6mm Electret & reusing BM800 PCB test

BertBert37 · Dec 14, 2023

You will not be able to realise the schematic shown as the 6.8 k resistors are not in access since they are burried in the preamp or mixer for the microphone. Therefore use the modified schematic as shown. The red resistor may be adjusted to get the desired supply voltage. At the same time the output 10 uF capacitor must show the plus to the output pin !

KZhack14 · Dec 19, 2023

Thanks for the tip!

Bert37 · Dec 19, 2023

Apart from my former remark - this is one of the most stupid 2 transistor circuit I have ever seen. I quite only a few of the bad points:
1. There is absolutely no feedback in the cicuit to care for low distorsion.
2. There are many unnecessary electrolytics of large value which make no sense but are expensive and a factor of reliability.
3. The total gain is not defined and dependends on the first transistor which may have a variation of beta for at least a factor of 2, if not more.
4. Although the second transistor has a defined gain of near 1, at current consumption also depends widely of its beta.

I lack time right now, but I will give a much better solution in due time.

Bert37 · Dec 19, 2023

Sorry for may typos - again:

Apart from my former remark - this is one of the most stupid 2 transistor circuits I have ever seen. I quote only a few of the bad points:
1. There is absolutely no feedback in the circuit to care for low distorsion.
2. There are many unnecessary electrolytics of large value which make no sense but are expensive and a concern for reliability. Most of them may be avoided.
3. The total gain is not defined and dependends completely on the first transistor which may have a variation of beta by at least a factor of 2, if not more.
4. Although the second transistor has a defined gain of slightly below 1, the current consumption also depends widely of its beta.
5. In a phantom power circuit, any other emitter follwer other than schoeps type with a pnp transistor using the phantom power resistor as emitter hookup is nonsense!

I lack time right now, but I will give a much better solution in due time.