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New TDA1541 based DAC - mods?

Discussion in 'd.i.y.' started by Dowser, Sep 3, 2019.

  1. Dowser

    Dowser Learning to bodge again..

    I just bought one of the Chinese TDA1541 DACs to replace my Rega DAC - I'm using it for TV and streaming audio duties. The Rega replaced the DAC in my Pioneer N50 (Pioneer just used as a streamer) - the Rega was better than the stock N50 and as always with Rega it does absolutely zero wrong but is missing a little in dynamic range (IMHO, and to my ears, of course :)).

    Just switching in the unit as stock improves on the Rega for me (which is good, I just sold the Rega for vast profit...I only paid £70 for it :)). But now to modifications - pictures below - first up I assume I can simply swap the 1541 for a 1541A S1 or late Taiwanese A, along with swapping the SAA7220/A to a /B?

    This will be my first action. Then I'll look at all the other mods relevant for TDA1541A players I am used to - but one question on the clock....where is it...I see no crystal inside?! I guess as a DAC it receives it's clock from the input? Can I change this and fit a local clock? But then I guess no way to sync the signal?

    It has a USB input as well that I have not tested, but saw on the chip's data sheet it was possible to set it as master or slave for clock.

    Thanks - anyhoo, pics;

    Cheers, Richard
  2. 337alant

    337alant Negatively Biased

    Richard looks good
    Q. does your board have a load of dip switches under the TDA 1541A chip?
    I have a similar board that does but I cant find a diag that explains what the dip switches do?

  3. Dowser

    Dowser Learning to bodge again..

    I haven’t checked Alan, but pictures on internet i reviewed as research before buying suggest not for this v1.2 board - the only real option was without or without the USB receiver board.
  4. Mike P

    Mike P pfm Member

    Lots to play with there ☺ When I have some spare time I'll write a proper reply with a bunch of suggestions for tweaks.
  5. 337alant

    337alant Negatively Biased

    Ah Ok no problem just thought I would ask on the off chance it was a similar board
    Anyway looks like a good project enjoy and keep us posted on your progress

  6. cubastreet

    cubastreet Espresso Fiend

    It's a while since I've messed with these, but iirc the 7220 normally provides clock and 4x oversampling.

    I'd guess the chip on the green adapter is another DAC being used as a SPDIF - I2S converter and pulling the clock off the signal.

    Good power regs to the 7220 and 1541 go a long way.
  7. Mike P

    Mike P pfm Member

    OK then, I've scribbled down a few notes based on an initial look at the pics. I'm sure you know it all already of course but it may be useful to others:

    Analogue output coupling caps – It looks like these might be the pair of Oscons near the RCA sockets. I really don't like Oscons for this and I'd get these swapped out to Elna Silmics, decent bipolar electros (e.g. Nichicon Muse) or better still some Wima MKS2 metalized films.

    Op amps – Having the op amps in sockets already is just begging for a bit of op amp rolling. OPA604 are some of my favourites or if your pockets are deep and you think the local power decoupling is good enough to keep ‘em stable OPA627. My recommendation for a ‘dark horse’ is the JRC5534DD, they’re low cost and to my ears sound significantly nicer than more common or garden varieties of 5534.

    Op amp power supply – What voltage are the opamps running at and do they have dedicated regs? If the regs are dedicated to the opamps and they’re only running at 12v you could tweak the regs to increase this to 15v. Opamps like 5534 and OPA604 tend to sound better at 15v than 12v.

    I don’t recognise the radial electro caps around the opamps. Presumably these are the power supply decoupling caps for the opamps and I’d swap these out to known ‘good’ sounding caps such as Silmics, Rubycon ZLH or Panasonic FC etc. I don’t like Oscons for this.

    TDA1541 – Swap to TDA1541A, preferably a Taiwan made TDA1541A.

    SAA7220 – If swapping to TDA1541A this should be changed to SAA7220P/B. If sticking with TDA1541 then retain the SAA7220P/A.

    Decoupling of the SAA7220 is critical. The power and ground pins are on opposite corners (pins 12/24) so it’s hard to keep the loop area down. I like to stretch a 0.1uF axial X7R under the PCB directly in a line between the power and ground pin. I’d make the local electro something like an Oscon or Panasonic FM but make sure this low ESR caps isn’t going to upset the reg. Add a ‘lossy’ electro to the output of the reg if concerned about stability.

    Regs – These look to be 317/337 types. For +5/-5 use a pair of red LEDS to set the voltage instead of a resistor. For higher voltages try a Zener diode of the appropriate voltage. At the very least make sure that there are bypass caps fitted in the C Adj position (at least 10uF and preferably more).

    Which components share voltage regs? I’d really like to see the SAA7220 have its own dedicated reg.

    Rectifier diodes – I like Schottkys and use 11DQ10 or SB1100 a lot for this sort of thing.
  8. a.palfreyman

    a.palfreyman pfm Member

    The CS8412 can extract the clock signal from the I2S input. I built a bitstream dac based on one of these receiver chips (or the CS8414, can't remember now) some time ago. Some say the 1541 / 7220A has a slightly bigger sound whereas the 1541A and 7220B is maybe a bit more refined.
    If you do change the chips, might be interested in these as spares for my CD160.
    Watching with interest...
  9. Dowser

    Dowser Learning to bodge again..

    Thanks All - appreciated.

    @cubastreet - they offer the same PCB without the small USB board, and there’s still no onboard clock for the 7220 on that one, so don’t think clock comes from there. There’s also a physical switch on rear panel to switch between spdif/toslink & USB.

    @Mike P - yep, thanks - I sort of know the normal mods, but first step for me will be to trace the rail strategy for the various regulators when I swap the 1541 for a 1541a s1 (I try your Taiwan late model later, I’m familiar with the s1) :)

    @a.palfreyman - sure, I also have a socketed cd160 I use for testing 1541s and 7220 s - I let you know how I go
  10. martin clark

    martin clark pinko bodger

    Yes, there is a difference between , A, B, and C variants of the SAA7220 - the C is the one you don't want to see!

    <rummages around local HD a bit../>


    edit to add - Naim used the B variant, certainly that's what's in my CD2.
    Mike P likes this.
  11. Dowser

    Dowser Learning to bodge again..

    Yep, thanks Martin - I have a collection of 12 or 16 tested /b items (tested in the cd160 mentioned above, so 1541 non-A chips work fine with /b 7220s) :)
  12. cubastreet

    cubastreet Espresso Fiend

    Interesting, what's between the spdif input and the 7220?
    I really wanted to make a stand alone 1541 DAC about fifteen years ago from a Phillips CDP, but was told on here that it was in the too difficult / too expensive category.
  13. Dowser

    Dowser Learning to bodge again..

    Not sure currently, hence my interest on the clock source. I’ll update when I pull it apart it a bit...but it currently sounds good, so it will stay put until nights draw in I suspect :)
  14. Dowser

    Dowser Learning to bodge again..

    This sounds surprisingly better;

    Wasn't expecting much really, it is just handling streamed FLAC, internet radio and TV - but internet radio sounds much better!

    I also tried a pair of the Burson big red discrete opamp thingies I picked up a while back - one of them distorted immediately, by time I got power back off, red plastic case had already dimpled from the heat! I bought them 2nd hand, but original packing for them was all sealed so they'd never been used - I try a warranty claim. Anyhow, NE5534s sound fine :)

    @ Cubstreet - there is actually a 12Mhz clock on that USB add on board. However, you could also buy this PCB without the USB functionality - and there's a switch on back panel to go between SPDIF/optical and USB - I'm using SPDIF coax. I need to go and do some reading on DIY audio about what options I have for clocking - I suspect, via coax digi in, I am taking clock from the source as a slave - no idea whether I can change this and fit a clock within the DAC to make it the master (or, even, if it would make any difference if I did!).
  15. chartz

    chartz pfm Member

    The Burson modules measure very badly, according to someone who measured them extensively.

    Nice project. I’d like to know how better this sounds than a vintage Arcam 70.2 that used the same chipset.
    Julf likes this.
  16. Julf

    Julf Facts are our friends

    Any pointers to the measurements?
  17. chartz

    chartz pfm Member

  18. Julf

    Julf Facts are our friends

    Thanks! Forces me to refresh my French...
  19. chartz

    chartz pfm Member

    Good luck then!
    Julf likes this.
  20. The Chronicals

    The Chronicals Disruptor

    Be careful with those Chinese 1541 chips, most of them are fake. If you can find a genuine 1541A or S1/S2, you'll notice the difference.

    I previously owned a MHDT Orchid, with a genuine 1541A, which I upgraded to the S1 and then a double crown S2 which cost me a small fortune, so got used to spotting the fake chips.

    Aliexpress sellers/factories caught on to the market in the fake 1541 chips, and started churning them out, and then progressed into selling them as fake S1's.

    I think I still have a genuine 1541A somewhere but it has a broken lug, could be soldered I guess? Welcome to it if interested and I can find it in my bit box.

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