Dual TDA1541 Dual balanced DAC PCB (batteryman)

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batteryman

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Joined 2011
#1
I have been listening to various dacs over the last few months, including a Cambridge Audio Dacmagic (dual TDA1305), Chiurutu's discrete logic ladder dac, and a Topping E30 dual AKM 4493. Years ago I built an Audio Note DAC1 (single AD1865) and valve output stage.

But then I go back to my dual TDA1541a dac, and realise everytime that I it prefer over all the others although I can't explain why. I think it's like comparing fresh water with distilled water - they are both H2O but the distilled water is bland.

I built it with Nichicon UKL ultra low leakage 100uf dem caps and use IanCanada's Fifo II and I2S to PCM board to supply the +- data for simultaneous mode. The dem clock runs at the specified frequency. I2S comes from a DIR9001 coax/optical interface. (or originally, direct from a CD player modified to provide I2S)
I/V is thanks to a pair of Sowter 1465 I/V transformers with 75r resistors. (there is no issue with the output offset current)
Power is from a Lithium battery bank with onboard low noise regulators.

I now want to experiment with other dem caps so have ordered 20 boards and 15 will be available to members.
If anyone wants one, please let me know. The cost is about £5ea + postage. (cost confirmed when they are delivered in case taxes are added)

The design is below and it is what it is and is far from perfect but cannot be changed. There are no surface mount parts.

bmadac.jpg
 
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#5
Hey I would be interested in a board, I use an old DacMagic that has been recapped as they all have leaky capacitors by now in my experience.

Do you have any photos of boards that are complete, and where do you source your TDA1541a from?

Thanks - should I just PM you?
 
#6
Attached is a photo of my own dac.

I used Nichicon UKL ultra low leakage 100uf dem caps.

My TDA1541s came from a Dutch member who is selling them on ebay. (for much more than they cost a few years ago)

https://www.ebay.co.uk/itm/225636566889

There is a seller with some allegedly new ones but his prices are almost as steep. They seem to be Chinese unbranded ones so be wary - no photo from above.

https://www.ebay.co.uk/itm/384770773444

However, I do have two spare 1541As for £90 the pair. Used by me for a few years so known to be good.

Please pm me if interested in a pcb and/or the chips.
 

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#14
Sorry, I never made one.

I used Nichicon UKL ultra low leakage 100uf 16v for the dem caps but you can use whatever you want, same goes for the dem oscillator.
The rest are decoupling caps - I used Panasonic or Tantalum and 100n film.

The voltage regulators can be on board or off board and either 78/79xx type, or one of the very low noise TO220 alternatives (LT3045/3094)

The datasheet might be helpful.
 

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#18
I built an external DAC psu which uses two banks of 5 cells, in a separate housing, with taps after 2cells for the +,-5v regulators & after all 5 for the -15v.

They are 8000mahr so don't need recharging too often but I do have to remove them and charge two at a time in separate Li-ion compatible chargers. (they are 22650 cells which are too large - the charger is meant for 18650 cells and could charge 4 of them at a time.)

I bought a multi cell charger / BMS with sensors for each cell but haven't fitted it yet. It would avoid the need to charge them outside of the DAC psu.

Quick blow fuses provide short circuit protection.
 
#20
I use Iancanada's I2s to PCM board and you need to set the dacs to simultaneous mode by connecting pin 27 of both to -5v. The point of simultaneous mode is that all latches are updated at the same time and then the bit clock is stopped which also keeps digital noise out when the actual digital to analaogue happens.

I haven't tried any others.

I did also have a FIFO II and dual clock between the I2S in and PCM board, but sold these. The FIFO II has the advantage of two switchable I2S inputs.

I just supply the PCM board with I2S from a spdif interface (switchable from coax to optical)
 

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