Expand the description to see the chapter links, there are three sections to this video! Also for the links to schematics etc. I've not done any audio processing at all on these recordings, so there is ambient noise from the PC and also electrical noise from that powering the Focusrite, somewhat extreme when I turn the gains to maximum; it is an audio quality test so I did not want to skew anyone's perception by noise reduction or gain levelling. There will be two further videos for the dynamic mic preamp: Building one on stripboard, and assembling the surface mount version in to an inline casing.
Hi there. Very interesting an awesome video. Could you perhaps do a video on converting a cheap battery powered Lav like a Boya BY-M1 to allow powered connections to "plug in power" mics. I have a Rode Video Micro which is really awesome but you cannot connect it to a mixer directly to line in given that it requires plug in power. The Boya BY-M1 uses a tiny battery which allows it to work as a line in device but can also work with plug in power. Would be really cool to see if the circuit can be made into a "plug in power" system. So instead of a Lav mic at the end, it would instead have a 3.5mm female connector? Thanks again for the awesome content.
Hi, apologies for the delay, I somehow missed your comment. If you are wanting to connect such mics to XLR mic input mixers, you could use the circuit from my condenser mic mod board; see the "Cheap mic mods part 3" video, follow the link in that to the project page on my site, then see the "Mic audio PCB parts and diagrams" link in that. Mics with 3.5mm plugs that need external power generally just electret capsules in housings. If you follow the diagram using the components in the input section list for a two terminal electret capsule & whichever output section you prefer, that should work as an adapter to run a 3.5mm mic through to an XLR mic input with phantom power.
Hello, very interesting project, I want to build one to activate a passive ribbon microphone, unfortunately the ZTX851 transistor is not available here where I live, but I found something that could perhaps replace it, I am talking about the BC546b, which supports about 60V and is Designed for audio applications. In your opinion, could it work in this circuit? And if yes, should I change any polarization value? Thank you very much.
Hi, just about any decent NPN transistor that has suitable voltage ratings and gain should work OK. The 2SC2545 (or 2SC2546/2SC2547) would be excellent, as they are also very low noise & good gain, if you get any of those?
@@RJTC Hi, Just last night I finished mounting the BC546b and it sounds great! Very low noise and very good gain, thank you very much for sharing your research.
Hi, can you give me an advice how create a preamp for wm-61a capsule ? my setup is focusrite solo 3gent with phantom powered input, i make a simple connection this capsule to xlr ( wire 1 and 2 pin with 27kOm resistor and i got 9,6v for my mic ) BUT! To hear something i need increase gain lvl till 80-90% ( at this gain lvl i got background noise ) and now i thinking about make preamp, but idk how
Hi, the circuit for my mic mod board could be used - there is an option in the assembly info giving the parts for an electret capsule, I believe? Grab the assembly instructions PDF from the page here - it also has full schematics: robert-jenkins.co.uk/site/index.php/electronics-and-audio/designs-projects/23-microphone-modification-upgrade-circuit-boards
I've been through the chapters in the discription must be my phone i only see a faint wiring diagram can't see any values but thanks anyway I'll have to get a better phone 👍
@@martindoyle766 OK, they are quite clear on a PC, so I don't know what to suggest there.. If it's the Dynamic mic circuit, the resistor values are, approximately left to right: Input to ground: 4k7 Emitters to ground: 2K2 Bases to ground: 100K Base to collector: 470K Collectors to XLR pins 2 & 3: 47R Gain pot between the emitters: 1K Input coupling capacitors: 10uF, positive to transistor bases. The "PC Mic preamp" - Input to smoothing caps & output to smoothing caps: Both 4k7 Collector-base resistor: 220K, or somewhere between 100 - 470K by trial and error.. Emitter resistor, 100 Ohms or below, or a link. Smoothing cap(s) 47uF + optionally a 0.1uF Input cap to base: 47uF, positive to input.
Cheers I made a nice LM486 amplifier circuit with gain control potentiometer and volume potentiometer large capacitor 2000mf for a nice base output to the speaker there was no background noise at all I was impressed an IC so low powered could do so well so I made a BC547 simple Mike circuit to listen to the base of the speaker and flash led lights I fitted on top of the box to impress my little daughter it worked but the performance was bad it had to be right against the speaker to pick up the base of the speaker so that's why I want to try your Mike out it sounds a lot better to pick up the base of the speaker
@@RJTC thanks again for your help I can make it now it's far better than a low component mike there not worth waisting your time or components on cheers top man thanks 👍😁
I assumed that when one adjusted the gain they changed the amount of output amplification, but your video indicates the gain only changes the voltage/current from the microphone? If that's the case why not extend the gain in the Focusriite. Or add your circuitry? My guess is they want to maintain a certain level of noise or distortion. Can you explain more what's going on? Thanks!
Amplification within an audio system is usually done over a number of stages, each providing part of the gain (amplification). A preamp such as my design adds one more stage in front of the existing amplification chain, increasing the overall system gain. Audio gear or interfaces such as the Focusrite are optimised to work with the majority of microphones, with their gain adjustment range allowing any of the expected sources to be set to normal (just below clipping) level. The Shure SM7B is the only mic out of my entire collection that cannot work acceptably when connected directly to the Focusrite - and when I researched the mic online, it is a common problem as they have an unusually low level output. Many users resort to an inline preamp to get the SM7B audio level up to the same range as other mics. (But the available preamps are rather expensive, for what they are, so I made my own).
@@RJTC Interesting. Thanks! My 2-cents on the SM7B (I own one) is that is is designed to be used a few inches from ones mouth. That's where its large diaphragm's quality shines. So I've had no problem with my audio interfaces. If I need a mic to be further than a few inches I use something else! I find the RE20 a tad more forgiving. So that's what I use. But not arguing you or anyone shouldn't use it where you want it and with what amplification you want!
@@MaxoticsTV The Shure SM58 hand mic is frequently used in live performances with it virtually (or literally) touching the performers mouth, to maximise wanted audio vs. noise from other sources. In contrast, the SM7B is a fixed mount mic, so it's generally going to be further away from the users face - but its far less sensitive than the SM58! In my tests I have the two mounted side by side. The SM58 still gives ample output a foot or two away, which is vastly different to the SM7B. You certainly can use one without a preamp, but then the recorded audio needs boosting to reach -6db peak level, which also boosts any system or interface noise. A low noise preamp between the mic and interface avoids that problem.
@@RJTCthanks for your reply sir, after looking that tr in local shops, theres not available, the most common tr here is BD139 (80v) if I use it instead which component should I change to. I try to find BD137 but a little bit hard too. and also I want to ask about R near output (47) what happen if I change it smaller (33) or larger (68) which one better if (47) not available thank you sir
@@qrdaudio Unfortunately I do not think they would work well in that circuit. The datasheet minimum gain at low current is just 25, with no typical value listed. You really need transistors with a a gain near 200, or higher, for it to work well. If you want to try the BD139, get some spares and try to gain match them? Start off by replacing the 470K bias resistors with 220K, and see what voltage you get on the transistor collector; it should be somewhere between 24 - 36V or so. Try different transistors if needed to try and find two that give as near the same collector voltage as you can get. If then they have too high collector voltage, change both bias resistors down to 150K, or 100k, as needed. If it's too low voltage, increase both resistors - 270K, 330K or whatever works?
Expand the description to see the chapter links, there are three sections to this video! Also for the links to schematics etc.
I've not done any audio processing at all on these recordings, so there is ambient noise from the PC and also electrical noise from that powering the Focusrite, somewhat extreme when I turn the gains to maximum; it is an audio quality test so I did not want to skew anyone's perception by noise reduction or gain levelling.
There will be two further videos for the dynamic mic preamp: Building one on stripboard, and assembling the surface mount version in to an inline casing.
Always love to watch about microphone, low noise, noise cancelling.... but simple❤❤❤
Great video, great ideas!
Hi there. Very interesting an awesome video. Could you perhaps do a video on converting a cheap battery powered Lav like a Boya BY-M1 to allow powered connections to "plug in power" mics. I have a Rode Video Micro which is really awesome but you cannot connect it to a mixer directly to line in given that it requires plug in power. The Boya BY-M1 uses a tiny battery which allows it to work as a line in device but can also work with plug in power. Would be really cool to see if the circuit can be made into a "plug in power" system. So instead of a Lav mic at the end, it would instead have a 3.5mm female connector?
Thanks again for the awesome content.
Hi,
apologies for the delay, I somehow missed your comment.
If you are wanting to connect such mics to XLR mic input mixers, you could use the circuit from my condenser mic mod board; see the "Cheap mic mods part 3" video, follow the link in that to the project page on my site, then see the "Mic audio PCB parts and diagrams" link in that.
Mics with 3.5mm plugs that need external power generally just electret capsules in housings.
If you follow the diagram using the components in the input section list for a two terminal electret capsule & whichever output section you prefer, that should work as an adapter to run a 3.5mm mic through to an XLR mic input with phantom power.
Hi thank you so much for this. Much appreciated
Hello, very interesting project, I want to build one to activate a passive ribbon microphone, unfortunately the ZTX851 transistor is not available here where I live, but I found something that could perhaps replace it, I am talking about the BC546b, which supports about 60V and is Designed for audio applications. In your opinion, could it work in this circuit? And if yes, should I change any polarization value? Thank you very much.
Hi,
just about any decent NPN transistor that has suitable voltage ratings and gain should work OK.
The 2SC2545 (or 2SC2546/2SC2547) would be excellent, as they are also very low noise & good gain, if you get any of those?
@@RJTC Hi,
Just last night I finished mounting the BC546b and it sounds great! Very low noise and very good gain, thank you very much for sharing your research.
@@maramassaferro Great stuff! Thanks for letting me know!
Hi, can you give me an advice how create a preamp for wm-61a capsule ? my setup is focusrite solo 3gent with phantom powered input, i make a simple connection this capsule to xlr ( wire 1 and 2 pin with 27kOm resistor and i got 9,6v for my mic ) BUT! To hear something i need increase gain lvl till 80-90% ( at this gain lvl i got background noise ) and now i thinking about make preamp, but idk how
Hi, the circuit for my mic mod board could be used - there is an option in the assembly info giving the parts for an electret capsule, I believe?
Grab the assembly instructions PDF from the page here - it also has full schematics:
robert-jenkins.co.uk/site/index.php/electronics-and-audio/designs-projects/23-microphone-modification-upgrade-circuit-boards
Could not see wiring diagram as to faint to see might be my phone
The schematic PDF links are in the description, if you expand that?
I've been through the chapters in the discription must be my phone i only see a faint wiring diagram can't see any values but thanks anyway I'll have to get a better phone 👍
@@martindoyle766 OK, they are quite clear on a PC, so I don't know what to suggest there..
If it's the Dynamic mic circuit, the resistor values are, approximately left to right:
Input to ground: 4k7
Emitters to ground: 2K2
Bases to ground: 100K
Base to collector: 470K
Collectors to XLR pins 2 & 3: 47R
Gain pot between the emitters: 1K
Input coupling capacitors: 10uF, positive to transistor bases.
The "PC Mic preamp" -
Input to smoothing caps & output to smoothing caps: Both 4k7
Collector-base resistor: 220K, or somewhere between 100 - 470K by trial and error..
Emitter resistor, 100 Ohms or below, or a link.
Smoothing cap(s) 47uF + optionally a 0.1uF
Input cap to base: 47uF, positive to input.
Cheers I made a nice LM486 amplifier circuit with gain control potentiometer and volume potentiometer large capacitor 2000mf for a nice base output to the speaker there was no background noise at all I was impressed an IC so low powered could do so well so I made a BC547 simple Mike circuit to listen to the base of the speaker and flash led lights I fitted on top of the box to impress my little daughter it worked but the performance was bad it had to be right against the speaker to pick up the base of the speaker so that's why I want to try your Mike out it sounds a lot better to pick up the base of the speaker
@@RJTC thanks again for your help I can make it now it's far better than a low component mike there not worth waisting your time or components on cheers top man thanks 👍😁
I assumed that when one adjusted the gain they changed the amount of output amplification, but your video indicates the gain only changes the voltage/current from the microphone? If that's the case why not extend the gain in the Focusriite. Or add your circuitry? My guess is they want to maintain a certain level of noise or distortion. Can you explain more what's going on? Thanks!
Amplification within an audio system is usually done over a number of stages, each providing part of the gain (amplification). A preamp such as my design adds one more stage in front of the existing amplification chain, increasing the overall system gain.
Audio gear or interfaces such as the Focusrite are optimised to work with the majority of microphones, with their gain adjustment range allowing any of the expected sources to be set to normal (just below clipping) level.
The Shure SM7B is the only mic out of my entire collection that cannot work acceptably when connected directly to the Focusrite - and when I researched the mic online, it is a common problem as they have an unusually low level output.
Many users resort to an inline preamp to get the SM7B audio level up to the same range as other mics.
(But the available preamps are rather expensive, for what they are, so I made my own).
@@RJTC Interesting. Thanks! My 2-cents on the SM7B (I own one) is that is is designed to be used a few inches from ones mouth. That's where its large diaphragm's quality shines. So I've had no problem with my audio interfaces. If I need a mic to be further than a few inches I use something else! I find the RE20 a tad more forgiving. So that's what I use. But not arguing you or anyone shouldn't use it where you want it and with what amplification you want!
@@MaxoticsTV The Shure SM58 hand mic is frequently used in live performances with it virtually (or literally) touching the performers mouth, to maximise wanted audio vs. noise from other sources.
In contrast, the SM7B is a fixed mount mic, so it's generally going to be further away from the users face - but its far less sensitive than the SM58! In my tests I have the two mounted side by side.
The SM58 still gives ample output a foot or two away, which is vastly different to the SM7B.
You certainly can use one without a preamp, but then the recorded audio needs boosting to reach -6db peak level, which also boosts any system or interface noise. A low noise preamp between the mic and interface avoids that problem.
can we swap transistor with bc 141 sir?
They should work fine in that circuit; I'm not
sure what the noise level of those would be though.
@@RJTCthanks for your reply sir, after looking that tr in local shops, theres not available, the most common tr here is BD139 (80v) if I use it instead which component should I change to. I try to find BD137 but a little bit hard too.
and also I want to ask about R near output (47) what happen if I change it smaller (33) or larger (68) which one better if (47) not available
thank you sir
@@qrdaudio Unfortunately I do not think they would work well in that circuit. The datasheet minimum gain at low current is just 25, with no typical value listed.
You really need transistors with a a gain near 200, or higher, for it to work well.
If you want to try the BD139, get some spares and try to gain match them?
Start off by replacing the 470K bias resistors with 220K, and see what voltage you get on the transistor collector; it should be somewhere between 24 - 36V or so.
Try different transistors if needed to try and find two that give as near the same collector voltage as you can get.
If then they have too high collector voltage, change both bias resistors down to 150K, or 100k, as needed.
If it's too low voltage, increase both resistors - 270K, 330K or whatever works?