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Archived from groups: rec.audio.pro (More info?)
This is a follow-on thread to the recent "Bypassing Caps" thread.
I too have a Soundcraft 200 series console waiting to be gone through. (A
reasonable beast to work on; lots of room on the boards and Harmon was
good about emailing the schematics.)
My plan has been to replace the TLO7x chips with better opamps that also
have zero (or darn near zero, <1mV) offset regardless of rail asymmetries,
and then hopefully getting rid of many coupling caps. (The OP275 is one
such device that usually holds zero offset under most power conditions.)
I've gone back and looked at several old threads related to this topic;
some have been quite interesting, but here are some additional questions:
Several threads had someone who was "about to" rechip a console, but I
didn't see any follow up as to which chip they finally liked best, or how
things turned out.
My current choices, based in part on personal experience (OP275) and also
several excellent posts by Monte McGuire (among others; sorry for not
mentioning all the great posters by name), are the OP275, 2604, and
OPA2132. There are other possibilities, but the prices start getting
rather high.
Any more recent thoughts on the best amps to use? My application is
primarily acoustic and classical recording/mixing; I'm not after a
particular "sound".
I will be adding power decoupling at each chip and will be watching
for oscillation, and am buying new linear power supplies. I will be upping
the wattage of the current limit resistors in each module to accommodate
the hungrier chips.
Any cautions about replacing coupling caps with a piece of wire? (PS
failure is one concern, but supposedly chips such as the 275s will
continue with zero offset even with a rail gone. I do plan to run
redundant supplies, coupled through diodes.)
Obviously I'll leave in the mic input couplers (pres are transformerless),
and perhaps one or two where the signal interfaces to the outside world,
but this console seems to have a large number of coupling caps in the
signal path.
Thanks for any new advice. I will make a report when this project is
concluded (the plan also includes adding EQ bypass switches in several
places and insert pre-post switching -- lots to do).
Frank
--
.
This is a follow-on thread to the recent "Bypassing Caps" thread.
I too have a Soundcraft 200 series console waiting to be gone through. (A
reasonable beast to work on; lots of room on the boards and Harmon was
good about emailing the schematics.)
My plan has been to replace the TLO7x chips with better opamps that also
have zero (or darn near zero, <1mV) offset regardless of rail asymmetries,
and then hopefully getting rid of many coupling caps. (The OP275 is one
such device that usually holds zero offset under most power conditions.)
I've gone back and looked at several old threads related to this topic;
some have been quite interesting, but here are some additional questions:
Several threads had someone who was "about to" rechip a console, but I
didn't see any follow up as to which chip they finally liked best, or how
things turned out.
My current choices, based in part on personal experience (OP275) and also
several excellent posts by Monte McGuire (among others; sorry for not
mentioning all the great posters by name), are the OP275, 2604, and
OPA2132. There are other possibilities, but the prices start getting
rather high.
Any more recent thoughts on the best amps to use? My application is
primarily acoustic and classical recording/mixing; I'm not after a
particular "sound".
I will be adding power decoupling at each chip and will be watching
for oscillation, and am buying new linear power supplies. I will be upping
the wattage of the current limit resistors in each module to accommodate
the hungrier chips.
Any cautions about replacing coupling caps with a piece of wire? (PS
failure is one concern, but supposedly chips such as the 275s will
continue with zero offset even with a rail gone. I do plan to run
redundant supplies, coupled through diodes.)
Obviously I'll leave in the mic input couplers (pres are transformerless),
and perhaps one or two where the signal interfaces to the outside world,
but this console seems to have a large number of coupling caps in the
signal path.
Thanks for any new advice. I will make a report when this project is
concluded (the plan also includes adding EQ bypass switches in several
places and insert pre-post switching -- lots to do).
Frank
--
.