Using CD player without Preamp?

Kr4...There you said it!! "If the VC is digital (and, therefore, loses data when attenuated)...". Maybe you could explain how data is lost. It doesn't have to be so.

If the data was left shifted the LSB would indeed be lost, but the remaining bits would be worth half their original voltage, and no digital volume control I have heard has steps that large.

Al, there are specific DACs which are intended to be used without an active preamp. My Audio Synthesis Dax is one. It has a much higher quality output section than a cheap integrated player. The question does not involve the device in question KNOWING what it is driving but the quality of the output stage in it. A cheap stage will do better supplying a small signal to a good preamp than doing the whole job itself. Such DACs will naturally be more expensive and complex as they are doing a job the others were not really designed for. Check the Audio Synthesis web site for their take on this.

Maybe you could explain how data is lost. It doesn't have to be so.

It is lost through "quantization" error due to rounding. Normally a CD will be dithered when it is produced from a higher resolution source - preserving 93 db SPL of dynamic range. Not ALL digital volume controls are implemented properly and include the necssary dithering. I think that was what Kal's warning is about.

If you turn the volume down to low levels you may be left with only 5 bits with loads of horrible harmonic distortion - if this is simply truncated or re-sampled rather than re-dithered before re-sampling then it can sound awful....many PC software volume controls do this and sound awful - PC audioo can be a minefield.

Stan -- Thanks for your response. I took a look through the Audio Synthesis site, and I believe that their most relevant statement to this question was in a description of the DAX Decade D/A, which I think was a predecessor to the model you have:

The final analogue output signal is immaculately behaved and capable of a direct connection to any power amplifier over any choice of cable and without concern for potentially damaging operational transients which are expertly handled by intelligent muting. To offer such a direct connection we have carefully optimised the DAC and designed it to work at low output levels with extremely low noise and dc offset. Such low background noise level allows the use of more sensitive loudspeakers with an 8 ohm sensitivity figure in excess of 90dB/W/m if preferred.

To me, all of that adds up to simply having a quality well-designed output stage, that is capable of driving the cable, the load impedance, and the level and gain characteristics of the component that it is connected to. Whether that component is a preamp or a power amp I don't think is in itself particularly significant.

If the output stage has excessive noise or dc offset, putting a preamp in between the player and the power amp will not help (except in the specific case where the power amp is dc coupled and the preamp provides ac coupling that eliminates the offset). If the output stage cannot drive the cable or the input impedance of the power amplifier it is connected to, it is equally unlikely to be able to adequately drive a preamplifier, assuming similar cable lengths and input impedances. If it does not adequately control potentially damaging transients, it is just a poor design and having a preamp in front of the power amp is not likely to help.

So I still don't think it is quite right to speak of a cd player or dac output stage as being "designed to drive a power amp." I think the right perspective is that the output stage should be selected to be a good match to whatever cable and load device it will be working into, and beyond that it should simply be selected to be a quality design.

Regards,
-- Al

I think we are saying the same thing. My point was that the output staged of many cheaper players are not comfortable driving a power amp directly, they were not really designed to do so. In an age where a $1000 preamp is considered low end we shouldn't be surprised if the output stage of a $500 player is significantly worse sounding than going through the preamp. My
Two decoders are comfortable driving amps directly but I have heard others that were not. They sounded all right supplying a small level signal to a preamp but not supplying 2 volts.