I looked a bit further into the 20V into 50 Ohm challange. Basically hooked up the +5V +12V and -12V to linear lab-supplies limited to 1Amp
tl;dr; It *barely* matters. Maybe even makes it a tiny bit worse.
- 15Vpp into 50 Ohm with 12V rail: 6.72Vpp from -3.36V to +3.36V
baseline. Flattened, but still balanced
- 15Vpp into 50 Ohm with 15V rail: 6.8Vpp from -3.52V to +3.28V
Slightly more signal, but looses balance. I wonder if that is my device only.
- 20Vpp into 50 Ohm with 12V rail: 7.68Vpp from -3.92V to +3.76V
Now 12Vrail too the top half looses more then the bottom half
- 20Vpp into 50 Ohm with 15V rail: 7.68Vpp from -4.00V to +3.68V
Does not even address Vpp, just more unbalanced
So what I conclude is that only upping the power from the PSU is not going to help. Not on my device anyway.
In fact, in my case it brings a tiny bit more imbalance, not sure if that is my device only.
Yellow is 50 Ohm loaded wave, Blue is non-loaded sine, for shape compare
I also measured current with *both* channels 50 Ohm loaded on 20Vpp: -15V was 101mA and +15 was 99mA and +5V was 394mA
Current does not vary from 10KHz to 20Mhz and above that Vpp drops anyway.
However, when going down to 0.01Hz (practically DC) we do get an increase whenever the crest is moving by: -15V at 130mA and +15 was 128mA
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Regarding a new PSU: I was thinking: a dual 15V or 18V transformer may be enough.
Two good + and - 15V regulators, as well as a cheap 5V DC to DC switched regulator.
Because if you look at the schematic, you will see the 5V from the PSU is *never* used as rail. Instead it is used to make the lower voltages 3.3V, 1.8V etc.
And the actual system board 5V rail is taken from the +12V supply.
So a small switched 5V module at 400mA would only need 150mA from an unregulated rectified 18V (so hooked up before the 15V regulator)
A simple dual 15V (or 18V) transformer capable of 250mA may be smaller, cheaper, easier then a triple one. Make it 500mA for some headroom.
Of course, I have no proof more power actually helps. Not with the stock OpAmp at least.