Join Date: Sep 2006
Location: Pleasant Hill, CA
MXL 770 - any opinions about modifications?
Recently I recorded a very rare record, but it has harsh highs unfortunately, like a little bit of a broken glass when a singer was breezing. It was the first time I switched off -10dB switch on MXL 770 microphones in order to gain the more as possible of dynamic range of the Yamaha MX-400 mixer.
If anybody played with mics, what is the main buttleneck? I suppose it is the transformer that overloads internal transistor amp? I searched the Net and found schematics of some MXL mics, one is original that contains an emitter follower afrer a source follower, another is a modification that uses no output transformer, but splitted load of the FET and ballanced output by pair of PNP emitter followers. I don't like thos mod since it decreases phantom power voltage needed for the capsule.
Also, I've found Neumann 2-tube schematics with a cathode follower and a 1 - stage amp, with 220K (!) in anode, and a transformer is connected to the cathode for a PFB by current. Very clever!
But is it possible to find such a transformer somewhere? I'd use a single 6AK5 since the mic is big and should have a lot of space inside... However, a filament power will be needed, since a phantom power is too weak even with a DC/DC converter for the filament, in such case more voltage may be provided for anode, anyway I will need a power source...
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