What value cap to bypass power supply cap?

Dracule1, no I would not recommend Mundorf for AC line filter. What I meant is that all your caps are most likely connected in parallel and then to the amp's circuitry. At the input to this circuitry I would put 1uF cap.

When you connect caps in parallel wire going to circuit should be from the very last cap and not the one close to rectifier.

Dracule1, 1% cap won't do much to reduce ripple but will deliver current when demanded during high frequency transitions where main caps is too slow (inductive).

It will also work to suppress high frequency interference. Imagine that high frequency interference contains 90kHz and 100kHz frequencies. When they appear on non-linear element like output transistor (noting is perfectly linear) sum and difference of them is created (modulation). Sum is inaudible 190kHz but the difference is 10kHz. It gets worse when interference contains a lot of frequencies making a lot of new audible junk. Almarg posted few times on this subject stressing importance of protecting audio system from high frequency interference.

Oh I see. That makes sense, but I thought you want the bypass caps as close to the power supply caps as possible? The further away the bypass cap is, the less effective the filtering, no?

I thought the 0.1 microF cap will handle those high frequency noise you just talked about.

I would connect 12 capacitors parallel cap #1 to #12 to connect back to #1 (form circle). Now connect rectifier's output to cap #1 and load to cap #7 (opposite side of the circle). High frequency bypass cap should be, in my opinion, at the load to eliminate any wire inductance that can slow down response. If not then at least 1uF cap at main cap #7. Don't spend too much money since you already have very good (film) main caps and might not gain much from Mundorf caps. What kind of wire you use for connection?

Forgot to ask you question about 938s - I found that marked absolute phase doesn't correspond to membrane going forward when connecting battery plus to red and battery minus to black terminal. I tried opposite phase and got worse leaner sound. Is it possible that this phase inversion was done by Hyperion on purpose?

Hi Kijanki, I will need to think about your wiring scheme to make sense of it. I'm not an experienced DIYer.

I think I will use high purity copper wiring with Teflon jacket.

As for the Hyperions, I'm not sure if I can answer that question. However, there was some controversy with phase of the midrange drivers on the 968s:

http://www.iar-80.com/page157.html