Manley Laboratories Voxbox Owners manual

OWNER'S MANUAL

MANLEY

VOXBOX

MANLEY

LABORATORIES, INC.

MANLEY LABORATORIES, INC.

13880 MAGNOLIA AVE.

CHINO, CA. 91710
TEL: [phone]
FAX: [phone]

email: emanley @ netcom.com

http://www.manleylabs.com

CONTENTS

SECTION PAGE

INTRODUCTION 3

FRONT PANEL MIC PRE 4

COMPRESSOR 5
EQ & DE-ESSER 6

BACK PANEL 7, 8 & 9

GENERAL DISCUSSION

OVERVIEW AND BLOCK DIAGRAM 10
MIC PREAMP 11
COMPRESSOR 12
EQ 13
DE-ESSER 14 & 15

SAMPLE SETTINGS 16

TECHNICAL DETAILS

MAINS CONNECTIONS 17

TUBE, TRIMMER & JUMPER LOCATIONS 18

CALIBRATION 19

TROUBLESHOOTING 20 & 21

SPECIFICATIONS 22

CURVES 23 & 24

WARRANTY 25

WARRANTY REGISTRATION 26

APPENDIX 1 - TEMPLATE FOR STORING SETTINGS 27

INTRODUCTION

3

THANK YOU!...

for choosing the Manley VOXBOX. This unit is the result of our customers asking us to make a vocal
oriented combination from some favorite Manley designs. We combined the Manley Mic Preamplifier,
Electro-Optical Limiter, and Mid Pultec and then went further. Uniquely, we put a compressor before a
minimalist mic preamplifier. This can substantially reduce distortion while having no more sonic imprint
on the signal than the mic pre by itself because the compressor is just a passive light dependent clamping
resistor. For those who want the shortest path to tape, but use compressors, this has to be the ideal solution.
We added attack and release controls to the compressor with some "very special" settings such as one
that simulates a LA-2A, another "tuned" for drums and a setting that works like a great engineer "riding"
a fader. Then we extended the PULTEC MEQ down to 20 Hz and up to 20 kHz so its not just a mid EQ
anymore. To this we added a new de-esser circuit and gave it a "Limiter" setting. This final de-esser /
limiter is completely independent of the compressor and is post EQ.

We wanted the VOXBOX to be "Manley quality" and the first and only "analog combo" (other than
consoles) to make a serious entry into the major studios. We provided our style of balanced inputs and
outputs and used fewer but better parts. It only required five Manley audio transformers, six multi-tapped
inductors, two expensive Multi-Caps, four mil-spec JAN tubes, four Vactol opto-isolators, five regulated
power supplies, six Bournes conductive plastic pots & seven Grayhill gold contact rotary switches. A few
of these items are likely to cost more than other manufacturer's total parts. With all these serious
transformers we even provided ways to go transformerless,the minimalist and purist way to go. We went
to great lengths to eliminate typical clicks and pops from switches. The compressor and limiter can be
switched in while recording and the change happens smoothly. We added auto-mute circuitry to eliminate
the turn-on & turn-off thump and regulated all the power supplies. In fact many of these developments
are being incorporated into our next versions of our other pro products.

While we were designing the VOXBOX we couldn't help but notice how well it would work on other
instruments besides voice. There were some great settings for drums (unusual), bass, guitar and keys.
So don't just use it for voice - you can use it everyday and in any situation regardless of how well equipped
the studio may be. The name "VOXBOX" represents only the beginning and the most obvious application.

Please take a few moments to read through this manual carefully as it contains information essential to
proper operation of this unit and we scattered little hints all over. Thank you again, and please enjoy !

GENERAL NOTES

LOCATION & VENTILATION

The Manley VOXBOX must be installed in a stable location with ample ventilation. It is recommended,
if this unit is rack mounted, that you allow enough clearance on the top and bottom of the unit such that
a constant flow of air can move through the ventilation holes.

WATER & MOISTURE

As with any electrical equipment, this equipment should not be used near water or moisture.

SERVICING

The user should not attempt to service this unit beyond that described in the owner's manual.
Refer all servicing to your dealer or Manley Laboratories.

FRONT PANEL

A B C D E H J K N W X Y Z

2K
3K
4K

5K
7K 1K5

POWER

ON

OFFTHRESHOLD

READY

6K4

8K

5K

10K

4K

13K

3K

16K

2K

20K

ON

PHANTOM
48 VOLTS

120

80

FLAT

PHASE / IN

0˚

INST LINE

180˚

INPUT GAIN

50
48
45

42
40

MANLEY
VOXBOX

PRE O/P

EQ OUT

LINE IN

DSGR

THRESHOLD

COMPRESS 3:1

BYPASS

ATTACK RELEASE

FAST

MED FAST

MEDIUM

MED SLOW

SLOW

PRE
O/P

DE-ESS

BYPASS

EQ IN

BYPASS

EQ INPUT

INSERT

LINE IN

100

70
50
35

20

9 KHz

LOW PEAK

150

12 KHz

MID DIP HIGH PEAK

+100

200
300
500

700
1K

0 +100

-10

1K5

1K
700

500

300
200

F G I L M O P Q R S T U V

A INSTRUMENT INPUT: 100K ohm input impedance. The PHASE switch should be in the middle

position to use this input so that the mic input transformer is disconnected. Inserting a phone jack
here will interupt the back panel LINE INPUT. Compression will lower this impedance and can
cause some HF loss on guitars but a few dB of compression is OK. Two ways around this are use
a preamp or effects pedal between this input and the guitar or use the limiter part of the de-esser.

B PHANTOM POWER SWITCH: This is a "locking switch" for safety - Pull out to toggle. Turn

down the monitors before toggling. Use the 48 volt phantom power with FET CONDENSOR
MICS but not with dynamic or tube mics. See page11 for more on phantom power.

C PHANTOM LED: Lit when phantom power is on.

D LOW FILTER: This is a minimum phase shift "high pass" filter that is available for the mic, line

and instrument input. The slope is a gentle 6 dB per octave. FLAT = BYPASS

E PHASE SWITCH: A more correct term is polarity. This function is only available for the mic

input. The "0" position is normal (non-inverting). The "180" position reverses the phase of the mic
signal. The middle position marked "LINE" disconnects the mic transformer and optimizes the
LINE and INSTRUMENT inputs. One might also use that line position to act as a "mute" if no
line input is used (or better, the 1/4" jack is shorted). One uses the 180 position, for example, on
the bottom of a snare or with vocalists if the headphones or mic is out of phase.

F INPUT: This is the main level control for all inputs to the preamplifier. It is before the compressor

and preamplifier. It allows hot signals to be attenuated before any significant distortion can
happen.

G GAIN SWITCH: This is not a "pad". It sets the amount of negative feedback which has an effect

on gain, transient accuracy, noise, clipping characteristics, etc. It is normally used as a tone control
and/or to optimise noise. See page 11 for more on this control.

H VU METER: This is a true standard VU. It is not supposed to "agree" with peak meters. The VU

is preferred for recording to analog tape and is intended to show a reasonable representation of
how "loud" the signal will be heard. Use your tape machine's meters to safely set an output level.

I METER SELECT SWITCH: The VU meter shows 3 isolated audio inputs and 2 positions that are

used to indicate the amount of gain reduction from the compressor and de-esser / limiter. Because
the VU meter is a little slow it may not show some fast peak reduction that is actually occurring
but will tend to show the "audibility" of gain changes by the amount and rate of needle swing.

4

COMPRESSOR SECTION

J COMPRESSOR BYPASS: With this switch up the compressor is engaged. This switch

is uniquely designed to be used during music. No clicks, no pops and the change of level
occurs smoothly. The compressor is uniquely before the preamp so that transients are
"tamed" before the signal enters the tube circuit. This makes it possible to have
exceptionally clean, smooth tracks. It also allows the normal "mic preamp into outboard
compressor into tape" to be essentially "purist mic pre direct to tape" with compression
invisibly taking place. We use a passive opto-isolator for the gain control element which
adds no measurable distortion or noise and only 0.1 dB of insertion loss.

K COMPRESSOR THRESHOLD: Turning this control clockwise increases compression.

This control is after the INPUT control. There is no "make-up gain" control so some
degree of balancing between INPUT and THRESHOLD is expected. Adding the make­up gain or output level would have compromised the sonic integrity for the sake of
conventionality. The compressor "ratio" is program dependent and non-linear but is
generally similar to 3:1 ratios on VCA based compressors.

L ATTACK: This controls how the compressor reacts to transients such as explosive

consonants or drums. Slower settings tend to "ignore" transients and let them through
untouched. Faster settings tend to reduce transients which has an audible effect of
reducing, for example, the strike of a drum or the "P"s as in "puppy". Vocals will usually
be best with medium settings. Engineers most familiar with compressors will notice the
unusual way the "attack" rides above the reduction set by the release. Attack changes
are most noticable on slower releases on this unit.

M RELEASE: This controls how fast or slow the compressor returns to full volume.

Because various RC networworks are switched in this control also has some effect on
attack rates. The final release as reduction approaches 0 dB is a "bonus" function of the
Opto. Each setting is actually a separate complex set of "tuned" time constants. The
FAST setting mimics the Manley Electro-Optical Limiter and works best in the range of
3 to 8 dB of compression. The MED FAST setting is much like old LA-2A's but is also
tuned for drums and bass and works well with dynamic broadcast audio. This setting is
designed to pump a bit with the Attack at Slow. MED and MED SLOW are the usual
choices for vocals. SLOW is a very slow release and is for the most inaudible
compression. RELEASE SLOW + ATTACK SLOW uniquely mimics a good engineer
"riding" a fader. Good for great singers, questionable for dynamic material.

LA-2A = FAST ATTACK & MEDIUM FAST RELEASE or FAST RELEASE (or LIMITER)
LA-3A = SLOW or MEDIUM ATTACK & MEDIUM SLOW RELEASE

N LINK: Switching up connects or links a second VOXBOX for stereo applications. It

ensures that when either compressor channel reduces gain that both units will reduce the
same number of dBs. This is so that a center image does not drift when a peak is on one
side. Both sets of controls should normally be set to the same positions. It links both the
compressor and the de-esser to the second VOXBOX if RCA LINK interconnects are
between both units. The RCA male to male interconnect can be any typical stereo hi-fi
type.

5

EQ and DE-ESSER SECTION

O EQ BYPASS: Switching this up engages the EQ section. This is a passive PULTEC MEQ style EQ with

only one capacitor, one inductor (coil or choke) a conductive plastic pot and a gold contact switch in the audio
path for each band of EQ. There are no tubes in the EQ and certainly no ICs or transistors. The tube circuit
is only used for flat, fixed make-up gain and is always in circuit. The EQ is before the de-esser / limiter and
before the tubes.

P EQ INPUT: Three inputs are available to feed the EQ / De-esser / Line amp. The LINE IN is a split from

the same LINE IN that can feed the mic preamp section. The PRE O/P is the output of the mic preamp /
compressor section and is not through the output transformer. When using a line input into the compressor,
these two positions allow you to compare compression to no compression without the drop of gain you get
just using the compressor BYPASS switch. The INSERT setting allows yet another line input to feed this
section. It allows you to insert (or bypass) an external device such as a noise gate between the preamp output
and the EQ section. It also allows you to use the VOXBOX for two different tracks. These 3 inputs are
switched with high quality sealed relays near the back panel & transformers for the shortest signal path.

Q LOW PEAK FREQUENCY: This simply selects the center frequency to be boosted with the LOW PEAK

control. The "Q" or bandwidth is fixed and consistant with the original PULTEC MEQ. There are now 11
positions between 20 Hz and 1 kHz. The settings below 200 are new and were not on PULTEC MEQs. See
page 14 for a few tips if you want.

R LOW PEAK: Adjusts between 0 or flat and typically up to 10 dB of maximum boost.

S MID DIP FREQUENCY. 11 frequency bands between 200 Hz and 7 kHz (7,000 Hz). 1K5 is "British" for

1,500 hz or 1.5 kilohertz or kilocycles.

T MID DIP: Adjusts between 0 (flat) and up to (minus) 10 dB of maximum cut. Many top engineers suggest

that by using cut EQ (mostly from 200 to 1K5) rather than boost reduces phase shift problems and improves
the general clarity and punch. Cutting a bit at 5 or 7 kHz can reduce the resonance of some vocal mics. (It
helps to boost 16 or 20 kHz on the High Peak to compensate for lost brightness.)

U HIGH PEAK FREQUENCY: Again 11 positions but from 1,500 Hz (1K5) to 20 kHz. The settings above

5 kHz are new. Some frequencies may cause sibilance problems.

V HIGH PEAK: Adjusts between 0 (flat) and up to 10 dB of maximum boost.

W DE-ESS BYPASS: Switching up engages the de-esser or limiter. This function is also passive and can be

switched in silently during music!

X DE-ESS SELECT: This rotary switch selects frequency band the de-esser will dip or notch. The 3 KHz

position is may be used for occasional de-essing or may help control sounds that tend to "hurt". Our hearing
is most sensitive in that band. The LIMIT position removes the frequency selection and works as a "flat"
electro-optical limiter much like an LA2-A.

Y THRESHOLD: This sets how loud an "ess" (or transient in Limit) has to be before it can be reduced. Turn

clockwise for more de-essing. Normally we try to make the sibilance natural rather than removing the"esses"
entirely. A good way to set the threshold when limiting is to look at the tape machine peak meters and set
it to prevent overloads.

Z POWER. The meter will light immediately. There is a relay that mutes the outputs for about 20 seconds after

power is turned on and immediately after power is turned off to prevent "thumps". The LED marked READY
lights when audio can pass. This circuit will ignore quick "blackouts" for live sound work. This feature can
be totally bypassed (or the delay shortened). The VOXBOX should be turned off between sessions - to
extend tube life.

6

REAR PANEL

Q P O N M L K J I H G F

MIC INPUTLINE INPUTINSERT INPUT

TO PROTECT SPEAKERS:
BEFORE PATCHING

MICROPHONE:
VERIFY MONITORS
ARE TURNED DOWN.
BEST TO TURN OFF

XLR PINOUT: ALL TRANSFORMER BALANCED
PIN 1 = SHIELD = GROUND
PIN 2 = HOT = POSITIVE PHASE
PIN 3 = LOW = NEGATIVE PHASE

1/4 PHONE INPUTS : BALANCED OR UNBALANCED
SLEEVE = SHIELD = GROUND
TIP = HOT = SIGNAL POSITIVE
RING = LOW = NEGATIVE OR GROUND

1/4 PHONE OUTPUTS : UNBALANCED ONLY
SLEEVE = SHIELD = GROUND
TIP = HOT = SIGNAL POSITIVE
BYPASSES TRANSFORMER / DISABLES XLR OUT

THIS SPACE FOR SERIAL NUMBER

HANDCRAFTED IN USA

MANLEY LABORATORIES

13880 MAGNOLIA AVE., CHINO, CA 91710

PHONE [phone] FAX [phone]

email: [e-mail]

CAUTION: RISK OF ELECTRIC SHOCK. DO NOT OPEN.
REFER ALL SERVICING TO QUALIFIED PERSONNEL ONLY.
WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK.
DO NOT EXPOSE THIS UNIT TO RAIN OR MOISTURE

POWER FUSE

REPLACE ONLY WITH
SAME TYPE AND VALUE:

CIRCUIT

CHASSIS

CE

GROUND

STEREO LINK
COMPRESSOR

STEREO LINK

DE-ESSER

PREAMP OUTEQ OUT

UNBALANCED UNBALANCED+ 4 dBm + 4 dBm

BLOCK DIAGRAMGAIN

INSERT

SWITCH BALANCED

INPUT

INPUT

PASSIVE

OUR 40 dB

OUTPUT

UNBALANCED
OUTPUT

PASSIVE EQ

DE-ESSER

BALANCED
OUTPUT

UNBALANCED
OUTPUT

A B C D E

A IEC POWER CONNECTOR: Use the IEC detachable power cable that was packed with the VOXBOX.

The correct mains voltage is factory wired for your country. The third pin ground is connected to the
chassis internally.

B MAINS FUSE: Replace only with the same value and type which is 1 AMP SLO BLO. A generic type

is MDL 1 and its size is 1 1/4" X 1/4". A second or third blown fuse may indicate an electronic problem
needing repair especially if it has turned black. If it appears to be a serious problem, you should send the
VOXBOX to your dealer or to MANLEY LABS for repair.

C GROUND TERMINALS: These are used to find or fix hum or to prevent ground loops with a variety

of studio wiring techniques. The CIRCUIT GROUND may be also called audio ground or "technical
earth" and it simply is the common ground of the audio circuits in this unit. The CHASSIS GROUND
is the third pin mains ground and the chassis. Separating CHASSIS GROUND and CIRCUIT GROUND
is the same as breaking off the third pin of the AC plug except that it includes the chassis which is also
probably grounded to the rack. These two terminals are normally joined by a small piece of metal called
a ground strap. If you loosen the posts you can move the strap to the side - you can also lose the strap
if you don't re-tighten the posts. For some studio grounding techniques the AUDIO GROUND can be
connected to the console with a piece of wire. If you have a hum, experiment here first.

D BLOCK DIAGRAM: Shows a simplified drawing that shows the basic signal flow. This diagram is also

on page 10 in this manual.

E CONNECTOR PIN-OUT: A list of how the XLR and phone jacks are wired that might help the person

building the cables. This info is also in detail below.

F MIC INPUT: The mic cable gets plugged in here. 48 volt Phantom Power is available on this connector

(see page 5). The input impedance is 2400 ohms and is matched for most professional mics. The PIN­OUT of all the XLRs is as follows: PIN 1 = CIRCUIT GROUND = SHIELD

PIN 2 = HOT = positive going signal +
PIN 3 = LOW = negative going signal -

G LINE INPUT. For balanced or unbalanced +4 line level sources. Transformer coupled 1/4 inch phone

jack. The PIN-OUT is :

BALANCED - (using a stereo phone plug ) UNBALANCED - (using a mono or stereo plug)
TIP = HOT = positive + TIP = SIGNAL = HOT
RING = LOW = negative - (RING = GROUND = SHIELD)
SLEEVE = GROUND = SHIELD SLEEVE = GROUND = SHIELD

7

H LINE INPUT. XLR For balanced or unbalanced +4 line level sources. Transformer coupled. The PIN-

OUT is : PIN 1 = CIRCUIT GROUND = SHIELD

PIN 2 = HOT = positive going signal +
PIN 3 = LOW = negative going signal -

I PREAMP OUT (PHONE JACK). The signal from the mic preamplifier and compressor before the

transformer. It is designed to be the cleanest output for direct to tape recording. The output phone jacks
are different from the inputs. The phone jack outputs can only be unbalanced and are designed to bypass
the output transformers. Some people don't like transformers. One of our favorite studio owners sez "I
hate the sound of bad transformers and love the sound of good ones". These are great transformers and
have very little color. You can verify this by comparing the phone and XLR output one at a time. At
"worst" the XLR outputs seem to have slightly more bottom and punch. When you insert a phone plug
it cancels the XLR output because it removes the transformer right out of the circuit. This unbalanced
output is coupled with a MULTICAP for you audiophiles out there. It will be fine driving balanced inputs
as well as unbalanced inputs and is designed for pro +4 dBu nominal levels
The PIN-OUT is : TIP = SIGNAL

SLEEVE = GROUND
and if you must use stereo plugs connect the RING to SLEEVE and/or if you are sending to a balanced
input connect LOW or negative to the SLEEVE at either end.

J PREAMP OUT (XLR): A transformer balanced version of the mic preamplifier and compressor output.

Note that a 1/4 inch phone plug in the jack below will kill this output. The PIN-OUT is :

PIN 1 = CIRCUIT GROUND = SHIELD
PIN 2 = HOT = positive going signal +
PIN 3 = LOW = negative going signal -

K INSERT INPUT (PHONE JACK): Like the LINE IN can be used balanced or unbalanced. This input

only goes to the EQ section. It is intended as a return for a noise gate or other processor between the mic
pre and EQ. It is also a way to bring in a second input to use the VOX BOX for two separate tracks. The
PIN-OUT is the same as the LINE INPUT and the same electronically.

BALANCED - (using a stereo phone plug ) UNBALANCED - (using a mono or stereo plug)
TIP = HOT = positive + TIP = SIGNAL
RING = LOW = negative - (RING = GROUND = SHIELD)
SLEEVE = GROUND = SHIELD SLEEVE = GROUND = SHIELD

L INSERT INPUT (XLR): For balanced or unbalanced +4 line level sources. Transformer coupled XLR.

The PIN-OUT is : PIN 1 = CIRCUIT GROUND = SHIELD

PIN 2 = HOT = positive going signal +

PIN 3 = LOW = negative going signal -

M EQ OUT (PHONE JACK). The signal from the EQ and De-Esser before the transformer. The phone jack

outputs can only be unbalanced and are designed to bypass the output transformers. When you insert a
phone plug it cancels the XLR output because it removes the transformer right out of the circuit. This
output is also coupled with a MULTICAP. It will be fine driving balanced inputs as well as unbalanced
inputs and is designed for pro +4 dBu nominal levels
The PIN-OUT is : TIP = SIGNAL

SLEEVE = GROUND
and if you must use stereo plugs connect the RING to SLEEVE and/or if you are sending to a balanced
input connect LOW or negative to the SLEEVE.

N EQ OUT (XLR): A transformer balanced version of "M". This is also the final output or main output.

Note that a 1/4 inch phone plug in the jack below will kill this output. The PIN-OUT is :

PIN 1 = CIRCUIT GROUND = SHIELD
PIN 2 = HOT = positive going signal +
PIN 3 = LOW = negative going signal -

8