in parallel the phantom voltage will drop by ~11V already. And that's only like 4mA which is going to make for a super dim LED.

Low consumption LEDs are bright with 2mA

https://www.banzaimusic.com/5mm-low-current/

 

[Whoops]

Hello friends,
I have some doubts on how to make a Bipolar cap out of 2 Lytic capacitors.

In the Crown notes for the circuit for the Mic Mute circuit, there's a 1000uf 6,3v non-polarized capacitor, they say to use 2 caps in parallel to achieve a Bipolar cap:

"To create the 1000 uF capacitor, you could use two 470 uF polarized capacitors in parallel, wired in opposite polarity."

I've followed this advise in the past and have done it this way for this circuit, but then everywhere I read on this subject people say that to do a Bipolar cap out of 2 Polarized capacitors you need to connect them in series and join the - (negative terminal) ends.
I see no one advising on connecting them in paralel wired in opposite polarity, this is what I've seen recommended:

"Connect in the following manner
--|(--)|--
Short both the -ve terminals. The other two +ve terminals can be used as leads of a non-polar capacitor.
I know that if you do like this the capacitance will reduce by 1/2."

Which is the correct way of doing this?

Maybe there's a mistake in Crown notes for the circuit

Thanks

 

[mjmajilton]

Hello friends,
I have some doubts on how to make a Bipolar cap out of 2 Lytic capacitors.

In the Crown notes for the circuit for the Mic Mute circuit, there's a 1000uf 6,3v non-polarized capacitor, they say to use 2 caps in parallel to achieve a Bipolar cap:

"To create the 1000 uF capacitor, you could use two 470 uF polarized capacitors in parallel, wired in opposite polarity."

I've followed this advise in the past and have done it this way for this circuit, but then everywhere I read on this subject people say that to do a Bipolar cap out of 2 Polarized capacitors you need to connect them in series and join the - (negative terminal) ends.
I see no one advising on connecting them in paralel wired in opposite polarity, this is what I've seen recommended:

"Connect in the following manner
--|(--)|--
Short both the -ve terminals. The other two +ve terminals can be used as leads of a non-polar capacitor.
I know that if you do like this the capacitance will reduce by 1/2."

Which is the correct way of doing this?

Maybe there's a mistake in Crown notes for the circuit

Thanks

Series neg to neg is correct.

 

[Hubbub]

My thinking is it depends on the voltage you expect across the combined capacitors. For high voltages connect equal value caps in series neg to neg. But I learned to always add a diode across each cap to prevent any significant reverse voltage on either cap. Note that those diodes complicate the effective capacitance result. If significantly charging / discharging the combo the capacitance is 1/2 the rated value until a diode starts to conduct, at which point the capacitance increases to the full rated value. Might not work well for audio!

Since an aluminum electrolytic can tolerate a modest reverse voltage (3V?) it makes sense that for very low operating voltage (which is likely the case for a 6.3V rated cap) that one can just parallel two equal value caps back-to-back and get an equivalent capacitance that is twice the individual value. So I agree with the Crown suggestion, but only if there is minimal DC across the capacitors.

 

[Whoops]

Thank you so much for the explanation Hubbub

 

[Hubbub]

Now that I went back and looked at the mute switch schematic I see it is across a phantom powered mic cable. Ideally the cap would see zero volts across it, but with 5% resistor values the cap might see a few percent of the 48V phantom supply, say 1V at most. Definitely the 2 back-to-back 6.3V 470uF caps is the way to go.

 

[Whoops]

Thank you

 

[Newmarket]

Now that I went back and looked at the mute switch schematic I see it is across a phantom powered mic cable. Ideally the cap would see zero volts across it, but with 5% resistor values the cap might see a few percent of the 48V phantom supply, say 1V at most. Definitely the 2 back-to-back 6.3V 470uF caps is the way to go.

Except that back to back 470u caps will give you total 235u.
You need to double the value when in series (back to back) so you'd need 2 x 2000u caps (or equivalent network) "back to back".

 

[Newmarket]

And that's only like 4mA which is going to make for a super dim LED.

Just use low current / high efficiency leds. 2mA is usual. Adjust down to taste. Viewing angle can be as/more important than brightness alone.

 

[Whoops]

Just use low current / high efficiency leds. 2mA is usual. Adjust down to taste. Viewing angle can be as/more important than brightness alone.

I already built units with the PRR circuit for the LEDs,
I don't remember at the moment if I used Low Current LEDS or not, probably yes but not sure,
anyway the circuit works great and the LEDs light are easily seen, no problems with that.
Also most Concerts are at night or in dark places, so that even gives some extra help.

But the PRR circuit is great.
I miss PRR tremendously, what a Star he is

This is the Final correct circuit, it's built and Tested many times,
it works Great, no clicks and no Pops while switching and the LEDS work great also, it's 100% tested:

 

[Whoops]

This was the first unit I did, no PCB, the component count is so reduced that I did it Point to Point.
It’s used in Live Shows all the time, works great