This FAQ is no longer updated. Please visit the QSC forum for a list of updated FAQ's. 


Most Frequently Asked Questions

What is the warranty on my QSC product?

In the off chance your product should need repair, QSC provides a 3 year warranty from the date of purchase. Additional warranty coverage for 6 years is available within the first three years of the original purchase. This extended warranty option converts your 3 year limited warranty into a 6 year full warranty. These warranties are fully transferrable.

Some amplifiers have a free 6 year extended warranty. All that is needed is to register your product online after purchase. You may register from this link:


Products eligible for the 6 year warranty are as follows:

  • K Series
  • KW Series
  • GX Series
  • PLX2 Series
  • RMX Series
  • HPR Series

I would like to know the age of my QSC product. Can you tell me when the amplifier was built?

The serial number of your QSC product will let you know the manufacturing date, thus giving you it's age. Please refer to this literature which discusses how to determine the manufacturing date of your product.

I am looking to buy pair of second-hand used QSC product. Will QSC honor the original warranty?

Yes, QSC will honor the original warranty of the first-time buyer from date of original purchase.

What is bridge-mono and how do I enable it?

Bridge-mono is a feature on most QSC amplifiers (except for the GX and some PLX2-04 models) that works by combining Ch1 and Ch2’s outputs and connecting the speaker load across Ch1+ and Ch2+. This creates a single more powerful channel at the cost of losing control of a channel, so now you have one “mono” channel.  Bridge-mono has some limitations. The wiring on the output of the amplifier can be done via binding posts, barrier strips, or Channel 1's Speakon connector.

If the Speakon connection is used, a NL4 style Speakon connector is required and the wiring must be internally adjusted to use CH1+ and CH2+ connections, as in the figure below.



Does QSC sell rack ears?

QSC has limited quantity on rack ears for its amplifiers.

There is a third party rack ear which supports the most of our 2RU and 3RU amplifiers. Here's a link:

Amplifiers - General

Is it ok to run only one channel on my amplifier and can I mismatch loads?

You may do both. Your amplifier can be loaded with a very wide range of speaker impedances. The minimum impedance is 2 ohms for stereo operation while it is 4 ohms for bridge mono operation. All QSC amplifiers are designed to operate safely into infinite load impedances (no speakers). Loading arrangements from one channel to the next can vary in any way you wish. In fact, you can load one channel with a distributed voltage load, using an output transformer, and use the other channel to drive a direct low impedance load. 

What is the difference between parallel and bridged mono modes?

The "Parallel" setting duplicates the effect of cross-patching the two inputs, using an internal switch to save the hassle of an extra cable. The two input jacks are connected together, so that a signal on either jack now appears in BOTH channels (therefore only a single signal should be connected). Each channel's Gain control regulates its volume as usual, and separate speakers are connected to each channel as usual. When using this mode, DO NOT combine the output of both channels into a single speaker; this is likely to damage the amp. The Parallel mode is useful when you want to drive several speakers with the same signal, but with two separate volume controls. Bridged Mono mode reverses the polarity of the signal going to Channel B, and matches its gain to Channel A. This makes the voltage between the two red speaker outputs DOUBLE the usual value, which allows several times the normal power to be delivered to a single speaker. This also increases the stress on the amp; this is not "something for nothing" but is a way to combine the 4-ohm ratings of both channels into a single 8-ohm load, or the combined 2-ohm ratings into a 4-ohm load. The Bridged mono setting is useful when you want to deliver the entire power of the amp to a single 8 or 4 ohm speaker.

How do I set my amplifier into the Bridge-Mono mode?

This depends on the amplifier you have. Generally, you will first turn the power off, set the bridge mono switch to the bridge position and attach your speaker wires onto the two red binding posts of each channel. It is then necessary to apply your input signal to channel one on your amplifier and adjust the gain as needed. For some amplifiers, the gain of channel 2 must be turned all the way down while others are required to be all the way up. Furthermore, with other QSC amplifiers, it does not matter where channel two's gain control is.

Where should the gain controls of my amplifier be set?

We recommend that the gain controls be set between half-way and fully up. The input sensitivity of QSC amplifiers is at about 0dBV or (1Vrms). Amplifier gain controls set at a lower position require input signals to be set to a higher level to obtain suitable power levels. There are other noise and gain alignment considerations. Particularly with unbalanced input lines, the hotter your signal is at the input of an amplifier, the more noise propogation you will have into your amplifiers. Also, the gain structure of your system may become such that you will reach the maximum gain travel of a fader, at your source device, before obtaining expected power within your amplifiers.

What is the difference between Class AB, Class G, and Class H technology?

    Actually we are describing two different aspects of amplifier output stages.
  • IDLE CURRENT: Class AB refers to the amount of idle current flowing in the outputs at zero output. Amplifiers have positive and negative output transistors which handle their respective halves of the output signal. They must "hand off" the output current to each other as the signal passes through zero. A "Class A" output stage begins to transfer current well above its "cutoff point", resulting in much current overlap. This eliminates any chance of "crossover distortion" but generates tremendous waste heat at idle, limiting the possible power of the amp. A "Class B" output stage attempts to make the transfer at exactly zero current, which is impossible to maintain perfectly and leads to "zero crossing distortion" (more commonly called "crossover distortion", a buzzy form of distortion most audible at very low levels). Class AB is the practical compromise--just enough idle current to ensure a smooth transfer between the positive and negative output transistors, without a wastefully high idle current.
  • POWER SUPPLY DESIGN. The other major source of waste heat, even in a class AB design, occurs at moderately high output powers. The output transistors drive the speakers by coupling a precise amount of audio voltage from the amplifier's "power supply", which is a steady reservoir of fixed voltage. Most of the time, the output transistors are called on to only deliver a fraction of the power supply voltage to the load, and the unused fraction is consumed as heat in the output devices. We can reduce the losses by providing two or more"tiers" of DC voltage, with "steering circuits" which draw from the lowest possible voltage supply. This way the waste heat in the outputs is reduced. A "Class G" design does this by using two different sets of output transistors, one coupled to the lower voltage and one to the full voltage. The signal transfers from the low to high voltage set as required. A "Class H" design uses additional circuitry to connect a single set of outputs to lower or higher voltage as required. Both approaches are capable of good results; the Class H can be designed for somewhat lower costs, especially in amps with more than two power supply "tiers".

Why don't you use an air filter for your fans?

Air filters quickly clog with dust, blocking air flow and causing overheating. Although some dust collects internally without air filters, the spacing of the heat sink fins is much greater than the fibers in the air filter and much of the dust blows on through. The internal air flow pattern is designed to avoid dust buildup in critical places. Occasional cleaning is recommended in very dusty environments, but our experience is that "dust tolerant" designs cause much less trouble for customers than air filters.

Is it possible to change the input sensitivity within your amplifiers?

In theory, yes, but only by changing certain resistor values, which requires opening the covers and exposure to dangerous voltages. This should be done only by qualified service personnel, or under the guidance of QSC Technical Services.

The power up synchronization between channels is off. Is this ok?

Yes, certain amplifier models have completely independent muting circuits for each channel. It is normal for the turn-on delay to vary slightly.

The clip LEDs on my amplifier flash upon power up before the muting cycle ends. Is this normal?

During the muting cycle, the "front end" of the amplifier is internally disconnected from the output transistors, ensuring that they are fully turned off in the event of overheating or during routine on/off muting. When disconnected from the feedback loop, the front end circuits may have enough stray signal to flash the Clip LED's. This is perfectly normal, and will stop as soon as the amp enters the normal "run" state.

Should the fan in my QSC amplifier run all the time?

Almost all QSC amplifiers have 2-speed or variable speed fans that operate at low speed immediately upon power up. Two-speed fan designs reach the highest speed once a certain temperature is reached. Variable speed fans change rotation speed as amplifier operating temperatures change. The exceptions to this are the USA400 / Series One 1200 which are convection cooled amps.

Does your clip indicator represent true output clipping?

Yes, the LED is driven only when the amplifier output fails to track the input. This condition normally results only from clipping, which occurs when the power amp reaches either its voltage or current limit. The LED begins to become visible at 0.1% distortion, and reaches fairly full brightness at 1-10% distortion, which is clearly audible. Therefore the brightness corresponds to the likeliness of hearing the distortion.

Some amplifiers include Clip Limiter or GuardRailcircuitry which more safely limits the voltage/current limits of the amplifier.

The output voltage on my amplifier measures from 0Vdc to 0.3Vdc. Is this normal?

Small amounts of "DC offset" do not indicate a problem, although normally it should be less than 0.05 volts (50mv). At 0.3Vdc, we are dissipating 0.011 watts (11 mw) in an 8 ohm load which is clearly negligible. The 1400/USA 850/USA 900 models may measure several volts on the output if not loaded, but the voltage will promptly settle to zero if a normal load is connected.

I am getting a lot of hum and hiss from my system. Is the amplifier causing this to occur?

The fastest way to tell if the amplifier is the cause of the noise, is to disconnect the input cables from the amp. If the noise is still there, it may be the amplifier; if it's gone, it's a source device inducing noise into the amplifier. If after removing the input connectors from the amplifier you find the noise still present, it will then be necessary to determine if the noise is coming from the AC line. This further isolation may be helpful. Try relocating the amplifier using a different AC service, if the same level of noise is present, the amplifier is likely to be the cause. If the noise is lower, the AC service may be the cause.  

What type of general maintenance should be performed on my amplifier?

It is recommended clean out all dust inside the amplifier at least once a year. Remove the top or bottom cover and gently spray compressed air on the circuit board. Make sure to spray air through the venting columns of the heatsinks and remove all dust buildup on the fan blades. It is not recommended to leave amplifiers outside in a damp environment because corrosion and rust can destroy the amplifeir indefinitely. Always store amplifiers in a cool dry place.

What is the lowest and highest temperature that amplifiers can be stored at?

QSC does include temperature ratings in the specifications. There is no minimum or maximum temperature that an amplifier can be stored at, however, if condensation develops then that could cause rust and corrosion issues. Amplifiers should be stored in a cool dry place free of condensation.

One of the channels on my amplifier is outputting less volume or sound than the other channel. Is there something wrong with my amplifier?

This symptom could apply to one or many pieces of audio equipment in the system. It is important to isolate the problem first. The first and easiest thing to check is cabling. Remove all cables in the system and replace them with new or known good ones. If the volume is still different on both channels, then check the audio equipment.

An easy way to locate a problem is to swap connections on channels. For example, if Channel 1 is louder than Channel 2, swap the speakers and see if the problem moves from Channel 1 to Channel 2. This would indicate a problem with a loudspeaker.

Alternately you could swap inputs from Channel 1 to Channel 2. If the problem moves from Channel 1 to Channel 2, then a problem exists before the amplifier, most likely in upstream audio equipment. This means that the audio source or mixing equipment is bad. If the problem never moves from Channel 1 to Channel 2, then the amplifier is either setup incorrectly or has failed.

How do I setup the DIP switches on the back of the amplifier? What do the switches on the back of the amplifier do? What are the best settings for these switches?

The functions of the DIP switches are clearly labeled on the back of the amplifier. Moving a switch to the left or right would engage the the feature described next to it. The DIP switches enable or disable specific features in the amplifier. Refer to the User Manual for a full description on each feature. There is not a best setting for the DIP switches because audio systems can be setup in different ways. It is important to know how each system is run before adjusting the switches.

My amplifier is dead, caught fire, smoked, spilt liquid, or submerged. What should I do?

Some ampifiers may still be repairable, depending on the extent of the damage. Liquid spills or submerged produts are not covered under warranty. Please read about your Service and Support Options.


My amplifier doesn’t power up. The power LED does not come on or the power LED flashes. What should I do?

First try to power up the amplifier in a known working AC outlet with a grounded plug. If the amplifier still does not power up then you must send it in for service. Please read about your Service and Support Options.

Why does my amplifier produce a weak (low volume but clear sound) when volume control is already set at maximum?

This is usually an indication that there is a lack of input signal going into the amplifier. If you are plugging a microphone, instrument, or other low-level device directly into the amplifier then a pre-amp must be used between the audio source and the amplifier. Devices like microphones or guitars output a lower level than pre-amps and mixing consoles. Most QSC amplifiers only accept line-level signals, which is why a pre-amp or mixing console should be used between the audio source and QSC power amplifier.

My amplifier is outputting a low frequency hum noise. How do I fix this?

First try to isolate the amplifier as the problem. Disconnect all inputs (XLR, 1/4", RCA, barrier strip) but leave the speakers connected. Power on the amplifier and turn the gain controls to maximum. If no hum is heard through the speakers then the problem exists before the amplifier. Replace all input cables with new or known good ones. A broken ground wire can cause this type of hum. Make sure to use properly shielded cables. If audio cabling is fine then a ground loop may exist in the system. A common cure for ground loops is to place the QSC amplifier and audio equipment power cords on the same powerstrip. If that does not fix the problem then a product called a "ground loop isolator" is available for purchase from third party sources. The ground loop isolator would go between the two sources that have a ground loop. This may potentially fix the hum noise.

I tried plugging in microphones into the XLR inputs of my QSC amplifier and there was no sound. Why doesn't this work?

Most XLR microphones will not work straight in because they are "mic-level", not "line-level". Mic-level is a very weak signal. You need a pre-amp in between the mic and QSC amplifier for that to work.

What is the difference between EIA and FTC amplifier ratings?

Taken directly from an article by QSC's founder Pat Quilter, "The EIA rating, established by The Electronic Industries Association, reflects the power output for a single channel driven at mid-band – typically 1 kHz – with 1% THD clipping. This standard inflates the amplifier’s power points to 10 to 20% higher than the FTC ratings.

Of the two, the FTC rating tells you much more about the product than the EIA rating. The FTC rating gives you the average power output for both channels over a wide frequency range and lower distortion level. This is a much more conservative – and realistic – measure of an amplifier’s average output power. But in order to claim more power, some manufacturers might list only the EIA numbers; others will disclose both FTC and EIA output ratings enabling you to easily compare manufacturer’s specs."

Are QSC amplifiers suitable for home audio use?

Most QSC amplifiers were certainly not designed with home audio use in mind. Most home audio amplifiers are convection cooled and fan-less, which make for a very quiet, comfortable environment. Most QSC amplifiers are fan-cooled.  These amplifiers are only recommended for home use if the amplifier is relocated to different room than the one you’re listening in.

The fan is too loud on my amplifier, does QSC offer a quieter fan?

QSC does not have a quieter replacement fan because it was designed to be a PA amplifier (not a studio amplifier) where noise is not an issue. If you wish to replace the fan with something other than the original manufacturer's fan, the warranty will be void.

How do you change the resistance between 2, 4 and 8 ohms on your power amplifiers?

QSC amplifiers do not have impedance selection switches on them because they are constant voltage devices. The amplifier will run all impedances down to the lowest rated impedance. Check the specification sheet for these ratings.

Can QSC amplifiers be converted from 120V to 230V single phase power or vice versa?

Unfortunately we cannot convert voltages, or instruct on how to do so, on any amplifiers due to UL/CE regulations. Please do not call or ask how to do so.

Newer amplifiers, like the PLD or CXD, are universal and can accept both voltages. No conversion is needed.

Do you recommend any type of surge protection to protect QSC amplifiers from brief power outages and surges/spikes?

Simple shunt-type AC mains surge suppression as you find in typical outlet strips works for most applications, though they do wear out without any warning or indication from repeated surges. Some facilities install a central mains surge suppressor at the electrical service entrance. If a central surge protection scheme is not practical, but you would still like something more robust than you find in an outlet strip, take a look at series-mode products such as those made by Surge-X.

Power outages, on the other hand, are not known to cause any harm to power amps.

Do QSC amplifiers accept a stereo 1/4" plug or connector?

QSC amplifiers do not accept a "stereo 1/4" plug. There is a difference between a balanced 1/4" connector and a stereo 1/4" connector. Both are 3-conductor cables and have the same connector type (TRS). The biggest difference is that a balanced 1/4" carries ONE signal, consisting of a positive, negative, and ground (shield) signal. This is a pro-audio level connection. The stereo 1/4" connection carries two signals, consisting of Left, Right, and ground. QSC amplifiers do not accept this stereo 1/4" signal connector because it has two signals in one. 

Amplifiers - GX Series

Can I run the GX3, GX5, or GX7 in bridge-mono or bridged connection across the both channel's positive outputs?

The GX series does not support bridge-mono operation. If you force the amplifier into bridge-mono the amplifier will most likely fail and/or become unstable. Do not run the GX series in bridge-mono. 

The power switch in my amplifier feels flimsy. When I turn on the amplifier there is a sparking or arcing sound coming from the switch. Should I replace it?

The power switch should definitely be replaced with a new one. Fortunately the power switch is very easy to replace. Unplug the power cord from the amplifier. Remove the top-cover and remove the two wires from the power switch. Replace the switch with a new one and reconnect the two wires. You can order the switch from our online web store.  

QSC part#: SW-000088-GP

When using the crossover option on the GX series, can I run a different speaker impedance on each channel?

Yes, the GX series still outputs the same power to both channels when the crossover option is enabled. This means that you can run a 4 ohm load on one channel and an 8 ohm load on another. The specifications do not change when the crossover option is enabled. The GX Series supports this mode with a Crossover switch that splits the full-range input entering Ch 1, sending 20 Hz -100 Hz to the sub (Ch 1) and 100 Hz - 20 kHz to the top box (Ch 2). The front panel gain controls balance the sub and top box levels.

Would there be an issue with mounting a GX amplifier vertically in a rack?

The GX3 can operate in vertical position.  The vents on the upper sides of the rack appear small and that may trap the hot air inside.  If you push the amplifier near the onset of clipping at 4 ohm load per channel, you may need to  add a fan on the upper side to draw the hot air out, effectively that will prevent the amplifier from overheating and possibly thermal shutdown in the middle of the show / program.

Amplifiers - RMX Series

I have an amplifier and the sound cuts in and out intermittently. When the volume or gain controls are moved, it makes a scratching or crackling sound. How do I fix this?

You may be able to repair this gain control problem yourself with electronic contact cleaner spray. Deoxit D5 works great for cleaning potentiometers. Remove the top cover and spray the contact cleaner on the potentiometers while twisting the knobs back and forth, working the contact cleaner solution inside the part. That could clear it up.

A fail-safe solution would be to replace the gain potentiometers with new ones, which requires soldering. If you do not have experience with soldering, do not attempt this repair. An authorized service center can perform the work for you. See a list of Authorized Service Centers.

Refer to the part numbers below for QSC part numbers for ordering purposes. All of these parts can be ordered through our online store. The value of the gain pot is printed on the part itself.

10k: PT-310006-GP
2.5k: PT-225000-GP

Amplifiers - ISA Series

Amplifiers - PLX2 Series

Amplifiers - CX Series

Loudspeakers - General

What is the lowest and highest temperature that loudspeakers can be stored at?

QSC does include temperature ratings in the specifications. There is no minimum or maximum temperature that a loudspeaker can be stored at, however, if condensation develops then that could cause rust and corrosion issues. Loudspeakers should be stored in a cool dry place free of condensation.

I would like to purchase individual parts for my QSC loudspeaker. How do I find the QSC part number for ordering these wanted parts?

Most QSC loudspeakers parts can be found in the exploded view diagrams. Use the Document Center to filter results by family and document type of "schematic". Once the correct document is opened, locate the part on the exploded view diagram and find its associated QSC part number in the lookup table. Go to the online web store ( and type in the QSC part number in the search field. Follow through with the ordering process.

My active loudspeaker is outputting a low frequency hum noise with an input connected, how can I fix this?

First try to isolate the active loudspeaker as the problem. Disconnect all inputs (XLR, 1/4", RCA) but leave the power cord connected. Power on the loudspeaker and turn the gain controls to maximum. If no hum is heard through the speakers then the problem exists before the input of the loudspeaker. Replace all input cables with new or known good ones. A broken ground wire can cause this type of hum. Make sure to use properly shielded cables. If audio cabling is fine then a ground loop may exist in the system. A common cure for ground loops is to place the QSC loudspeaker and audio equipment power cords on the same powerstrip. If that does not fix the problem then a product called a "ground loop isolator" is available for purchase from third party sources. The ground loop isolator would go between the two sources that have a ground loop. This may potentially fix the hum noise.

Can you connect a POWERED loudspeaker to a POWERED mixer? What would happen if I did?

A powered mixer's speaker-level outputs are meant to go to a passive (non-powered) speaker, not an active (powered) speaker like the K or KW series. Connecting the K or KW series loudspeaker to a powered mixer won't result in smoke, but, the loudspeaker will definitely not play audio anymore. If the powered mixer has non-powered, line-level outputs, then that would be the jack that you want to connect your QSC speakers to. Be very careful when using a powered mixer with QSC powered speakers.

Can I install a different manufacturer's driver or transducer in my active loudspeaker?

It is definitely not recommended to install a different driver because the DSP is perfectly voiced to the drivers that are connected to them. Placing a different driver would frankly make the speaker sound worse. 

I am looking to purchase new grills for my active loudspeakers because they are dented and scratched up. Where can I purchase them?

New grilles are available for purchase as a service part. Some older models of loudspeakers are not available because stock has been depleted. Please visit the spare parts store to locate the grille replacement. 

Loudspeakers - K, KW, & KLA Series

What is the purpose of the small green plastic (terminal block or euro style) connector that came with my speaker?

The green plastic connectors, which are called terminal blocks or euro connectors, are used to remotely control the gain of the speaker from an external source. This is not be confused with an infrared remote that controls your TV.


The entire K Family of active loudspeakers include a feature which is every installers dream, that is the ability to use an external pot (potentiometer) as a remote volume control for individual or ganged loudspeakers. This is extremely useful for applications where you have mounted the speakers to a wall or ceiling, making it difficult to access and adjust the gain knobs on the rear of the loudspeakers, or where you need to control separate zones or loudspeaker groups. You can simply mount the remote pot on a wall plate in a convenient location and wire it to the supplied Euro-style connector on the rear of each K Family loudspeaker(s).


The value of the external pot is not critical—any potwith a total resistance of 1 kΩ up to 50 kΩ and a linear taper will befine. These are typically quite inexpensive and available from just about any electronics parts supplier. If you do plan to connect more than 20x loudspeakers together, we recommend using a lower value potentiometer (less than 5 kΩ).


For your convenience, 10k volume pots already pre-mounted on single gang decora wallplates are available from QSC Audio - P/N “WCP-1“.


It is important to note that NO audio is passing through this pot, or its associated wiring - this is merely a control signal, therefore any convenient three-conductor cable (or two-conductor with a separate shield wire) can be used for this pot. You may choose to use more expensive shielded twisted pair (STP) microphone cable, or simply use a low cost unshielded Twisted pair (UTP) phone or data cable such as CAT5e, which is perfectly acceptable for this function.


Was the K8 designed to be laid on its side and used as a stage monitor? 

The K8 is not designed to be used as a stage monitor because of its wide coverage pattern. It’s almost too wide to be used as a stage monitor which is why it does not have the rubber feet. The K10 and K12 have the rubber feet because the coverage is more narrow and better for stage monitor use.

Should I use some sort of surge protector with the K Series, or can they be plugged directly into a normal household (grounded) AC wall outlet?

There is some surge protection built into the K series, but it will never hurt if you plug the K series into a power strip or surge protector.

Channel B in my K series loudspeaker is not as loud as Channel A. I have Channel A set to "Mic". Is something wrong?

In K and KW series loudspeakers, Channel A includes a built-in pre-amp, which boosts the input signal. This is used for lower level signals like microphones and instruments. To engage this pre-amp on the K series, you must set the switch to "Mic". To engage this pre-amp on the KW series, rotate the mic selector switch to any settings above 0dB. Channel B does not have a built-in pre-amp and accepts line-level signals. If a lower level signal is plugged into Channel B, there is no capbility to boost its level, like Channel A has.

What is the best level to set the gain control on the K or KW series speaker to?

The gain control on the K, KW, and KLA series adjusts the sensitivity of the signal going into the amplifier. Of course down the line and at the end of it all, this affects the overall volume of the loudspeaker. However, you can be at the maximum volume or potential of the speaker at ANY level on the gain controls. This means that you could have an extremely high signal coming through your XLR or 1/4" inputs and have full volume of the speaker, even at the 9 o'clock position on the gain control. On the flip side, you could have an extremely low signal coming in with the gain control maxed out, and you still wouldn't be able to reach the full volume on the speaker. This is all because the gain control is only a sensitivity setting - it is not directly a volume knob.

The fan on my K or KW series loudspeaker is not turning on. Should I be concerned?

You do not need to be worried. The fan will turn on when it needs to. Class-D amplifiers (like the one in the K and KW series) are very efficient - meaning a high percentage of the power produced by the amplifier is sent to the drivers themselves. A very low percentage of this power is wasted via heat. Because of this, the fan doesn't need to turn on in many situations. The only time you will begin to need the fan is when the amplifier is working very hard AND the ambient temperature outside of the speaker is high. A good example is when the speakers are running outdoor at a hot summer festival.

Changes made to the K or KW Firmware

A change was made to the K and KW series fan behavior (in particular date codes) that makes the fan spin ONLY when the temperature of the amplifier gets hot. Before, the fan would spin at idle no matter what the temperature. In all models, the fan stops spinning when the amplifier goes into standby.

Hardware changes were also performed during the same time as the firmware changes so going to a different firmware revision would affect speaker performance. Changing the firmware is not possible.

What is the front LED behavior on the K, KW, and KLA series? What does PWR, LIMIT, and OFF mean?

The behavior of the front LED depends on what you have the switch "Front LED" set to in the back of the speaker. 

If the switch is set to "PWR" the front LED will remain fully lit all of the time. It will turn off when the amplifier goes into standby. Standby occurs after the speaker does not see signal for 5 minutes.

If the switch is set to "LIMIT" the front LED will illuminate very bright when you have reached the limit of the speaker, notifying you to back down. When not limiting, the front LED will be dimly lit.

If the switch is set to "OFF" the front LED will be off...

Channel B in my KW series loudspeaker is not as loud as Channel A. I have Channel A set to "Mic". Is something wrong?

In K and KW series loudspeakers, Channel A includes a built-in pre-amp, which boosts the input signal. This is used for lower level signals like microphones and instruments. To engage this pre-amp on the K series, you must set the switch to "Mic". To engage this pre-amp on the KW series, rotate the mic selector switch to any settings above 0dB. Channel B does not have a built-in pre-amp and accepts line-level signals. If a lower level signal is plugged into Channel B, there is no capbility to boost its level, like Channel A has.

My KW series loudspeaker has sections where the paint/finish has come off. Do you sell, or have any information on, this black textured paint for repair?

We have information on the paint, but do not sell it. If you are looking for paint for touch-up purposes, use water or acrylic based paint with RAL color code 9011 (black). RAL refers to the RAL Classic system, mainly used for varnish and powder coating.  Do not use oil-based paint.

Loudspeakers - HPR Series

What is the difference the HPR i, HPR F, and HPR W models?

The first HPR models that QSC released were the F and W models. These HPR models were not used in the installation market because they were not installable or flyable. When QSC released the new HPR i models, M10 fittings were added to the enclosure for suspended installations. The "i" in HPRi stands for "install". QSC also reduce the gain sensitivity on i models. Please refer to service bulletin HPR0001 for more information on how to match HPR models.

Loudspeakers - AcousticDesign

Can a pole mount cup be added to the AD-S282H?

Answer, yes and no. The i82H screw-in pole mount adapter should never be used with the 282 products. There is a plastic pole mount cup in the ISIS-i282H that can be added to the AD-s282H. This is not a stocked accessory and the replacement involves changing quite a few fasteners. It will work but it's an emergency fix only, it's not convenient. 

Can I suspend an AD-S82 or AD-S82H using the brass inserts eyebolt?

No, this is a bad idea. The brass inserts were never designed for suspension.

Loudspeakers - AcousticDesign Ceiling

What type of application are the mud rings used for with the ceiling speakers?

The 'mud rings' are only used for sheetrock and plaster situations. They feature a raised flange, which helps in the plastering process and also makes it impossible to accidentally install sheetrock over the ring without first cutting a hole to accomodate the speaker. This allows the builder to install the mudrings to the framing of a building, which specifies exactly where the speakers need to be mounted, and not having to worry that the sheetrock contractor plasters over the speaker openings. 

What type of application are the new construction rings used for with the ceiling speakers?

The new construction rings are completely flat, and feature holes for mounting to studs/joists in a wall or ceiling.

Network Audio Systems - Q-Sys

How to Setup CobraNet bundle assignments for the CCN32 CobraNet card?

Please see the attached PDF for assignment instructions.

CobraNet CCN32 Card Q-Sys Setup, rev1

The Q-Sys Designer software is stuck on "Discovering Core". How can I resolve this?

When Q-Sys Designer is stuck on "Discovering Core" when deploying a design to a Core, this is typically caused by the fact that the name of the actual physical Core DOES NOT match the name given to the Core in the design.

In order to avoid this error, you must use "Show Q-Sys Configurator" (found within Q-Sys Designer > "Tools" drop-down menu) to EITHER rename the physical Core to exactly match the name in the name of the Core in the design OR to change the name of the Core in the design to exactly match the physical Core.

This is covered in the Q-Sys Software "Overview" found on the Q-Sys Training Website.

The Q-Sys Designer software is displaying an error message “Exception has been thrown by the target of invocation”. How do I resolve this?

Q-Sys Designer versions prior to v3.1.X are incompatible with MS DotNet Framework v4.5. If you don't specifically need DNFWv4.5 for any other application, you can uninstall it and install (or reinstall) v4.0, or you can install QSD v3.1.x or newer.

I can ping the core but I can’t see the Core in Configurator. What gives?

If you can’t see the Core in the Configurator window then either UDP 6504 isn’t open or the multicast discovery address isn’t routed. If you don’t want to allow the Multicast address to the PC, setup a hard-link route in the Designer software.

If you can see the Core in the Configurator window but can’t control it, then port 1700 isn’t open.

Make sure the following routes are set up so you can ping from the client PC to the Core.

  • TCP port 80 (management)
  • TCP 1700 (control)
  • TCP 1701 (if external control is used like an AMX) UDP unicast port 6504 (discovery)

If multicast discovery is used: Multicast IP, ports 2467, 2468, 2469, 2470 must be routed.
Otherwise a hard link must be set up in Q-Sys designer ( File -> Preferences… -> Hard Links )

Network Audio Systems - QSControl (BASIS, RAVE, DSP, CM16a)

What is the CM16a Amplifier Network Monitor?

The CM16a Amplifier Network Monitor offers powerful amplifier management in a QSControl networked audio system, using Ethernet technology to communicate with the host system controller. The System Controller uses application software to operate the networked audio system, including the CM16a units and their amplifiers

How does the control data get from CM16a to the amplifier and how does the PC (System Controller) communicate with the CM16a?

The data is transferred between the CM16a and the amplifier using a HD 15 DataPort cable. Monitor data goes from the amplifier to the CM16a and the control data goes from the CM16a to the amplifier. Communication between the Controller (PC) and the CM16a is accomplished via a CAT5 cable with RJ45 connections. If a switch/hub is being used, a standard straight through cable is needed. However, if the CM16a is connected directly to the PC, a cross-over cable must be used.

How many amplifiers can I control and monitor with a single CM16a?

The CM16a can handle up to 16 channels of audio using it's 8 dataports. Each DataPort cable carries 2 audio channels (audio pairs). So it is a function of the number channels, rather than the number of amplifiers.

What if my CM16a (s) fails? Do I lose audio?

The CM16a comes with a bypass switch located on the front panel. If the unit crashes you can bi-pass the CM16a to allow audio to pass through.

What are the some of the functions that I can control and/or monitor using the CM16a?

The QSControl system can monitor and control a variety of functions. ON/OFF/Standby, amplifier mode, Voltage/Current/Impedance, clip, protect, gain, temperature, and more. The CM16a also has 4 monitor ports for additional audio monitoring.

How do I update the firmware in my CM16a?

See Service Bulletin CM160005b as it provides a detailed procedure on how to update your firmware. It is located on Click here to view the bulletin: CM160005_B.pdf

Is the CM16a compatible with QSC's DSP products?

Yes. With the exception of the DSP-30 (non-DataPort), the CM16a is compatible with other QSC DSP products.

Will the ISA work with CM16a?

No. The ISA has a “V2” DataPort and has limited functionality.

Is the audio in the CM16a digital or analog?

The audio within the CM16a is in digital format. The CM16a converts the analog input to digital and back to analog for audio output.

Is the CM16a compatible with all amplifiers?

No. The CM16a is designed as part of a system using QSC DataPort amplifiers only (excluding ISA models).

My amplifiers have a red “X” over them in my System Manager tree - what does this mean?

Either the amplifiers are not ON or the CM16a is not online.

Can I put QSControl on a network with other computer traffic?

It is not recommended that QSControl traffic be on the same network with other computer traffic. Use two physically separate networks or partition a single physical network into two virtual LANs using managed switches.

What is the minimum recommended specifications for the system controller?

  • Processor: 866 MHz Intel Pentium™ III processor
  • RAM: 128 MB, 133 MHz bus
  • Hard Disk: 4 GB or greater Ultra DMA
  • Floppy: 3.5" 1.44 MB drive
  • CD-Rom: 40x or greater IDE
  • Network: 10/100BASE-T
  • Network Configuration: TCP/IP host
  • Modem: 56k V.90 internal PCI (optional)
  • Video: 2D/3D Graphics, 133/100 MHz, 4 MB Display cache or better
  • Sound: Sound Blaster® compatible (optional)
  • Keyboard: 104 key, PS/2 compatible
  • Mouse: PS/2 compatible
  • Operating System: Windows NT-4 (SP-6) or Windows 2000 (SP-2)

How do you determine and configure the audio resolution on RAVE products?

 "S-24" labeling for the analog units and "s" labeling for the digital units, both of which must have at least firmware version 2.8.5, identifies 24-bit capable RAVE units. RAVE products are shipped from the factory with audio resolution configured for 20-bit. RAVE transmitters populate a bundle with 8 channels of 20-bit audio while receivers decode a bundle with 8 channels of 20-bit audio as well. Audio resolution from the AES receivers or ADCs is always 24-bit. Audio resolution can be determined at the receiver or transmitter via software access to the management interface (MI) variables using SNMP.Configuration of audio resolution is available on a per channel basis by altering the MI "txSubFormat" variables at the transmitter.

Can a RAVE unit operate on an asynchronous transfer mode (ATM) network?

ATM has long proclaimed to be the solution to isochronous networks. This is due to cell-based switching which uses a fixed packet size. Theoretically, this should allow for predictable and fixed latency throughout the network. Unfortunately, ATM protocol implementations from one manufacturer may not provide for interoperability with another.Additionally, bridging of Ethernet packets to ATM may cause problems. However, QSC has successfully implemented RAVE on a few ATM networks. Note that RAVE products are supported by QSC Audio Products for use with Fast Ethernet repeaters, switches and approved media converters only.

What is the maximum length of a single CAT-5 UTP segment in a RAVE network?

100m or 328 feet

How many audio channels make up one network channel or bundle on a RAVE?

Assuming the RAVE is configured with the factory default settingd, eight channels make up one network channel within a RAVE system.

How many transmitting network channels (bundles) can have a specific network address?


How many bits of audio resolution can a RAVE unit support?

The CobraNet protocol supports audio delivery over the network in word lengths of 16, 20, or 24-bits. QSC Audio's RAVE products began support of 24-bit audio delivery with CobraNet version 2.8.5 firmware.

Why would one consider a repeater network for a new RAVE installation?

At one time this was one of the more common questions for new installations. Now that network switches are competitively priced with repeaters, the install base has moved almost entirely to switched LANs. Ethernet repeaters are still supported though and provide at least one benefit over network switches for small installations. Repeaters allow the use of more multicast bundles and do so more reliably. Each LAN or virtual local area network (VLAN) in a switched network design should limit multicast delivery to no more than 4 bundles. Repeaters allow at least 8 multicast bundles per LAN. If the system requirements call for no more than 64 audio channels that must be multicast to two or more destinations, a repeater network may still be a viable solution.

How many bundles is the MIB browser capable of routing per RAVE?

There are 4 bundles per RAVE.

Can I assign multiple receivers to the same network address?

Yes, if the system is set up for a multicasting configuration.

Can I run RAVE units and an office LAN on the same network?

We strongly recommend that you keep your RAVE network separate from others. Normal LAN traffic is unregulated and non-deterministic, whereas RAVE network data adheres to a rigid time schedule and packet size.

Digital Signal Processors - DSP-30

What amplifiers is the DSP-30 compatible with?

The DSP-30 is essentially a stand-alone, rack-mount version of the DSP-3. It uses its own AC power, has XLR inputs and outputs and does not have a DataPort. Therefore, it is compatible not only with any amplifier, but with any line-level stage in an audio system.

What kind of cable do I need to connect my computer to the DSP-30?

Use a standard RS-232 serial cable, which is available in many computer or electronics stores. The connector on the DSP-30 is a 9-pin female; the serial port on your computer might have either 9 or 25 pins, so make sure you have the appropriate cable or adapter.

My DSP-30 doesn't seem to pass signals. What could be wrong?

If the blue LED on the front panel isn't lit, the DSP-30 isn't turned on or doesn't have AC power. If the DSP-30 is on, check the input and output cables, and make sure they are connected properly. Also check how the DSP-30 is configured; if you set up a configuration in the Signal Manager application and forget to complete the signal paths from inputs to outputs, or at some point along the signal paths you mute or greatly attenuate the signal, it will appear that the unit doesn't pass signals.

My computer won't communicate with the DSP-30. How do I fix it?

Make sure that you have the latest version of QSC's Signal Manager application; you can download it from

In Signal Manager, select Options from the Tools menu, then click the DSP tab. Make sure you have the correct COM port selected. Also, check that no other programs or utilities are using the COM port to which the DSP device is attached. For example, HotSync (for Palm Pilots) is often set to automatically start when the computer is booted up, and you must manually close it before the PC can communicate with the DSP unit through the same COM port. Laplink and HyperTerm are two more examples of applications which "take over" the COM ports, which may prevent Signal Manager from accessing the DSP device.

The Signal Manager application automatically adjusts the COM port settings, but you may have to set them manually if you have difficulties communicating with the DSP-30. Select these attributes: 38400 baud, 8 data bits, no parity, 1 stop bit, flow-control NONE.

In Signal Manager, why do red X's appear over the processor blocks when I attempt to configure my DSP-30?

The X's indicate that the configuration is not valid, usually due to unconnected objects (blocks) or ‘wires,' and the DSP-30 will not accept it. You will not be able to apply the configuration to the DSP until all objects and wires are connected.

To check a configuration for unconnected wires and DSP objects, right-click on the Signal Manager workspace. A pop-up menu will appear; click on Show Unconnected. Unconnected ends of wires will be marked with yellow X's, and unconnected with red X's. Delete erroneous wires and connect the objects as required.

I need to know how my DSP-30 is configured. Can I retrieve it into Signal Manager?

Unfortunately, no—the DSP-30 can't do that. Whenever you create a configuration in Signal Manager that you might later want to reuse, review, or modify, you should save it as a file. You can back it up, e-mail it, copy it, share it with colleagues, etc. And you can load it into the DSP-30 as many times as you need.

The audio through my DSP-30 is distorted. What could be the cause?

First, check the audio signals going into it. If they are distorted, the DSP-30 will not clean it up.

Distortion could occur within the DSP-30 if the input signal levels are too hot, because they may clip the input stage. Open the configuration in Signal Manager and make sure you select an appropriate input sensitivity.

Also, if you put too much gain in the DSP blocks of the configuration—whether in gain or EQ blocks—you'll get "digital clipping," in which the audio data exceeds the processor's bit depth; this type of distortion is extremely harsh and nasty sounding.

The signal seems a bit weak out of the DSP-30. What could be the culprit?

The DSP-30 might be configured that way, with insufficient gain or less-than-optimum filtering in the signal paths. Use Signal Manager to check—and if necessary, correct—the situation.

The DSP-30's inputs and outputs are active balanced. But if you run unbalanced interconnections between it and the other audio equipment, make sure that you use the non-inverting input and output terminals (pin 2) for the signal connection, and connect the inverting terminals (pin 3) to ground. You could lose some signal level if you don't do it correctly.

Do I need a computer if I want to change the processing settings in the DSP-30?

The DSP-30 allows you to load up to eight different configurations into its memory. They are recallable as presets.

You need a suitable computer and the Signal Manager software in order to create and load these presets, but once they are in the DSP-30, you don't need the computer; you can scroll through and select the presets by using the front panel buttons and display.

What are the pinouts of the RS-232 connector on my DSP-30?


Digital Signal Processors - DSP-4

Can I control multiple DSP-4's from one computer?

Using a serial RS-232 connection, only one DSP-4 can be configured before having to rewire the connection from the control computer to another DSP-4 module. Using the QSC CM16a as a network bridge, any number of DSP-4 modules can be accessed via a QSControl Ethernet network. As an added bonus, the CM16a delivers amplifier control and monitoring functions useful in setup and diagnostics of an audio system.

The control computer must have the QSControl Software package version 4.0 or later installed, which includes a networked version of Signal Manager.

What are the system requirements to run Signal Manager?

To use QSC Audio's Signal Manager software, you need the following hardware and software:

  • An IBM compatible 200 MHz. or greater Pentium Processor.
  • Windows 2000, Windows NT 4.0 (SP6 or greater), or Windows 98.
  • SVGA display at 800 X 600 resolution, 1024 X 768 recommended
  • CD-ROM drive
  • 32 MB or more of RAM
  • 10 MB or more of free hard disk space

An available RS-232 serial communications port (COM port) capable of 38.4k baud, (or a 10BASE-T network card if running in network mode).

Can I program a DSP-4 without a computer?

No, the DSP-4 is configured (programmed) by using the included Signal Manager software. The software must be installed on your PC and the PC must be connected to the DSP-4 using a 9-pin serial cable and an available COM port. Once programmed, the module can operate without any connection to the computer. Any time changes are needed to the DSP's configuration, the RS-232 connection must be active (cable connected). Software operation instructions are provided in the form of an in-depth Help file in the Signal Manager software.

My DSP-4 is not communicating through my com port?

COM Port settings are set automatically by the software. However, if you cannot communicate with your DSP device, you may have to set them manually. Set the attributes of the COM port you wish to use. This can be done by going to the system Control Panel and selecting "Ports" (in Windows NT) or "System\Device Manager\Ports" (Windows 95/98). Set the attributes as follows:

38400 baud, 8 data bits, no parity, 1 stop bit, flow-control NONE.

What is the 15-pin (DataPort) connector on the DSP-4 used for?

When using the DSP-4 module with QSC's amplifier network monitors, the audio input to the module can be delivered through the DataPort along with amplifier control and monitoring signals. This is the normal application of the DataPort. Connection from the module to the amplifier network monitor is made using a DPC-X receptacle-receptacle QSC DataPort cable. Alternatively, the DataPort connection can be used ONLY for control and monitoring, while the audio is input via the XLR inputs. If using the DSP-4 in this manner, do not apply audio via the DataPort as it will be mixed with the XLR audio input.


My DSP-4 is not powering up, what could be the problem?

QSC's DSP-4 module has been designed to attach directly to the DataPort connector of QSC's CX, DCA and PowerLight 2 series amplifiers. When attached to CX, DCA and PowerLight 2 amps manufactured 08-99 and later, the module receives its power through the DataPort from the amplifier. Modules connected to earlier models of those just mentioned, all PowerLight amplifiers (the "non-2's") and non-QSC amplifiers require an external DC supply (DPX-1 15VDC 300mA).If the DSP-3 is attached to a CX, PL2, or DCA amplifier, it is also possible that an internal amplifier fuse may be open.

Can the DSP-4 be used with other manufacturer's amplifiers?

Yes! DSP-4 can be used as stand-alone 2-channel digital signal processors. To accomplish this, you would need an external power supply (such as the QSC DPX-1) and we recommend a suitable mounting surface such as the DPX-4 Accessory Mounting Bracket. Both units provide line level balanced and unbalanced audio I/O. Simply patch the processors inline as you would typically use any signal-processing device. The RS-232 port is your gateway for controlling these processors from your computer.

Why do I get red X's over the processor blocks, when I attempt to configure my DSP-4 through Signal Manager?

If a configuration contains any unconnected objects or ‘wires', the DSP will not accept a configuration set up. You will not be able to apply the configuration to the DSP until all objects and wires are connected.

To check a configuration for unconnected ‘wires' and DSP objects, right-click on the program Workspace; a pop-up menu will appear, choose ‘Show Unconnected'. Unconnected ends of ‘wires' will be marked with a yellow X and unconnected objects will be marked with a red X. Delete erroneous ‘wires' and rewire the objects as required.

How do I daisy chain my DSP-4's?

The DSP-4 has two XLR audio outputs, one for each channel. These outputs may be used for daisy-chaining the post-DSP signal to other amplifiers or for monitoring purposes. The XLR outputs may be used for daisy-chaining even when the DataPorts are used for input/output. Do not use Output Power Limiting when daisy chaining.

To daisy-chain the DSP output, connect the output jacks of the DSP-4 to the input jacks of the next amplifier. Then connect the paralleled signal from the first amplifier to the second amplifier, and so on, up to a maximum of five amplifiers (including the output DataPort if connected to an amplifier). Make sure that all interconnecting cables are balanced and connected properly.

What are the pin outs of the RS-232 connector on my DSP-4?

Note: PowerLight 6.0 and PowerLight 9.0 amplifiers require that pin #9 be removed from the remote mounting interconnect cable (DPX-2). Amplifier damage may result from use of cable that has pin #9 connections present.

Digital Signal Processors - DSP-3

Is the DSP-3 hot swappable with QSC power amplifiers?

No. Attempting to mount or remove a DSP-3 located on a dataported amplifier could cause an internal amplifier fuse to open. This fuse is located between the 15V supply within the amplifier and the DataPort jack on the DSP-3.

My DSP-3 doesn't communicate with my laptop. What can I do?

Under the Tools menu within your Signal Manager software, click Options and select the DSP tab. Ensure the correct COM port is selected. Also, check that no other programs or utilities are using the COM port to which the DSP device is attached. For example, HotSync (for Palm Pilots) is often set to automatically start when the computer is booted up, and must be manually exited before the PC can communicate with the DSP unit through the same COM port. Laplink and HyperTerm are two more examples of applications which "take over" the COM ports, preventing Signal Manager from accessing the port which is connected to the DSP device. For further details, refer to the DSP0002 Service Bulletin.

What type of cable do I need between my DSP-3 and computer?

The DSP-3, -4, and -30 do not use a null modem cable to connect to the PC. Instead, use a straight-through serial cable, which is quite common. This cable is often sold as a "serial extension cable", with a male connector at one end and a female connector at the other. You can purchase this serial cable off-the-shelf from any computer products store. The RS-232 pin-out is found in the appendix of the DSP Hardware Manual, or you may download a PDF version of the manual(s) from here: DSP-3 User Manual, revE. If you still encounter problems connecting to the DSP device using a standard serial cable, check that the correct COM port is selected in the Signal Manager application.


What external power supply requirements are necessary for my DSP-3 module?

The DSP-3 requires a 15V DC supply with a current capacity rating of at least 300mA. The output termination is via a 2.5mm barrel type (coaxial) connector. Center pin is positive.

Can I drive multiple amplifier channels with the use of my DSP-3?

Yes! Each DSP-3 channel has an output terminal block for post DSP audio. This connection serves as a balanced output to drive additional power amplifiers which in turn might be connected in parallel with other amplifiers.

My DSP-3 doesn't come on. What could be the problem?

The DSP device has a blue LED which illuminates to indicate the device is turned on. This may seem obvious, but power may have been disconnected. If the device is supposed to be receiving its power from a DataPort-connected QSC amplifier (such as a CX, PL2, PL3, or DCA amplifier), make sure the amplifier is turned ON (not off, or in Standby mode). If the device is using some other means of power (either an AC adapter for a DSP-3 and DSP-4, or a standard AC power cord for the DSP-30), make sure it is connected to a live AC circuit.If the DSP-3 is attached to a CX, PL2, or DCA amplifier, it is also possible that an internal amplifier fuse may be open.

What are the pin outs of the RS-232 connector on my DSP-3?


What is the DataPort connector on my DSP-3 for?

The DataPort connector is a 15pin HD female receptacle that serves as an interface between the DSP-3 and QSC's control and monitoring system. This connector may also serve as an alternative audio port provided no audio connection is placed at the terminal blocks of the DSP-3.


There seems to be an undesirable noise coming from the DSP-3 attached to my amplifier. What can I do to verify the DSP-3 is or is not the cause?

To quickly determine if the DSP-3 is the source of noise, isolate an amplifier and DSP-3 pair from the system. With the gain controls of the amplifier in full position, attach the DSP-3 to the amplifier with AC power turned off. With the DSP-3 mounted, remove all source audio attached to the DSP-3 and attach small monitor loudspeakers to the amplifier's outputs. The DSP-3 and amplifier pair should be free standing with not input audio and loudspeakers attached to the power amplifier outputs.When the amplifier and DSP-3 pair are powered up, the noise floor should be relatively inaudible. If there remains an objectionable level of noise present, a fault condition may exist.

How do I achieve a hard wired standby control through my DSP-3 while it's attached to my amplifier?

Each end of a SPST contact switch may be connected between pins 2 and 6 of the female DataPort connector of a DSP-3 to achieve remote AC standby functionality. By shorting these two pins together, a dataported amplifier is placed into AC standby mode.