Dynamic mic, pre amp vs amp

Well, the microphone of my headphones got broken and had to replace it with a dynamic microphone of 600 ohm.

As expected, the input is very poor in amplitude. I use it for classes and study group meetings, and would like zoom and discord not having to amplify the signal so much, so I already bough an amplifier circuit and a pre amplifier circuit that I didn’t receive yet.

I’m using a desktop PC with a regular sound card. My question is, Which of the circuits is a better choice?, Do I risk damaging my sound card if using one or another at about 5 volt?

The idea is amplifying the signal in a hardware way so my software not having to amplify it that much.

had to replace it with a dynamic microphone of 600 ohm.

Stage/studio microphones (with an [u]XLR connector[/u]) use a balanced (3-wire) connection and they are not (properly) compatible with a laptop or soundcard. In addition, pro condenser mics need 48V phantom power which is supplied by the audio interface, preamp, or mixer. Electret condenser computer mics get mics get 5V from the soundcard. (Dynamic mics don’t require power.)

and would like zoom and discord not having to amplify the signal so much, so I already bough an amplifier circuit and a pre amplifier circuit that I didn’t receive yet.

I’m using a desktop PC with a regular sound card.

The preamp output goes to line-in on your soundcard (usually color-coded blue).

Do I risk damaging my sound card if using one or another at about 5 volt?

The output signal from a preamp should be approximately [u]line level[/u] which is not directly related to the power supply voltage. (You shouldn’t connect a speaker-output to line-in.)

the microphone of my headphones got broken

That’s not headphones. That’s a headset. A set of headphone and microphone.

You don’t have a good combination of parts left even if it is a good dynamic microphone. If you get it to work electrically, you still have to find a way to hold it while you perform.

How much is it to replace the headset?

Koz

Replacing the headset would have be more expensive than the circuits I already bought (and spent my last cents on them).
So I decided to make use of this hand microphone I already have (the one that I mentioned to be of 600 ohm).

I have some alternatives, but was wondering if I could avoid them by simply using this mic and one of the circuits in the mic plug.

If really necessary, I guess this programs I use admit using the line-in as voice feed.
And I also got a UCA222 in april, however the quality of this microphone doesn’t justify its use, it is just a cheap mic.

And I also got a UCA222 in april, however the quality of this microphone doesn’t justify its use, it is just a cheap mic.[/quote

The UCA222 does NOT have a mic input, only a line-input.

If you’re not trying to get “studio quality” any cheap “computer microphone” should work with your soundcard (without an amplifier) as long as you are close-enough to the mic.

Or, a USB mic doesn’t need a preamp or soundard.

Your soundcard has a built-in mic preamp but it’s designed for a computer mic. (Your 600 Ohm dynamic mic probably isn’t a computer mic.)

Replacing the headset would have be more expensive than the circuits I already bought (and spent my last cents on them).

What “circuits” did you buy?

What microphone did you buy?



P.S.
Your dynamic mic might work with [u]Windows microphone boost[/u] depending on the balanced/unbalanced connection situation.

Yes, I know about the UCA222, however I think there is a chance this programs accepting a line-in as voice feed, however I was trying to avoid that.

The microphone is: Panasonic RP-VK21

The amplifier is a PAM 8403 based circuit

And the pre amplifer is a Tda 1308 based circuit

The microphone is: Panasonic RP-VK21

If that has 2-conductor[u]TS[/u] plug adapter it might work. I think it should work! I’m not surprised it has lower output than an electret condenser, plus you probably don’t have it as close to your mouth as your headset mic. (A 3-conductor TRS balanced connection can cause “weird problems” with a soundcard.)

The amplifier is a PAM 8403 based circuit

That’s a power amplifier (designed to drive a speaker). It’s designed for a line-level signal and it doesn’t have enough gain to work directly from a microphone.

And the pre amplifer is a Tda 1308 based circuit

That’s supposed to be a headphone amplifier. The chip itself has enough gain for a microphone do it depends on the circuit design. Typically, a “headphone amplifier” also takes a line-level signal so I wouldn’t count on it working with a mic.

Preamps can be tricky because it depends on the type of microphone you’re using. Stand-alone mic preamps for stage/studio mics are expensive! It’s cheaper to buy a USB audio interface with an appropriate mic input, or a mixer with a mic input (or a USB mixer). But those things are also beyond your budget.

I know about the UCA222, however I think there is a chance this programs accepting a line-in.

“Voice” is fine but NOT a microphone signal. And it’s not related to the software. A microphone signal is about 10mV and a line level signal is about 1V (100 times higher). The actual voltage depends on the loudness, the sensitivity of the microphone, and the distance between the sound source and the microphone. A microphone preamp typically has a maximum gain of about 1000 (60dB) with a volume/gain control so you’re not normally using all of the gain. The preamp in a soundcard probably has a gain of about 100.

About that this microphone should work, I’m already using it, but I need to get very close to it, and even that way, the input has low amplitude, I verified it with Audacity’s meter.

When saying that Discord and Zoom let me choice a line-in (or even stereo mix) as voice input, I mean that the sound from the source of my choice will be “bridged” so others to listen at that source instead. That’s why using the line-in or the UCA222 would be an option, however if my pre amp is not adequate, then I will have to keep yelling at the mic, since I was planing to use the pre amp to connect the mic into a line-in.

Tda 1308

Do you have the circuit board or just the 1308 chip? If it’s just the chip, you’ll have to build half of one of those boards (it’s stereo). Do you have it sorted where you’re going to get your five volts from?

Screen Shot 2020-09-18 at 6.32.22 PM.png596×521 310 KB

C1 and C4 are the DC blocking capacitors to keep battery out of the sound system.

R1 and R5 are the gain setting resistors. On a quick look that’s a gain of 10 or 20dB.

Pin 8 is (+) supply or 5 volts and Pin 4 is (-) supply or ground in this case.

There is no Right sound. so you don’t need C5, C2, R2, and R6.

I can’t quite sort what C3 and the two unnamed resistors are doing. I wonder if they’re setting the amp’s mid point at 2.5 volts—right in the middle.

Koz

I will have the whole board assembled (i bought it assembled, still waiting it to arrive), and I’m thinking in getting the 5 volts from a USB port or a cellphone charger.

You plugged the mic into your soundcard and it works, but not loud enough?

So your microphone cable has one of these on the end?

1/8" or 3.1mm or 3.5mm however they converted it. Does it have one black ring on the metal end or two like these?

Koz

It is a mono mini plug, like the 3.5 mm TRS without the “ring”, so 3.5 mm “TS”
(with ring I’m no meaning the black ring, but the ring that the R from TRS stands for)
In other words, it has just one black ring.

How are you going to get that signal into your little card when it comes?

Koz

Basically, I where going to connect the microphone to the input by welding a wire with a TRS plug and attaching an adapter to it in order to connect both 3.5 mm plugs.

Then I would weld another similar wire to the output, always respecting:

T → left
R → right
S → ground

The last step is welding a regular USB wire to the VCC.

However I’m still wondering if connecting the output to the mic in of my PC is a good idea, or if I should use the line-in instead.

There is no left & right and connecting a mono balanced signal won’t work properly.

However, if you have an unbalanced (TS) mono connection it’s OK to connect both left & right amplifier channels.

Typical Mic-In may give you 40dB of gain unless you’re on Windows and use the “Mic Boost” service. This adapter is good for about 20dB boost plus the 40dB giving you the 60dB gain you probably should have had in the beginning.

You’re building a Cloud Lifter. The Shure SM7 is a terrific microphone, but it doesn’t have a lot of volume. They made a device which goes between the mic and the mixer that uses Mixer Phantom Power (which the SM7 doesn’t need) to goose the volume enough to be useful. The Lifter and the SM7 are frequently sold as a bundle.

If you do overload the Mic-in, it will be pretty obvious. You’ll get flat tops on the waves and you won’t be able to control it.

If you do plug into Line-In, I expect it to be worse than you started out. The 20dB of the card will not be enough to do anything.

There is one downside to your lash-up. You may get a lot of SHSHSHSHSHSH hissing noise. Microphone amplifiers are rated by how quiet they are. This board is not expecting a super tiny voice signal. It doesn’t care what its noise is. But you might.

You’re not welding, right, you’re soldering?

Koz

One other handy number. One of my commercial dynamic microphones has a rated output under normal use of -56dB. That’s why your dynamic microphone makes you scream into it to make up difference between that and the 40dB boost of your computer soundcard. An extra 20dB boost should make up the difference without screaming.

And a word on dynamic microphones. That just means moving coil. Wave a coil of wire in front of a magnet and it will make a tiny electric signal. Make your voice vibrate the coil and it will make a voice signal.

That’s it. We just designed a dynamic microphone.

Koz

Ah, soldering, I see.

But, why there is no left & right?

And, Which are those thing we are supposed to connect to a line-in if connecting a speaker out is not a good idea? I mean, What is the line-in for in that case?

But, why there is no left & right?

There will be if you make one. The little board has two independent amplifiers and the only thing common is the five volt rails and ground.

Solder your dynamic microphone “hot” wire to both Right and Left channel inputs. The microphone shield goes to the GND connection in the middle.

That will send the microphone signal down both of the amplifiers on the little board.

It’s the output of the little board where it gets a little magic. The volume boost of the chips is the ratio of two resistors. In the case of Left, that’s R1 and R5. In one of the designs I saw, one is ten times the value of the other. That’s a boost of ten. Plug that into the dB formula.

20LogV1/V2. V1/V2 comes out 10. Log of 10 is 1, times 20 is 20. So whatever you jam in there is going to come out 20dB louder and it doesn’t much care what you connect to the output. That’s why I wasn’t horrified when you said what you wanted to do. I expect it to work.

The only difference between a signal amplifier, headphone amplifier, and speaker amplifier is the horsepower, not the volume. Speaker amplifiers are big and beefy to get rid of the heat they make horsing around a speaker to make loud sound. If you don’t have speakers or headphones, there is no heat.

It’s pretty simple to connect the little board L OUT to the L IN of your stereo soundcard. R OUT to the R IN. The only problem with that is the little card only has 20dB of boost and you need 60dB. The computer soundcard has no boost at Line-In. That’s what the Mic-In does.

I hope you have your soundcard instructions. Mic-In connections can be magic.

https://www.kozco.com/tech/audioconnectors/audioconnectors.html

It’s a snivvy out of date, but plain computer soundcards still work like this. Many computer microphones need power from the computer to work. That’s the electret condenser microphone thing. It needs an amplifier to work right and that means you have to power it somehow. This is how. Battery goes up on the ring (middle connection) and sound comes back down on the tip.

So I would take the little card LEFT-OUT and jam that into the MIC-In tip and the Card ground or shield and put that on the connector shield and don’t worry about the battery. It’s isolated and won’t blow anything up. You know when you plugged your dynamic microphone straight into the soundcard Mic-In? You were shorting out the battery connection.

That’s only one of the configurations of computer soundcard. This is where you go for your instructions.

But if it’s pretty normal, I expect your voice to go through way hotter than it was…along with an increase in the background noise (fffffffffff).

Post back how it goes.

Koz

Missed one. If you do use the Mic-In, you don’t use the Right amplifier on the little board.

Koz