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connecting external mic pre to Firewire interface inserts
Old 9th April 2009
  #1
Lives for gear
connecting external mic pre to Firewire interface inserts

I'd like to connect my mic preamp (balanced TRS outs) to the insert socket
of an Echo Audiofire 8 interface, which has a pair of front panel 'universal' combo XLR mic
pre/line inputs connected to the two rear panel inserts. The channel
inserts are wired: tip = send, ring = return, and sleeve = ground, and are
intended to connect a serial effect (eg compressor, eq) to the 2 front panel
universal XLR mic/line inputs. Thus I'd be using the insert socket to bring in
my 2 external mic pres as line level inputs .... do I need to reconfigure
them as unbalanced (TS) inputs, or can I bring them in as TRS balanced ?
Should I insert them only to the first 'click stop' in the insert ?
For more info see page 15 of the manual (and specs on pages 56/57) at:
http://www.echoaudio.com/Downloads/M...ual%20v2.0.pdf
From the manual it states:
"To record a guitar or line level signal, just plug a cable with a ¼"
connector into one of the universal inputs. Whenever a ¼" cable is
connected to a universal input, the guitar/line preamp is enabled and the
gain range of the trim knob is set to range from 0 to +45 dB. The
guitar/line preamp can support both guitar & line level signals. "

It's certainly the easier way to do it (plugging into the front panel
mic/line input vs the insert) but what I was hoping to do was avoid going through the Echo
mic preamp circuitry altogether (even though when that Echo mic pre gain is
set to 0, there should be no gain added by it)...in effect using it as a passive line in minus any gain stage. That was my rationale in
using the insert socket as my external preamp's input point...as I hoped it
would bypass the Echo's mic pre altogether ? I guess it would help to know
where in the chain the Echo's insert was positioned: pre or post the
universal inputs preamp ? In effect I'm looking for a non-amplified line
in, independent of the Echo's mic preamp circuitry. As I understand it,
using a 1/4" plug for line in at the 'universal XLR input' gives you a gain
range of 0 to +45dB compared with the +10 to +59dB of the mic input, but it
doesn't bypass the inbuilt preamp's circuit ? Hope this isn't too long winded or redundant.....and I appreciate any help from folks out there.
Ray
Old 9th April 2009
  #2

Aren't there 6 line ins on the back of that unit???




-tINY

Old 10th April 2009
  #3
Lives for gear
Quote:
Originally Posted by tINY View Post
Aren't there 6 line ins on the back of that unit???




-tINY
There sure are....and I use them all ! Plus I even want 2 more for 8 simultaneous lines in ! I'm just trying to figure out where in the input signal flow chain the inserts are positioned...are they after the mic preamps' gain stage ? If yes, then I'm not really getting the benefit of a higher quality external preamp because in effect I'd be 'double amplifying' the mic signal ! What I'd like to do is bypass those two Echo mic inputs and substitute them with the external pres...but I'm not sure that's possible ?
Ray
Old 10th April 2009
  #4


The inserts will be line level - after the pre amp. But, using the single-ended return may be less desireable than just running the internal pre amp with low gain.




-tINY

Old 10th April 2009
  #5
Lives for gear
Quote:
Originally Posted by tINY View Post

The inserts will be line level - after the pre amp. But, using the single-ended return may be less desireable than just running the internal pre amp with low gain.




-tINY
I think you're right Tiny....the internal preamp with 0 gain should be pretty transparent, although bypassing it altogether feels intuitively better to me...and it's just a foot or so of unbalanced line cable in, so I wouldn't expect much noise. Thanks for your guidance...I'll try both input methods and see which sounds best ! There's also the option of getting a 2 channel line in D>A converter and feed the external preamps into that, then taking the SPDIF out and feeding that to the Audiofires' rear panel digital in....but that's getting a bit complicated !
Ray
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