Read more here, it all goes back to some comments audio modding "guru" Jim Williams made on many occasions:
http://forum.sslmixed.com/index.php?topic=261.msg2161#msg2161EDIT: Also see Pat's post below - he explained it really well.
1. The coupling caps in the signal path are there to filter out DC, they act like a High Pass Filter. Increasing the value of the coupling caps moves the frequency of the "High Pass Filter", and also it's phase shift, lower (C9 was 10uF before, now 220uF). I can measure extended low end after changing the value.
2. The added "bypass"Film-cap could be called esoteric, but it is said to improve the higher frequencies and transients. Basically, the added value of capacitance is so small that it doesn't change the value, but the added smaller Film Cap reduces the inductance in the higher frequency range. I'm not qualified enough to explain it properly, but I kinda understand what it's doing.
It certainly doesn't hurt and my recapped channels sound very clean on the VCA path. In fact the low end of my VCA path measures better than the Monitor Path (haven't changed any Cap Values on the group card yet).
Try to google "coupling caps film bypass jim williams".
Here's a link that goes more into detail:
http://www.gearslutz.com/board/geekslutz-forum/578503-bypass-caps-air.htmlOnce my entire console is recapped, I will experiment with 1 or 2 channels that have some heavier mods, like replacing the 5534/5532 OP-Amps with LME49710/20, which have such a low DC Offset that interstage coupling caps might not be required (they are important on Input Cards, Inserts, etc.).
But that might change the character of the console and brings other issues to the table (like high frequency oscillation), so it gets very experimental.
I would love to have more modding discussions on here, just to learn what parameters can be influenced.
Hi Marcmozart,
great work.
Could you explain better this mod you've done to the VCA card?
VCA Card (top left) on which I increased C9 to 220uF and added MKP Bypass-Caps 0,01uF on C8 and C9 (soldered to the back of the PCB)G-Series Channel Amp Card (top right) and Dynamics in the front.
regards
Nick