Also this process involves removing two covers from your Technics and hence exposing bare connections to electrical terminals potentially at mains voltage.

The fabulous 1200 MKII and 1210 Mk II DJ turntables from technics are like a reliable car they go on and on as long as you look after them.

The pitch is one of the most common things to start causing you problems and is of course crucial to any DJ who is beat matching. When your turntable starts slipping its pitch or takes the occasional crazy you must get it sorted out or risk looking like a beginner when out playing your latest set.

There is of course the possibility that you need something replaced ( I will touch on this at the end) by an experienced technician and the process of setting up you pitch is something that does require specialist test equipment and an understanding of all things technical.

Lets Get started.

You need to turn off the power to your turntable and remove the plug from the wall.
Remove the platter by placing one finger in each hole and pulling directly upward. This can be quite tricky and you must make sure to pull straight upwards with equal force so as not to damage the central spindle.

Under the platter you will find there is a black vented panel held doen by about five philips screws. Undo these to reveal the motor and control board. The area will look a bit like this but with lots more colourful components (just the ones you need to know about are here).

To make this adjustment you will need a frequency meter that is acurate to two decimal places at a up to 500kHZ range. Most good multimeters will give this functionality.

Set you pitch fader to the zero position and ensure the green light lights up.

Place the two probes of you meter on the two test points marked in red and have a small philips screw driver ready to adjust the pitch control adjustment VR301.

ENSURE THAT YOU ARE WELL CLEAR OF THE POWER SECTION OF THE UNIOT TO THE RIGHT HAND SIDE OF THE BOARD SHOWN ABOVE.

No you need to plug in the unit and turn the power on using the power on knob.

Your meter should hope fully read something around 260kHz.

Adjust the Variable resistor (VR301) until you achieve 262.08kHZ plus or minus 0.05kHz

Turn off the power and re-assemble the unit.

You turntables pitch has now been correctly calibrated to the zero point of you pitch slider.

This is important so that your tunes play at the right speed but can also cause problems at the extremities of th pitch fader if the value is to far away from the nominal value.

The next step is to adjust your pitch variance which I will come back to in a future post

Neil Silver
SI Sound and Light and Quality DJ

Check out our new project

Lighting Control

Check out this info from Sennheiser and Gain tech note from Rane to supplement it.

Connecting the power supply
When connecting the power supply you should be aware that the right unit with the proper voltage is being used. Use the strain relief and secure the power adapter with a cable tie. It is easy to trip in dark clubs.

Battery installation
Do not be stingy in this department! It is very important to always use a fresh 9 Volt battery (type LR61). Rechargeable batteries last up to three hours of continual use. If your band is known for its endless concerts you should use Alkaline batteries. These last up to eight hours of continual use. Even better, especially in cold temperatures, are lithium cells. Please be aware that simple zinc-carbon batteries are not suitable for this type of use.

Troubleshooting the battery compartment
If the battery flap has problems closing and the transmitter will not turn on, then the battery has been inserted incorrectly. If the battery terminals are accidentally reversed, the transmitter will not function. Even more important to avoid is accidentally mixing up empty, or half-empty batteries. The worst thing is to be up on stage and sing into a mic and have no sound come out. It is a good idea to always have a fresh supply of batteries, just in case. Just as a guitarist never leaves home without a spare set of strings, right?

Operating the wireless microphone
First, turn on the receiver – the transmitter is still off. Increase the AF output level and listen to the signal: Does the signal sound clean? If this is not the case you must find the proper frequency that hisses but without unnecessary buzzing and popping. Clean hissing means that no other unit is active on that frequency. If, for example, the opening band is also using a wireless mic it could cause some problems. If a number of different transmitters are set to the same frequency it can cause some pretty serious interference.

In this case it is best to adjust the frequency at least 0,4Mhz. The best thing to do is simply select another preset frequency that is not in use. That way you are sure the audio signal will not be affected by external transmitters.

Squelch (noise gate) adjustment
In the Squelch menu, increase the dB value until the hissing is fully suppressed. Do not go any further, otherwise you will lose sensitivity. An unnecessary high dB value reduces range.

Selecting a microphone
For maximum feedback rejection, microphones with cardioid or super-cardioid patterns are unbeatable.

The distance of the wind screen to the mouth should not be more than 20cm. Cardioid mics react better to vocal material from the sides, and reject pops and handling noise better than super cardioid mics.

Adjusting the transmitter
First, deactivate the muting switch. Watch out, this is a sliding switch. Do not try to push on it.

The scale of sensitivity of the input amplifier is adjustable in 10dB steps from 0db (for whisperers) to –30db (for screamers). A standard setup with –20dB headroom is a good starting point. A small hint: No band is as loud at sound-check as when they perform. Adrenaline tends to add a few more decibels.

Gain Structure Additional Info – from rane

Field test
Test the reach of the transmitter always under “worst-case scenario” conditions. Hold the microphone close to your body and walk up and down the entire stage. When dropouts occur you should adjust the antenna to a better position. Those people known for their wild stage shows should be aware of the range of the transmitter, so that no unpleasant interruptions happen during the performance.

Antennae
Remote antennae (e.g. type A1031) allow better reception for the transmitter than the usual telescoping type attached to the receiver.

Just attach two antennae with a crossbar to one mic stand. If you are still having problems with reception, raise the mic stand as high as possible. Do not extend it more than 10 meters from the ground, without using an antenna booster.

Now the show can start – have fun!

Aims

This short document aims to present the common control standard used in the lighting industry today and give a short explanation of their development, uses, advantages and disadvantages.

Introduction:

Lighting can be switched on or of and it can be dimmed that is the light output of the lighting source varied to different levels in between off (no light ) and full on ( the maximum light output of the source)

Electrical Dimming

When halogen lighting is in use the dimming is simple and can be carried out either remotely or locally. A dimmer of this type (for a halogen load) achieves the dimming by reducing or increasing the level of the r.m.s. voltage and hence the average power.

Traditional Triac or thyristor dimmers use switching techniques to achieve this varying voltage. Inductors are the other main component of the dimming circuit and these are used to suppress interference caused by the switching. When a dimmer is at 50% they are switching the greatest voltage and the interference in the circuit is at its maximum. This is the cause of the vibration in the inductors that causes a buzz to be heard near to the dimming units. The inductors add weight to the dimmers and the suppression provided is often not sufficient to prevent the buzzing being heard on audio systems that share a closely related power supply.

Although the most simple form of dimming this type of dimming is not without it’s problems:

Low voltage lighting is now in very frequent use in projects using a wirewound or electronic transformer to provide a 12 v voltage for the lamps.

Traditional wirewound transformers provide an inductive load to the dimmer and the current of the load lags behind the voltage. Once triggered a triac requires the flow of current to the load through the device to maintain its operation. When the current falls below this threshold the device will switch off. If the current lag from an inductive load is sufficient the current flow in the circuit will not reach a sufficient level to maintain the triac and the device will turn off giving flashing and unwanted effects.

To avoid this effect the length of firing pulse on the dimmer can be varied to last long enough for the current to ‘catch up’ .

When using electronic dimmers only dimmers designed for use with a dimmer should be used although others may work they will not work for long.

Electronic Dimming

Electronic ballasts

Fluorescent and High intensity discharge lamps are frequently used in both residential and commercial projects. These use electronic ballasts to provide the supply to the lamp or lamps. Electronic ballasts usually change the frequency of the power from the standard mains (e.g., 50 Hz in uk) frequency to 20,000 Hz or higher, substantially eliminating the stroboscopic effect of flicker (100 or 120 Hz, twice the line frequency) associated with fluorescent lighting (see photosensitive epilepsy). These devices are often based on SMPS topology and allow dimming via pulse width modulation.

Generally these ballasts will be permanently connected to a mains power supply and also have one set of control connections either two or three core dependant on the type of control.

LED Electronic controllers

Led lighting is more and more popular due to the energy efficiency and the colour change possibilities without the need for filters.

LED units are however more complicated to dim than halogens. Dimming using a traditional dimmer above at best will not work and at worst will cause damage to your control gear and your dimmer.

Electronic controller specifically designed for controlling LED’s exists in both single channel devices and most commonly in three or four channel devices to accommodate colour change.

These devices provide a constant current supply to the LED and vary this supply using pulse width modulation to lower the duty cycle of the led and create a dimming effect.

These devices come in many shapes and sizes depending on what you wish to control. They also come as either integral units with LED power supplies or stand alone units which are connected in conjunction with and LED power supply.

Control either local or remote and if remote using 0-10V DC, DMX generally.

Cold Cathode Electronic controllers

The term Cold cathode is usually used to describe concealed lighting in coffers of cornices and is often used as an indirect up lighter. The name is in fact a description of the technology (fluorescent lighting for example is known as hot cathode). Cold cathode tubes are usually divided into two groups, those filled with Neon (red) gas and those filled with Argon (blue gas). The range of colours available is created by the use of different phosphors on the inside of the tubes which react with the ionized gases and emit the particular colour light.

Control Standards –

0-10v DC (also described as analogue)

The most basic of these control signals is 0-10V DC (the same as is used as the basis of most Triac dimming systems!) However small electronic ballasts are always located locally to the fitting and hence the DC control pair must travel from the processor to the fitting and may be susceptible to interference.

Pros

· Simple to wire and understand

· Simple to test with simple test equipment

Cons

· Most common fault is inverted +/- wiring

· Susceptible to noise

DSI – Digital Serial Interface

DSI is a digital protocol for controlling lighting in permanent installations. The standard uses uses a single byte to communicate the lighting level ( 0-255 or 0×00-0xFF).

In a DSI system each lantern or group of lanterns has it’s own control cable running from the processor or controller. There is no addressing of lanterns to be set.

Pros

· Simple to wire .

· Relatively simple to test with relatively simple test equipment

Cons

· Large systems have many control pairs running back to central system

· Initially a proprietary standard exclusive to Tridonic

DMX-512 –Digital Multiplex

DMX is a well know control protocol based on RS485 standard. The standard was developed for use in the entertainment industry to control multiway dimmers and intelligent lighting. Until recently the standard was never used in construction applications however due to the advent of RGB LED and cold cathode systems requiring more detailed control DMX has become the protocol of choice in these situations.

A DMX512 controller is connected to fixtures or devices in a multi-drop bus topology commonly called a “daisy chain”. 512 fixture attributes can be controlled on each DMX universe and if control of more is required additional universes can be added.

A fixture attribute may be a single channel of a dimmer.

Or a single colour on an RGB LED controller.

Fixtures are addressed using a menu structure or DIL switches. If a device has multiple fixture attributes such as a 12 channel dimmer, a 3 channel LED driver or a 32 channel intelligent light then the address of the channels first fixture will be set and the following channels will follow in sequence.

e.g. a 3 channel LED driver with starting address 1 will use

Ø Channel 1 Red

Ø Channel 2 Green

Ø Channel 3 Blue

Channel 4 and onwards are “free” to use for other fittings.

Many devices utilize automatic addressing and while this has it’s place for certain applications I must say that from experience I am not a fan.

Pros

· Strict adherence to the daisy chain topology must be followed (no Y-splits).

· Allows very accurate control.

· Long distances are possible even without buffers.

·

Cons

· Specific shielded cable must be used CAT 5/6 is not suitable.

· Difficult to fault find at signal level

DALI – Digital addressable Lighting Interface

DALI is and open standard protocol introduced as a rival to DSI and a successor to 0-10V control systems which still dominate the industry. The protocol allows control over a number of fittings using bi-directional data exchange over single bus with a maximum of 64 devices.

Devices are addressed individually and in addition to allowing control over the device feedback is provided to the system giving status of the device.

DALI has group and scene commands as part of the protocol allowing the reduction of data traffic and reduced network latency.

Pros

· Simple to wire – It requires only a pair of wire to form the bus connecting all devices on a single DALI network.

· Relatively simple to test with relatively simple test equipment

· No topology restrictions STAR and T’s are OK!

Cons

· The limiting factor of 64 addresses is not enough for large installations.

· Difficult and expensive to test and fault find

· Speed of the system (1200 bits per second ) can mean visible delay in larger installations

Copyright Neil Silver SI Sound and Light 2008

Neil Silver is the Technical Director of SI Sound and Light. He carries out a wide range of design and programming work in both commercial and domestic lighting controls systems.

www.sisoundandlight.co.uk

service@sisoundandlight.co.uk

The mixer has three jack connections on the rear of each channel seen below:

Two of these are good quality metal fronted jack connectors while the central insert connection (which gets the most abuse) is an all plastic type which is commonly found on budget devices.

The plastic connector takes much less mechanical abuse than the metal equivalent and hence the board connections to the insert are liable to dry joints and will require attention.

This dry joint causes a very weak signal to reach the main or group mix although the input signal on the PFL is still a strong level.

This list should cover all Pioneer CDJ & CMX models : CDJ-100s, CDj-200, CDJ-400,CDJ 800 CDJ-800MK2, CDJ 1000, CDJ-1000mk2, CDJ-1000mk3,MEP7000, CMX-3000 and CMX-5000.