2-Bus LT Manual - Dangerous Music
Contents
1. REMOTE ONLY This connector is not used DC IN It is best to make sure that the power supply is unplugged when connecting the DC power cable to prevent damage to contacts in the connectors MAIN OUT The Main Output feeds the mixdown A D converter MON OUT These jacks have the same signal as the Main Outputs They are to feed the Dangerous Monitor or other monitor section 3 Front Panel and Use O DANGEROUS R 6340 56 738 M0 M2 BU 15 16 l ao oa oo aco oo oo l O O 2 BUSir mono DANGEROUS 2 BUS LT FRONT PANEL There are two types of front panel controls on 2Bus LT MONO switches put the signals of a pair normally panned hard left and right up the middle of a mix The Output Level Trim is a mix fine gain adjustment used to get the signal level just right to the mixdown A D converter or EQ Compressor if in the chain The switches on the front panel are laid out so that the inputs can be treated as stereo pairs also known as stems or as individual inputs panned up the middle of a mix For sounds that are panned somewhere in between the two extremes a pair of D A converters is used and the Mono button is not engaged For example let s say that one wants to mix a drum kit with bass guitars a lead vocal and reverb signals together To keep things simple let s say that the engineer has a DAW with 8 D A channels available to patch to analog2. 0 00e 1 Hz 100 kHz within 0 2dB TAD GTS Sine on earonkienawnenrnmeesacwennss 0 003 22 kHz band limited IMD60 451 oc svccucsacecesiacereiniersenins 0 004 Crosstalk esserne an REEERE 97dB 1 kHz Noise HMO asserere aiarren 82 dBu audio band limited Maximum signal level 26dBu Nominal operating level 4dBu Input impedance esc saucacekieswnse teens 12k ohms bridging Output impedance 668 50 ohms Power consumption 0 08 25 watts WalraiNhy ccoxessevat vxdextevrexerzeixeecs Free 2 year extended warranty with online registration Standard warranty 90 days parts and labor subject to inspection Does not include damage incurred through abusive operation or modifications attempted repair by unauthorized technicians Dangerous Music Inc USA Europe Dangerous Music Inc Dangerous Music Inc 231 Stevens Road Stieleichenweg 55 Edmeston NY 13335 50999 K ln Tel 49 2236 393731 Email info dangerousmusic com E mail info dangerousmusic de 11
3. high end analog recording systems in terms of sound quality preservation of spatial detail and no latency ergonomics In today s portable environment and with the cost of maintaining and housing legendary recording equipment the choice of a big desk is impractical for many users of DAW systems We want to bring together the best of both worlds It is in this spirit that the Dangerous engineering team is designing and manufacturing an exciting array of summing mixing monitoring metering and mastering equipment to meet the needs of today s recording engineers producers and artists Hook up SLA fe 9 9 o o QO a OQ L ppansionn R IN 9 16 REMOTE ONLY DC IN L manour R L moxour R DANGEROUS 2 BUS LT REAR PANEL The 2Bus LT is designed to mix the outputs of two eight channel D A converters to a stereo recorder 16x2 The 2Bus LT is easily stackable to increase channel numbers and system functions when linked with another 2Bus LT Mixer Monitor or 2Bus All the XLR s are pin 2 hot and the connector groups are described as follows EXPANSION IN Patch from the Main Output of a 2Bus LT or Mixer to sum into the mix bus IN 1 8 IN 9 16 The inputs are arranged into eight sets of XLR s They can be plugged into directly from the D A converters but system flexibility and fun goes way up with the addition of a patch bay for ease of outboard equipment use The pin out is on page 10
4. in the US have historically used the VU meter for system alignment and level monitoring so naturally with many years of precedent there are holdovers today from that system derived from the telephone and broadcast industries The standard of OVU comes from the Bell Telephone engineers needing a convenient way to measure signal levels in phone lines and switching systems 600 ohm balanced lines were the norm and 1 milliwatt of energy was a pertinent amount of juice moving through phone circuits A building out resistor was added to the VU meter to avoid loading the audio circuit down and the reference level cranked back up so the meter read OVU The resulting standard level wound up at 4dBu or roughly 1 23 volts AC RMS This standard has been with us for more than 60 years now the world over and is the reference level to which most professional audio systems are aligned Alignment Chart Volts AC VU dBu dBfs recording dBfs mastering 9 76 v Tilt 22 0 full scale Tilt 6 16 Vv Tilt 18 4dBfs 0 full scale 1 23 v 0VU_ 4dBu 18dBfs 14dBfs EE ee _ A D converters in a recording situation are usually set to have a 22dBu maximum input level to achieve full scale This allows for occasional loud hits to not clip the converter D As for this system would typically be aligned to have unity gain with the A Ds This is done by running a 18dBfs signal at 1 kHz with the digital oscillator to the individual D A outputs
5. one channel at a time Turn the 2Bus LT output gain knob all the way up and measure the voltage across pins 2 and 3 of the 2Bus LT output connector If there is a device in the studio that has a calibrated VU meter tape machine compressor Dangerous MQ patching the 2Bus LT into it makes for convenient adjustment Set the D A converter gain so that the volume indicator reads 0 VU or 1 23 volts AC on the voltmeter After the D As are aligned the A Ds are aligned by using the oscillator and one of the D As as a source Feed that signal into the A Ds one at a time and meter it in the DAW Adjust the A D for 18dB full scale Once all the converters are aligned the system becomes easier to handle because there is a wonderful consistency from channel to channel This makes cross patching and bussing assignment seamless Mastering systems are typically calibrated at 14dB from full scale for a maximum analog signal level of 18dBu The reason for this is because mastered signals tend to be compressed and bright There is a lot of rapid change slew rate in the signal that overloads processing gear and converters before the amplitude gets up to 22dBu Some savvy 2Bus LT users set their D A converters as if they were mastering to be able to take full advantage of the dynamic range such a calibrated system has to offer In other words A Ds are set to avoid clipping for recording and D As are set to avoid overloading the mixdown converter This is done by a
6. the speakers when the input cable is connected to LT but goes away when the input cable is unplugged that means the source equipment needs a ground reference from the LT output driver Male XLR Female XLR LT input receiver Pine signal hot or side Pin3 D A ground Pinl cable shield V no output ground reference input shield lift jumper closed i equipment ground The way to do this is to close the input shield lift jumper located on the main audio board where the input wires connect These tactics rarely need to be performed but if they do please work on a well lighted table or workbench We always clean off enough space to have plenty of room so as to not lose screws and tools Using a cloth or other pad underneath the equipment will prevent scratches and damage both to the gear and to the table There are also input shield lift jumpers for the Expansion inputs A If one is uncomfortable with opening gear and changing jumpers or making adjustments please seek qualified help if necessary If adjustments or jumper changes are required please disconnect the mains plug before opening the top Grounding Revisited Next is a quick set of hints about where to look when trying to cure buzz troubles in a recording studio While the techniques are not meant to be taken as Gospel some techs might disagree with this treatise so be it these bits of knowledge were gleaned from decades of experience in test equip
7. The Dangerous Music 2Bus LT Manual Thank you for choosing products from the exciting line of Dangerous Music recording equipment Many years of dependable and trouble free performance can be expected from our gear This has been made possible by careful design construction and top shelf component choices by recording industry veterans This manual will assist the user in the installation of the 2Bus LT and calibration of the system O O DANGEROUS 12 34 56 18 910 112 1314 15 16 ao oe oo a ce ac oo oo Oo O 9 BUSir Contents IntrOGUCHION j 5 1450c oisidiavasrariseedeceeasacs 1 Safety TEVIEW eresse saronrin iis entenis sanis 2 Overview and Hook up 00ceeee 3 Front Panel and Use 4 Calibration inscenaninsadabenasvacccomhe wen dtimanwes 5 Balanced connections 6 Unbalanced connections 008 7 Grounding TEVISITED 50250sec0 ccesre sees ciaense 8 Connector Pin Outs 0 ccee cee eee 10 DPCCWICATONG cicsacysannaempaecearanasaatacer 11 Safety Review The exclamation point within an equilateral triangle is intended to alert the user to the presence of important operating and maintenance servicing instructions in the literature accompanying this product Certain precautions should be taken when using electrical products Please observe the safety hints by reading the manual and obtaining qu
8. alified help if necessary to adhere to the precautions 1 Always use a properly grounded power supply cord with this product Please do not defeat the ground pin on the mains plug This connection provides earth to the chassis and signal grounds inside the device for clean and quiet operation The Grounding and interface section can help the user installer clear up a buzz problem if one develops 2 Avoid high temperature operation in equipment racks by providing air circulation The number one killer of electronic gear is HEAT Vented rack panels may look like wasted space to an interior decorator but they look like beauty to a technician or equipment designer If the front panel is hot it is roasting inside the box 3 Avoid areas of high magnetic fields The steel chassis of 2Bus LT is designed to shield the circuits from EMI and RFI magnetic and radio interference When installing equipment in racks it is prudent to put power amplifiers and large power supplies at least several rack spaces if not in a different rack away from equipment that deals with low level signals Separation of high level and low level equipment can pre empt trouble caused by heat and EMI 4 Care should be taken to avoid liquid spills around equipment If a spill occurs please shut off the gear and disconnect the mains A qualified technician should investigate accidents to prevent further equipment damage or personnel hazards caused by spills 5 If one
9. d Mixer are stackable to accommodate systems of any size 4 Calibration The following sections provide a more detailed look at some of the aspects of recording studio setup and trouble shooting While it is not absolutely necessary to read the material we feel that a basic understanding of the principles of calibration equipment interface and grounding issues can go a long way to helping engineers before the going gets rough If one encounters inconsistent levels or hum problems in the studio the following hints may help in understanding the issues and resolving the problems These issues apply to recording gear in general not just the 2Bus LT The Dangerous 2Bus LT comes to you fully calibrated and ready to hook up In order to enjoy the full benefits of a 2Bus LT system the D As used with it should be aligned This can be done with the aid of a Voltmeter VU meter in a compressor or other piece of gear on hand and the digital oscillator found as a plug in in most DAW systems While it is not necessary to align the system better and more consistent mix results will be obtained if this is done There are two analog operating levels that most digital recording systems have converged upon depending on whether the situation is for recording or mastering The difference between the two worlds is whether the maximum electrical stress is imposed by amplitude limiting recording or slew rate limiting mastering Professional recording systems
10. ield lift wiring permanently into its receiving end connector 9 Connector Pin Outs All of the XLR connectors are wired pin 2 high pin 3 low and pin 1 shield Due to back panel space limitations we were forced to use D connectors conforming to the Tascam standard for the main audio input wiring sorry Actually this makes wiring the LT into a modern patchbay very easy as most of the other manufacturers use the same standard Those that don t get verbal abuse at AES conventions D connector pin out pin Channel signal 1 8 high 14 8 low 2 8 shield 15 7 high 3 7 low 16 7 shield 4 6 high 17 6 low 5 6 shield 18 5 high 6 5 low 19 5 shield 7 4 high 20 4 low 8 4 shield 21 3 high 9 3 low 22 3 shield 10 2 high 23 2 low 11 2 shield 24 1 high 12 1 low 25 1 shield 13 not used The AC Mains cable A mains cable uses a standard IEC connector Please use pre wired AC cables for this device unless a technically qualified person makes the connections to a mains plug In this case use only high quality mains plugs like Hubbel Thomas amp Betts or a similar type Remember in America Black is hot White is neutral and Green is ground In Europe Brown is hot Blue is Neutral and Green with a Yellow stripe is ground It is critical to get this correct Double check that it is 10 Specifications Frequency response
11. is uncomfortable with opening gear and changing jumpers or making djustments please seek qualified help if necessary 6 If adjustments or jumper changes are required please disconnect the mains plug before opening the top Dropped screws or tools on a live circuit board can manifest themselves as burn marks and smoked components While we feel your pain been there subsequent damage is not covered by the warranty Dangerous Music Incorporated reserves the right to change the specifications or modify the designs of its equipment Sending in the registration card is our way of keeping in touch with users of our equipment should this become necessary Registration information is always kept confidential and never disclosed to third parties for any reason Company contact information is on the last page of this manual The CE sign on this product signifies the fact that the 2Bus LT has been tested and verified to conform to the applicable standards of 89 336 EEC EN55103 1 emissions EN55103 2 immunity and EN60065 2002 safety requirements Overview The 2Bus LT is a 16x2 summing amplifier designed to help the users of digital audio workstations achieve better mix performance through the use of existing equipment in their studios The designers and their colleagues have noted that while DA Ws offer unprecedented flexibility in multitrack recording and editing the resulting mixes from these systems generally don t equal those of
12. ligning one D A at 18dBfs and using it to calibrate the A Ds as above Then set the all the D As so that 14dB full scale is OVU by running the digital oscillator at 14dB and adjusting the D A output levels to read 1 23 volts ac or OVU This allows one to run the stems at hot levels without overloading the mixdown A D converter Balanced and Unbalanced connections output driver Male XLR Female XLR LT input receiver Signal hot or side signal lo or side A cable shield equipment ground input shield lift jumper a equipment ground The beauty of balanced connections is that they promote the idea that current should be prevented from flowing down cable shields while letting the audio pass Pins 2 and 3 carry a signal across them transverse mode and any interference that gets through the shield is picked up equally by the wires common mode The common mode noise is canceled by the differential action of the instrumentation amplifier in the first stage of the 2Bus LT Signal gets through and the grounds stay put inside their respective pieces of gear Unbalanced Connections output driver Male XLR Female XLR LT input receiver signal hot or side D A _ground cable shield equipment ground input shield lift jumper a equipment ground Unbalanced lines are usually treated the same as balanced because the 2Bus LT will let the signal through while isolating the equipment grounds If a buzz develops in
13. manufacturers are required to connect all the shield pins of audio and data connectors to the chassis grounds of their gear Sometimes this can cause noise problems in large systems where pieces of equipment are spread out around a facility because two grounds are never quite at the same potential This can cause ground loops hums or buzzing if the cable shields are allowed to connect two chassis that are at different potentials due to location circuit wiring or induction Below is a diagram showing how a typical ground loop is made and why it is important to pay attention to the wiring scheme in a studio The input shield ground lift jumpers in Dangerous Music equipment and that of many other manufacturers can help in avoiding ground loops and the associated poor noise performance Another Rack o Stuff Rack o Stuff interconnecting OOM 000 cables O Or outlet A 888 888 888 outlet B sse e82 o o oooo T Ground Loop eooo FF current Mains grounds meet at the power panel If the audio cables between the racks connect the equipment grounds together via the shields and the racks are at even slightly different potentials on different circuits with different loads long distance etc the shields will try to equalize the potential difference Juice will flow down the shields and broadcast hum into the signal wires they were supposed to p
14. ment use manual reading facility design construction trouble shooting and being the chief of maintenance in some of the world s top studios as well as problem solving in the home studios of rock stars and remote recording live sound situations These hints have proven to work in many situations while keeping systems safe and quiet While the usual scenario in hooking up equipment is that one plugs in the cables and starts to work the more complicated a system the more likely it is that something will not work correctly as far as hum and noise performance is concerned While some would blame the equipment this is the equivalent of blaming the eggs for a bad souffl Usually hum and noise problems and jitter or clock troubles in digital interfaces can be traced to poor planning and implementation of the studio s grounding situation It is illuminating to realize that the engineers of yore in the recording broadcast and communications industries have been through these troubles and figured out the solutions History can teach us a lot about how to avoid ground loops and their associated problems The manuals of many test instrument and recording equipment manufacturers from the 50 s to the 80 s had chapters on how to fix hum and noise problems and it is from this wealth of information that the writer draws ideas from for trouble free grounding schemes To comply with international standards and wiring practices recording equipment
15. output processing if desired and then the 2Bus LT This mix has 8 tracks of drums one bass two guitars one vocal with reverb and effects for maybe 2 dozen tracks total Usually a DAW user would mix this to 2 tracks and then bounce the result to a new pair of tracks but by using 4 pairs of outputs audio flexibility can be improved by assigning the drums to DAW outputs 1 and 2 the bass and vocal to 3 and 4 the guitars to 5 and 6 and finally the effects returns to 7 and 8 The bass and vocal want their own channels so they are assigned straight to the outputs with no panners and the MONO button on the 2Bus LT is pressed to pan them up the middle The 2Bus LT Main Output is then sent to an A D converter that is recording back into the DAW or an external device like an editing system tape machine or CD burner using the Output Trim Level to set the gain precisely Since the tracks are spread among several busses in the computer the individual levels can be run much hotter inside the box resulting in a mix that has better clarity detail and punch The use of outboard processing means that individual stems can be made to slam without using outboard loops in the DAW and suffering another A D conversion with the inherent time delay issues and another digital fader with its loss of detail This example is a bare bones mix The effect of setting a system up like this becomes more apparent as more tracks have to be mixed The 2Bus LT 2Bus an
16. rotect or wind up imposed on the reference ground of the receiving equipment This situation manifests itself as the all too familiar buzz of a ground loop The intensity depends on many variables but can go from unnoticeable to raging Some people in desperation resort to using AC plug ground lifts to defeat the mains safety grounds in a random fashion until the system quiets down a bit This in our view and the view of the safety standards organizations is an unacceptable method of taming ground buzzes The simpler way is to make sure that all the gear has a good mains ground and to lift the shields on the receiving ends of the audio cables The principals at Dangerous Music have wired up large world class facilities using this scheme and have brought room after room online with no buzz problems from the moment of power up This is why many gear manufacturers have shield lift jumpers inside their equipment If a noise problem crops up changing the jumper position will almost always cure the problem Planning out the wiring system to minimize the formation of ground loops solves problems before they happen Many powered speakers seem to get their audio reference ground from the input cable This means that these shields should not be lifted at the XLR One favored technique for trouble shooting buzz issues is to make a short XLR cable with the shield lifted on the Male connector and use this to test whether or not an interface warrants a sh
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