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|19th November 2009, 04:18 AM||#1|
Join Date: Sep 2008
Presonus Bluetube makeover
Hello all -
The subject of the Presonus Bluetube mic preamp was mentioned in another thread as a possible subject for mods. To get the ball rolling - kevinkr offered these suggestions :
"I replaced the original quad op-amps with National LME49740 - see here: LME49740 - Quad High Performance, High Fidelity Audio Operational Amplifier
The supply in this thing is one of the real weak points IMO and a separate toroid and full wave rectification of the rails would be a real enhancement. A separate winding for the tube would be good too."
thx to all --
|19th November 2009, 04:26 PM||#2|
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Here's that link again since it did not copy over correctly to the new thread:
LME49740 - Quad High Performance, High Fidelity Audio Operational Amplifier
These parts are SOIC (surface mount) so some skill in their replacement is required.
The 12AX7A in mine was Chinese, nothing special. I replaced it with a vintage Mullard..
Again I have no idea what effect these changes will have on the sound of this mic pre as I have not yet used it to record anything.
The tube in the Bluetube pre is really there to add some distortion, err, warmth in the signal path. This isn't a tube mic pre in any sense.
One thing worth considering as I pointed out in another thread is power supply improvements. A nice toroid and an entirely outboard supply providing +/-15V or so and 60V for the tube would be worthwhile I suspect. The supplies are mostly regulated, but IIRC there is nothing special about the circuit, and because a wall wart (18VAC) is used as a source all of the supplies are half wave.
"Extraordinary claims require extraordinary evidence." - Carl Sagan
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