Recently built a pre amp based on a opamp, worked, but had hella hissing noise. Found your channel, liked the results you presented, replicated the circuit. Works like a charm. Thanks dude
Works beautifully. I packed in into a plastic box which I coated from the inside with aluminum foil and then insulated. The foil is connected to the ground (minus) and all noise is gone.
I've built this and also got a local FM station just like you. Wound a common mode choke in an FT-50 -43 ferrite at the input and it almost cured the noise. But when placed a 100pF across the base and emmiter of Q1, it made One of the quietest DIY preamps i've ever listened.
Interesting, thanks! The next time I have to change the 9V battery, I'll give that 100p cap a try as well and see if I can detect a further noise reduction.
Did anayboy: 1. use the design with an mic input transformer? 2.used it with alectred microphones? 3.designed a build low pass filter? Thank you Regards Peter
I really like your circuit and also the box you made for it . I was wondering,is there a way to connect this to a laptop?The laptop doesnt have a line in,only a standard audio jack same as in mobile phones..
It seems like the base bias for Q2 is kinda flapping in the breeze... I've been taught that it's best to use divider of one kind or another (resistors, diodes), or some other method to make sure you have the voltage you think you're supposed to have at the base. I wonder... is tha why the gain is unexpected for a couple of you folks?
@@user-nx6ep7jz4w That 3.3meg resistor sets the amount of negative feedback to control the gain of the output stages. It could be made smaller or larger for less or more gain.
Really like this project. Although I don't have a mike to test it on yet, but I understand this is more suited for a dynamic rather than condenser type. What would be the modifications to make this project suited to a condenser mike? I'd be quite interested in building that one! Anyway, I sub-ed and think that your channel is awesome and deserve alot more subs than you have now.
Yep, the link is broken. I've reached out to the author, waiting for a reply. If there's a new site I will update the link. For now I've updated the comments to show it as broken.
Thanks for the tip. The PG48 definitely picks up every tiny mechanical vibration. Its actually an annoyance, I have to be very careful not to touch it while I'm speaking. Wouldn't buy one for blogging, but it was what I had so I roll with it.
Hi Darren, first wish you channel to be successful. I am also thinking of building a mic-amp. When I put your (or Andy Collinson's) circuit into a simulator (I used the now free Micro-Cap software), I found that the gain of this amp is over 2700 (1mV in 2.75V out), instead of 97 as claimed by Andy. Since this is much higher than required, I also looked at your SPICE simulation result and found that your result is about 750/57.5dB (2mV in 1.5V out), although much lower than mine, it's still too high for a mic-amp (for dynamic mic's). In fact I believe the gain should be best around 100/40dB as Andy's stated. Do you have to tune the volume down a lot? Or do you have any idea to tune down the gain?
Thanks for the comments! Yes, I have found this amp to have a lot more gain than I need to drive the mic input on my PC. I have the pot around 10% - 20% of full travel and that is plenty of drive. At higher drive, it has enough oomph to provide a line level signal.
The gain is set by the relation of the collector/emitter load of Q1 and Q2. 10k/0.47k*23.5k/0.566k = 883, which is pretty close to 750 (57.5dB). You'll get the ridiculously high gain (in simulation) if you forget to put the mike output impedance (600 Ohm) into the equation. Why 23k5/0.566k and not 47k/0.6k? Because there is a 47k pot and a 10k resistor in parallel with the collector/emitter load of Q1, respectively. All these values are theoretical, as they ignore the input impedance of every next stage - which is both far from infinite and varies with frequency, so the real figures might be about half that. This circuit has no global negative feedback, and therefore the actual gain of the system (and the DC bias at the Q3 emitter) will vary greatly depending on the transistors type, their temperature, and probably the wind direction and the weather on Mars too. Its PSRR is virtually non-existent, so all the noise at the supply rail will be amplified and transferred to the output. The circuit is old. It probably goes back 4-5 decades, because I can totally see the valve origins of some of the design ideas.
Yep, the link is broken. I've reached out to the author, waiting for a reply. If there's a new site I will update the link. For now I've updated the comments to show it as broken.
Hello. Great work. I have a question about this preamp. I built my own and plug it into "line in" port in my computer and it makes a lot of noise and weird sounds. I have tried few preamps based on transistors and any work good enough. I have used bc547 in this circuit. Can it be problem with sound card or I must ground circuit or something? I use headphone speaker like microphone and it's impedance is about 40ohm maybe it is a problem. Anyway good content I subscribed 🔥
Thanks for subscribing! I would think the BC547 is fine, that's what Andy's original circuit used. I would suggest to try it without a mic plugged in, to see if the issue remains. If so, then there likely is something amiss with your circuit construction. Also make sure you're using a dynamic mike, I am not sure if this would work with a condenser mike.
Try isolating the preamp from your computer. You can take a small speaker, say a 0.25 watt 2" size speaker, and connect it to the output of the preamp. With the gain potentiometer turned up to near max, you should be able to hear your voice when you speak into the mike. If it sounds good, then the problem is in your computer, if it sounds bad, then there is something miswired in your preamp.
@@levelupeelab I did like you told and it work without noise but sound is really distorted but I think It is ok becouse of high gain. In this attempt I used cheap mic with good impedance ~600 ohm but when I plug this 40 ohm speaker like a mic and rotate potentiometer it becomes a frequency generator😆. I plug also coil with ferrite like you and it works a little better. I think it is problem with all electromagnetic stuff so I will try metal case for it and find some better wires to good electromagnetic isolate. What do you think ☺️
i had the same problem try changing the power supply many power supplies dont have a (isolated) ground connection and this can cause noise i took a computer PSU and used an isolated from the mains ground connection and had no noise problem
Recently built a pre amp based on a opamp, worked, but had hella hissing noise. Found your channel, liked the results you presented, replicated the circuit. Works like a charm. Thanks dude
Awesome, thank you!
Works beautifully. I packed in into a plastic box which I coated from the inside with aluminum foil and then insulated. The foil is connected to the ground (minus) and all noise is gone.
I've built this and also got a local FM station just like you.
Wound a common mode choke in an FT-50 -43 ferrite at the input and it almost cured the noise. But when placed a 100pF across the base and emmiter of Q1, it made One of the quietest DIY preamps i've ever listened.
Interesting, thanks! The next time I have to change the 9V battery, I'll give that 100p cap a try as well and see if I can detect a further noise reduction.
Nice project.
Not sure if the PG48 has a balanced output, but using a balanced connection between the mic and the preamp, will cancel out most noise...
Thumbs up.
Did anayboy:
1. use the design with an mic input transformer?
2.used it with alectred microphones?
3.designed a build low pass filter?
Thank you
Regards Peter
I really like your circuit and also the box you made for it .
I was wondering,is there a way to connect this to a laptop?The laptop doesnt have a line in,only a standard audio jack same as in mobile phones..
I regularly use this with the microphone input on my laptop. I have to dial the gain down really low, though. But the fidelity is still really good.
I want to build a similar preamp for using SM58 with IC-705
It seems like the base bias for Q2 is kinda flapping in the breeze... I've been taught that it's best to use divider of one kind or another (resistors, diodes), or some other method to make sure you have the voltage you think you're supposed to have at the base. I wonder... is tha why the gain is unexpected for a couple of you folks?
@@user-nx6ep7jz4w That 3.3meg resistor sets the amount of negative feedback to control the gain of the output stages. It could be made smaller or larger for less or more gain.
Really like this project. Although I don't have a mike to test it on yet, but I understand this is more suited for a dynamic rather than condenser type. What would be the modifications to make this project suited to a condenser mike? I'd be quite interested in building that one! Anyway, I sub-ed and think that your channel is awesome and deserve alot more subs than you have now.
Thanks! I'm not sure if the circuit would work with a condenser microphone, as it needs phantom power. The 100uF input cap will block DC.
Hi, would this work for a unidirectional microphone?
Can't seem to get anywhere from the link for the circuit layout
Yep, the link is broken. I've reached out to the author, waiting for a reply. If there's a new site I will update the link. For now I've updated the comments to show it as broken.
Shure SM58 would be better when holding in hands (lower handling noise)
Thanks for the tip. The PG48 definitely picks up every tiny mechanical vibration. Its actually an annoyance, I have to be very careful not to touch it while I'm speaking. Wouldn't buy one for blogging, but it was what I had so I roll with it.
Hi Darren, first wish you channel to be successful. I am also thinking of building a mic-amp. When I put your (or Andy Collinson's) circuit into a simulator (I used the now free Micro-Cap software), I found that the gain of this amp is over 2700 (1mV in 2.75V out), instead of 97 as claimed by Andy. Since this is much higher than required, I also looked at your SPICE simulation result and found that your result is about 750/57.5dB (2mV in 1.5V out), although much lower than mine, it's still too high for a mic-amp (for dynamic mic's). In fact I believe the gain should be best around 100/40dB as Andy's stated. Do you have to tune the volume down a lot? Or do you have any idea to tune down the gain?
Thanks for the comments! Yes, I have found this amp to have a lot more gain than I need to drive the mic input on my PC. I have the pot around 10% - 20% of full travel and that is plenty of drive. At higher drive, it has enough oomph to provide a line level signal.
The gain is set by the relation of the collector/emitter load of Q1 and Q2. 10k/0.47k*23.5k/0.566k = 883, which is pretty close to 750 (57.5dB). You'll get the ridiculously high gain (in simulation) if you forget to put the mike output impedance (600 Ohm) into the equation. Why 23k5/0.566k and not 47k/0.6k? Because there is a 47k pot and a 10k resistor in parallel with the collector/emitter load of Q1, respectively.
All these values are theoretical, as they ignore the input impedance of every next stage - which is both far from infinite and varies with frequency, so the real figures might be about half that. This circuit has no global negative feedback, and therefore the actual gain of the system (and the DC bias at the Q3 emitter) will vary greatly depending on the transistors type, their temperature, and probably the wind direction and the weather on Mars too. Its PSRR is virtually non-existent, so all the noise at the supply rail will be amplified and transferred to the output.
The circuit is old. It probably goes back 4-5 decades, because I can totally see the valve origins of some of the design ideas.
Nice video. But the link is broken, can you point to the project i another way?
Yep, the link is broken. I've reached out to the author, waiting for a reply. If there's a new site I will update the link. For now I've updated the comments to show it as broken.
Hello. Great work. I have a question about this preamp. I built my own and plug it into "line in" port in my computer and it makes a lot of noise and weird sounds. I have tried few preamps based on transistors and any work good enough. I have used bc547 in this circuit. Can it be problem with sound card or I must ground circuit or something? I use headphone speaker like microphone and it's impedance is about 40ohm maybe it is a problem.
Anyway good content I subscribed 🔥
Thanks for subscribing! I would think the BC547 is fine, that's what Andy's original circuit used. I would suggest to try it without a mic plugged in, to see if the issue remains. If so, then there likely is something amiss with your circuit construction. Also make sure you're using a dynamic mike, I am not sure if this would work with a condenser mike.
@@levelupeelab thanks for response. I checked circuit without mic and noise is more acceptable. I don't know what to do next
Try isolating the preamp from your computer. You can take a small speaker, say a 0.25 watt 2" size speaker, and connect it to the output of the preamp. With the gain potentiometer turned up to near max, you should be able to hear your voice when you speak into the mike. If it sounds good, then the problem is in your computer, if it sounds bad, then there is something miswired in your preamp.
@@levelupeelab I did like you told and it work without noise but sound is really distorted but I think It is ok becouse of high gain. In this attempt I used cheap mic with good impedance ~600 ohm but when I plug this 40 ohm speaker like a mic and rotate potentiometer it becomes a frequency generator😆. I plug also coil with ferrite like you and it works a little better. I think it is problem with all electromagnetic stuff so I will try metal case for it and find some better wires to good electromagnetic isolate. What do you think ☺️
i had the same problem
try changing the power supply
many power supplies dont have a (isolated) ground connection and this can cause noise
i took a computer PSU and used an isolated from the mains ground connection and had no noise problem
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