I need a class AB 100mW (ish) amp circuit for experimenting.

[mkiijam]

Any body have a simple, but "abusable" class AB schematic I can build?
NEEDS:

1. Bipolar supply
2. Class AB
3. Discrete output, but preamp could be opamp
4. Only need 100mW to maybe 250mW
5. Anything less than a Watt is fine

 

[Brian Roth]

What load impedance? Not that I have anything specific in mind, but driving a 2 Ohm load is different than driving 600 Ohms.

Bri

 

[mkiijam]

True. Good catch.

The next stage after this little experimenter would some other piece of line gear, not speakers. So way up there?

 

[Brian Roth]

OK, 100 mW is +20 dBm. 1 Watt is + 30 dBm. Just sayin'....

Bri

 

[Brian Roth]

True. Good catch.

The next stage after this little experimenter would some other piece of line gear, not speakers. So way up there?

While anytime an audio voltage is fed into an input with a finite impedance, there will be at least some power transferred into that destination. More power transferred into a lower impedance. less into a higher impedance load.

Perhaps you should be more specific about your application.

In "modern" gear that typically has a relatively high impedance input, we think more in terms of signal voltage.

For instance, 1 Volt into 600 Ohms is approx. 0.0017 Watt (1.7 mW). 1 Volt into 10,000 ohms is 0.10 mW.

Bri

 

[gyraf]

..perhaps a headphone amp would do?

e.g. https://groupdiy.com/threads/gyraf-audio-hpamp-question.78887/

/Jakob E.

 

[KA-Electonics.com]

https://ka-electronics.com/shop/index.php?route=product/product&product_id=67

Available as a bare board: https://ka-electronics.com/shop/index.php?route=product/product&product_id=81

 

[Voyager10]

If you're wanting to tinker with the circuit itself, you could always start with a discrete op-amp, e.g. these threads

• API 2520: https://groupdiy.com/threads/origin-of-2520-schematic.62035/#post-786284
• Melcor 1731: https://groupdiy.com/threads/melcor-1731-teardown.87070/

Neve's BA340 and BA440 amps might also be worth a look.

The @KA-Electonics.com board is largely going to reflect the op-amp's performance (i.e. practically faultless) and I doubt that any tinkering would improve it, if that was your intent.

 

[mkiijam]

..perhaps a headphone amp would do?

e.g. https://groupdiy.com/threads/gyraf-audio-hpamp-question.78887/

/Jakob E.

There are many "RED" leds, what is the voltage drop supposed to be?

 

[gyraf]

Enough to run the 23mA in class A, by setting ca. 1025mV across each of the 47R resistors

 

[JohnRoberts]

Enough to run the 23mA in class A, by setting ca. 1025mV across each of the 47R resistors

1.081V ?

JR

 

[gyraf]

Yup, if you want it in metric