I'm jumping in here but you've got 0.4V across V+ and V- of the op-amp.
Have you simply tried a continuity check to see where the supplies have gone ?
I think you've got a poor connection here somewhere.
You should have 0 Ohms from the cathode of the diode to V+.
You should have 0 Ohms from the bottom of the switch to V-.
Have you simply tried a continuity check to see where the supplies have gone ?
I think you've got a poor connection here somewhere.
You should have 0 Ohms from the cathode of the diode to V+.
You should have 0 Ohms from the bottom of the switch to V-.
With the 9V battery you should have 9V - the diode drop (0.7V) = 8.3V across the op-amp.
If you haven't you've got a poor joint somewhere.
It might sound silly but do check the battery, if you have made a mistake the battery could be drained.
Looking at the poor soldering, I would take it all apart, clean all the joints and the perf board as already suggested and try again.
If you haven't you've got a poor joint somewhere.
It might sound silly but do check the battery, if you have made a mistake the battery could be drained.
Looking at the poor soldering, I would take it all apart, clean all the joints and the perf board as already suggested and try again.
Last edited:
I'm getting 700 ohms from the cathode of the diode to the VCC+ so yeah, probably my bad soldering. The battery is 9.3v so that's all good.
I was hoping I'd be able to fix it without redoing it all but I guess it's a bit too far gone. My first time soldering anything on a perfboard so I'm not really surprised that it's not working.
I'll take it apart and clean everything. Any other basic things I should next time?
I was hoping I'd be able to fix it without redoing it all but I guess it's a bit too far gone. My first time soldering anything on a perfboard so I'm not really surprised that it's not working.
I'll take it apart and clean everything. Any other basic things I should next time?
Whenever my perfboard circuits didn't work it was because I'd made a connection mistake somewhere, and it always took ages to find it. The best thing I did was to get one of those plastic push in breadboards Breadboard - 830 tie points - Jaycar Electronics .
Another circuit here if you want to experiment http://www.diyaudio.com/forums/parts/90937-diy-microphone.html
Another circuit here if you want to experiment http://www.diyaudio.com/forums/parts/90937-diy-microphone.html
Last edited:
Hm... Would I get significantly better performance out of this op-amp based circuit or the one in the thread you linked than a more simple one like this one Powering microphones
As the original author says the gain is 23 ( with the switch across the 27K closed) and just over 2 open(2.16). So perhaps try opening the switch to get the higher gain. Also if the pot doesn't change anything, something is wrong with it, maybe check that it is wired correctly and is indeed 10k log.
The opamp is probably your best and easiest option to use.
In order to get any better than a opamp (if it is of good quality such as in your original schematic) you have to be very selective of the type of transistor you use.
You must use a very low noise type to beat the performance of a good opamp such as MAT02.
I have some of those, and some types are a bit on the costly side like the MAT12 at about $30 a piece,
http://www.electroschematics.com/106/microphone-amplifier-with-low-noise/
High performance microphone preamp's in pro-audio equipment do use transistors on their frontend driving an opamp and the signal to noise ratio of those circuits are -110db to -130db and better.
Here is just one such example,
http://www.circuitosimpresos.org/wp-content/uploads/2011/08/pream-microfono.gif
http://www.circuitosimpresos.org/2011/08/29/circuito-impreso-para-preamplificador-de-microfono/
And there is a whole bunch more here,
https://www.google.com/search?q=mic...php%2Fviewtopic.php%3Ff%3D6%26t%3D164;921;650
jer
In order to get any better than a opamp (if it is of good quality such as in your original schematic) you have to be very selective of the type of transistor you use.
You must use a very low noise type to beat the performance of a good opamp such as MAT02.
I have some of those, and some types are a bit on the costly side like the MAT12 at about $30 a piece,
http://www.electroschematics.com/106/microphone-amplifier-with-low-noise/
High performance microphone preamp's in pro-audio equipment do use transistors on their frontend driving an opamp and the signal to noise ratio of those circuits are -110db to -130db and better.
Here is just one such example,
http://www.circuitosimpresos.org/wp-content/uploads/2011/08/pream-microfono.gif
http://www.circuitosimpresos.org/2011/08/29/circuito-impreso-para-preamplificador-de-microfono/
And there is a whole bunch more here,
https://www.google.com/search?q=mic...php%2Fviewtopic.php%3Ff%3D6%26t%3D164;921;650
jer
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.