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USB Soundcard (minimal size)

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  • dl7jp
    Dear all, I plan to build a little /p trx for digital modes based on a softrock RXTX; the idea is to include a 10W PA and a ZM-2 ATU, all in one (reasonably
    Message 1 of 54 , Mar 31, 2007
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      Dear all,

      I plan to build a little /p trx for digital modes based on
      a softrock RXTX; the idea is to include a 10W PA and a ZM-2
      ATU, all in one (reasonably small) box.

      Since my laptop suffers from the usual "mono input syndrom", I
      am looking for a small, external soundcard. From earlier postings I
      gathered that an Audigy 2 ZS notebook card might be an option,
      but I would prefer to include small USB soundcard directly into
      the box (since this allowed to use the TRX also with a PC).

      I am wondering what the smallest USB-soundcard would be that
      makes sense for a softrock RXTX... tnx fer hints!

      Joachim / DL7JP
    • Terry
      ... a year ... so I can ... affects the ... components, ... should be ... the ... the ... the ... and ... done ... that ... codec. I ... in the ... affacted
      Message 54 of 54 , Jul 31, 2007
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        --- In softrock40@yahoogroups.com, Ignacio Cembreros <eb4apl@...>
        > Guido wrote:
        > >
        > > On 7/30/07, *Ignacio Cembreros* <eb4apl@...
        > > <mailto:eb4apl@...>> wrote:
        > >
        > > Terry, Guido et all.
        > >
        > > I bought the same kit mentioned in Nuts and Volts, more than
        a year
        > > ago. Finally I found the kit documentation in digital format
        so I can
        > > describe the problems I had.
        > >
        > > The picture has an error, a swapped resistor pair, which
        affects the
        > > balance. If you have followed the picture for placing the
        > > like me, you swapped R11 and R13. R11 should be 6k8 and R13
        should be
        > > 3k9 and they must be located as per the silkscreen, not per
        > > picture.
        > >
        > > Another error is in the PCB itself which doesn't agree with
        > > schematic and is related to the supply method. This affects
        > > performance, according to TI.
        > >
        > > My solution is to cut the trace which goes from C2 to a via
        > > finally
        > > to U3 pins 8,9 and 27; do it just after C2 and solder a wire
        > > jumper from
        > > C2 (or C1) to R9 (VBUS in the schematic). All this rework is
        > > in the
        > > bottom side of the card.
        > >
        > > As you can see, both problems can be easily fixed, and after
        > > I use
        > > this mini card for demos with an SR40 with reasonable results.
        > >
        > > 73 de Ignacio, EB4APL
        > >
        > >
        > > Hello Ignacio,
        > >
        > > Thanks for reporting about your experience with the PCM2900
        codec. I
        > > have no access to the Nuts and Volts schematic, but presume the
        > > circuit is not different than the typical circuits as published
        in the
        > > datasheet [1] ? Could you indicate which of the components
        > > the performance?
        > Guido,
        > I was referring to a PCB layout error in the Nuts and Volts kit
        > not in the schematic which is close to the TI evaluation boards,
        > minor variations.. If you are interested in the schematics and the
        > description, let me know it and I will send it directly to you.
        > According to TI, the circuit can be powered from the internal
        > or an external one. The use of the internal regulator affects
        > negatively to the harmonic distortion and maybe the noise, I don't
        > the application notes here but are on the TI site. So TI
        recommends to
        > use a cheap external regulator, except for very cost sensitive low
        > applications.
        > --
        > 73 de Ignacio, EB4APL
        Thank you for the above information. I checked my ADDA board, and it
        has both the problems you mentioned above. I purchased the assembled
        units, not the kits, but the resistors were wrong anyway.

        I ahve made both the changes you outlined above, and will test the
        board for improvements. It certainly cannot be worse that the board
        originally performed!!

        It will likely be a week before I can test it, as I have some travel

        Thank you again for highlighting the two problems above. I do not
        have the original Nuts & Volts article. I have only the schematic
        that came with the board, and the TI datasheet.

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