Stereo encoder Pro 2 Dimension (L x W x H): 147mm x 72mm x 20mm Stereo encoder Pro2 is a stereo encoder board with professional class sound quality and features. Its design combines analogue and digital techniques to use the best of both worlds. Features Balanced audio inputs Switchable Preamp Phases (0, 50 µs, 75µs) Optional feed forward audio limiters Soft audio clippers Kristal controlled 15KHz switch cap audio filters Digitally generated multiplex carriers Sinusoidal 19KHz pilot tone High channel separation >55dB @1KHz audio Clean spectral output Low noise operational amplifiers 19KHZ output to synchronise to an RDS system RDS input Rev 3 04-2016 Page 1 from 5 www.fmbroadcastparts.com
Product description Stereo encoder Pro2 is a stereo encoder board with professional class sound quality and features. Its design combines analogue and digital techniques to use the best of both worlds. We start with balanced inputs, then a choice of preamp phase 0, 50 µs or 75µs. Next you can add optional feed forward analogue audio limiters from Analog Devices. These plugin devices are very small but have professional class sound quality. If you want to limit overshoot from the analogue audio limiters or want to optimum compress your audio, we added two soft clip clippers to have a clipped audio signal that keeps round edges for a less digital sound. It also helps to keep your audio within 75KHz bandwidth. To be sure that your audio and harmonics from the clipper does not exceed the 15KHz audio limit, we added two Maxim Integrated crystal oscillator controlled switch cap filters. These switch cap filters keep your audio below 15KHz and suppress the 19KHz from your audio with more than 55dB. Your audio can now be combined to build a multiplexed audio source. We use digital techniques to build the multiplexed L-R & L+R signal, but we transfer the digital 19KHz pilot tone to an analogue sinusoidal signal for cleaner output and better modulation quality. The combination of techniques give a very flat response from 20Hz to 15KHz that results in a high channel separation of >55dB from 20Hz to 10KHz and >50dB from 10KHz to 15KHz. As last feature we did not forget an RDS input to add a RDS signal the multiplexed audio. MPX spectral output from 1Hz to 93KHz with audio sweep source from 20Hz to 20KHz. Audio level > 0dB into soft clippers, preamp phase 0µs. Rev 3 04-2016 Page 2 from 5 www.fmbroadcastparts.com
Overall Electrical specifications min typ max Power supply 13 15 18 Volt DC Supply current 280 ma DC Stereo encoder specifications Input impedance 10 K ohm Input level 0 +6 dbu Output impedance 1 K Ohm Output level 0 dbu Preamp phase 0/50/75 µs Channel separation @ 1KHz 55 60 db Signal to noise ratio 65 70 db Output spurious <56KHz -65-70 db Output spurious >56KHz -50-55 db Optional audio limiter board Input level 0 dbu Output level 0 dbu Limiter attack time 9 10 12 ms Limiter release time 90 100 120 ms Rev 3 04-2016 Page 3 from 5 www.fmbroadcastparts.com
Overall absolute maximum rating Symbol Parameter Value Unit Vs Power supply 18 V dc Is Supply Current 350 ma dc Tstg Storage Temperature Range 0 / +60 C TC Operating Temperature 50 C Connections & settings Connections and settings explained Left input Right input Balanced input for left audio channel. If you want to use this unbalanced, then connect your hot signal to the + pole and solder your shielding to the pole and the pole in the middle. For both balanced and unbalanced, audio level should be 0dBu or higher for best audio quality. Balanced input for right audio channel. If you want to use this unbalanced, then connect your hot signal to the + pole and solder your shielding to the pole and the pole in the middle. For both balanced and unbalanced, audio level should be 0dBu or higher for best audio quality. Preamp Phase Setting For a preamp phase correction in your audio, connect a short to the middle connection pin and the left (75µs) or right (50µs) connection pin. Clipper To limit overshoots from the optional limiter board or other audio processing connect a short to these pins. Use of the soft clippers can also be used to optimise your audio compressing or keep your audio within 75KHz bandwidth. Rev 3 04-2016 Page 4 from 5 www.fmbroadcastparts.com
Limiter Connection For use with optional limiter board. Remove the short from the pins and connect limiter board on the 5 pole connector. Note: Always remove power from the board before placing the board. See picture for correct position Channel separation fine tune Stereo On/off 19KHZ pilot level MPX clipper Variable resistor to fine tune channel separation, only for experienced electronic engineers. For mono use, short these pins with a short. 19KHz Pilot tone will be disconnected. These pins can also be used to connect the 19KHZ tone as a reference for an RDS system. Variable resistor to set 19KHz pilot tone level, only for experienced electronic engineers. Additional soft clipper to limit total audio level. Only for use in extreme circumstances, do not use in normal operation. +15V +15V DC input ( always use a DC regulated power supply) GND System ground ( = 0V ) RDS input MPX output RDS input for RDS systems Multiplexed audio output Note: Stereo encoder Pro 2 has to be built in a metal or aluminium enclosure with a proper ground connection. Use metal standoffs, screws and bolds to connect the board at least 5mm above the bottom of the enclosure and use all 4 holes in the corners. For audio connections, use a good quality shielded audio cable. Connect audio shielding to the ground connection closest to the hot connection. IMPORTANT NOTICE FMBROADCASTPARTS RESERVE THE RIGHT TO MAKE CHANGES TO THE PRODUCT(S) OR INFORMATION CONTAINED HEREIN WITHOUT NOTICE. FMBROADCASTPARTS ASSUMES NO RESPONSIBILITY FOR ANY ERRORS WHICH MAY APPEAR IN THIS DOCUMENT. WARRANTY INFORMATION APPLICABLE TO THE PRODUCT IDENTIFIED HEREIN IS AVAILABLE UPON REQUEST. NOTHING CONTAINED HEREIN SHALL CONSTITUTE A WARRANTY, REPRESENTATION OR GUARANTEE OF ANY KIND. FMBROADCASTPARTS EXPRESSLY DISCLAIMS ALL OTHER WARRANTIES, EXPRESS AND/OR IMPLIED INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY, AND OF FITNESS FOR A PARTICULAR PURPOSE, USE OR APPLICATION. WARNING FMBROADCASTPARTS PRODUCTS ARE NOT INTENDED FOR USE IN LIFE SUPPORT APPLIANCES, DEVICES OR SYSTEMS. USE OF A FMBROADCASTPARTS PRODUCT IN ANY SUCH APPLICATION WITHOUT WRITTEN CONSENT IS PROHIBITED. No part of this document may be copied or reproduced in any form or by any means without the prior written consent of FMbroadcastparts. Rev 3 04-2016 Page 5 from 5 www.fmbroadcastparts.com