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Is no preamp the best preamp of all?

As an experiment I hooked up my OPPO BDP-95 (which has a volume control) directly to my amp. I was very pleasantly surprised to hear a significant improvement in clarity and sound quality. Typically I have the analog outputs on the OPPO running through my preamp in Analog Direct. I have heard that the circuitry within preamps can cause cross-talk in the analog signal, deteriorating the quality of the signal. So, would having no preamp (and therefore no other circuits to interfere with the signal) be better than an expensive analog or digital preamp running in Analog Direct? I am not really interested in Room Correction or DSP of any kind. I was considering purchasing a Bel Canto PRe6 (which I've read is excellent for multichannel analog), but would it be better to just have the OPPO running directly to the power amp?
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georgehifi's avatar
georgehifi
10,312 posts
 
08-26-11: Daverz
I'm aware that I'm losing information when I use digital attenuation, but how does this translate into what one hears that is different that what one hears when an analog volume is lowered. Saying that one "loses resolution" is not really telling me anything as I don't know how a "loss of resolution" sounds different from just a lower volume.
Daverz

Below around 75% on a digital volume control, you start to get what's called "bit striping" this sounds like the early 1st gen 14bit Marantz cdp's, sweet smooth but a loss of air and detail/dynamics compared to the harsher sounding 16bit Sony's of the same era. The lower you go with a digital volume the more bit striping happens, 12bit 10bit and so on.

Cheers George
daverz
487 posts
 
@Atmasphere

I don't follow. Why doesn't it work like that? I'm not trying to be obtuse, I just don't see what you're trying to get at. We agree that detail that was at 30dB before the volumen was turned down is at the very threshold of hearing afterwards, and that the detail that was between 0 and 30 dB is no longer audible, right?

@Georgelofi: Thanks for that subjective description of the effect. Do you mean "bit stripping"? Googling "bit striping" only gives me a bunch of pages on RAID. I'm aware that as you lower the digital volume you are losing some of the least significant bits.

atmasphere's avatar
atmasphere
12,048 posts
 
Daverz, those least significant bits contain detail.

Now to your issue about the 30 db. Think about in terms of a magnifying glass. Without the glass you can see a small object and depending on your eyes, all the detail is there. When you use the magnifying glass (volume turned up) the detail is still there but its **size** is increased- in fact the **size** of the object is increased through the glass. But when you take the glass away the object is still there. Volume controls work the same way. In a sense, they make the sound bigger or smaller. Ideally the relationship between the smallest and largest sounds is not changed. Its just the overall size that has changed.
daverz
487 posts
 
I'm sorry, but this analogy is even less illuminating than the last one. I'm not afraid of a bit of technical language if you want to use it.

"those least significant bits contain detail."

Of course, I never disputed that, though it is disputable how much detail can be heard at -80 or -90 dB down. What I'm am disputing is the idea that turning down an analog volume control does not also lead to a loss of information in the signal that reaches one's ears.
daverz
487 posts
 
OK, after a bit of thought I think I see what you are trying to say with the analogy. It helps me to think of it in terms of arithmetic. If you start out with 16-bit audio you have 2**16 different peak-to-peak voltages available. If you reduce the volume by 12 dB you then only have about 2**14 available voltage steps, which is perhaps where the don't-go-below 75% maxim comes from (75% being about a 12.5 dB cut in .5 dB steps.) So don't go below 75% or you playback sounds like an old 14-bit CD player!

But most digital volume controls these days are 24-bit or 32-bit. The Squeezebox outputs 24-bit words, and shifts 16-bit audio to the most-significant bits of each word. This doesn't magically give you 24-bit resolution, but it does mean that with a 24-bit DAC you retain at least 16-bit resolution even with a quite large attenuation (theoretically 8 bits or about 48 dB; but that's nearly the full range of the volume control). Even with 24-bit files, I wouldn't worry until the attenuation was more than 24 dB (or about 4 bits) since you can't really expect to get more than about 20 bits of resolution anyway.
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