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LM4702 + SAP15 amplifier - new design

Wawrzo. 4617 14
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  • LM4702 + SAP15 amplifier - new design
    I just thought that if anyone was interested, maybe they would benefit. The test project was created in EASYEDA and it even looks quite good, after Christmas I will start it.
    https://easyeda.com/wawrzo1970_7526/lm4702_darlington_mt200
    The project itself is available in four versions:
    with transistors: sap15, std03, darlingtons in MT 200 and TO3 housings, the last two versions are in the process of being finished, because they require slightly larger PCBs. I encourage you to modify it yourself.

    Cool? Ranking DIY
    About Author
    Wawrzo.
    Automation specialist
    Offline 
    Wawrzo. wrote 261 posts with rating 20, helped 16 times. Live in city Radom, i inne..... Been with us since 2001 year.
  • #2
    simw
    Level 26  
    Not bad. If I remember correctly, the LM4702 can be found in the Arcam AVR500 and AVR600 series receivers. These receivers were great both for home theater and stereo. I think I have 2 chips and SAP15 left after the damaged CambridgeAudio. Maybe I'll be tempted with the next pcb order. Thanks for sharing.
  • #3
    User removed account
    Level 1  
  • #4
    Wawrzo.
    Automation specialist
    The LM4702 does not have a separate power supply for both channels and the division of the transistors themselves seems pointless in this case, it will only cause an unnecessary expansion of the system. Two bridges are supposed to give the effect of faster charging of the capacitors, especially when loaded with bass. A proven solution in a few other amplifiers.
  • #5
    User removed account
    Level 1  
  • #6
    Nepto
    Level 16  
    Interesting. It is a pity that both the LM4702 and SAP15P / N transistors are no longer produced and the chance of getting the originals at a reasonable price is probably negligible.
  • #7
    Wawrzo.
    Automation specialist
    As for the parallel connection of the bridges, in this case the assumption was to reduce the dynamic resistance of such a tandem, which causes when the bridges connected in such a way are loaded with a short current pulse - of course below the maximum forward current - much faster recharging of the filter capacitors. But you can solder a single one.
    As for the separation of the power supply - that was my concept, maybe after testing - if the sound is satisfactory, I will add something to it.
    I also have a prepared board on the LME49830 chip and ECX10N20 / ECX10P20 (EXICON) lateral transistors and there are other solutions there - the circuit is monoblock.
  • #8
    User removed account
    Level 1  
  • #9
    Wawrzo.
    Automation specialist
    To me personally and subjectively, the bass on the two bridges seems warmer, but this is my subjective opinion resulting from listening to the STX Quant 300 speakers and the DIORA WS600 amplifier (with minor modifications). The design is generally available and nothing prevents you from modifying it to your own needs and preferences.
  • #10
    User removed account
    Level 1  
  • #11
    dktr
    Level 22  
    Quote:
    To me personally and subjectively, the bass on the two bridges seems warmer

    How is the "temperature" of the bass measured?
  • #12
    User removed account
    Level 1  
  • #13
    Wawrzo.
    Automation specialist
    A subjective feeling, if a colleague had doubts, and besides, he does not measure, but feels. We can only measure physical values according to the laws of physics. An example would be temperature. Ehh ...
  • #14
    Jawi_P
    Level 35  
    dktr wrote:
    How is the "temperature" of the bass measured?

    Are you clinging? You may have asked what the author thinks that term means. Unfortunately, when describing sound impressions, similar expressions cannot be avoided, either someone understands them intuitively or not. There are no audio-woodo tours in this thread.