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hollowman
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Volume control -- optimal setting

In the 11/1998 Stereophile, B. Damkroger noted the following about the CL-15's (Calif. Audio Labs CD player) digital volume control:

Volume control is implemented in the digital domain, so it doesn't change the analog gain but rather the digital-to-analog scaling. According to CAL, reducing the volume won't result in a loss of resolution as long as the CL-15 is operated in the top two-thirds of its output range, with less than 18dB of attenuation. 

I assume by "resolution", one means bit depth. In any case, if the volume is truly controlled ONLY in the DIGITAL domain, can anyone (JA?) comment on why CAL may have made that comment?

On a more general note, at what volume scales -- for either analog or digital volume controls -- is audio quality "better"? E.g., two o'clock -> 100% on tradit. analog rotary volume knobs (this seems to work best for me on preamps, tho' often I can't use preamp vol. levels that high because the source volume/gain is high and non-adjustable) .

 

There could be multiple (concurrent) reasons for the above including:

 

-- better impedance matching between volume control and the stage following it, etc.

 

-- less (noisy) resistive material for signal to pass thru (for tradit. analog pots)

-- etc.

Thx!

JoeE SP9
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Quality?

I don't know about there being a quality difference at different level settings with an analog control. I do know that most preamp/amplifier/receiver(s)  with analog volume controls are at unity gain somewhere around 50% of maximum rotation.

hollowman
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Yes, QUALITY...
JoeE SP9 wrote:

I don't know about there being a quality difference at different level settings with an analog control. I do know that most preamp/amplifier/receiver(s)  with analog volume controls are at unity gain somewhere around 50% of maximum rotation.

Still, at 50%, the signal is going thru more resistive material than at full. However, I don't think the resistive material (in the analog pot) makes much diff. -- so the diffs. I perceive are probably due to other factors.

Level matched, (using Radio Shack dB SPL meter), I do note an improvement in SQ if I use my CDP's digital vol. control (to reduce gain) but use my preamp's analog pot at a higher setting.

Another -- and rather large -- SQ improvement I've noted is in a portable (but high-quality) HiFiMan-like player (Colorfly CK4) with its Line Out (I use it with a preamp or a separate headphone amp). The CK4 has digital vol. control that acts on BOTH headphone out and Line Out (it controls it's DAC's -- the CS4398 --  digital vol. control. One can't bypass it for Line Out). Dunno exactly why but SQ is best -- for LO use -- when vol. is at about 66%. This was serendipitous as I'd thought prev. that for these portable source devices, with digital-scaling level control, 100% would yield best results.

Doctor Fine
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Gain Staging

What you are referring to is what in the recording industry is called "gain staging."

Digital output at just below digital clipping yields the maximum bit depth.  In other words set your digital domain output stages (as digital signals on a digital signal meter) at just below digital clipping on the loudest songs you have.   For instance the output of an adjustable DAC should all ways be set at just below clipping using its meters.  Set thusly it will have full bit resolution and should be outputting a signal of about a half volt (-10dbV) or one and a half volts (+4dbV).  A nice FAT signal indeed.

Analog gain should also be run as a rule using this scenario:   Run nice HOT unbalanced line signal levels at -10dbV or approximately one half of a volt in power.  Professional balanced line level outputs should average +4dbV or about one and a half volts.  In other words you want fat OUTPUT signals on loud passages to be nice and hot so as to "wake up" the next input stage of your power amp or whatever.

It pays dividends to in general hit your INPUT stages HOT and as you go down the line adjust each following output stage so that it is as HOT as the next device can handle ,-10 for line devices, +4 for Pro line devices, and whatever output wattage your speakers can handle without undue strain for a power amp setting on loudest passages.

I have found that a power amp with accurate non-drifting volume controls on the unit can come in mighty handy when you want to maximise the clarity of the overall system at the very end of the playback chain.  I can't for the life of me accept the arguement that volume controls on power amps add grunge and should be avoided.  Using high quality ALPS pots or the like should give you an advantage without any sonic grunge penalty.  Are you LISTENING manufacturers?

The advantage of experimentation with gain staging is like finding free money lying around.  Greater clarity, less distortion overall, and higher resolution.

All from simply knowing what you are doing.  All this assumes your devices have controls on them.

Would somebody please tell me why the McIntosh 275 lost its volume controls on the new "improved" re-issue?  Madness.

And on a completely unrelated but similar gripe---why would ANYBODY take out the "balance' control on a stereo pre-amplifier?  As a professional mastering engineer I can tell you for a fact that there are significant differences in clarity and "focus" obtainable simply by being able to tighten up the center focus using a balance control. 

If you think there is some agreed upon absolute "standard" with which record companies set where the "middle" of the signal is---I have a nice bridge I will sell you.

More madness.

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