24-bit-R2R-Audio-DAC Burr-Brown PCM1704 U-K
provisional price 150,- € per unit (highest selection, new, purchased via RS Components),
shipping, taxes etc. not included, as static sensitive SMD-IC no refunds or replacement if the sealed antistatic package was opened
also available on a PCM63 adapter board
At the moment (2015-03-13) there is a remainder of stock left at the distributors, commercial customers find two digit numbers at reasonable prizes e.g. at Mouser, Farnell and RS. With TI's withdrawal note obviously came a "last order" call, perhaps a distributor or some hifi manufacturer orders some, a "limited edition" as a last reissue of a classical unit isn't that unlikely. But I assume, that about one or two years after TI's withdrawal nothing genuine will be available any more.
Among experts the PCM1704 is considered as one of the best, if not the best audio DAC ever. The only real competitor one could mention was the TDA1541A, discontinued before the turn of the millennium. Obviously Texas Instruments now (early in 2015) stops production for this - together with Burr Brown incorporated - flagship. Probable motivation may be the high unit costs combined with low sales volume. For these last parallel direct and with extremely low noise+distortion working converter of highest precision trimming and calibration are necessary during production, such fabrication steps are not needed by the 1-Bit (delta sigma) successor converters, even not at significant higher integration density - and those can further on crow with gimmicks, which old "one-purpose-converters" only can dream of. A complete universal processing for digital input signals of any kind nowadays is more standard than exception. You can assume, that the production line of the PCM1704 can meanwhile be used for nothing else - and the other way round on later machinery - optimised for smaller scales - the "old" chip cannot be produced one to one without design changes.
original picture, formerly I had just a symbolic picture without production code - for mine were still all antistatic and moisture safe sealed...
...but now I opened two bags for my own CD player
With the PCM1704 a whole technical generation vanishes from the screen - regardless the protest of connoisseurs - on the summit of their development - by the red pencil of electronic and musical analphabets from the controlling department of a concern. The biggest impertinence in my eyes is the comment on the TI homepage saying, the product were not recommended for it were somehow technical obsolete and the successor "offers better audio performance". However you should have a look into the data sheet, on page 4 are some figures, one cannot imagine they would ever have the heart to publish for their actual bit stream (wiggle-)converters. There you can see sine waves at -110dB and -120dB pictured, clearly to be determined as a sine wave. A pulsed converter would leave just something like "scrambled egg" of such a signal, but surely nothing you could clearly recognize like this. To let through smallest and fines signals undisturbed by the continuous full scale level of pulsed bit stream integrators was always the domain of the parallel converters. And the result can be even more improved with many Burr Browns (with this one too) and also with the Philips R2R types by utilizing the current output and taking the I-U-conversion in ones own hand, beside an own digital pre-processing.
All these issues are wonderful pre-produced and inaccessible integrated in actual cheap common-or-garden DACs, but fore these the rule is: better is not possible. Regrettably.
Anyhow the laborious produced and trimmed R2R-DAC veterans - even more in their finest selection - regarding audio processing, in acoustic relevant issues are superior compared to their inherent linear, money saving successors. That is true for the here offered examples of safe origin to a great extent.
When the discontinuing notice came from Mouser lately and RS confirmed, the actual stock would be the last, I built up an own stock.
There is one thing I must put into each customer's shopping cart: the DAC alone makes no good reproduction. The environment must be right, else it would be "casting pearls before swine".
Even in theory the precision of such a chip can be only used with appropriate:
- clock (just from my memory, please look up... 24 bit at 8x become useless without a clock precision about <<2 picoseconds)
- supply and ground-routing, all voltages should be constant, all reference points free of damaging parasitic coupling...
- well supplied and routed I/U-converter and a very well decoupled line buffer output stage, designed to all rules of an state of the art amplifier
With my limited stock I will give out some of these seldom samples only, if I am (was) convinced of their reasonable use. I will also use part of them myself.
Supplement February 2016
Meanwhile obviously also the appropriate digital filters DF1704 and DF1706 expire worldwide, thus I made a last minute order at Mouser for a number that meets my PCM1704 stock, one half each the one and the other type. The DF1704 needs a 5V supply, the DF1706 3.3V, the output levels of both versions are accepted by the converter. The DF1706 has the additional feature of a switch down to 4x oversampling mode, further I cannot decide by the data sheet, if not the active level of the mute input was changed - in all other respects the chips are pin compatible. Running the DF1706 on 3.3V has the obvious advantage of less power consumption and interference, the DF1704s TTL compatibility on the other hand side provides a safer signal level handling.
If you want to buy a set of DACs from me, you also can order a suitable filter for them. Provisional price 70€ per unit. Also available on a SM5813 adapter board.