I'd buy a Si4735 shield from sparkfun. I did some custom mods and added an XBee on it using a voltage divider(10k/10k) on xbee DIN. Also, GPIO wasn't work because a mistake from sparkfun guys. As said on http://arduino.cc/forum/index.php/topic,66554.0.html, I added a diode and it's working now. I can get volume, frequency, RDS, etc...
Now I want to learn how a preamp and a amplifier work to get a good sound from it.
I have an old NE5532 preamp board that I bought from ebay a long time ago(like this http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110711886084#ht_2681wt_1114). I found that it has a gain of 3 times.
I plugged this preamp using 12-0-12 15VA transformer on shield and my iPod headphone. I can hear but the volume is low. I saw that R3 and R5 on board = 33k, they say that I can change this resistors to have a greater gain. I have a bunch of 1% resistor with different values. May I swap with higher or lower resistors to increase the gain? Will I be able to use only the preamp to drive the headphone?
Also, I'll make a gainclone(LM3886 chip amp) amplifier. It'll work fine?
Some Si4735 info:
| Parameter | Min | Typ | Max | Unit | | - | - | - | - | - | | Audio Output Voltage | 72 | 80 | 90 | mV RMS | | Audio Output L/R Imbalance | - | - | 1 | dB | | Audio Frequency Response Low | - | - | 30 | Hz | | Audio Frequency Response High | 15 | - | - | kHz | | Audio Stereo Separation | 32 | 42 | - | dB | | Audio Mono S/N | 55 | 63 | - | dB | | Audio Stereo S/N | - | 58 | - | dB | | Audio THD | - | 0.1 | 0.5 | % | | Audio Output Load Resistance | 10 | - | - | kOhm | | Audio Output Load Capacitance | - | - | 50 | pF |
Wagner Sartori Junior