Can I add an LED to the Schoeps/Alice circuit ?

[smikofficial]

@Екатерина
thanks for your reply.
Are you saying to use 6.8K resistance instead of zener?
If not, do you mean to connect a new 48V power supply to the led part end of this circuit? I'm sorry. I'm a beginner, so I don't understand your explanation.

 

[Lampie519]

Drawing extra current from your phantom power supply for a LED is just plain silly...
The voltage drop of all resistors involved WILL add extra noise and could even be too much to feed your mic (that is your main goal isn't it).
The 6.8k's are standard in every phantom power supply and need to be accounted for when drawing power from it. Knowing that some phantom power supplies don't even reach the 48V it becomes clear that adding more "consumers" is not helping here....

 

[Khron]

The common power supply parameter is 48V30ma, but now most of them are only about 20ma.

Well, considering the absolute max you can draw through that pair of 6.8k's (that are insider the preamp) is 14mA, and that's at short-circuit (so 0v left for supplying ypur circuit), that 30mA figure is sort of a moot point, i'd say. Maybe that's what you should aim to supply to a pair of mic inputs?

If not, do you mean to connect a new 48V power supply to the led part end of this circuit? I'm sorry. I'm a beginner, so I don't understand your explanation.

Since you yourself admit you're that new at electronics... I promise i don't mean to be mean/cruel or to gatekeep, but... Might it be a better idea for you consider learning to "walk", before you "run"? And also, consider asking yourself why you might want to perform a mod like this, as in, what might be the practical purpose (if any), etc.

 

[smikofficial]

Well, considering the absolute max you can draw through that pair of 6.8k's (that are insider the preamp) is 14mA, and that's at short-circuit (so 0v left for supplying ypur circuit), that 30mA figure is sort of a moot point, i'd say. Maybe that's what you should aim to supply to a pair of mic inputs?



Since you yourself admit you're that new at electronics... I promise i don't mean to be mean/cruel or to gatekeep, but... Might it be a better idea for you consider learning to "walk", before you "run"? And also, consider asking yourself why you might want to perform a mod like this, as in, what might be the practical purpose (if any), etc.

@Khron
I understand the meaning of what you're trying to say. In the electronic circuit section, I've been studying it part by part, but I don't think it's easy to learn about the problems that arise when you try to put them together (with these microphones and preamplifiers). Nevertheless, I think it is desirable to continue studying.
If you could be a little considerate of this, I would really appreciate it.

 

[Khron]

Fair enough, but that still doesn't really explain why you feel you "need"(?) to do this modification in this microphone / circuit.

But by learning to "walk" before you "run", i meant more like, mess around with an adjustable power supply, or a battery, and some LEDs & resistor, measure things, experiment with those on their own first, understand them. Same goes for zener regulators.

Once you comprehend how those work (if not why), THEN you can start seeing how you can cobble them together.

But i'd anyway like to redirect your attention to the first paragraph of this message...

 

[smikofficial]

Fair enough, but that still doesn't really explain why you feel you "need"(?) to do this modification in this microphone / circuit.

But by learning to "walk" before you "run", i meant more like, mess around with an adjustable power supply, or a battery, and some LEDs & resistor, measure things, experiment with those on their own first, understand them. Same goes for zener regulators.

Once you comprehend how those work (if not why), THEN you can start seeing how you can cobble them together.

But i'd anyway like to redirect your attention to the first paragraph of this message...

I'm adding LEDs because I want to DIY a microphone like a conference microphone. If you look at products such as conference microphones, they are placed just below the capsule so that you can see the ON-OFF status with LEDs. Of course, there are products that are sold on the market, but it is to DIY the new microphone that I originally had. I am attaching a microphone picture that I have.

 

[Khron]

Ok, finally we're getting somewhere!

I'm quite sure, to all the rest of us, without this key piece of background information, your idea / request sounded "only" like adding some "bling" on a whim, for no practical or useful (audio) reason.

What sort of body will your mic be using, then?

 

[smikofficial]

Ok, finally we're getting somewhere!

I'm quite sure, to all the rest of us, without this key piece of background information, your idea / request sounded "only" like adding some "bling" on a whim, for no practical or useful (audio) reason.

What sort of body will your mic be using, then?

Body ? What metal housing do you mean? aluminium ! I already have new 16mm and 9.7mm capsules, and I also have xlr 3-pin connector. I'm going to change all the components inside that conference microphone.

 

[Екатерина]

Well, considering the absolute max you can draw through that pair of 6.8k's (that are insider the preamp) is 14mA, and that's at short-circuit (so 0v left for supplying ypur circuit), that 30mA figure is sort of a moot point, i'd say. Maybe that's what you should aim to supply to a pair of mic inputs?



Since you yourself admit you're that new at electronics... I promise i don't mean to be mean/cruel or to gatekeep, but... Might it be a better idea for you consider learning to "walk", before you "run"? And also, consider asking yourself why you might want to perform a mod like this, as in, what might be the practical purpose (if any), etc.

Oh, sorry, this parameter may be misleading. 48V30ma is the standard of a long time ago. I forgot where the standard is. I have seen many 30ma power supplies, and the largest one can provide 60ma. It may be used for multiple microphones. Generally, the overall current consumption is about 12ma in design. This led lamp may be more used for decoration. I have seen it on many Chinese microphones

 

[Екатерина]

It may be futile to modify the circuit of the conference microphone. It only needs to get clear sound, and even to limit the frequency band to 100hz~8khz in order to remove noise

 

[Lampie519]

In a conference situation there should be a DSP involved that will be able to take care of this...

 

[Migs 31]

Body ? What metal housing do you mean? aluminium ! I already have new 16mm and 9.7mm capsules, and I also have xlr 3-pin connector. I'm going to change all the components inside that conference microphone.

Good morning @smikofficial, "dobroe outro" to @Екатерина and the rest of you.

I can see the idea behind the led mod. I have seen leds and red lights who turn green, mainly in conference rooms/corporate meetings, usually with DSP yes.So the mic lights up when you are live etc.

But...I understand why most people in THIS forum are horrified by that idea. Most folks over here tend to put sound quality and performance above all the rest. Putting a led on this mic will draw more current and most likely add noise to your circuit. Exactly what I would't want.

Trying to be helpful. I have been working on a similar type of mic and once the microphone was connected, what I get at the XLR pins 2 & 3 - 37.1V and 10.7 mA. So, not even the 12mA that Ekaterina mentioned above. These are real life measurements on my mics with a commercial mixer.

Now, in other non-mic related circuit builds, my red leds need about 1.6V. Feed them with 12V trough a 1K resistor for roughly 0.01A (10mA). So that would mean almost no juice left for a mic circuit in itself.

PS: attached a pic of an Audio Technica conference type mic. All AKG, Sennheiser, Shure and other quality mic brands that I have used, have no LED. The way it is...

 

[Khron]

So there'

I have been working on a similar type of mic and once the microphone was connected, what I get at the XLR pins 2 & 3 - 37.1V and 10.7 mA. So, not even the 12mA that Ekaterina mentioned above. These are real life measurements on my mics with a commercial mixer.

Can't get around Ohm's law - phantom power being fed through a pair of 6.8k resistors, ANY current you draw WILL drop the voltage at the mic's XLR.

 

[smikofficial]

@Екатерина @Lampie519
I'm not trying to modify the conference microphone circuit, I'm trying to make a new PCB itself inside.
It is not intended to be used for a conference.

@Migs 31 thanks for reply.
I know conference microphones from famous companies. But I have a desire to make up what I have.
I understand that people in the forum don't use LEDs. I would like to get help from this question to study the desire to make and electronic circuits.

I learned from Phantom Power that adding new power for LEDs is not beneficial.
Even if I fail, I'm going to try it.

 

[rogs]

I've been trying to follow some of the points in this thread, but I have to say I'm confused? ..... Adding an LED in series with the Zener - as suggested in posts #6 and #7 by Lampie519 and Khron is the most obvious way..... As you've drawn in your series schematic in post #12

Slight loss of headroom (you'll never notice) and no extra noise or current drain. The zener noise decoupling from C2, C1 and R3 will perform just as effectively with or without the LED. You might like to add a further 100nF PET decoupling cap across C1 to remove any stray HF noise missed by C1, but it's probably overkill.

As this is not required as a remotely DSP controlled 'on' indicator, I can't see how any alternative way would be simpler or better?

 

[Khron]

Slight loss of headroom (you'll never notice) and no extra noise or current drain.

Would that be because the JFET gain rises with the rise in supply voltage?

 

[smikofficial]

Slight loss of headroom (you'll never notice) and no extra noise or current drain.

Would that be because the JFET gain rises with the rise in supply voltage?

@Khron
gain rises-> Mic level rises -> headroom loss?

@rogs
In fact, a very small loss of microphone sensitivity is fine. The sensitivity and sound of the microphone I used were not good either.

Of course, I learned that if you connect it in series, this problem is easily solved.
But I wanted to know how to add an LED to a circuit as an "optional" (how an LED exists in a circuit, but a circuit can work without having to connect it), so I thought it would be nice to know how to connect it in parallel. Thanks to the teaching of many people, I think using jumpers would be one way to connect in series and not use LEDs.

 

[Khron]

Thanks to the teaching of many people, I think using jumpers would be one way to connect in series and not use LEDs.

What jumpers, and connecting what in series with what?

 

[rogs]

Would that be because the JFET gain rises with the rise in supply voltage?

Not sure it would?...If anything, I think the 'extra volts' should probably add to headroom..
Think I may have had a senior moment there!

The schematic with the LED is series in post #12 doesn't show the details of the front end to be applied.
If the capsule is an electret. the phase splitting doesn't even need to be a FET....

I've found the attached schematic works well (Capsule does not have to be an EM204 specifically )

 

[Khron]

Not sure it would?...If anything, I think the 'extra volts' should probably add to headroom..
Think I may have had a senior moment there!

I don't know about that - i know the gain scales along with the supply voltage, just not sure how linearly (or not) I may well be way off the mark, but the clipping point is(?) correlated with the input voltage, rather than the supply

But i could still be talking out of my rear end, so don't quote me on that