PCM1798 - looking for advice on cheap and simple I/U

[Alexium]

I'm building my first DAC based on PCM1798. I'm new to this, and I'm not very good with electronics (though I'm trying to learn). That's why I ask for your help.
I am about to assemble the I/U and adder according to datasheet using NE5532. Are there possible improvements to be made in this schematics, or is it good enough as it is? Advices or references to other good outputs for 1798 would be much appreciated.
Thanks in advance.

PCM1798 datasheet. Subject schematics is on page 19.

[Alexium]

This is the schematic:

[SoNic_real_one]

Replace the 5532 with another decent OpAmp
LM4562 are not that expensive and sound great. Others might be slightly better, but way more expensive...

[Alexium]

I know 5532/34 are not much appreciated, but some other people say they can sound good enough when applyed correctly. They are so cheap that I want to experiment with them.
And I have a problem with price/availability of some opamps in my region. LM4562 are avaliable, but they are more expensive than AD811/826 etc., OPA2132, OPA627 and such. It's $7, to be specific, which is not cheap here.
I can get very cheap LM2904; OPA1632 and OPA2134 are also available for a reasonable price.
And I still hve to resolve the problem of obtaining the "right" schematics - most suitable for the particular opamp, I mean. They say datasheet schematic has its issues, and I'm not good enough to understand it...

There's a problem with the picture above, and I can't edit messages, so this is the right one:


P.S. Sorry for my English, I'm doing my best to be clear, but sometimes I fail...

[SoNic_real_one]

I have tried the OPA 2134 and was OK.
I have tried also OPA 1642 and that is better than the 2134... You should try it. The 22pF compensation it is not necessary for it, it is unity gain stable.

[Alexium]

Thanks! I'll try OPA1642 then.

[abraxalito]

Originally Posted by Alexium

I know 5532/34 are not much appreciated, but some other people say they can sound good enough when applyed correctly. They are so cheap that I want to experiment with them.

My sentiments entirely - the 5534 is amazing bang for the buck, so experiment away and let us know how it goes. In my experience (I'll get around to putting it on my blog soon) layout and power supplies (noise control in general) are more than 90% of the sound of a DAC. Changing opamps once the layout is exemplary seems to make almost no difference.

And I still hve to resolve the problem of obtaining the "right" schematics - most suitable for the particular opamp, I mean. They say datasheet schematic has its issues, and I'm not good enough to understand it...

I don't consider the datasheet recommended schematic that you posted up to be ideal. My guess is this one that gives the best numbers for the datasheet but it doesn't give me the best sound. The 2700pF feedback cap is way too big, I've experimented with less than a tenth of this value and such a reduction seems to open up the sound considerably. I'd also take issue with the first stage passive filtering - the 220R/27nF is too low a load, even for a 5534. I'd scale up the resistors to at least 680R here, with a proportional reduction in the capacitor size. Be very careful in regards to the grounding of the decoupling capacitors if you want the highest transparency. Beyond that, see what sounds good.

[Alexium]

abraxalito, thanks a lot for your input on improving the circuit. I'll start building the DAC soon, and I sure will experiment a lot

[Nazar_lv]

In my experience (I'll get around to putting it on my blog soon) layout and power supplies (noise control in general) are more than 90% of the sound of a DAC. Changing opamps once the layout is exemplary seems to make almost no difference.

+1

[SoNic_real_one]

Sure, if the PS is so bad that will induce noise in the outputs, the PS is the point of improvement. I see here people that complain about hum, ground loops and such. Yes, OpAmps won't make a difference there.

But if we are talking about TDH+N below -60dB, the cheap, "bargain" OpAmps are the weak point. In all my mods that involved swaping OpAmps in existing DAC's, the results where noticeable - from 'wow' to just a slight change.