The datasheets for both the 8-pin TDA1543 and 1545 dacs note a Vref connection to the non-inverting side of the right and left I/V op-amps. See schematic for both DACs (pg 3 or pg 4).
http://www.lampizator.eu/lampizator/LINKS AND DOWNLOADS/DATAMINING/tda 1543.pdf
http://vasiltech.narod.ru/files/TDA1545A.pdf
Pulling out my old projects, I realize that for the discrete (non-op amp) I/V stage I built, I did use the most of the datasheet schematic but did not connect Vref (pin 7) to the I/V.
I recall other DIYers at the time doing the same thing.
And sonics are very good and clean.
However, in OEM cd players that use TDA1543 (or 1545), the service manual schematics [example from hfiengine.com: hfe_philips_cd110_130_140_service_en.pdf (1543) : https://www.hifiengine.com/manual_library/marantz/cd-36.shtml (1545) ] do use the full datasheet suggestion, including "elaborate" connections to the I/V opamps..
How important is to connect Vref to the I/V (opamp or discrerte) ?
http://www.lampizator.eu/lampizator/LINKS AND DOWNLOADS/DATAMINING/tda 1543.pdf
http://vasiltech.narod.ru/files/TDA1545A.pdf
Pulling out my old projects, I realize that for the discrete (non-op amp) I/V stage I built, I did use the most of the datasheet schematic but did not connect Vref (pin 7) to the I/V.
I recall other DIYers at the time doing the same thing.
And sonics are very good and clean.
However, in OEM cd players that use TDA1543 (or 1545), the service manual schematics [example from hfiengine.com: hfe_philips_cd110_130_140_service_en.pdf (1543) : https://www.hifiengine.com/manual_library/marantz/cd-36.shtml (1545) ] do use the full datasheet suggestion, including "elaborate" connections to the I/V opamps..
How important is to connect Vref to the I/V (opamp or discrerte) ?
Not important at all, its just a handy, ready-made positive voltage reference. On 1545 its a decoupled fraction of the VDD (1/6 to 1/3) that's fed to the opamps and not pin7. However, on 1543, pin7 is a stable voltage (~3 diode drops from GND).
The diyparadise Monica project also used a strange diode drop for Vref:
https://www.head-fi.org/threads/modding-the-monica-2-dac.127590/
Philips was all over the map in 1990s ... too many models, and strange datasheets filled with weird info, and even erroneous info like my recent mention of the 1305's datasheet omitting info about output DC blocking.
BTW: About the 1545. Will it allow MSB-First input?
https://www.head-fi.org/threads/modding-the-monica-2-dac.127590/
Philips was all over the map in 1990s ... too many models, and strange datasheets filled with weird info, and even erroneous info like my recent mention of the 1305's datasheet omitting info about output DC blocking.
BTW: About the 1545. Will it allow MSB-First input?
Hmm... will it (TDA1545A) work, w/o any glue logic, being fed from DF1704?
https://www.ti.com/lit/ds/symlink/df1704.pdf
Surely, an august fellow with the competence to critcise the datasheets should have no trouble in extracting information from said datasheets.
Actually ... yes.
The albums shown have The Secret messages as to why it works 😉
In that old Magnavox (CD2000, similar to CDB480, 490-492) -- orig had no oversampling OEM, and with a TDA1543.
I do have a little whine and noise at at quiet music passages (fade ups, fade outs) still. But when music starts playing at normal volume, I no longer hear the small distortion. I don't have the TDA1545A's Vcc pins bypassed, so decoupling is still an issue; and I also have to separate the power between DF and DAC. The V_ref pin 7 isn't connected to anything -- possible drawback -- on the I/V stage, which is Rudolf's Jocko Homo style.
Actually, music sounds quite good with decent separation -- Using L channel out for one 1545 and R for other..
Are you suggesting what we have accomplished is not working or is sonically compromised is some way? We're listening to it right now. "A Dream Within a Dream" and "Magic".
Good, hi-fi sound.
Why not try to repeat the experiment yourself?
We encourage all to REPEAT this experiment -- see photos and notes in this thread for how to do it. It works.
CAUTION: About datasheets ... the content within them is not as it appears. See:
https://statics.cirrus.com/pubs/proDatasheet/CS8416_DS578F5.pdf
pg. 24
=========== A little personal plug =====
UFO's are Real (1979)
.... and the follow up ...
https://odysee.com/@Eyes.On.UFOs_docs:e/Contact-From-The-Pleiades-1987:7Xs
All you have done is the equivalent of demonstrating that one person can ride a tandem. Thanks but I'll pass.
There is also this tabloid approach to V_ref for the 1545:
https://diyparadise.com/w/mojo-fy-your-mojo/
0.83V regulator for the TDA1545A VREF
https://diyparadise.com/w/mojo-fy-your-mojo/
0.83V regulator for the TDA1545A VREF
TDA1545 pin7 is nowhere called a 'VREF' in the datasheet. Its an 'IREF' pin which is rather different. Treating it as VREF can only lead to ineffective design....
The DS mixes up refs to "ref".
https://www.sowter.co.uk/dacinfo/TDA1545A.pdf
Pg. 4 (Fig.1 Block diagram.)
Also: Search DS for "Vref". Hits = 4x
Also, pg. 6:
Regardless ... is the 0.83V regulator for the TDA1545A VREF really an "ineffective design"? If so, why?