Ghost Story (cont.)
Sexy Mic Pres
The mic pres were an important consideration, but since I have custom made outboard mic pres, it didn't make sense to modify all 32 channels, so I just modified the first 12 channels which I normally use for tracking.
Part of the mic pre mod was done on the In/Out card (see picture) and the rest consisting of cap and opamp upgrades were done on the input module. Several opamps were tested on the front end, including the OPA1612, and OPA275, but this circuit proved to be most stable and noise free with the trusty old OPA2134. Even then, the biasing network tied to the non-inverting inputs of the 2134 needed tweaking to to find the sweet spot where everthing was happy. The end result is some nice sounding mic pres that rival a lot of outboard units.
Other mods included replacing the hard-to-locate talkback switch with a nice bright LED. The LED is illuminated when an internally mounted relay, that replaces the old switch, is activated by remote switches that plug into jacks on the backside of the console. I made up some cool little hand-held switches with LEDs that illuminate when the talkback is activated. Studio guests love these.
Of course we also visited the power distribution, which included upgrading all electrolytic filter and decoupling caps in the console to 105°C industrial grade, as well as rebuilding the rack-mount 300W power supply. I also removed the insidious heaphone jack from under the armrest. This might be considered a nice feature on a $300 mixer, but placing insert connectors in the main monitor path is a serious compromise.
I was also curious about how much noise (i.e. digital hash) was added to the noise floor by having the Ghost computer mounted right in the middle of the console, next to all the summing amps and where all the ribbon cables tie together. The only way to find out was to put a power switch for the computer on the back of the console. Other than switching mute scenes, the computer really doesn't do a lot these days. So I have the option to turn it off at any time. By the way, it is audible when the monitors are cranked and you turn the computer on and off.
Well, there are probably more things that were done that I forgot to mention, but I think you get the idea. It was a major project that kept me busy for a while. Would I recommend this to others? I don't know. It would have been extremely expensive to pay someone else to do this. I lost track of the hours and parts count, but I'm sure I spent upward of a grand on caps, opamps and jacks and other parts. I do know one thing for sure, this is no ordinary Ghost.
Ins and Outs
All 180 TRS jacks on the console were replaced with Neutrik connectors. The jacks can be problematic as they age, especially the insert normals. Notice the upgraded mic pre caps.
The Wima caps parallel the electrolytic mic pre input caps on the top side. The resitor is to provide a balanced impedance for the channel Direct Out.
The 3-way B Mix Bus Gain switch. Up for -6dB, down for -12dB, and the middle position is unity.