Re: Off topic- PL-390 ?'s-FARMERIK

Rick Robinson <w4dst@...>

On 12/24/2010 5:22 PM, farmerik wrote:
Could any one who has a PL-390 answer a few questions for me? Does the line input jack work as a line output jack as well? [my CR-1100 seems to]. 

What impedance are the speakers inside? 

How many mW output/channel?

 Does the headphone out use a small 20-40mW amp, or just connect the stereo head phones in place of the speakers? 

I am thinking of buying one to use more as a table radio with larger, but highly efficient speakers, or driving a stereo amp with the PL-390.- FARMERIK

Farmerik and others,

I've been hacking into all my ULRs and have found the same audio output chip in all of them.  My CCrane SWP, G8, PL-310 and PL-380, and I assume about any small Chinese made portable, use the same CD1622CD audio output chip.  This is a 16 pin 2 channel output SMT IC rated at 410mW per channel into 8 ohms with a maximum VCC of 8VDC.  The headphone output appears to merely take the place of the internal speaker or speakers, when plugged in.  I think it's a safe bet that the PL-390 is not different from any of the other ULRs as far as the audio output chip used.   From what I can tell about the Si473X family, they output both of their audio channels as mono unless stereo is detected in the FM band, in which case the output is stereo.  There are a lot of "smarts" in the Si473X chips, but another processor is used to drive the LCD, and input the parameters such as selectivity, frequency changing, memory, etc. to the Si473X.  Does anyone know what processor is used to drive the Si4734?

These CD1622CDs are most likely the source of white noise which folks find objectionable in their ULRs.  The CD1622CD is by no means an audiophile chip, it is merely a small low cost SMT device made for the portable radio industry.  In fact, the only data sheet I have been able to locate for the CD1622CD is in Chinese.  The specs do use English so it does make it easy to interpret the parameters.  Just because the specs call for an 8 ohm impedance for speakers, doesn't mean the speakers in the ULRs are 8 ohms.  It just means they will drive an 8 ohm speaker to a maximum of 410mW.  There could be 32ohm speakers in some of these ULRs, who knows?

Burkhard Kainka, the designer of the Elektor DSP receiver uses 2 LM386 8 pin DIP amplifier chips instead of the CD1622CD.  This is an improvement over the CD1622, still not audiophile quality but a significant step forward.  He also uses the well known and easily programed ATmega 168 microprocessor to drive the Si4735 in the Elektor DSP receiver.  His ATmega interface is almost identical to the Arduino Duemilanove board.

Rick W4DST

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