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Friday, January 16, 2009

Altec 1678c mod project

for all the details of the mod check out this link.

Ok, here is my project that I finished a few months back but never got
audio samples done. Basically its a 8 channel public address mixer that
I modified. The mod made it possible to have a control knob for the
input gain and output volume of each channel(8 separate outputs & inputs).
I got the audio samples done, so I decided to post them
up here. I played the drums, I'm not the greatest player in
the world, but hey, its just a sample of the preamp.

Gretsch 12inch maple Catalina tom. (Mic used Senn. MD421)

Gretsch 22inch Birch Catalina Kick drum. (Mic used AKG D112)

Ludwig Aluminum Supra Phonic snare 5x14. (Mic used Beyer M201)

XS Sabian Hi Hats. (the weak link in the set) (Mic used Oktava Mk219

(Neumann TLM 103 for the drum overhead mic)

Analog to Digital converter used- Lynx Auroa 16 thru AES16pci (soundcard)

recorded into computer using Sonar 8.
On a PC with Windows XP.

From mics to Altec, then right out of Altec, directly into converters.
(5 separate tracks)

Recording in a living room with no acoustic treatments at all!

Altec 1678c notes-
All mic preamp inputs were set at there lowest level, its a little too hot coming
in from the mics. I need to get some -10 db pads to put on the mic cables.
The mic placement was done in way to stop it from clipping and distorting.
So I had to play around for a hour or so to get the sound right, its ok though.
The pads will let me mic things closer and get more flexible with placement.

Dry mix, no overhead mic, simple mix of the 4 close mics

Dry mix, just the one overhead mic

Dry mix, all mics together, simple mix

Final mix

final mix -
kick - HPF @ 61hz
hi hats - HPF @ 196 & cut -6 db @ 741hz
thats the only EQ used, just the standard channel EQ in sonar 8

UAD precision buss comp on main buss
input, - 6.7db
threshold, -20db
ratio, 4:1
attack, 0.41ms
release, 0.43ms
no filter
output, -0.6db

then a precision buss limiter after comp
input, 3.75db
output, -0.10db
release, auto

no tracks were panned on any mix.
no EQ on main buss.

here are the guts and a front view of the preamp.


  1. Awesome.
    I might have to try these mods on mine, but it seems I have the straight 1678 model with just the single master out section.

    1. Sorry, not true! What I thought were the 8x line in sockets are indeed individual line outs. Nice!
      Did you get it hooked up with the pads in the end, or are there further mods you can do to the ALTEC unit itself, for optimal gain range?

    2. Sweet mix, also, by the way. Fat crunchy sound.


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