Hey guys I have an older Sony STR DH100 2 channel receiver which uses a DSP chip that's capable of 5.1 or 7.1 surround. Sony designed the PCB to use for several models as theres many places where componants can go that are missing on mine. Ive looked at the datasheet for the DSP chip (BD3474KS2) and there is multiple different outputs including 2 for a subwoofer. One looks to be a mono sub out and the other is a stereo left/right output. Do you think its as easy as tapping off the traces from those pins and Ill have a subwoofer out?
Datasheet for BD3474KS2 look at pages 4&5
Link is to alldatasheet.com website
Datasheet for BD3474KS2 look at pages 4&5
Link is to alldatasheet.com website
That is not a DSP, but an electronically controlled analogue sound processor. However, whether you can just tap the sub outs always depends on the MCU code, since everything seems to be programmable.
Thanks for your reply, I didn't think it was a DSP but saw somewhere in the datasheet they referred to a function as DSP so thought maybe it was a primitive form of it. I also wondered if the output was active or needed to be programmed for it but found little to no information about programming although there is a header on the PCB for programming. I decided to just try it and soldered a couple 10uf caps into the empty spaces on the PCB and jumpered the spot where the output relay would go with some 100ohm resistors and.... Got no output! Lol So seems as though it's not programmed for use unfortunately. I did manage to add some RCA outputs that are volume controlled by the digital potentiometer which is all I really needed anyway. I soldered 2 wires to the bottom of the PCB from the STK350 IC they call the "pre driver". I re-purposed one of the RCA jacks already on the unit and removed the caps to disconnect it from its associated input making it now an output.
Only thing that may or may not be an issue is the output is kind of high on voltage. I turned the volume up to higher than I'll ever use it at and measured almost 3v on the output RCAs. So I may have to attentiate them but not sure the best way to do that. Can I just put some resistors on the signal line? Maybe like a 220ohm in series with a 100ohm to ground or vice versa?
Ok so ran into my first problem. When using the added outputs to my subwoofer amp they work perfectly but when I tried using a tda7498e chip amp the highs were distorted in a weird way that's hard to describe. The tweeters were definitely not playing any of the notes they should be but rather a scratchy distorted tone. The woofers played the music but sounded slightly off. My first thought was that the predriver stk350 530 doesn't have enough power to drive the Sony's internal amp and an external but the signal measures 3v rms. Also when checking it with an oscilloscope the sine wave is clean. I didn't look at the sine wave while hooked to the tda7498e however. Could it be something to do with impedance?