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TDA1541A-R1 & SAA7220P/A DIY DAC from CHINA

xdd said:
For those that don't have their own TDA1541, there's this poor man's version based on TDA1387s : https://item.taobao.com/item.htm?sp...qOnqIx&id=539337411433&ns=1&abbucket=4#detail
Click to expand...

Was experiencing issues with the pins of my TDA1541 S1 contacting the socket in my Muji Studio DAC II recently and tried the 8x TDA1387 module in its place. While it didn't work in my other DAC its beautiful in the Muji Studio. A little less body in the midrange though has less sibilance and deeper, tighter bass. It's also more transparent so more of a sideways step to my mind. Still the S1 cost $280 and the 8x TDA1387 module only $15. If it works then the 8x TDA1387 module is better bang for your buck.

Then again, I've had it installed less than an hour. I expect improvement with burn in. ;)
 
Ok, this is better in every way to the S1 it replaced. Just spectacular. I can resell the TDA1531 S1 now and get some cash back :)

I find it very strange that the 1387 paralleled has far more in common with the 1541 in terms of sound signature than the 1543 does paralleled. The 1543 is quite rolled off sounding with treble and deep bass in comparison.
 
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Yes to my ears the 1543 is kind of soft like film whereas the 1387 is more starkly real, kinda like video. Which is why 1387 really needs quite steep low-pass filtering or it becomes hyper-real, just too much.
 
Sounds incredible with music though I've found there's just too much bass for the OPAMPS in the circuit in movies and TV shows which causes clipping.

Have ordered a 4x TDA1387 module which should sort this out.... Will also change from Burson V5i and V6 Vivid OPAMPS to 4x Sparkos SS3602 OPAMPS. Hopefully it'll do the trick. It's worth going in this direction I think.
 
Could the clipping be caused by too much output current? TDA1541 is +/-2mA whereas if you power 8 TDA1387s with 5V that's +/-4mA output current. You could try reducing the power to the module to 2.5V (a TL431 shunt reg) and see if that fixes the clipping.
 
xdd said:
You could try reducing the power to the module to 2.5V (a TL431 shunt reg) and see if that fixes the clipping
Click to expand...

I wouldn't recommend this. The 1387 is designed to operate from 5V (min 3V). It also needs a very clean PSU, so use a low noise linear regulator. You'd also need to ensure the input signal swings didn't exceed Vdd.

Assuming the Io of the DAC is fed to an op-amp I/V stage, you'd be better off halving the feedback resistor in that circuit. You would need to double the feedback capacitor in parallel with the resistor in order to maintain the same frequency response of the output filter. The 2k7/1n5 suggested by the data sheet gives a 3dB point of 39k3Hz.

http://pdf.datasheetcatalog.com/datasheet/philips/TDA1387T.pdf
 
cpt_paranoia said:
I wouldn't recommend this. The 1387 is designed to operate from 5V (min 3V). It also needs a very clean PSU, so use a low noise linear regulator. You'd also need to ensure the input signal swings didn't exceed Vdd.
Click to expand...

Good point about the digital input swings. I've played a lot with 1387s and know from experience they work down to 2.5V quite happily. The point where they give out in many cases is below 2V. The TL431 isn't the lowest noise regulator going but it is low impedance - lower at low currents than the typical LM317. How clean a PSU the DAC actually needs depends a lot on how its being used - into an opamp as virtual GND its not so critical. Most critical is when it has passive I/V.

As for halving the feedback resistor - yes it'll work but based on my experience won't sound as good due to doubling the load on the I/V opamp. Asking more current from it increases the load-dependent ripple on the supplies.

<afterthought> There is another way to reduce the output current of the module without desoldering chips (or pins). That is to set pin7 of half the chips to 0V, this disables the DAC. Perhaps the module already has ceramic caps decoupling pin7s - just short across 4 of the caps with a 0R 'resistor'.
 
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xdd said:
How clean a PSU the DAC actually needs depends a lot on how its being used
Click to expand...

I was originally going to say that the current wouldn't be changed much by Vdd, assuming it used a band gap reference to set the current. But then I looked at the spec, and saw that the current is determined directly by Vdd. Therefore, as stated in the spec, it needs a clean supply, otherwise Vdd noise will couple directly to the output.

317 family aren't that quiet, IIRC. More modern low noise regulators would be preferred.
 
A quick back-of-the-envelope calcuation says that assuming no decoupling on pin7 a reg with about 20uVRMS noise would give a DAC output noisefloor due to power supply of -98dB. This is the same as the DAC's own (typical) noise. I can't escape the conclusion that a modern low noise reg is overkill - an LM317 with an over-sized adjust pin cap can do about 20uV. If someone wanted to use a noisier reg than that then pin7 decoupling would make more economic sense than a fancy reg.
 
I thought we were tinkering with pre-built stuff, anyway, not going into production. If I'm modifying something, I'll use the best components I can, given that my time is by far the most costly part.
 
When modifying do you buy (for example) Vishay naked foil replacements for every single instance of a resistor in a circuit or do you just put the high-end parts where they can really make a difference?
 
Okay, fair point. But the cost difference between a modern low noise regulator and a 317 variant is negligible. And I have ready access to them anyway...
 
I've build the same board as the OP.
Are the LM317 supposed to get very hot?
I'm using a similar R Core transformer, 2x15v and 2x9v output, but it measures 19v and 11v respectively. is that within tolerance?
 
dirtyblues said:
I've build the same board as the OP.
Are the LM317 supposed to get very hot?
I'm using a similar R Core transformer, 2x15v and 2x9v output, but it measures 19v and 11v respectively. is that within tolerance?
Click to expand...
Loaded or unloaded? LM317 only needs a minimum of 2.5 V across the input and output. Any more than that is just waste heat.
 
dirtyblues said:
I've build the same board as the OP.
Are the LM317 supposed to get very hot?
I'm using a similar R Core transformer, 2x15v and 2x9v output, but it measures 19v and 11v respectively. is that within tolerance?
Click to expand...
If I remember correctly, my transformer read high as well. I've been using the device nonstop for months, no problems whatsoever.

Good or bad, the whole thing kinda puts off some heat. But again like I said, I've been using the device almost nonstop for several months now, no problems whatsoever.

I had a Topping D20 DAC before. It sounded good, but the TDA DAC just puts a smile on my face; it has this ability to make any music track sound better, more pleasant. Sweeter. The differences are subtle

I upgraded the output caps with WIMAs and upgraded the four op-amps with BB OPA604s.
 
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