Quote:
Originally Posted by Evgen_K
Also I wonder is the shunt resistor quality makes any sence? I'm going to use a high quality tantalum in signal path, but is it a good idea to use the cheapest carbons as shunts?
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The shunt resistor is also in the signal path!
To keep thermal noise to a minimum, choose a pair of resistors that add up to something in the 2k region. The output stage of the DAC should be able to drive that with no increase in distortion, but if in doubt, feel free to check to see which op-amp they used, and how much load its NFB network imposes.
You don't say how much attenuation you need, but for example, if the input sensitivity is in the region of 200mV, then try 1k5 and 510 ohms. Or 3k and 1k...
Having done that, the input impedance of the following amplifier is not a significant factor any more. Meaning the same network will work with any amplifier that requires that sort of signal level.
As has been said, bog-standard metal film resistors are absolutely perfect. Fashion is a cruel master in the DIY audio world - try to avoid the rabbit hole!
But is it actually necessary?
Few amplifiers will actually mind being fed with slightly too much signal.
The main practical downside will be that the volume control will be a bit more "aggressive" in use, perhaps resulting in difficulties at the lower volume settings, and potential channel imbalance at low volumes because the matching of the two ganged tracks might not be as good down there. And of course, you'd need to adjust the volume as you switch between different source equipment - which you usually have to with modern equipment anyway IME. Naturally, you won't be able to turn the volume control as far before the power amplifiers start to clip, but the clipping will take place at the same power output as it did before, so you're not losing anything.
But if those "operational issues" aren't a problem in practice for you, then I wouldn't worry about it. Certainly, I wouldn't be afraid to try it first of all before deciding whether to build an attenuator for operational convenience. Honestly, it would be a very poorly designed amplifier indeed that was overloaded by 900mV at a line input.