Manley VOXBOX - MVBXA 4/2003 - Manual (Page 15)

A note regarding how we’ve described LA-2A’s as fast and LA-3A’s as slower. Your experience
may disagree with our generalization. They both used the same opto part # and should be the same. We
believe there was a fair amount of variation over the years and we know of slow and fast versions in both
models. The LA-2A we used to compare was a faster type and the LA-3A was slower. Perhaps a better de-
scription is simply “slow and fast vintage opto” but we did emulate and compare with real vintage units.
THE EQ & DE-ESSER
The first part of the EQ & De-Esser section is the “EQ INPUT” select switch. The three inputs are:
1) LINE IN - from “Line In” XLR and phone jack - transformer balanced - The signal “splits” to both the
preamp and EQ sections and also to the meter.
2) PRE OP - The Mic Preamplifier and Compressor output. This signal does not pass through a transformer
but the preamplifier may still be affected by the output transformer unless you insert a plug into the
PREAMP OUT phone jack. The Pre O/P can be metered. These first two positions allow one to com-
pare the LINE IN signal with and without compression and gain. Of course assuming you are listening
to the EQ OUTPUT.
3) INSERT - This is a line input direct into the EQ. It can be used to “insert” an external device such as a gate,
delay, distortion or even more EQ and compression. It can also be used as a way to use the VOX
BOX as two separate channels. You could use the preamp for vocal and the EQ for bass. This input is
transformer balanced. With no jacks plugged into either the INSERT XLR or 1/4 inch phone jack there
will be no input when switched to this position. If you were to patch a short mic cable between the
PREAMP OUT and INSERT IN, it would add two transformers into the signal path when you switch
to “INSERT”. Some people like the “sound” of good transformers - some don’t. You judge.
The EQ is based on the MANLEY MID FREQUENCY Equalizer which was based on the PULTEC
MEQ. The original passive circuit was designed by Western Electric to improve the sound of voice through tel-
ephone lines. Pulse Technologies (Pultec) licensed it from Western Electric and Manley was given full permis-
sion and “blessing” from retired Eugene Shenk
who owned the Pultec name.
For the VOXBOX, we left the original frequencies untouched so that there is still a lot of mid control
but we extended the range of frequencies so that it could hardly be called a mid EQ anymore. It remains a pas-
sive EQ meaning that there is only a capacitor, inductor, rotary switch and conductive plastic potentiometer for
each band. There is no tube in the EQ circuit and there is definately no ICs or transistors. There is a vacuum
tube circuit following the EQ & De-esser which is used to make up gain lost in the passive EQ. The original
Mid EQ stopped at 200 Hz in the lows - we added 6 more frequencies so that it goes all the way down to 20
Hz now. The LOW PEAK is a boost only control from 0 to 10 dB with 11 “center frequencies” from 20 Hz to
1K (1000 Hz). The MID DIP is cut only also with a 10 dB range. There are 11 center frequencies from 200 Hz
to 7 K (7000 Hz). Similarly the HIGH PEAK is boost only and has been extended from 5 frequencies to 11
frequencies ranging from 1K5 (1500 Hz) to 20K (20,000 Hz). The BYPASS switch turns off the EQ function by
eliminating the EQ components from the path. Why does each band only give either cut or boost but not both?
It’s a Pultec. It’s passive. It would require twice as many components or a bunch of op-amps in the audio path
(like most EQs that will be forgotten 3 years from now). We prefer the approach that stands the test of time to
one that compromises sound for the sake of conventional controls. Each approach has advantages.
EQ techniques: The best place to adjust EQ should be mic choice and positioning and possibly room
choice. The better the mic choice the less EQ needed or wanted. This seems to be an effect that travels all the
way through to mastering and broadcast. If you start out right, you will save everybody a lot of correction work
- especially yourself. Some great engineers do not use EQ for the lead vocal track, even at mixing. Most do not
EQ to record but some may do a bit in the monitor path. Why? Quite often vocals are “a work in progress”
recorded on different days and different rooms and they compile phrases from each session.
If you gotta EQ, the place to start is cutting or dipping rather than boosting, according to the best
engineers. Before you boost highs and lows, dip a bit in the mids. It can be less intuitive because most of us
want to hear more “something” than less “something else”. Try it sometime.
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