Tweaker's Asylum

• IC pwr amp - john curl 16:29:03 03/14/02 (5)
  In Reply to: TDA7293 100W poweramp-IC from ST posted by groman on March 14, 2002 at 09:59:02:

  Thanks for the input, Groman. A while ago, Brian Cheney brought over to me, an IC (TDA7294?) based power amp to measure. The early version had big distortion, but it was even order, not odd order harmonic distortion. Apparently, it sounded very good, even with the extra distortion. This new IC power amp might be even better. Keep on Truckin! (I used to work for the Grateful Dead)
  
  

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  • MOSFET-out, and, yes, 2nd order dist - groman 01:47:27 03/15/02 (4)
    In Reply to: IC pwr amp posted by john curl on March 14, 2002 at 16:29:03:

    Thanks, john curl
    I like you being around, when feeling alone

    Yes, that is right!
    Even harmonics dominant, in whole spectrum
    Harmonics dist(1W/8ohms)
    f*2 -97.5 dB
    f*3 -102
    f*4 -103
    f*5 -110
    f*6 -107
    f*7 -117
    f*8 -109
    f*9 -120

    MOSFETs are used for OutputCurrents.
    Maybe that is why even harmonics dist
    is dominant?

    What is new, compared to TDA7294
    is you have a pin for driving
    the outputstage from external circuit.
    So you can separate input/output.

    What I also find great, is that you have separate
    power supply Pins, for pre- and output stage.
    LM3886 has that, too.

    Time for me to hold a LECTURE, again,
    of one of mine findings:
    ___________________________________________________________________
    One of the problems with making Poweramps,
    is that the heavy currents drawn by output-trasistors
    will corrupt pre-stage power-supply,
    and sometimes cause unwanted feedbacks.

    Those very fast, and popular, current-feedback (OP-)amplifiers
    are especially sensitive.
    For such amps separate or regulated supply
    to the Pre is recommended.

    I have never understood, why we should feed
    Pre-stage from same supply as Output in Poweramps.
    The few mA that is needed for inputstage can
    I get from a mini-trafo for a few bucks,
    and this can be a voltage that is at least 10V higher.

    This will give input and voltage amplifying
    transistors a better "workingspace":
    And all data will be improved.

    The improper method, to use common Powersupply
    for all stages,
    I think, COMES from COMMERSIAL GREED:

    "Put in as few and cheap components as possible,
    and take as HIGH PRICE as possible, from costumers.
    So we can make as high PROFIT MARGINS as possible
    and Shareholders will be happy.
    And SHAREholders/owners is in 80-90% of cases
    more important, than to keep the USER real SATISFIED."

    The big industries in Japan and USA
    are mainly to blame for the BAD practise
    to use only one mains transformer
    in Power Amplifiers.
    _________________________________________________________________

    And this is my firm view
    and I really feel that I am right!

    groman
    knows this

    do not forget to visit
    my FTP-server (on my harddisk)
    and help me make it useful/better.

    Groman1 FTP Server
    ftp://213.100.118.115/
    (anonymous login, port 21)

    so now you can get into my harddisk!!!!

    
    -Have a good time! As our life is so short.-

    
    
    

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    • Re: MOSFET-out, and, yes, 2nd order dist - john curl 07:30:03 03/15/02 (3)
      In Reply to: MOSFET-out, and, yes, 2nd order dist posted by groman on March 15, 2002 at 01:47:27:

      Groman, we have been separating the driver supplies from the output stages in all my power amp designs for Parasound for more than 10 years. This is not new, but it is important.
      The measurements that are the most important would be at approximately 3V out in the IC power amp. This is where the music will play, and where the earlier IC had much distortion.
      
      

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      • Glad to hear you have separated! - groman 07:41:19 03/15/02 (2)
        In Reply to: Re: MOSFET-out, and, yes, 2nd order dist posted by john curl on March 15, 2002 at 07:30:03:

        Separate,
        this is what every wise man does

        groman
        happy and separated

        
        -Have a good time! As our life is so short.-

        
        
        

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        • Re: Glad to hear you have separated! - rcrump 07:51:23 03/15/02 (1)
          In Reply to: Glad to hear you have separated! posted by groman on March 15, 2002 at 07:41:19:

          I had the worst time with a Borbeley amp that didn't have a separate supply for the input section as the Summers here in Houston are brutal and the power is low much of the year.....That amp would sound different as the power vacillated between 120 down to 112 volts depending upon the time of day so I had to run it on an automatic variac to keep it sounding the same......No such problems with my new amp with separate supply for the inputs and the old General Radio automatic variac could go away.....
          
          

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          • Re: Glad to hear you have separated! - groman 08:02:42 03/15/02 (0)
            In Reply to: Re: Glad to hear you have separated! posted by rcrump on March 15, 2002 at 07:51:23:

            yes, that is also one thing to consider.
            The variations in Mains voltage.

            Worst case could be round 10%
            This can have effect on idle-currents
            and also working conditions
            for transistors

            So a serious designer will try to make
            everything work as aspected
            even if WORST CASE situations arise.
            This could be Mains voltage or room-temperature.

            groman
            worst case of them all

            
            
            -Have a good time! As our life is so short.-

            
            
            

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• Re: TDA7293 100W poweramp-IC from ST - Red Pill 15:16:53 03/14/02 (4)
  In Reply to: TDA7293 100W poweramp-IC from ST posted by groman on March 14, 2002 at 09:59:02:

  There is a board dedicated to DIY amps from chips, especially as Gaincard clones. There are a couple of threads regarding the 7293/7294, one specifically mentioning that the Linn Klimax and Majik amps use these.

  I am going to experiment with the usual culprits (LM1875/3875) soon, and will look for the TDA's as well.

  Good luck.
  Live long. Party Hard.
  

  • TDA 7294/7293 thread

  
  

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  • What LINN uses can't be all bad - groman 01:56:32 03/15/02 (3)
    In Reply to: Re: TDA7293 100W poweramp-IC from ST posted by Red Pill on March 14, 2002 at 15:16:53:

    thanks,
    I now realise that
    AudioAsylum is not the only Audio FORUM

    Many interesting discussions
    can be found elsewhere

    
    groman
    somewhere else now

    
    -Have a good time! As our life is so short.-

    
    
    

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    • Also try - Red Pill 02:07:22 03/15/02 (2)
      In Reply to: What LINN uses can't be all bad posted by groman on March 15, 2002 at 01:56:32:

      www.diyaudio.com

      I think you'd like it there. Lots of good people, some even form your part of the world, with more of an emphasis on SS rather than tubes. There is even a special Pass Labs DIY forum.

      See you there.
      
      

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      • thanks again - groman 02:12:28 03/15/02 (1)
        In Reply to: Also try posted by Red Pill on March 15, 2002 at 02:07:22:

        I go there
        right now

        groman

        
        why wait until tomorrow
        -Have a good time! As our life is so short.-

        
        
        

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        • Re: thanks again - Red Pill 03:15:20 03/15/02 (0)
          In Reply to: thanks again posted by groman on March 15, 2002 at 02:12:28:

          My pleasure. Your posts make me smile.

          Cheers

          The music can only flow through you if you relax and let it.
          
          

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• Poweramp schematic in PDF - groman 13:25:17 03/14/02 (0)
  In Reply to: TDA7293 100W poweramp-IC from ST posted by groman on March 14, 2002 at 09:59:02:

  The designer, a german, has made a PDF about his
  TDA7293-based Poweramp. It is 1.5 MB.

  There is all technical data
  and SCHEMATICS, as been published in Elektor.
  On page 5 is a full schematic, not many components.
  And details of Powersupply.

  Go to poweramp: Endstufe 100 Rev 1.11
  See link below.

  His german homepage is
  http://www.ub-elektronik.de/

  He has designed Preamplifier, Poweramplifier and Loudspeakers.
  Seems to be a rather serious guy.

  As i can see it, a Hi-End amp for little money
  if you have some knowledge about building electronics.

  I wait for some comments
  Is rather lonely here

  poor lonely
  groman

  
  -Have a good time! As our life is so short.-

  
  

  • To poweramp page.

  
  

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• Some figures, prestanda - groman 10:31:15 03/14/02 (0)
  In Reply to: TDA7293 100W poweramp-IC from ST posted by groman on March 14, 2002 at 09:59:02:

  Forgot to mention
  TDA7293 amp in Elektor

  has got bandwidth 6.5 to 200.000 Hz (1W/8ohms)
  but the slewrate is only 8.5V/uS

  and it delivers 50W/8ohms 73W/4ohms, sinus 0.1% THD

  more info in Elektor magazine

  
  groman
  likes figures
  and percentages

  Do not forget to visit

  GROMAN1 FTP Server
  ftp://213.100.118.115/

  
  -Have a good time! As our life is so short.-

  
  
  

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