Anyone built Sijosae's class AB amp ?

Discussion in 'DIY (Do-It-Yourself) Discussions' started by ozshadow, Jun 1, 2006.

  1. ozshadow
  2. Blind Tree Frog
    Power looks to be batteries or wall power. 2 9 volts would probably work well enough.
     
  3. ozshadow
    I either want to build this next, or a Pimeta. It'll take me a while for either, but I want to start one.
     
  4. barkas
    Looks nicely compact and easy to get components.
     
  5. ATAT
    Oz - pimeta will be easier because of the PCB, doing something on perfoboard isn't a very fun experience..
     
  6. Tedro
    Quote:

    Originally Posted by ATAT
    Oz - pimeta will be easier because of the PCB, doing something on perfoboard isn't a very fun experience..



    edit: so MUCH fun!!
     
  7. thedoctor
    sounds much better than a CMOY, resembling a MINT, with a diamond buffer output stage. in fact, i like the diamond buffer used in the sijosae Class AB rather than the simplified diamond buffer used in the few new designs surfacing this few days.

    small enough to be fitted into a MINT tin, yet the donutboard might not be favorable to everyone.
    [​IMG]
    [​IMG]
    [​IMG]
    ^ with an integrated TREAD. the circuit is smaller if should you skip the TREAD implementation.

    [​IMG]
    [​IMG]
    [​IMG]
     
  8. Polaris111688
    The components are so densely packed.. I like it!
     
  9. barkas
    I'll probably build one.

    I already did eagle boards for power and amp, a lot less dense, but also a lot more clean, if somebody is interested, I'll post them.
     
  10. ozshadow
    I want to know how they sound compared to a Pimeta.


    I'll be using with Grados
     
  11. thedoctor
    Quote:

    Originally Posted by ozshadow
    I want to know how they sound compared to a Pimeta.
    I'll be using with Grados




    different taste for different application. the Class AB is meant to be a portable solution. the PIMETA isn't. them 3 channels with BUF634s will suck the battery dry in a few hours.

    and good luck trying to fit a PIMETA into a MINT tin. SMD versions don't count.
     
  12. ATAT
    Quote:

    Originally Posted by thedoctor
    different taste for different application. the Class AB is meant to be a portable solution. the PIMETA isn't. them 3 channels with BUF634s will suck the battery dry in a few hours.

    and good luck trying to fit a PIMETA into a MINT tin. SMD versions don't count.




    [​IMG] [​IMG] [​IMG] *grin*

    that grinning aside, Class AB is quite a nice way to get long battery life and that design looks nice.. Id probably say its better than a MINT, worse than PIMETA, or any of the buffered ground designs (i mean 3 channel).

    But BUF634 running in low current mode will draw less than a class-AB IIRC...

    Also thedoctor, how is sijosae's a diamond buffer? its just a push pull current mirror .. I fail to see how this is a diamond buffer...
     
  13. amb
    Quote:

    Originally Posted by ATAT
    Also thedoctor, how is sijosae's a diamond buffer? its just a push pull current mirror .. I fail to see how this is a diamond buffer...



    It's not a diamond buffer. It doesn't have any current mirrors, either. Don't let the schematic confuse you. If it had current mirrors the transistors' C and E junctions would have to be reversed... The two transistors on the input side are used merely as diodes (with the C-B junction shorted) to bias the output transistors, which are set up as a simple push-pull emitter follower.

    Btw, the virtual ground in this circuit is an open-loop buffer and has no opamp driving it and no negative feedback, so its output impedance is going to be a bit high. This means that the virtual ground potential will be modulated by the current it has to source and sink, and thus stereo crosstalk will be poor (built-in cross-feed!).
     
  14. barkas
    What if I drove the ground like the L/R channels using a uA741 and 2x220kOhm as rail divider as input for the uA741?
    That would probably get a lot lower ground impedance.
     
  15. guzzler Contributor
    Quote:

    Originally Posted by barkas
    What if I drove the ground like the L/R channels using a uA741 and 2x220kOhm as rail divider as input for the uA741?
    That would probably get a lot lower ground impedance.




    The rated output current for a 741 is only 25mA, ie, only 5mA greater than a TLE2426. You could use a OPA551 like amb used in his muting circuit: that's got a few hundred mA output
     

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