[percival007]

I recently discovered four TDA1540D’s in my box of tricks when tidying my shed. This coincided with me seeing for sale an eBay a circuit board from a chap in Italy which took the i2S signal and converted it to 14-bit Left and Right Data plus Clocks.
''What the heck’’ I thought,......''I need another DAC (I really don’t but can’t seem to stop making them, I do enjoy it!) and am in need of a little project’’ so set about designing.
I am fortunate that at work I have access to PCB CAD design software so was able to draw the circuit and create a PCB layout. The O/P files are then sent to a Chinese company and two weeks later a PCB arrives at a surprisingly reasonable cost!!!!!

I presume it was a marketing decision for Philips, 'who would want to buy 14 -bit CD Players when the Discs were 16 bit and Sony’s Players were also'? More bits had to be better from a marketing viewpoint and is technically true from a resolution point of view.
The early 14- bit Players from Philips always sound good to me, I own a few CD-104's, but this all made me wonder what ‘straight’ 14 bits would sound like with no over-sampling and noise shaping, which Philips engineers came up with to make their first players be technically as good, on paper as Sony’s first CDP-101.
This then is what I came up with. Buying the circuit board from the Italian fellow and incorporating into my design I have a DAC comprising of four TDA1540D’s. They are fed from either i2S from SPDIF sources converted by a Wolfson WM8805 or from a USB to i2S Chinese PCB.
From the O/P of the Italian PCB I then generated Left and Right Data Streams plus their complementary inverted Signals which I fed to the four TDA1540D’s respectively. The L & L- and R & R- Analogue current O/Ps from the DAC I.C.’s then feed a Transformer. This acts to ‘sum’ the Signal but also acts as the I/V conversion for the DAC chips.
This signal then feeds an ECC82 Anode follower gain stage and then a cathode follower O/P stage to be able to ‘drive’ loads down to about 20kOHM without much loss of signal.
A Chinese ‘knock-off’ Goldmund Hi-Fi case was purchased and consequently filled!
I don’t really know what I was expecting but I have to say I am very pleased with the results. I am not great at describing sound in Audiophile terms. Suffice to say I am enjoying it very much indeed.

The TDA1540D’s are the ‘original’ Ceramic encased devices which seem to fetch silly money now on eBay, £120 plus each!!! I have no idea if there is any sonic difference. The Plastic Packaged TDA1540P are relatively cheap at around £14 each so as these chips I have made socketed I may buy four to see what, if any, the differences are when funds permit.