Analogue clipping from digital sources

I guess what it boils down to is that in 2024, if you tell me your recent vintage preamp is clipping with 2V of input I am going to have trouble believing it is not malfunctioning.

OP: 

With modern amps, input impedance is usually quite high, 25kOhms or more, and plenty of voltage gain, so with many combinations of modern DAC's and solid state amps a separate preamp is no longer technically needed.

Best,

E

@atmasphere  but phono stages have additional gain just for them.  It's true that you almost don't need any gain for CD's, but tape decks and tuners were often near that, no? 

The 2V peak outputs should not be a surprise anymore.

Still, that's not to say any particular maker or model doesn't overload more easily than others.

“IMO Phillips and Sony made a stupid mistake when they set the Redbook spec to 2V output with digital gear, more than many amps need to overload.

The CD was invented in 1982, with full knowledge of this. The reasoning is that a PREAMP could/can easily handle 2V input. Amps may not, but since the idea was never to directly connect a CD player at full output to an amp, I’m not sure why this is an issue. Also, higher voltage = less noise (its complicated) and less need for additional gain downstream.

Also, Ralph is right for an AMP, 2V might be overload but preamps have been 100% aware of the CD standard since then and are built for it, so I disagree. Preamps (and preamp stages) today can easily handle 2 V input and put out whatever arbitrary fraction of that you need for an amp.

Older gear though had far too much gain or too low a supply rail which could cause an issue.  By too much I mean it had a lot more gain than we can use, which contributed to noise.  Better to have lower gain and wider use of the volume knob.

Technically, the best solution is to lower the output after bit depth conversion (16 to 24 or 32 bits) but before upsampling.

Roon calls this setting Headroom Management.

The end result of this 2-step dance is you can reduce the maximum output without reducing resolution while minimizing how much about the original recording you must know to avoid clipping.

I forgot one important point. Most preamps can take significant overload on the inputs.

Amplifier output is tied to input and usually 20x the input. So long as you don’t exceed the maximum output voltage they will take more than 2V in.  Stereophile may state the "maximum input voltage before clipping" or something like that.

Hey,

Have you actually heard this happening, or are you just theorizing?

There is risk of digital clipping, but it’s not from the output voltage. It’s from upsampling. There’s a good paper on it from Benchmark Media somewhere about what happens.

Imagine a 44.1kHz/16 bit recording. Let’s say it’s a simple sine wave and the original samples happen to reach maximum. At the top, you could have two samples at peak output in a recording. Not an uncommon thing as many mastering engineers push the max sample to the peak digital output to ensure the recording has plenty of dynamic range.  Depending on the precise timing, you could have two adjacent peak signals or one very close and the other at peak.

Anyway, if you convert from 44.1/16 to 88.1/16 with linear interpolation there will be no issue, but most upsampling (thanks to cheap compute power) use something like a French curve to interpolate.  Now our new  samples can exceed maximum digital output. That is true digital clipping. The solution is to slightly reduce the signal when upsampling. Not a horrible thing when you also increase the bit depth before doing so.