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Step on the gas

Paul's Posts — 29 October 2011

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Step on the gas

Have you ever been leery of turning up the volume control too high because you don’t want to push the system too hard?  I don’t mean in terms of volume level but stressing out the preamp by getting too close to its limits?  If that’s happened to you, you’re not alone.

It’s a common misconception that turning the volume control up near its limits will have negative affects on the sound when actually the opposite is true.  The higher you can set the volume control, the better your system will sound and here’s why.

Volume controls add resistance or a limiting element into the signal path.  If you were to remove the volume control altogether- just solder a wire straight across it – then the signal path would have a direct shot at the power amp and the sound would benefit from it.

Most people I know seem to have this vision in their head that relates the volume control to the gas pedal of a car.  It’s common knowledge that stepping on the gas all the way maxes out the engine and you’re much better off keeping it at half throttle.  But just the opposite is true in a hi fi system.

Think of the volume control more like the brakes of your car.  You can imagine that if you apply the brakes and the gas at the same time, the car is stressed out – so too is your system.  It’s much better to release the brake and let ‘er run.

The optimum solution is to match the sensitivity of your amp to your preamp so you’re volume control is mostly up at normal to loud listening levels.

Finally, someone’s egging you on to “step on the gas!”

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About Author

Paul McGowan

Paul McGowan is the CEO and co-founder of PS Audio Inc. a Boulder Colorado design and manufacturing company of high-end audio products and services. McGowan has been designing and building high-end products for nearly 40 years. Hobbies include skiing, music, hiking, artisan bread baking, kick boxing and cooking. He lives in Boulder Colorado with his wife Terri and his 4 sons.

(9) Readers Comments

  1. Frank LaFond

    October 29, 2011 at 9:43 am

    Paul, are you talking about standard potentiometer volume controls? In that case I can see the greater the attenuation, the greater the distance the signal is traveling through the resistive material of the pot. With other kinds of volume controls like switched resistors or CS3310-type digitally controlled volume attenuators, I wouldn’t expect any difference in the performance at different attenuation levels.

    While not directly related, this topic made me think of another “volume” topic I consider very interesting – due to the uneven spacing of the Fletcher-Munson curves (equal loudness contours), there is really only one “correct” volume to play back a piece of music. Play back at a volume higher or lower than the music was recorded at, and the recording and playback curves won’t match. The The University of New South Wales has a wonderful page to allow you to determine your own equal loudness contours.

    • October 31, 2011 at 6:25 am

      Frank – indeed – that’s a subject near and dear to me. There’s only one perfect volume level and I wrote about that in one of the posts located here: http://www.pstracks.com/pauls-posts/the-perfect-volume/2168/

      To answer your question – pots are worse than stepped attenuators mostly because they use lousier materials and contact area – but nothing’s better than a straight wire.

      • Frank LaFond

        November 4, 2011 at 11:28 am

        One step ahead of me as usual, Paul. :-) I’d better go back and check out the back posts – that was before I signed up…

  2. erich.j.henkel

    October 29, 2011 at 10:31 am

    Paul,

    It would be great if you could explain the difference between analog and digital volume control. I ´ve heard about the meaning of the lower 8 Bit and the benefits of 32 Bit depth for digital volume contrlo etc. but didn´t really understood it by now.
    Sometimes one can read that a high quality poti (e.g. from Alps) would be better, sometimes that digital is better. Accouphase seems to use a way to combine the benefits of both in the newest amplifieres.

    Kind regards
    Erich
    Erich

    • October 31, 2011 at 6:47 am

      A digital volume control works by changing the math of the digital audio and, if done correctly, won’t affect the sonics at all until you get into the very lower regions of the audio. An analog volume control works by inserting a resistor into the signal path which will always change the sound quality.

      I cannot imagine any way to do both effectively but maybe they’ve figured it out.

      From an analog perspective what we did with the Gain Cell preamp was probably the best – we changed the gain of the preamp and added nothing to the signal path.

      In the end, since the world is going digital, I support the digital volume control.

  3. machinehead

    October 30, 2011 at 1:15 pm

    Hi Paul,

    I would be interested if you could talk more about the specs and ratios to look for when matching preamps and amp.

    • October 31, 2011 at 6:48 am

      Output impedance and drive capability of the preamp. Most modern solid state preamps have little to no trouble driving long interconnects but in my experience there’s always a penalty to pay.

  4. Steve Parry

    November 1, 2011 at 5:03 pm

    Does the concept of “unity gain” apply to an active preamp?

  5. November 2, 2011 at 6:09 am

    Unity gain means there is no gain only an active stage – typically called a buffer. Ifd the buffer is built properly then that’s what you need to drive long interconnects.

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