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My current TDA1541 DAC at home

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Hi,

My own DAC is based on the Satch Kit, which is similar to Thomas's on-line project (where he solicited much advise from me but ignored all of it), but with most of the major design flaws he put into his design (and which all the chinese copycat's promptly copied) already resolved.

In my own unit I re-build pretty much everything.

The digital input section using a circuit that is a mixture of Pat "Jocko Homo" DiGiaccomo's input circuit and an inverted, single supply version of the two transistor buffer Jim Hagerman used in his "Chime".



Receiver is still the CS8414 on an adapter. I have added loads of SMD caps around the CS8414 (all the way to 10uF for supplies), both in PSU decoupling and for the PLL Filter. Around the CS8414 I use TL431 Shunt regulators (also a separate one for the input circuitry) on small PCB's that include the bypass capacitor for the feedback loop, for lowest noise.



The digital filter and the idiotic asynchronous reclocking have been removed. I used the divider and the crystal position on the PCB to implement DEM reclocking as per the diyaudio meta-mega-thread on TDA1541 DAC's by ecdesigns. The former digital filter position now holds a small PCB with the I2S attenuators (again, as per ecdesigns).

Overall on the input and digital side I have four individual shunt regulators, one for pretty much every section, each with a CCS. I have a bunch of Sanyo 2200uF/6.3V Low Impedance Cap's on the PCB plus Os-Con's and SMD Ceramic caps for decoupling.

The TDA1541A(S2) Uses Wima MKS and MKP capacitors for decoupling, with 8pcs 4.7uF MKS on the MSB's and then 2.2uF MKS and 1uF MKP. I would have preferred to use SMD Film Capacitors here, but that was not an option due to the PCB Layout. I used Elna Silmic Capacitors for decoupling plus SMD Film Cap's at the DAC Pins. Again, TL431 Shunt Regulators, actually in this case literally daisy-chained like a zenner string. Fed By CCS.

Analog stage is the diyhifisupply universal tube stage. I added external I/V resistors and the Non-OS high frequency rolloff compensation as per Pedja Rogic. I also replaced the filter resistor in the powersupply that is on the PCB with a choke and added an off-board 33uF/160V film capacitor. These two parts take almost the same space as they whole tube stage circuit board though, so I was lucky I had spare space left.



The actual powersupply circuit board of the Satch was also completely re-structured. The Power transformer in the Satch kit has two windings, one center-tapped to feed a lot of stuff, including the op-amp output stage and the DAC and another single winding.

I used this single winding and schottky diodes to make the basic supply. This is followed by an RC/RC/RC/RC Filter, the capacitors are some Nichicon 4,700uF/25V, I think I used 3.3 Ohm resistors, in both "ground" and "+V" line. As the Satch PSU has ton's of regulators I re-purposed them to give a chain of regulating the negative line with an LM337 (already in place) and using LM317 as current sources in the positive lines, all links.

I build another such supply for the DAC, this time using 3,300uF/50V Elna Silmic capacitors (so again schottky rectifiers -> RC -> RC -> RC -> RC) followed by an LM317 as positive voltage regulator and a second LM317 set up as current sink. This feeds the Zenner string.



Both basic supplies are completely separate and have a fairly high amount of filtering for both common mode and differential noise already. The passive RC filtering already attenuates the 100Hz by around 50dB and together with the LM317 regulators removes any noise from that source.

So the TL431 Shunts only need to deal with the noise from the LM317's (not a lot) and the AC signals dumped into the powersupplies by the actual circuitry.

Most will likely find my approach overbuild and unneccessary complex, but it works well.

Before anyone asks for schematics, sorry, there are non and unless I take my own working DAC apart and reverse engineer it I could not even draw a schematic. Most of the work was done without anything written down or drawn out.

So this is only meant to give some ideas.

Ciao T


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