Sid PSU optimized question

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Greetings.

I replaced the old-design psu with the new "optimized" one over the weekend, and no more 60Hz hum!  Problem is, it is replaced with high frequency SID noise that is in tune with the notes being played.  Even worse, the freekin' stuff is running through the ground of my whole modular synthensizer - I hear it even with the Sid output disconnected from my VCA.

Two ideas what it could be -

1.  I have a single ground point coming from the "center ground pin" on the 7 pin DIN from the C64 power supply that goes to the ground of all of the 1/8" input/output jacks.  The mbhp_4xsid_c64_psu_optimized.pdf doesn't show where to connect a "global" ground like this, maybe this ground is picking up noise?

2.  I didn't add a 2200uF cap as shown next to comment #5 - since there is a similar cap on the input side.  Also, I only have a single SID module hooked up, and wasn't sure if this cap was necessary?

Another question - I built an amplifier/attenuator for the output/input of the SID to bring its output and input levels to values resonable for a modular synth.  My PAiA wants 10V p-p oscillator voltages.  Any idea what the output voltage range is for the SID?  Also, what does it want to see on its input?  What is its input impedance?

Thanks for any ideas you may have,

-gerald

[TK.]

1.  I have a single ground point coming from the "center ground pin" on the 7 pin DIN from the C64 power supply that goes to the ground of all of the 1/8" input/output jacks.  The mbhp_4xsid_c64_psu_optimized.pdf doesn't show where to connect a "global" ground like this, maybe this ground is picking up noise?

I think that the best central ground point is between the modules. Means: the point where the ground cables to the modules and jacks are as short as possible. However, it won't bring you that much improvement if you are changing the wiring now, it's just a general hint.

2.  I didn't add a 2200uF cap as shown next to comment #5 - since there is a similar cap on the input side.  Also, I only have a single SID module hooked up, and wasn't sure if this cap was necessary?

absolutely, it is necessary. Add especially the so called "bypass caps" to all modules (especially CORE/SID/DOUT), not only the el-caps, but also the 100 nF caps (see also the most current MBHP module schematics). This should help to reduce the noise

Any idea what the output voltage range is for the SID?  Also, what does it want to see on its input?  What is its input impedance?

According to the datasheet the output range is up to 3V, when all oscillators are active and in phase

Input voltage: ca 1V, impedance: 150k

Best Regards, Thorsten.