TomWaterman
Well-known member
Hi guys,
I'd really appreciate it if any guru's can give some feedback on the revisions to the original design.
Essentially I have added:
Local regulation
Slow-start 48V (I hope)
Full output fader plus a third gain stage.
The EQ (once sorted) should patch in before the fader for a complete channel strip with hardwire EQ bypass. The preamp should have 75dB of gain and I think I've managed to find a way for it to work with a single pole 12 position switch, so Lorlins can be used throughout keeping the cost way down. A toggle is used to select gain ranges via the 2nd stages static gain...
Here is the original schematic.
Here is my new one (PDF). [Edited to correct the regulation error]
So far I am unsure of a couple of things - the phantom bypassing (C15, C16 and R29). How much will be needed if the supply is bypassed at the regulator?
Will my slowramp 48V+indicator LED work as I imagine - lighting slowly as the 48V reg ramps? (R36 and D10 etc).
The T-pad set to 20dB attenuator between stages 1 and 2 - should be fine right? I tried to get close to the loading of the original.
I'm also not certain about the value of C9, should it be higher like 470uF instead of 10uF as the value of R12 is quite low (2k32)?
Any thoughts would be fantastic.
Cheers Tom
I'd really appreciate it if any guru's can give some feedback on the revisions to the original design.
Essentially I have added:
Local regulation
Slow-start 48V (I hope)
Full output fader plus a third gain stage.
The EQ (once sorted) should patch in before the fader for a complete channel strip with hardwire EQ bypass. The preamp should have 75dB of gain and I think I've managed to find a way for it to work with a single pole 12 position switch, so Lorlins can be used throughout keeping the cost way down. A toggle is used to select gain ranges via the 2nd stages static gain...
Here is the original schematic.
Here is my new one (PDF). [Edited to correct the regulation error]
So far I am unsure of a couple of things - the phantom bypassing (C15, C16 and R29). How much will be needed if the supply is bypassed at the regulator?
Will my slowramp 48V+indicator LED work as I imagine - lighting slowly as the 48V reg ramps? (R36 and D10 etc).
The T-pad set to 20dB attenuator between stages 1 and 2 - should be fine right? I tried to get close to the loading of the original.
I'm also not certain about the value of C9, should it be higher like 470uF instead of 10uF as the value of R12 is quite low (2k32)?
Any thoughts would be fantastic.
Cheers Tom