That dynamic mic is little more that a short. If you adjust the variable resistor to zero something, maybe more than one component, will smoke. It is amazing the number of components you can take out like that, the pot, the mic, the transistor.
Since the gain of the transistor is such a variable, we're using the variable resistor to find the sweet spot where the transistor is a linear device.
Yes, you can use an 8Ω speaker as a mic. Intercoms use a simple switch, as switch the roles of the mic/speaker. The single transistor design basically sucks though, you can make it work, but you will never be happy with it.
The carbon mic sucks less, you will get recognizable results, but it still won't be good.
A dynamic mic and speaker are extremely similar, both use voice coils and magnets. A speaker has a much bigger cone, to produce more volume, while a mic has a small plastic diaphram, for fidelity. The basic physics is pretty similar too.
When it comes to mics, there are exceptions (as with speakers). The technology keeps changing, but I'll leave it at that.
If you do what I did, get a couple of cheap 8Ω speakers for your junk box.
If you want to run some real experiments with audio amps, the web abounds with plans. You can get good results with as few as two transistors, I've seen some people around here with them, including their own designs.
With chips it gets even simplier.
Since the gain of the transistor is such a variable, we're using the variable resistor to find the sweet spot where the transistor is a linear device.
Yes, you can use an 8Ω speaker as a mic. Intercoms use a simple switch, as switch the roles of the mic/speaker. The single transistor design basically sucks though, you can make it work, but you will never be happy with it.
The carbon mic sucks less, you will get recognizable results, but it still won't be good.
A dynamic mic and speaker are extremely similar, both use voice coils and magnets. A speaker has a much bigger cone, to produce more volume, while a mic has a small plastic diaphram, for fidelity. The basic physics is pretty similar too.
When it comes to mics, there are exceptions (as with speakers). The technology keeps changing, but I'll leave it at that.
If you do what I did, get a couple of cheap 8Ω speakers for your junk box.
If you want to run some real experiments with audio amps, the web abounds with plans. You can get good results with as few as two transistors, I've seen some people around here with them, including their own designs.
With chips it gets even simplier.
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