I wanted a pre-amp for electret capsules which allowed for higher SPLs and lower noise levels. I came across this design: Simple Stereo Electret Mic Preamp and it seemed like it would fit the bill.
Not sure what I did wrong but the output is really really quiet and sounds very tinny. There's also quite a lot of noise. I've removed the 27k resistor so the gain should be 23.
This is pretty much my first circuit so I'm not entirely sure what's going on here. I probably did something stupid.
Maybe these photos will help. Excuse the terrible soldering:
Not sure what I did wrong but the output is really really quiet and sounds very tinny. There's also quite a lot of noise. I've removed the 27k resistor so the gain should be 23.
This is pretty much my first circuit so I'm not entirely sure what's going on here. I probably did something stupid.
Maybe these photos will help. Excuse the terrible soldering:
Schematic would help.
You should have cleaned yopur board before you soldered any thing to it.
I scrub mine down with a green scrubby or some steel wool.
What type of mic. element are you using, They are not exactly quiet anyhow ,but some are better than others.
jer
P.S. The links do not work.
You should have cleaned yopur board before you soldered any thing to it.
I scrub mine down with a green scrubby or some steel wool.
What type of mic. element are you using, They are not exactly quiet anyhow ,but some are better than others.
jer
P.S. The links do not work.
There's a schematic in the link, I'll embed it here:
The element I'm using is by no means hi-fi. Cost me like $3. I'm not actually sure what it is tbh... I'm trying to get as much performance as I can out of it but I'm not expecting it to suddenly become amazing. It sounds much better with a simple one resistor, one capacitor, and a 9v battery circuit than with this though, so something is definitely not right.
What does cleaning the board achieve?
Thanks.
The element I'm using is by no means hi-fi. Cost me like $3. I'm not actually sure what it is tbh... I'm trying to get as much performance as I can out of it but I'm not expecting it to suddenly become amazing. It sounds much better with a simple one resistor, one capacitor, and a 9v battery circuit than with this though, so something is definitely not right.
What does cleaning the board achieve?
Thanks.
I think if you reduce the gain of the preamp you may have better luck as it is also amplifying the noise that Mic. is producing as well.
I tried doing this a long while back hoping that I could have decent mic to do some recording with.
The capsule I had got did have a good and clean sound to it, but in my case it was to noisy for me to work with on my recording equipment.
There just wasn't any way to get rid of the hiss.
The gain of your circuit is more around 34, this is much higher than you probably had expected.
Try reducing the gain significantly and maybe you can find a happy range.
You can replace the 1k with a Pot to make it adjustable and then when you find the proper range replace it with a resistor with the corrected value.
jer
I tried doing this a long while back hoping that I could have decent mic to do some recording with.
The capsule I had got did have a good and clean sound to it, but in my case it was to noisy for me to work with on my recording equipment.
There just wasn't any way to get rid of the hiss.
The gain of your circuit is more around 34, this is much higher than you probably had expected.
Try reducing the gain significantly and maybe you can find a happy range.
You can replace the 1k with a Pot to make it adjustable and then when you find the proper range replace it with a resistor with the corrected value.
jer
@fraseyboy, did you have permission to post that schematic? if not please edit your post to show links instead.....thank you...
The schematic is in the link I had in the OP (Simple Stereo Electret Mic Preamp), pretty sure that's the original author.
I don't think it's a result of the mic. Something definitely sounds 'wrong'. Like it's being recorded underwater...
Edit: I tried putting in a resistor to reduce the gain and it sounds pretty much the same... Also the pot I have doesn't seem to affect the volume at all.
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You also need to have the other opamp terminated else it can oscillate and cause noise withing the chip.
To do this tie the output to the -input and the +input to your virtual ground (IE 27K+27K point).
It could also be a bad capsule.
I once had gotten a bad one that didn't work as well.
And I was out $2.99 from Rat Shack!!
jer
To do this tie the output to the -input and the +input to your virtual ground (IE 27K+27K point).
It could also be a bad capsule.
I once had gotten a bad one that didn't work as well.
And I was out $2.99 from Rat Shack!!
jer
You also need to have the other opamp terminated else it can oscillate and cause noise withing the chip.
To do this tie the output to the -input and the +input to your virtual ground (IE 27K+27K point).
It could also be a bad capsule.
I once had gotten a bad one that didn't work as well.
And I was out $2.99 from Rat Shack!!
jer
Okay, I'll try that.
Oh, I thought my virtual ground was at the output jack? That's where I wired all my grounds to.
Right, I've done that. Also bypassed the input jack by soldering the positive and negative wires directly to an electret capsule. It doesn't seem to be working at all now... I've poked around with a multimeter and there seems to be voltage everywhere. I get about 4.3v on the positive input leg of the opamp and 0.3v on the negative input leg. Also I'm getting like 0.25v across the input and output legs of the pot and 2.5v across the positive and negative of the microphone. Are these all normal?
Ah yeah, I didn't connect the power directly to the mic, I just took the wires that were going to the 3.5mm jack and connected them to the mic instead to rule out a faulty jack or cabling.
The voltage I measured is DC on pin 2 and 3 of the pot, where ground is on pin 1. There's no voltage between pin 1 and 2 or 1 and 3. Is that not okay?
The voltage I measured is DC on pin 2 and 3 of the pot, where ground is on pin 1. There's no voltage between pin 1 and 2 or 1 and 3. Is that not okay?
It is hard to follow you since none of the components in the schematic have labels to them.
If pin 1 of the pot is connected to ground and there is no voltage between 1&3 and/or 1&2 then it is impossible for there to be any DCvoltage between 2&3.
There should not be any DC voltages on that side of the circuit.
Since you have now moved your power cables make sure that the opamp is getting power as well.
jer
If pin 1 of the pot is connected to ground and there is no voltage between 1&3 and/or 1&2 then it is impossible for there to be any DCvoltage between 2&3.
There should not be any DC voltages on that side of the circuit.
Since you have now moved your power cables make sure that the opamp is getting power as well.
jer
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