MANLEY VOXBOX OWNER’S MANUAL TUBES RULE REV.
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 MIC PREAMP & COMPRESSOR EQ & DE-ESSER 12 13 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.
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 configurations 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.
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. Export units for certain markets have a moulded mains plug fitted to comply with local requirements.
FRONT PANEL A B C D F G E H I J L K N M W O P X Y Z 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.
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.
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.
REAR PANEL Q A B P O N M L K J C D I H G F 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”.
H. LINE INPUT. XLR For balanced or unbalanced +4 line level sources. Transformer coupled. The PINOUT 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.
O. LINK COMPRESSOR: This RCA is used for connecting to a second VOXBOX. The signal on this connector is a changing DC voltage from the compressor section. It is both an input and an output. You can link the second VOXBOX with any typical hi-fi RCA interconnect as long as it is not longer than 6 feet. P. LINK DE-ESSER: This RCA is used for connecting to a second VOX BOX.
OVERVIEW and BLOCK DIAGRAM GAIN SWITCH MIC IN PHASE INPUT LEVEL INST IN INSERT INPUT BALANCED OUTPUT COMPRESSOR MIC PRE EQUALIZER NEW PASSIVE OPTO CIRCUIT OUR 60dB TUBE PREAMP PASSIVE EQ PULTEC STYLE LINE IN TRANSFORMER SYMBOL BALANCED OUTPUT DE-ESSER LIMITER LINE AMPLIFIER PASSIVE OPTO TUBE CIRCUIT UNBALANCED OUTPUT UNBALANCED OUTPUT TUBE GAIN STAGES SWITCHING PHONE JACK This block diagram is intended to give you a reasonable view of the signal flow in the VOXBOX.
THE MIC PREAMP & COMPRESSOR The VOXBOX can be divided into two main sections. The first is the Compressor and Mic Preamplifier. The input signal can be a microphone, instrument or line level signal. The mic and line inputs are on the back panel. The mic input is transformer balanced with 48 volt phantom power available, switched from the front. The line input has both XLR and 1/4 inch phone jacks and will accept balanced or unbalanced signal at either of the jacks.
The LOW FREQUENCY ROLL-OFF switch works on mic, line and instrument inputs. We use it to reduce room rumble, excessive proximity effect and sometimes to achieve hotter overall levels. It reduces bass a bit gentler and smoother than most mic pre filters. It is 6 dB per octave, rather than 18 dB per octave. A little note about the INPUT control. This control is before any other circuitry that might distort. In a sense, it is a variable pad.
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 description is simply “slow and fast vintage opto” but we did emulate and compare with real vintage units.
The MID DIP section has a number of typical uses. Most condensor mics have a peak in the frequency response. It is the normal resonance of the diaphram and is typically in the 5 kHz to 10 kHz range on the large diaphram mics that we tend to favor for vocals. Sometimes you can often get a sweeter sound by dipping a little at 5K or 7K and then boosting frequencies above 12K. It may be important to find a good balance between “presence” or “cut” and “breath” or “air”.
Is there a way to prevent the sibilance problems and still get an airy bright vocal sound without resorting to a de-esser? Usually, yes. “Boosting too much highs “ normally gets the blame but that may be an over-simplified view and not always accurate. Modern pop productions almost demand that bright airy sound that can only be arrived at by boosting highs. The wrong boost frequencies are those that correspond to the resonance of the mic or “whistle” caused by a gap in the singers teeth.
ADDENDUM Originally this page was supposed to show some user settings and we invited everybody to contribute. Nobody did, so this page was blank for 3 years. So now, we can use it for some collected comments and hints we have had since the introduction and for some info on versions and updates. The single biggest unexpected rave is from bass players - they want us to rename it “The BassBox”. It turns out the VOXBOX is pretty amazing as a direct box for bass. If you haven’t tried this yet, please do.
TUBE & TRIM LOCATIONS 12V FILAMENT REGULATOR D1 ON = No mute D2 ON = Shorter mute time D1,D2 OFF = Factory default mute timer ON E INSERT IN PRE OUT M 6414 EQ OUT EQ IN SELECT & MUTING 6414 MIC IN OPTOS 7 6 DS / LIM CAL 12AX7 / ECC83 3 EQ CAPS AND INDUCTORS MULTICAP OP COUPLING METER DS GR CAL OPTOS METER GR ZERO SET MULTICAP OP COUPLING Low noise graded 12AX7 / ECC83 D1 D2 Power turn on delay M E E ON SUPER YELLOW LED LIGHTS (remove 2 small phillips screws on meter back to acce
CALIBRATION PROCEDURE This procedure has been done by the factory and should not be re-adjusted unless absolutely needed and should only be done by a qualified technician. There are potentially painfull high voltages inside the VOXBOX so care should be taken even by good technicians. They have been known to get a shock but they also know to use one hand and insulated tools or gloves. The function of each trim is labeled on the diagram on the previous page (page 18).
TROUBLESHOOTING There are a number of possible symptoms of something not quite right. Some may be interfacing, others we will touch on as well. If you suspect a problem the following paragraphs should help. NO POWER, NO INDICATORS, NADA - Probably something to do with AC power. Is it plugged in? Check the fuseon the back panel. A blown fuse often looks blackened inside or the little wire inside looks broken or it’s resistance measures higher than 2 ohms.
IT MAKES NOISES WHEN THE FRONT PANEL IS TAPPED - An easy one. Some tubes become microphonic over time. That means they start acting like a bad microphone. Vibration has caused the supports for the little parts in the tube to loosen and now the tube is sensitive to vibration. Easy - Replace the tube. Which one? The one that makes the most noise when you tap it. Usually this will be one of the smaller (gain stage) tubes closest to the front.
MANLEY VOXBOX SPECIFICATIONS PREAMPLIFIER EQ SECTION BOTH Maximum Output : 1.5% THD Unbalanced: 20-20K Balanced: 1 KHz +31 dBv +31 dBv` +31 dBv +31 dBv +31 dBv +31 dBv Headroom (referenced to +4 dBv) 27 dB 27 dB 27 dB THD & Noise (1kHz @ +20 dBm) .3% .3% .
MORE VOXBOX CURVES 20 15 10 5 COMPRESSOR THRESHOLD AT MAXIMUM MED ATTACK / MEDIUM RELEASE SHOWS 3:1 SLOPE 0 -5 -10 -15 -20 -20 -15 -10 -5 0 5 10 15 +20 20 15 LIMITER THRESHOLD AT MAXIMUM 10 5 Slope starts at 5:1 quickly becomes 10:1 then towards 20 dB of limiting begins to return to normal.
TEMPLATES FOR STORING SETTINGS COPY THIS PAGE DO NOT WRITE ON THIS MASTER ARTIST INSTRUMENT / TRACK DATE SONG MIC NOTES ENGINEER ARTIST INSTRUMENT / TRACK DATE SONG MIC NOTES ENGINEER ARTIST INSTRUMENT / TRACK DATE SONG MIC NOTES ENGINEER NOTES 26
