Digital Drive

Let the Swenson/Vinnie mods begin (Toshiba SD-3990 Details)

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PeAK

(A)

For those who missed all the excitement with the SD-3950/SD-3960
upgrades, I've posted some internal details of the output stage found in this generation/current-version of the Toshiba DVD players.
Initial listening indicated promising but ever-changing sonics.
The neat thing is that some sort of passive balanced output stage may be possible by just adding one resistor and one capacitor to get a Balanced Swenson upgrade to mate with the "balanced inputs" on your high end preamp.
PeAK

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Re: Let the Swenson/Vinnie mods begin (Toshiba SD-3990 Details) - drummerwill 19:02:52 11/15/06 (1)
Been pretty happy with the Rope Caulk mod could definately hear the difference between the mod vs. stock.
Have fun
Willie
- re:mods...from Caulking to Output Stage Details - PeAK 06:36:12 11/16/06 (0)
  Hey Willie,
  The 3990 is somewhat lightweight and tinny so I'm not surprised that
  adding mass with "rope caulk" could alter its sound for the better.
  There is a "PT/Rega" school of thought that says to keep everything in a close loop via type coupling of the "internal noise sources" to the transmitting medium(chassis). In this alternate view, mass is not necessary but can still be used.
  P.S. Comments on the schematics of the output stage are now up ...what would have been a truly esoteric design back in the Theta Gen days
  cheers,
  PeAK
  - Schematic Details (Open in New Window)
Re: Let the Swenson/Vinnie mods begin (Toshiba SD-3990 Details) - rosconey 14:40:57 11/15/06 (3)
still use my 3950(the one that started it all) for dvd's-watched davinci's code today on it-
wonder how long till the smithsonian wants it-lol
- Re: 3990 mods...is 3950 still the one? - PeAK 06:58:11 11/17/06 (2)
  Cheers Rosconey,
  Thanks again for pointing out the 3950 to the inmates...and especially to Vinnie!
  As great as the 3950 was, the updated 3990 unit has gone back to a metal case and has gotten lighter and thinner. Moving the transport to the side has increase separation from the power supply. The drive is quieter. The unit does not power down automatically (after 15 minutes)anymore for those who believe in keeping their equipment always powered.
  The major difference is that the DAC architecture is now differential in similar ways that the landmark Art DI/O was. There are some great op-amps and modified filter arrangements just waiting for the audio hobbyist to try and
  the promise of possibly improved sound upon the 3950. I guess all of this (downstream upgrading) is contigent on the Zoran DAC being on par/better than the sweet Burr-Brown units in the 3950.
  PeAK
  - 3990 output stage (Open in New Window)
  - Re: 3990 mods...is 3950 still the one? - DouglasJesse 14:27:21 11/20/06 (1)
    PeAK,
    From using and looking at the Zoran chip and the analog output stage, I am certain that it is a voltage output dual differential design coming from the Zoran chip. Current output designs that I have seen in all the players over the years take the current signal right into the - input of the current to voltage opamp, with no signal parts in series before the changeover. Yes, you could do a balanced swenson mod, but watch because there will be low voltage/gain potentially. Look for some cool pro mods soon that have been cooking up.
    Any problems with lockups or glitches in the performance of the unit? I had this in about 50% of the 3960's I modded (over 30 of them) and a couple issues like this in the 3950, but the 3950 was a great platform that was introduced and I am confident the 3990 if glitch free, will be a much better unit to use once modified over all the previous models.
    Thanks alot, Douglas Jesse
    - Re: 3990 mods...is 3950 still the one? - PeAK 06:43:07 11/21/06 (0)
      Hi Jesse,
      I've measured the low frequency/DC gain of the circuit and it seems to be about 1 (i.e. 0 dB). The filter has a cascade of real poles and an arrangement that seems to limit the last active stage to signals that it can handle...it does sound surprisingly good, stock, for such a low cost op-amp. My only conclusion is that the the direct coupling (i.e. no coupling caps) offers many of the advantages of an AC couple circuit with a good/$$$ coupling cap.
      I do have a CD-R that I have not played in a while of compiled songs that is problematic toward the later tracks...but it may be the CD-R losing it's mind.
      It be interesting to see what you hear in the stock unit before you do your bypass, clock and op-amp magic to it. Personally, I think it rates with the Swenson 3950 once the isolation is taken car of and that is saying quite a bit. Kudos to Toshiba.
      
      cheers,
      PeAK

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