Hires 96/24 listening test of opamps

[maty tinman]

In my second system I can easily differentiate MP3 320 kbps (LAME) vs FLAC. The lack of treble is well-known. In other houses, with much more expensive equipment, I have been unable to differentiate between MP3 320 kbps (LAME) and FLAC!!! Again, the bottlenecks.

It is true that I do not listen to current commercial music, I can not stand it. On the AV Marantz tuner I only listen to RNE Radio Clásica.

Ogg -q9 is how I store the little music that I carry in the phone.

 

[Mooly]

What happens if you try this with the -120 dB tone?

Nothing. I wondered if the audio stages (10.5 yr old laptop) go into some kind of mute because there was total silence, no hiss even.

 

[PMA]

First - D/A of the notebook is nothing to call home about. You would need external DAC with higher S/N.

Second - you need a lot of gain to hear -120dBFS 24bit signal. For the same reason you need extra low noise aka very high S/N. Headphone amp will not make it.

Shall I post -80dB signal?

 

[Mooly]

Shall I post -80dB signal?

If you wish you can

I have the (in)famous Denon test CD with music recorded down to -90db (from memory). That is quite audible via normal means.

 

[PMA]

OK, no problem. This one you should hear even from notebook through headphones.

 

[Mooly]

Let me just stop the Beethoven on Minidisc first (Barenboim Op2 No2)

OK, so -80db is audible from 50% volume on this laptop. Flat response, played in Media Player.

(this is a more recent Dell, not the old Acer).

Thanks.

 

[PMA]

OK. With notebook, DAC (DacMagic Plus) and Sennheiser HD598 and no additional digital amplification I hear both -80dB and -100dB files. I do not hear the -120dB file.

This is maybe not so important for the test, but it indicates to limits of the chain used.

 

[mlloyd1]

Interesting, PMA.
I'm looking forward to trying this myself.
I'm expecting my DacPlus to arrive tonight and I use the same headphones.

mlloyd1

OK. With notebook, DAC (DacMagic Plus) and Sennheiser HD598 and no additional digital amplification I hear both -80dB and -100dB files. I do not hear the -120dB file.

This is maybe not so important for the test, but it indicates to limits of the chain used.

 

[Markw4]

With enough gain I can hear the -120dB tone on my main system.

 

[PMA]

Interesting, PMA.
I'm looking forward to trying this myself.
I'm expecting my DacPlus to arrive tonight and I use the same headphones.

mlloyd1

Good. Just make sure that your PC really sends 24bit data to your PC. If it is Win/WDM, 96/24 must be set in the control panel (as attached). Or, Foobar works well with the wasapi plug-in. Or use ASIO.

 

[PMA]

With enough gain I can hear the -120dB tone on my main system.

Yes, with DAC, preamp and power amp, right? That's the way it should be.

 

[Markw4]

DAC and Power amp. I added some extra gain in Reaper.

 

[billshurv]

There's always one

 

[Markw4]

I suppose it depends on the purpose of the test. If we want to know what the DAC output looks like at -120dB from full scale, then adding digital gain would ruin the test.

Thing is, I don't currently have a preamp in my system. I have some Grace Design 101 mic preamps around that I could patch in I guess.

 

[billshurv]

The DAC-1 is designed to drive the power amp directly and has adjustable gain. Isn't that a pre-amp?

 

[Markw4]

The power amp input attenuator trimpots are turned down to help avoid driving the NS-10s at well above full power. Since they are nicely balanced for stereo right now, I don't want to tweak them up all the way. Pain to get them adjusted back down again.

There are some similar trimpots inside the DAC-1 which can be switched in or out. Maybe I should be using them instead for rare cases like this, but the current configuration is probably safer.

 

[Markw4]

Okay, I patched in a preamp after the DAC, and no added digital gain this time. Can still hear the -120dB tone. Want to try for -125dB while I still have it set up?

 

[Markw4]

Not sure why, but first time through with the -120dB tone and digital gain, I was getting some noise. Going back to reproduce it, now I'm not. Don't know why. Hope its not due to old age.

 

[billshurv]

Interesting, thank you. For my listening on speakers these days its very quiet, probably not even 75dBA for -20dBFS which would mean that the -80 tone would not be heard. I'm not sure when I will get experimentation time as the living room is likely to become a bedroom for the next 4-6 weeks but will try. I suspect that the combination of children and a wife with sensitive ears means that I just don't hear things down that low as they are buried in room noise.

 

[Markw4]

Bill, I don't think the purpose of this testing is to simulate hearing or reproduction of very quiet sounds, but rather to get some idea of how well a DAC can resolve only a few bits of difference, and maybe how noisy it is.

When listening to the Hi-Res test files that I sorted, the listening volume was comfortable, maybe around 70dB SPL. But, the resolution of fine details was good enough to make possible detection of very small file differences, barely though.