Tone control Op-amp buffer or Inverting

[dr.power]

Hello guys,

I have made a baxandall tone control tone circuit and want to connect a mike to the input of it.
As I think the input impedance of a baxandall control is low for a mike I want to use a BUFFER or an INVERTING op-amp circuit for impedance improvement.
Which one of the below circuits are good for this job (the first stage for each circuit is different...)

Thanks a bunch...

P.s The op-amp I am using for both stage is TL072

 

[Nigel Goodwin]

You don't need a 'buffer' you need a mike preamp before the tone controls, the specific type depends entirely on your type of mike.

 

[dr.power]

You don't need a 'buffer' you need a mike preamp before the tone controls, the specific type depends entirely on your type of mike.

What's the difference then?!!!
regardless of the gain needed for an electret mike, An electret mike just needs a biasing resistor So why it should not work with the above circuits?!

 

[canadaelk]

For any mike you need amplification to get useable level, 20 to 40 dB should do.
The first circuit is preferable. You have double inversion of the signal, giving you the same polarity on the output as on the input and you can mod the first amp to give you the rquired gain. E

 

[Nigel Goodwin]

What's the difference then?!!!
regardless of the gain needed for an electret mike, An electret mike just needs a biasing resistor So why it should not work with the above circuits?!

The signal level is far too low, the tone control circuit works at line level.

As you've now specified an electret mike, there's a suitable preamp in the opamp sticky (from Audioguru).

 

[unclejed613]

use a mic preamp before the first circuit. the low impedance of the tone control circuit won't have an effect on anything connected to it's input, because the first op amp isolates the input. the first circuit has an input impedance of 22k, because the - input of the op amp is a "virtual" ground. the second circuit has an input impedance set by the input termination (in this case 100k), but would be theoretically infinite if the resistor weren't there (with a TL072, it's 10^13 ohms).