Your search for an amplifier for your DAC has ended today https://www.diyaudio.com/community/threads/solid-state-tube-amplifier.401469/post-7406121
By the way, IPS was inspired by this paper: DOUBLE-POLE COMPENSATION AND THE PUSH-PULL TRANSIMPEDANCE STAGE IN DISCRETE AUDIO FREQUENCY POWER AMPLIFIERS
You were right. All of the current was passing through common base transistors instead of equally sharing between the two.
The fix is to select zener to bias to the half of the power supply voltage.
I verified by isolating bootstrapped cascoded IPS.
Now all of the power dissipation is nicely shared between LTP transistors.
Square wave response is nice and clean with no ringing.
Attachments
Will use this amplifier with the best speakers I have.
The goal is to create a design that is reproducing music with low distortions and great musicality.
Also, just to have fun along the way.
After just to compare other amplifiers with this one.
So far the best sound I got was with two TDA7293 in parallel with disabling IPS/VAS for one of them.
Hopefully this one will sound even better.
Aiming at high Loop Gain at 20k as some people suggest this what makes amp sound good.
Will also have Modulus-86 amp ready soon - curious how that will perform and compare to TDA and to discrete design.
It is journey for me and I am enjoying!