op amp impedance converter

[marconine]

Hello, can anyone suggest me a valid op amp circuit to reduce the impedance from 10k ohms around to 600 ohm?
Best regards
Marco

 

[Newmarket]

Sketch of what you want to do ? Sounds like a simple unity gain opamp buffer would do it ?

 

[gyraf]

Source impedance, input impedance? Why?

see e.g. The XY Problem

 

[marconine]

I have a low audio signal with an output impedance of about 10k Ohm and I want to amplify it with a microphone preamplifier that has a lower input impedance

 

[warpie]

DI box?

 

[Lampie519]

A resistor?
How hot is your signal?

 

[gyraf]

agree, di-box

 

[JohnRoberts]

Op amps generally have high input impedance so can simple buffer hi z sources. The typical tool to transform high impedance to low impedance involves using a "transformer". Impedance is transformed by the turns ratio squared.

JR

 

[marconine]

but the di-box is not used for higher impedances?
Is it a good solution to convert a line signal to mic?

 

[user 37518]

but the di-box is not used for higher impedances?
Is it a good solution to convert a line signal to mic?

A DI will work. But, if you have line level equipment, you can just lower the level with a resistor and a buffer, then, if you want differential outputs, you can add an inverter or a THAT IC solution. All of that will probably be less expensive than a good transformer.

 

[Matt Syson]

Mic input amplifiers usually have a minimum of around 1K input impedance (5 times a nominal 200 Ohm mic OUTPUT impedance to reduce losses) . The original question is too vague to give a definitive answer, such as what the source impedance really is, whether the mic amp is a typical 1K or more INPUT impedance and whether galvanic isolation (transformer) would be a benefit (reduces chance of ground current induced hum) and whether being balance/is also an advantage.

 

[JohnRoberts]

Mic input amplifiers usually have a minimum of around 1K input impedance (5 times a nominal 200 Ohm mic OUTPUT impedance to reduce losses) . The original question is too vague to give a definitive answer, such as what the source impedance really is, whether the mic amp is a typical 1K or more INPUT impedance and whether galvanic isolation (transformer) would be a benefit (reduces chance of ground current induced hum) and whether being balance/is also an advantage.

"Bridging" input terminations are generally considered 10x the nominal 150-200 ohm mic source impedance so 1.5k to 2k ohm.

JR

 

[Matt Syson]

Indeed but 'back in the day' amplifier gain was expensive (why use an extra valve if you can add a few more turns to a mic transformer until the frequency response really starts to suffer) and if it was for 'pa' (sound reinforcement) use then anything beyond 100 Hz to 5 or 6 kHz was a 'bonus'. So, as with everything you have to write out your full list of parameters before you can make an informed decision. Yes Bridging was 'around 10 times the impedances (nominally related to output drive capability) but microphone circuits tended towards 'matching' when using a transformer to obtain the best POWER transfer, because 'Power' output capability is what microphones lacked (lack).