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NEDSP900 Development Board

Addendum to PCB Model A07-001-10 (Issue:1)

Due to some tracking errors, two traces have been omitted on the PCB.

The main omission is of the 2

audio amplifier output to the Headphone/Speaker socket.

The affected PCB’s have all been modified as shown in the attached pictures below:

Wiring underside of the PCB

Connection to socket on the topside of the PCB

If and only if adding any of the Balanced Microphone

amplifier

components and making use of

this facility, then the following modification needs to be carried out. This has not been
corrected as this needs the appropriate Balanced Input Amplifier components added to the
amplifier.

Locate and identify R44, to be found on the bottom end of IC3.

Содержание NEDSP900

Страница 1: ...Ltd Document HB07 003 10 Issue B PO Box 318 Burgess Hill RH15 9NR England Tel 44 0 1444 870333 info bhi ltd com www bhi ltd com Picture of a basic assembled unit Handbook for NEDSP900 Development Boa...

Страница 2: ...Input Selection 2 5 Overload Indicators 3 0 Gain Settings 3 1 Setting the gain for SK7 Microphone input 4 0 Noise Reduction Settings 5 0 Outputs 5 1 Line Drive 5 2 Headphone Speaker Output 6 0 Other...

Страница 3: ...cifically in Section 7 0 and the various Appendices The board has been created such that it can be mounted on standard M3 type pillars for ease of use However the format also allows a standard extrude...

Страница 4: ...Input Mono Microphone Input Line Output Headphone Low power Speaker Output Power 2 1mm Coaxial Power Jack Various other connections using 0 1 connectors mainly Molex KK have been provisioned for monit...

Страница 5: ...nput 2 Tip JP4 Not JP2 JP2 Not JP4 None Below is a picture to assist in the location of the above jumpers Above Jumpers set for Speaker Level Inputs Above Jumpers set for Headphone Level inputs Note F...

Страница 6: ...a Stereo 3 5mm jack plug on it then it s likely that it requires Bias on the middle ring of the plug This is standard for Microphone or Headset being used with a PC For a standard 3 wire PC type micr...

Страница 7: ...ance Audio Signal Dual Stereo balance microphones or signals 2 5 Overload Indicators Each channel has an Overload indicator Marked OV RLD on the PCB these are located next to the Power Indicator The o...

Страница 8: ...AGC action and is designated as a Speaker or high level audio channel therefore high gain settings are not required Gain dB SW1 Gain Bit 1 SW1 Gain Bit 0 LSB 0 OFF OFF 12 OFF ON 15 ON OFF 18 ON ON No...

Страница 9: ...y responds to changes in voice level and not the general audio signal Manual Gain setting A nominal gain setting for an Electret microphone would be about 28dB This is set by selecting the gain using...

Страница 10: ...uce the mean audio level so that everything sounds quieter This is mainly because the noisy parts of the signal are being removed to improve the overall speech quality of the signal 5 0 Outputs There...

Страница 11: ...ir use is easily identifiable from the Circuit Diagrams see Appendix A 6 1 Audio Monitor Points A set of audio Monitor points has been provided for the user to hook into the audio signals before and a...

Страница 12: ...NS0 Weak Pull up Pull Down to Activate 7 Channel 1 Suppression NS1 Weak Pull up Pull Down to Activate 8 Channel 1 Suppression MSB NS2 Weak Pull up Pull Down to Activate 9 Gnd 10 5v You will note from...

Страница 13: ...than Circuit a packaged together in a small surface mount pack They come in a variety of input and Base to Emitter resistor values Again these will perform a logical inversion Circuit c This is the si...

Страница 14: ...gorithm reduces its effectiveness In certain intercom configurations where there may be bursts of clean audio this can lead to problems and small periods of noisy audio may be heard while the algorith...

Страница 15: ...Inputs PL12 PL13 Any 0 1 standard Wire to PCB connector 3 Way Molex KK or similar Not Fitted see Appendix A Balanced Microphone Phantom Power PL10 PL11 Any 0 1 standard Wire to PCB connector 2 Way Mol...

Страница 16: ...NEDSP900 Development Board 16 Appendix A PCB Documentation and BOM Board Topside Layout Board Bottom side Layout Power Input on this end...

Страница 17: ...NEDSP900 Development Board 17 Schematic Diagram Sheet 1 of 5 Output Buffer and Line Driver...

Страница 18: ...NEDSP900 Development Board 18 Schematic Diagram Sheet 2 of 5 NEDSP900 and Control Switches...

Страница 19: ...NEDSP900 Development Board 19 Schematic Diagram Sheet 3 of 5 Balanced Audio Inputs See also Appendix B...

Страница 20: ...NEDSP900 Development Board 20 Schematic Diagram Sheet 4 of 5 Speaker and Microphone Input Interface with Overload Indicator 1 2...

Страница 21: ...NEDSP900 Development Board 21 Schematic Diagram Sheet 5 of 5 Power Input Filtering and Regulation with Headphone Amplifier...

Страница 22: ...10R 2 72 9800 Rapid R63 R64 22R 2 72 9804 Rapid R18 R19 100R 2 72 9816 Rapid R72 R73 120R 2 72 9817 Rapid R76 330R 1 72 9824 Rapid R7 R8 R55 R56 470R 6 72 9826 Rapid R50 R52 R54 R74 R75 2K2 5 72 9838...

Страница 23: ...C61 C71 C76 10nF 3 71 2014 Rapid C60 C72 C73 C75 100nF 4 71 1854 Rapid Capacitors SMT 0603 C4 C11 330p 2 145 8854 FEC C6 C9 C12 C13 C50 C52 1nF 13 71 1834 Rapid C1 C5 C55 C69 10nF 4 71 1844 Rapid C2 C...

Страница 24: ...mper headers 3 54 3943 Rapid Misc Jumpers for above 6 22 3555 Rapid SKT for IC1 13 way 2mm SIL Socket 2 19 0080 Rapid PL20 2 1 DC Socket 1 20 0970 Rapid SK3 SK6 SK7 SK10 3 5 mm Stereo Jack socket 4 20...

Страница 25: ...s with an output of around 5 mV P P The gain of the circuit has been set to provide around 26dB in order to bring the level up to that commensurate with a standard Electret Insert PCB as normally supp...

Страница 26: ...on Mode Signals I e Similar signals that are traveling along both of the inputs are minimised when amplified R25 and R26 form the input resistance to the Op Amp R27 and R28 are the feedback resistors...

Страница 27: ...g input IN of the Amplifier components via R30 to half the rail voltage using R44 and R45 This is a common practice C39 then ensures that this new reference point is held steady and provides a path fo...

Страница 28: ...0uH 9 233 3632 FEC Capacitors SMT 0603 C25 C28 680p 4 249 6911 FEC C21 C24 C29 C30 C31 C34 1nF 6 71 1834 Rapid Capacitors Tantalum SMD C39 C46 C48 C49 10uF 10V Case B 4 498 660 FEC Electrolytic Capaci...

Страница 29: ...a little spare room in this enclosure to accommodate further circuitry however if a much larger volume is required the Hammond Manufacturing 1457N1601 may be used This gives about double the height wh...

Страница 30: ...B A A A C HOLES A 5 5mm Dia 4 Positions B 9 5mm 2 Positions C 12mm 1 Position Above End panel drilling patterns note that the dimensions should be taken from the centre of the side of each panel Note...

Страница 31: ...PCB jumper sets JP5 JP6 and JP7 have been provided on the PCB These need to be cut with a scalpel which will then leave only the headers active Suitable interfacing connectors for PL3 PL21 through to...

Страница 32: ...NEDSP900 Development Board 32 Front Panel of PCB fitted to Hammond manufacturing 1455L1602 case Rear Panel of PCB fitted to Hammond case...

Страница 33: ...ified as shown in the attached pictures below Wiring underside of the PCB Connection to socket on the topside of the PCB 2 If and only if adding any of the Balanced Microphone amplifier components and...

Страница 34: ...arp scalpel gently remove the solder resist on the ground area opposite the end of R44 c d While fitting R44 make sure that the end of the resistor is soldered to the pad and to the area where the Sol...

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