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Troubleshooting Reference Chart 

16 

Symptom: 

Recommended Action: 

No output Power indicator is off. 

(There is a normal delay of up 

to 30 seconds on turn-on.) 

Be sure power outlet is “live” Be 

sure power switch is “on.” 

No output Power indicator LED 

cycles on and off. 

This indicates a short-circuit 

condition on the output. Discon-

nect speaker wires and turn 

amplifier power switch on.  If 

amp stays on, the problem is in 

the output wiring or speakers. 

Power indicator on; no output 

from one or more channels. 

Check input level controls, input 

and output cables, input signal 

and speakers. 

Low volume in one or more 

channels. 

Check input level controls, input 

wiring and input signal levels. 

Be sure speakers are the same 

impedance. 

Amplifier overheats and/or 

shuts off. 

Review section on Thermal  

Considerations. Check clip lights 

for indication of overdriving. 

(NOTE: overdriving for a long 

period of time can cause  

thermal shutdown.) 

Distorted output. 

Check input signal level and  

signal source. (Set gain by  

turning amplifier volume all the 

way down, set preamp level to 

normal, turn up amplifier  

volume to desired level.) 

Noise on output. 

Check signal source for noise.  

Long unbalanced lines can 

cause noise, change to balanced 

lines. (See set gain above.) 

Contents 

 

 

 

 

 

 

Special Features……………………………………………….……...…6 

 

Front Panel Features……………………………..…………….…...10 

 

Rear panel Features …………………………………………….…… 11 

 

Installation……………………………………………………………...….12 

 

Troubleshooting………………………………………………………....15 

 

Technical Information………………………………………………...17 

 

 

 

For The Record 

 

 

 

 

In the spaces below, record the Model, Serial number  

and Purchase information of your Power Amplifier. 

 

Model Number:  ______________________________  

 

Serial Number: _______________________________  

 

Purchase Date: _______________________________  

 

Purchased From:  _____________________________  

 

Retain this information for future reference. 

 

 

 

Summary of Contents for DA-70 Series

Page 1: ...Stewart Audio 14407 Cuesta Court Sonora Ca 95370 Tel 209 588 8111 Fax 209 588 8113 www Stewartaudio com DA 70 Series Professional Power Amplifiers Owners Manual WHEN THE PERFORMANCE DEPENDS ON IT ...

Page 2: ...MOVE COVER OR BACK NO USER SERVICABLE PARTS INSIDE REFER SERVICING TO QUALIFIED SERVICE PERSONENEL CAUTION RISK OF ELECTRICAL SHOCK DO NOT OPEN The lightning flash with arrowhead symbol within an equilateral triangle is intended to alert the user to the presence of uninsulated dangerous voltage within the product s enclosure that may be of sufficient magnitude to constitute a risk of electrical sh...

Page 3: ...laced on a rug sofa or similar surface which impedes the airflow across the chassis Airflow through the ventilation openings should be unobstructed The amplifier should only be connected to a properly grounded AC outlet as indicated under AC Power Con nections in this manual Do not defeat the ground or polarization of the power plug Route all power cords and other cables so that they are not likel...

Page 4: ...cupying just one half standard rack space The DA 70 Series Amplifiers are convection cooled and require no noisy fans for cooling We at Stewart Audio strive to bring you the finest in professional electronics and we thank you for your choice which we see as an appreciation for our efforts The Stewart Audio Design Team 4 Specifications 17 8 Ohm Stereo Power 35 Watts Ch 4 Ohm Stereo Power 70 Watts C...

Page 5: ...view section on Thermal Considerations Check clip lights for indication of overdriving NOTE overdriving for a long period of time can cause thermal shutdown Distorted output Check input signal level and signal source Set gain by turning amplifier volume all the way down set preamp level to normal turn up amplifier volume to desired level Noise on output Check signal source for noise Long unbalance...

Page 6: ...interface and control Stewart s ap proach was to develop a new Class D amplifier that utilized digital control This approach enables lower cost through digital integration as well as eliminating performance degradation due to analog component variations 6 Trouble shooting If you experience difficulty in operating your new DA 70 Series amplifier Chances are good that you will be able to remedy the ...

Page 7: ... D amplifiers utilize binary or BI state op eration Binary consists of only two switching states positive power and negative power Ternary or tri state operation consists of three switching states positive negative and a zero power state The third state is unique to this design During the time when neither supply connection is required both speaker terminals are connected to each other providing d...

Page 8: ...tom and exhausted out the top The amount of airflow necessary will be deter mined by a number of factors including ambient tempera ture the amount of heat generated by other equipment in the rack the properties of the enclosure being used and how hard the amplifier is working In extreme cases it might be necessary to install a cooling fan in the rack for additional cooling In free standing install...

Page 9: ...fore while a DA 70 2 runs very cool the DA 70 4 PFC will require a little more attention to cooling Multiple amplifiers can be racked on top of one another without leaving a full rack space between them as long as sufficient airflow is maintained to allow heat to escape out the when power is not available from the wall The power supply must act as a local reservoir of power from which the ampli fi...

Page 10: ...turned on Additional LEDs one for each channel will illumi nate when the amplifier is being pushed into clipping Level Controls The DA 70 Series has been equipped with a level control for each channel conveniently located on the front panel With typical program level present adjust each channel to provide 10 the desired output level If undesirable distortion is pre sent check preceding components ...

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