Bypa
NP.
Bypassing filter caps is far from new in Audio Circles. Sansui added power supply bypasses with their X17 series back in the 1970s with a single large film cap, which gave many of the Sansui amps that warm sound many like. John Curl while laying out the Parasound high current designs did quite a bit of bypasses and multiple bypasses in the 1990s and 2000s with HCA series and later the Halo series..
Each film cap value will affect certain frequencies. The CX-1 has two main filter caps in the main supply. Think I used a 0.47, 0.22, 0.047 and a 0.01uf on each of the 4700uf caps. A good starting point is a .47 or a .33 paralleled with a .01uf. From there if you want to clean up an upper midrange, you can experiment with a .047 or .022. Its also important to note the intermediate cap values will have a different effect if that .01uf is not included. Now if you go smaller than a .01uf, say a 1000pf, you will clean up super treble frequencies, but at the same time change the tonal balance of the preamp.
But you can also over do it. As an example if a power supply has 4 caps instead of 2 (2 on each side of the center ground buss), may just want to bypass one cap on each side of the plus and minus supply. Doing all 4 may be a bit too much.
I also added bypasses on the phono stage PS caps.
And speaking of the phono stage, its extremely good on the CX-1. A lot of engineering efforts went into the MC and MM stages. If the listener is a phono person especially with LOMC carts, then would strongly suggest dialing the MC phono stage so its as close to ruler flat as you can get. You will be surprised at how good and organic sounding the MC carts will become. To dial in the response, you will need a NAB broadcast test disc, or similar type of LP that has the RIAA frequencies cut into it. connect a DVM up to a set of tape outputs, play each test freq. and record the AC voltage coming out of the tape loop. You can change the loading resistors to get it very flat. My favorite LOMC cart at the time was the Madrigal Carnegie One. Plugged into the MC stage on the CX-1, I was able to get the response flat within 1.5db from 30hrz to 18Khz, which is saying something. Without the dial in, most phono stages are lucky if they are flat within 5-8db, with some being a bit worse. But need to measure it before you do anything.
If you don't want to solder resistors in each time you can temp solder in some leads to the resistor positions on the pcb, clip resistors in place measure the points calculate how much is needed, plug in the resistor value. Once you have it dialed in, then solder in the correct value.
