DAC AD1862: Almost THT, I2S input, NOS, R-2R

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#5,121
miro1360 said:
My prototype of the TDA1541A plays quite well, nice clean output :hphones:
Time to buy out the whole eBay and rise the price of this DAC even more LOOL 🤣
  • no digital filter, NOS
  • full THT with glue-logic to maintain the nostalgia
  • simultaneous mode (I2S input)
  • big foil capacitors
  • power supplies will be on the PCB (78/79xx regulators)
  • opamps remain for the I/V
Click to expand...
Hi @miro1360
First of all, I would like to praise this excellent project.
One small recommendation, avoid LM78/79 regulators or in general series regulators for TDA1541, rather put LM317 as CCS and TL431 for shunt, resistor values are easy to calculate. Instead of LM317, a better solution is two depletion mosfets in cascade.
My friend is currently working on a similar NOS DAC with TDA1541, using Salas shunts and OS-CON, and my first DAC with TDA1541 (picture below) also had shunt regulators with LM317 and TL431 and OS-CON.
I recently did a comparison of the improved shunt regulator from Walt Jung article with the ADM7151(0) in the PMD100 power supply, maybe the ADM7151 has better numbers but is sonically worse.

Best
 

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#5,124
miro1360 said:
@Zoran TDA1540 is slightly different from TDA1541A ... BCK is inverted for both, but TDA1541A must see the stopped BCK on the 0 (TDA1540 is 1), otherwise the LE is not accepted (this took me a few days to figure out because I used the BCK logic from TDA1540 and it did not worked even though the signals were aligned) 😉
Click to expand...
On my schematic it is solved bu adding (od removing) one inverter before BCK stop logic module. On the PCB could be done by jumper.
.
I nave tried before few years the CPLD for I2S/TS format conversion. And worked same very well for 14bit/TDA1540 and also 16bit/TDA1541A.
But I did not check out the signals with logic analizer? 🙁
.
So how about the sound when data are moved from LE edges in the center of Fs?
I suggested this pages ago... 🙂
 
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#5,125
...I will avoid TL431 ref for the 3 TDA1541A rails ...that is antic design. I will however keep the idea of the CCS but with a filtered diode as a ref and an emitter follower with no resistor feedback and just a hf decoupling at the main voltage tda1541a and a very carrefully chosen cap as filtering smoothing cap.. Saying that I am surenthese advices will not be followed here, lol! I also will avoid Oscons and even more the newest one, and absolutely avoid the sepc and sepf...if the antic religion is your, you eventually can take the less bad sep serie, but it is colored...
Of course the DEM decoupling should have low inductance... means rigth to the legs of the dac chip. Despite its mkt and not mkp blah, I would give a try to the 2.5 mm pitch wimas mkt. It is just to stay through hole because there is better smd solution there. For the standalone Dem clock cap, mkp or silver mica is mandatory if through hole, in this case Fkp2 (non metal) is just the rigth thing to do.

And of course to stay cheap but good sound I will follow the little around oap and i/v ref I advised before in the thread for the ad1862 than noone tried despite the extensive test on a sota transparent speakers.

I will sqy nothing about the ground layout as I know I will be not heard too, ahaha, lol, aha, etc ! 😉 🙂
 
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#5,126
jensenhoffman said:
I've got a Altium source file, a TDA1541A DAC PCB with many interfaces, including I2S.
Anyone interested? Maybe I can put it here or share the GERBER file.
Click to expand...
Oh damn, see that huge ground loop in the i2s signal return path.... not a sota design. But nothing bad if free (generous offer in the thread spirit), the regs are good, while I prefer discrete regs here also.
 
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#5,127
NIXIE62 said:
Has anyone tried these? I ask because their SS3601/3602 discrete op amps have performed quite well. Perhaps the same is the case with voltage regulators.

https://sparkoslabs.com/product/ss78xx-d...regulator/
https://sparkoslabs.com/product/ss79xx-d...regulator/

In my opinion and experience the 78xx/79xx and the LM317/337 are not at a sufficient level for a high-end DAC or preamplifier.
Click to expand...
I would like to add these as well.
https://www.newclassd.com/index.php?page=250
 
#5,132
pistollero said:
this ebay board, but is heavy modified.

PCM1702 decode board finished | eBay

using jlsounds i2soverusb direct on the pcm1702 chips.
only using first i/v opamp.
changed all caps even the rectifier diodes

here the link how it sounds:
YouTube
YouTube
Click to expand...

old post but exactly what I'm puzzled .......

as I understand you, you're saying that there is setting of JLS XMOS package, allowing direct connection to pair of PCM1702, without need for input signal(s) shifters?

can you tell something more about that and if yes, what are (jumper) settings on JLS XMOS?

if I could find necessary data in data for JLS XMOS, I wouldn't bother ......

TIA!
 
#5,137
jensenhoffman said:
Free. BTW, are you able to modify the file or correct the ground loop you said?
Regards,
Click to expand...
Without the files, not possible. If the top is the gnd you can scratch the varnish just before and after the i2s resistors that cross the split and solder a zero ohm resistor across or a piece of wire. But I should wait what Miro is doing or spend a little of monney at Audial Audio that has sota design with sometimes cheap stock for diyers (bare pcb). I see many defaults in this pcb picture...a classic when not knowing well this chip. tda1541a is wonderfull but a b...h about the pcb layout.

Hum...wonder if @Zen Mod would have a little emitter follower discrete reg voltage for it and Miro : - and + 5V and -15V with his wodoo ?
 
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