ExtremA, class-A strikes back?

[AudioSan]

the dissipation will be the same.
yes it's halv the supply voltage. but twice the current.

 

[pinnocchio]

The supply voltage for the OPS in 100W/8ohms is according to Sassen, +/-26Vdc per rail. So ~18Vac should do it BUT with experience with this amplifier, I strongly suggest you move to lower power since the dissipation just becomes monstrous. 15Vac (~21Vdc) supply should be more than enough for the amplifier to drive most speakers, even inefficient ones.

Ciao!
Do!

 

[xrk971]

How do you get 100w with 26v rails? I can barely eek out 50w with 35v rails on most of my class AB amps. Is it simply more current with this class A design?

 

[abraxalito]

Its bridged so the output swing is doubled. 26V rails would give 52V peak with no OPS losses.

 

[BesPav]

What happens if the source is NOT balanced? If the "negative" input is grounded, the "negative" branch of the output stage would stay at GND, right?

No, the amp are inherently differential. It is very different than just two channels in opposite direction.
T25/T26 LTP ensures, that centerpoint voltage will be at the groung potential.

 

[lydlaug]

🙂

Here is my low power modification that uses slightly modified ExtremA output stage in the opamp feedback loop, together with measurements performed with Audio Precision AP 2700 series system:

PM-A4 power amplifier

Hi Pavel,

Much appreciated. By coincidence I was actually tracing your diyaudio posts of this amplifier. Any chance you will post the components values? Some of them can of course be deduced, but others might have required some experiments.

Cheers,
Mogens

Pavel.

Could you please post the component values for your low power Extrema? 🙂
I have been playing around with LTspice for some time ago by using LM4702 and 498XXX to get some more power than using an ordinary audio op-amp. Do you think that could be an idea that work?

Thanks and regards