Hi All,
If you are not interested on reading long posts, then simply jump to Actual Question section below.
I'm new to this forum.
Last weeks did some play with pc line-in, and just connected my mobile phone to PC's line in with an AUX cable. when did play music on mobile and heared it from headphone, i just thought it is ultra clear sound for me! currently my PC is very old, probably my case cost about $20-$30 overally, but the onboard line-in does a good job at 24bit, 48KHz sampling. So decided to create a mic and preamp instead on Buying one. so bought several electret mic, which seller told me they have reasonably good quality for the cost:
I would like to use two of electret microphones (triple wire electret mic) and through a pream, feed it into line in of my PC. Was not able to find appropriated preamp schematic specially for this purpose.
The reason i'm doing this is line in of my PC have a pretty good quality as I've said (24bit 46KHz) but mic-in had terrible noises.
When directly connect mic to my line in, then (as expected) there is high noise with a little non-noise sound 🙂
All i understand from searches is to need to amplify the mic-level to line-level, which approximately need 1000x amplification (+60 db of gain). After hours of searching i've seen several preamps which is tested and seems working good:
There is also another one which is 1000x gain amplifier is three 10x stages: https://sound-au.com/project158.htm
So based on those two preamps, did designed some schematics for new 1000x gain preamp. Which mixes two electret mic output and convert to the line-level signal. which you can see below:
Also note that i'm newbie in the electronic field, more i'm a progammer guy instead of electronic one.
Consider this schematic. It have two electret mic input, after 10x amplify of each one, mixes them into one signal, and through another two 10x stages, the final result is ready. total gain is about 1000x which i think is quite good for converting mic level to line level.
Microphone: there are two electret mics (each have 3 pins). i do feed a 1.5V AA battery bias to it and feed the output of mic to the schematic below
Stage 1: There are two mic signal, which have about 500mv DC offset. amplify it with 10x the (I know 500mv ofset also amplified), then use 2 caps to remove dc from signal, and then simply mix the both signals with shorting them together.
Stage 2 & 3: output of stage 1, is 10x amplified. stage 2 and 3 also each one 10x amplify the result and finally I think there should be 1000x gain 🙂
What do you think about this preamp? Does it work the way i expected? do you see any specific points which it will fail? I would be thank full for your opinions.
Because I'm newbie to this area, I need your talented guys's opinion about this schematic. Then i'll start to make and test it
Link to full schematic:
https://oshwlab.com/epsi1on/5532-preamp
If you are not interested on reading long posts, then simply jump to Actual Question section below.
I'm new to this forum.
Story and motivation
=============Last weeks did some play with pc line-in, and just connected my mobile phone to PC's line in with an AUX cable. when did play music on mobile and heared it from headphone, i just thought it is ultra clear sound for me! currently my PC is very old, probably my case cost about $20-$30 overally, but the onboard line-in does a good job at 24bit, 48KHz sampling. So decided to create a mic and preamp instead on Buying one. so bought several electret mic, which seller told me they have reasonably good quality for the cost:
I would like to use two of electret microphones (triple wire electret mic) and through a pream, feed it into line in of my PC. Was not able to find appropriated preamp schematic specially for this purpose.
The reason i'm doing this is line in of my PC have a pretty good quality as I've said (24bit 46KHz) but mic-in had terrible noises.
When directly connect mic to my line in, then (as expected) there is high noise with a little non-noise sound 🙂
All i understand from searches is to need to amplify the mic-level to line-level, which approximately need 1000x amplification (+60 db of gain). After hours of searching i've seen several preamps which is tested and seems working good:
So based on those two preamps, did designed some schematics for new 1000x gain preamp. Which mixes two electret mic output and convert to the line-level signal. which you can see below:
Also note that i'm newbie in the electronic field, more i'm a progammer guy instead of electronic one.
Current Scehamtic
============Consider this schematic. It have two electret mic input, after 10x amplify of each one, mixes them into one signal, and through another two 10x stages, the final result is ready. total gain is about 1000x which i think is quite good for converting mic level to line level.
Microphone: there are two electret mics (each have 3 pins). i do feed a 1.5V AA battery bias to it and feed the output of mic to the schematic below
Stage 1: There are two mic signal, which have about 500mv DC offset. amplify it with 10x the (I know 500mv ofset also amplified), then use 2 caps to remove dc from signal, and then simply mix the both signals with shorting them together.
Stage 2 & 3: output of stage 1, is 10x amplified. stage 2 and 3 also each one 10x amplify the result and finally I think there should be 1000x gain 🙂
Actual Question
==========What do you think about this preamp? Does it work the way i expected? do you see any specific points which it will fail? I would be thank full for your opinions.
Because I'm newbie to this area, I need your talented guys's opinion about this schematic. Then i'll start to make and test it
Link to full schematic:
https://oshwlab.com/epsi1on/5532-preamp
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Sixty dB is rather high for those microphone capsule. The first section of the schematic makes little sense to me.
I think it is drawn wrong with the 10uf cap shorting out the 9K resistor and the resistor leads connected wrong.
I think it is drawn wrong with the 10uf cap shorting out the 9K resistor and the resistor leads connected wrong.
Did replaced the 10uf with 1nf, I think it is better now. also about wrong leads you are right 🙂 they are fixed now
i coppied from this:
Sure, do the resistor values seems right for tl072 non-inverting amplifier? i mean 1k and 9k resistors in stage1.
Thanks
I don't know...the last time i made a preamp for electret mics was18 years ago...just look up for a known working schematic.There must be zillions of them outhere.I only remember using jfet opamps for lower noise.
I think you connected wrong the microphone.
1. Electret microphones need power and you didn't put one.
2. Taking into account "1." I think that one of the wires of the microphone you have is for its internal power supply.
1. Electret microphones need power and you didn't put one.
2. Taking into account "1." I think that one of the wires of the microphone you have is for its internal power supply.
Just use a circuit like this. None of those shown will work at all,
and there are not even any single supply modifications added, which are absolutely necessary.
Use one TI circuit for each electret mic, then the two outputs go into a simple two input mixer,
which could even be just two resistors.
https://www.ti.com/lit/ug/tidu765/tidu765.pdf
and there are not even any single supply modifications added, which are absolutely necessary.
Use one TI circuit for each electret mic, then the two outputs go into a simple two input mixer,
which could even be just two resistors.
https://www.ti.com/lit/ug/tidu765/tidu765.pdf
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the power supply for mic is outside this schematic.
this is the order of triple pinned electret mic:
Will feed 5v directly to mic, simple ignore parts and use Audio and GND pins to input of my schematic
Thank you for the reply.
There is mistake in schematic which is fixed now (replaced GND with -VEE for opamp). this is update one.
Will this schematic work for dual supply? my schematic is dual supply VCC/GND/VEE. have an old AC adapter and will use the output to make dual supply.
Thanks
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I'm almost sure it won't work.
How is polarization achieved for the repeater transistor in the microphone? Drain and source at the same voltage?!? Where does the signal from the sound sensor travel?
And even if the polarization is realized somehow, you add in phase two signals that should be in antiphase and after the addition they cancel.
How is polarization achieved for the repeater transistor in the microphone? Drain and source at the same voltage?!? Where does the signal from the sound sensor travel?
And even if the polarization is realized somehow, you add in phase two signals that should be in antiphase and after the addition they cancel.
Perhaps, but there is too much is missing to say. The entire circuit, from input to output, must work together properly.
latest schematic: https://oshwlab.com/epsi1on/5532-preamp
guys this is latest version, with edits you mentioned:
this is only stage 1, full schematic available at
this is stage 2 and mixing:
Thanks
guys this is latest version, with edits you mentioned:
this is only stage 1, full schematic available at
edits to main schematic should make it clear now, not sure if points you mentioned are resolved. Can you please give more explanation or some keywords for googling?
this is stage 2 and mixing:
Thanks
Attachments
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Why?
To the OP: congratulations for getting into Electronics 🙂
That said, you can build any properly designed "working" design, as is, respecting it, and you will succeed, but you are still too "green" to design on your own.
There is so much wrong with those schematics that it´s useless to correct all errors one by one, ... just to find new errors later.
Which is avoided by building a properly designed and tested one.
The proper sequence is crawl > walk > run in due time, do not jump steps.
You are not actually "designing", just copypasting bits and pieces here and there.
End result "may" work ... only by sheer chance, better take the proper steps, rewards will be immense.
Drawing seems to show so, but it´s not a balanced mic input, just 2 independent Electrets picking up ambient sound.
Probably some gross grounding or miswiring problem, you will not solve that with a preamp.
PS: I see you show an ESP design.
Cool, Rodd Elliott is a great guy, very generous with his knowledge, and a very solid, foots on the ground designer, I suggest you read all he writes and build all projects you wish as-is , can´t go wrong with any of them.
PS2: you do NOT want 1000X gain with an electret mic by any means; they are "loud" to begin with (unless you want to pick whispers 100 feet away), 10X is enough for normal conversation levels into a PC Aux In
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Because of the link found at the bottom of this post:
https://www.diyaudio.com/community/...32-mic-pre-amp-schematic.391231/#post-7147564
Sorry, not sure which one.
Many links in this thread and "the bottom" one keeps changing all the time.
Many links in this thread and "the bottom" one keeps changing all the time.
I think the version of post #11 could work with these changes:
U8 and U9 are way too high, 10 kohm would be more reasonable - or whatever value is recommended by the microphone manufacturer, they have to conduct the current needed to bias the JFET inside the microphone capsule
U7 and U17 are too small, 1 kohm would be better
Please add power supply decoupling capacitors for each NE5532
Is 1.5 V drain voltage enough for the microphone capsules? If not, that also needs changing.
When that is done, the first stage might clip due to the amplified DC bias voltage at the microphone output. One way of solving it is putting 22 uF electrolytic capacitors between U4 and ground and U5 and ground.
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I wouldn't want excessive gain to pick up whispers at 30.48 m distance either. When the gain is high enough to make the microphone noise dominate over the sound card noise, any further increase just reduces headroom unnecessarily.
Besides, U16 and U14 are still a bit on the high side and cause some treble loss, 220 pF or so would be better.
By the way, it's unusual to use Usome_number as a reference designator for all components, it's usually used only for integrated circuits and for modules. Resistors are typically called Rsome_number, capacitors Csome_number, diodes Dsome_number and transistors Tsome_number, Trsome_number or Qsome_number depending on who you ask.