Manley MVBXA 4 User Manual
MANLEY
VOXBOX
OWNER’S MANUAL
TUBES
RULE
REV. MVBXXAxxxx
rev3/15/2011cd
CONTENTS
SECTION PAGE
INTRODUCTION 3
QUICK START 4
MAINS CONNECTIONS 5
FRONT PANEL
MIC PRE 6
COMPRESSOR 7
EQ & DE-ESSER 8
REAR PANEL 9
GENERAL DISCUSSION
OVERVIEW AND BLOCK DIAGRAM 12
MIC PREAMP & COMPRESSOR 13
EQ & DE-ESSER 15
ADDENDUM 18
TECHNICAL DETAILS
TUBE, TRIMMER LOCATIONS 19
CALIBRATION 20
TROUBLESHOOTING 21
SPECIFICATIONS 23
CURVES 24
APPENDIX 1 - TEMPLATE FOR STORING SETTINGS 26
INTRODUCTION
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 low noise graded tubes, four Vactrol
opto-isolators, three 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. Many of these developments have since been incorporated into revisions 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.
3
QUICK START
So you just got your VOXBOX (congratulations!), and all you want to do is plug it in and
get on with recording. But there are so many darn switches and input/output jacks all over
the dang thing! Where to even begin?!?
Don’t panic. Described below are a few quick-start I/O congurations and settings so you
can start making music right away. Feel free to experiment, and remember - if you don’t
hear any sound, make sure your front-panel settings correspond with your Ins and Outs. 98
out of 99 times, “xing” your VOXBOX involves ipping one switch.
MICROPHONE TO VOXBOX, ALL SECTIONS OF VOXBOX AVAILABLE
Rear Panel: Microphone in via XLR to MIC INPUT. Line level out via EQ OUT.
Front Panel:
- “Phase” set to 0° or 180° (not LINE)
- Meter set to EQ OUT
- EQ INPUT set to PRE O/P
MICROPHONE TO VOXBOX, PREAMP/COMP ONLY
Rear Panel: Microphone in via XLR to MIC INPUT. Line level out via PREAMP OUT.
Front Panel:
- “Phase” set to 0° or 180° (not LINE)
- Meter set to PRE O/P
LINE LEVEL TO VOXBOX, ALL SECTIONS OF VOXBOX AVAILABLE
Rear Panel: Line in via XLR or 1/4” to LINE INPUT. Line level out via EQ OUT.
Front Panel:
- “Phase” set to LINE
- Meter set to EQ OUT
- EQ INPUT set to PRE O/P.
LINE LEVEL TO VOXBOX, PREAMP/COMP ONLY
Rear Panel: Line in via XLR or 1/4” to LINE INPUT. Line level out via PREAMP OUT.
Front Panel:
- “Phase” set to LINE
- Meter set to PRE O/P
- EQ INPUT set to PRE O/P.
LINE LEVEL TO VOXBOX, EQ ONLY
Rear Panel: Line in via XLR or 1/4” to LINE INPUT. Line level out via EQ OUT.
Front Panel:
- “Phase” set to LINE
- Meter set to EQ OUT
- EQ INPUT set to LINE IN.
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MAINS CONNECTIONS
Your VOXBOX has been factory set to the correct mains voltage for your country. The voltage setting is marked
on the serial badge, located on the rear panel. Check that this complies with your local supply.
Exportunitsforcertainmarketshaveamouldedmainsplugttedtocomplywithlocalrequirements.Ifyourunit
doesnothaveaplugttedthecolouredwiresshouldbeconnectedtotheappropriateplugterminalsinaccordance
with the following code:
GREEN/YELLOW EARTH
BLUE NEUTRAL
BROWN LIVE
As the colours of the wires in the mains lead may not correspond with the coloured marking identifying the terminals in your plug proceed as follows:
The wire which is coloured GREEN/YELLOW must be connected to the terminal in the plug which is
marked by the letter E or by the safety earth symbol or coloured GREEN or GREEN and YELLOW.
The wire which is coloured BLUE must be connected to the terminal in the plug which is marked by the letter
N or coloured BLACK.
The wire which is coloured BROWN must be connected to the terminal in the plug which is marked by the
letter L or coloured RED.
DO NOT CONNECT/SWITCH ON THE MAINS SUPPLY UNTIL ALL OTHER CONNECTIONS HAVE
BEEN MADE.
Note: Units are purpose built for original destination country’s mains voltage: 100V, 120V, or 220-240VAC as
indicated on the serial number badge. Power transformer must be replaced in order to change mains operating
voltage.
120VAC units may NOT be rewired to put the primaries of the power transformer in series for 220-240V
operation or a large radiated eld of hum will develop. If changing locations/voltages, the power transformer
must be replaced with the dedicated one for the voltage at which it will operate.
Waste Electrical and Electronic Equipment (WEEE)
Informationforcustomers:
TheEuropeanParliamentandtheCounciloftheEuropeanUnionhaveissuedtheWasteElectricalandElectronicEquipmentDirective.ThepurposeoftheDirectiveisthepreventionofwasteofelectricalandelectronicequipment,andtopromotethereuseandrecyclingandotherformsofrecoveryofsuchwaste.Assuch
the Directive concerns producers, distributors and consumers.
TheWEEEdirectiverequiresthatbothmanufacturersandend-consumersdisposeofelectricalandelectronicequipmentandpartsinanenvironmentallysafemanner,andthatequipmentandwastearereusedorrecoveredfortheirmaterialsorenergy.Electricalandelectronicequipmentandpartsmustnotbedisposedofwith
normalhouseholdwastage;allelectricalandelectronicequipmentandpartsmustbecollectedanddisposedofseparately.
Productsandequipmentwhichmustbecollectedforreuse,recyclingandotherformsofrecoveryaremarkedwiththefollowingpictogram:
Smallproductsmaynotalwaysbemarkedwiththispictograminwhichcasethisispresentintheinstructionsforuse,ontheguaranteecerticateandprintedon
the packaging.
Whendisposingofelectricalandelectronicequipmentbyuseofthecollectionsystemsavailableinyourcountry,youprotecttheenvironment,humanhealthand
contributetotheprudentandrationaluseofnaturalresources.Collectingelectricalandelectronicequipmentandwastepreventsthepotentialcontaminationof
naturewiththehazardoussubstanceswhichmaybepresentinelectricalandelectronicproductsandequipment.
YourMANLEYorLANGEVINretailerwillassistwithandadviseyouofthecorrectwayofdisposalinyourcountry.
5
FRONT PANEL
A B C D E H J K N W X Y Z
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 page 13 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” lter 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 preamplier. It is before the compressor and
preamplier. It allows hot signals to be attenuated before any signicant 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 13 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.
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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 make-up 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 ElectroOptical 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 & ME-
DIUM 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.
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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.
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