Using CD player without Preamp?

Shadorne...That's what I supposed about "digital" volume controls. Thanks for the details. It is no coincidence that they all seem to have the same 1/2 dB resolution.

I just got my McCormack MAP-1 6 channel preamp back from repair. (Kudos to CJ which now owns McCormack. No charge, even shipping).
My problem was no output from the center channel, and the fix was to replace the Center/Subwoofer volume control IC.

Tduffy1,
I'm in the same situation you are - driving an amp directly from a CD player. In my experience only, I have compared the CD->AMP Vs CD->PRE->AMP combinations within my system using an Audio Aero Capitole MKII SE CD player, First Sound Presence Deluxe MKII preamp and Art Audio PX25 SET amp.

Here's what I found:
(A) CD->AMP
* more detailed, for example it was easier to distinguish the words a vocalist was singing and mids & highs were a bit clearer -- this makes sense as fewer pieces in the audio signal path should be less damaging to the signal

(B) CD->PRE->AMP
* more bass
* more dynamic

The preamp section of the Audio Aero is very good and uses an analog volume control, but I suspect it can be bettered by either custom modifications to it or with a very expensive preamp. . .

I chose to go with the CD->AMP config as musical details across an entire freq spectrum are more important for me than a slight increase is bass and dynamics (as I'm using 97dB efficient speakers they're already quite dynamic). I can improve the bass amount and dynamics when I plan to buy a pair of subwoofers and put a high-pass filter ahead of the SET amp thereby reducing the heavy bass demands on it to improve dynamics.

Hope this helps in some small way.

The gain of the analog output circuitry can be changed
under digital control.

Exactly! A Crystal digitally controlled resistor network volume control chip with
0.5 db SPL intervals costs around $10 and has excellent performance.
(Surprisingly this is actually an expensive item as far as electronics go...although
it is far cheaper than the front fascia of most amplifiers or the volume control
knob itsef!!!!)

Shadorne...Left shifting a digital word, be it 16 or 24 bits, is a divide by two. Quanta size will be doubled. We are talking about "truncation" not "rounding".

I have no doubt that representing audio with 5 bits will sound rotten, and dither won't really help. My point is simply that the volume control of a CD player can be implemented in ways other than left shifting (or "dropping bits" as some like to say). The gain of the analog output circuitry can be changed under digital control.

Usually the manual for your CD player tells you that your player has a gain section made to drive an amplifer via direct hook-up without a separate pre-amp. My Wadia 830 manual specifically addresses this issue, and I'm sure that other companies do as well. When I have the remote volume control set at about the half-way mark, the sound is very loud and quite musical. In other words, the Wadia was made specifically to do this, as were other companies' CD players, I cannot speak to your Phillips.--Mrmitch

either way (digital or analog) it is compromised. Especially if digital as Kal said. However that compromise, whichever it is, may still be better than the preamp you had before going direct. Full output with internals in the Phillips bypassed and a good exterior passive between the CDP and amp would be better (and more costly). Even a "good" volume pot is bad, that's why CJ doesn't use pots in their preamps anymore, they use resistor ladders made w/good quality resistors. Experiment, Enjoy!

ET

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.

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

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.

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.

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.

I agree with Polk as long as the output stage was actually designed to drive a power amp. Despite having a nominal output high enough many CD players will not be as good as a good preamp in driving a power amp. But if they have been designed to do so then adding anything else will degrade the sound to some degree.

Stan -- You made a similar statement in the other recent thread that you referenced, which was questioned by another member. Please explain how the output stage of a cd player would "know" whether it is driving a preamp or a power amp, assuming the input impedances of the preamp and power amp are comparable, and the cable length that would be run to either device is the same. Also, how is one supposed to know if the output stage of the cd player is "designed to drive a power amp"?

I can certainly envision reasons why a specific combination of cd player and power amp might sound either better or worse with or without a preamp in between, some of which were mentioned in the other thread:

http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1228927169

But pending your answer I would not speak of a cd player as being "designed to drive a power amp."

Regards,
-- Al

If you think you are missing something do you mean in sound or technology? There are many very good points above but I think you should try another player to see if there may be benefits in sound quality over the Phillips units. I liken the Oppo 980H or higher. You may find more air or spaciousness along with depth, etc. Then again you may not. On the technology side you will know. The Oppo IMO is as good or better than most units selling for 10 times as much. Plus, you have a volume control too. (Some DAC's will render the volume control un-useable) I prefer mine to run through a DAC and preamp. I use a Scott Nixon tube DAC with great results. I went on a 6 month attempt to find a better cd player but I haven't found anything as of yet. But I'm using a tube preamp (VanAlstine Super PAS3si of Vanalstine's design) and tube DAC as mentioned above. Not only is it very very musical but I have heard some other units in the upper ranges ($$$) and they don't impress me as much.
I say take a test drive and see if you are missing anything and it will only cost you $185.00 shipped.

IMHO, it depends on the volume control in the Philips. If the VC is analog, a direct connection may be great. If the VC is digital (and, therefore, loses data when attenuated), the direct connection is a bad idea. I suspect the latter is the reality.

yup,old business,check out the recent thread.....good luck

There is another post on this subject from a few days ago. I agree with Polk as long as the output stage was actually designed to drive a power amp. Despite having a nominal output high enough many CD players will not be as good as a good preamp in driving a power amp. But if they have been designed to do so then adding anything else will degrade the sound to some degree.

No. The best preamp is no preamp. The only thing you may be missing is other sources of music. Phono, tuner, tapes, equalization. If you're happy with your system, save your money for more music instead of electronics. I myself, like all the other sources, but that's me. You have nothing else to degrade your sound the way you are set up.