AMP power setting with PC

[newtoaudio90]

Hi guys

As some of you may know I have been waiting on a new system for some time for my PC.

Today I got my PSB image B5s with topping TP20 working and its great .

Anyway- random question. I have never had speakers of this level attached to a PC (infact have never had speakers and amp running to a PC).

That being said- seeing you can adjust volume with both the PC controls AND by turning up the amp how high would you leave the amp set?


I figure- turn it up most of the way and then control with the PC?

Would leaving the amp turned down a little be a 'safety mechanism' in that I would be less likely to overdrive the speakers into clipping (seeing my amp is only 20watts - more likely to damage them from low power than high).

Can clipping occur if i turned the speakers up to full through the PC BUT turned the amp down a little so it cannot go as loud int he first place?

 

[ruenigma]

The volume "should" be controlled from the amp. The PC is just the source and "Thou shalt not control volume at the source" (Unless the source is also your Pre-amp )

Ideally set the PC to full volume and forget it. Control volume at the topping.

About the clipping, in the scenario you mentioned it's unlikely that damage inducing clipping may occur.

 

[koushik]

Digital volume control using software will cut bits from the signal resulting in drop of resolution and quality of source signal meaning drop of overall sound quality. Anything less than 0dB will start deteriorating the quality.
So the control should be done from the analogue device - Volume control of Pre or Integrated.

 

[Thad E Ginathom]

There are other possibilites. One reason for 24-bit sound (or upsampling to 24 bits) is that you can then cut the lower bits, thus controlling the volume without actually loosing any information. Please don't take this as a technical explanation, but as a suggestion to google sources which can give a proper explanation which I can't.

All that is part of learning about digital sound. In purely practical terms, I would echo koushik and say to keep that digital output at 100% (0dB) and control at the pre-amp. In most PC+monitors situations, the control is either going to be on one of the speakers or on a desktop amp, thus it can easily be within arm's reach. This is, absolutely, the "correct" answer.

That is what I would do --- and it is what I do do!

But, digital sound is a world in itself, with a heap of things to learn, so experimentation is good too. Try the software volume control. Also you can probably get addins for your software that reduce the bit depth, and you'd be surprised how few bits one can actually get away with. On the other hand, just listening to the music is fine too

 

[newtoaudio90]

Wow thanks guys,

never would of guessed. Just curious, if changing volume from the source (PC)- the dropping of quality would only occur during the change, yes?

Or you only get full quality when sound is on maximum (at the source)?

On the note of clipping. By having the PC on full and the amp turned down- wouldn't this be a risk. The speakers trying to go loud as the computer tells them and if the amp is turned down then they may not be getting the power required? i.e. can you induce clipping from the source? And rectify it by turning up the sound at the amp (i know this inst the typical scenario but ma curious - for learning sake)

 

[Thad E Ginathom]

if changing volume from the source (PC)- the dropping of quality would only occur during the change, yes? ... Or you only get full quality when sound is on maximum (at the source)?

The way that digital volume control works is to take each sample and chop some of the bits off. Those bits may or may not actually contain musical information. If they do, you will loose it. This loss may or may not result in an audible loss of quality. People use the term resolution, and one would think that reducing the resolution automatically reduces the quality. People use JPEG picture compression as an analogy, but actually audio does not quite work in the same way.

As I said, please go to better sources than me for explanation, but just to give a very simple numeric example:

00110101 chopped to 10101 has lost some information
00010101 chopped to 10101 has not lost any information

People say, they want bit-perfect music. ie, every single bit that is in the file delivered to the DAC just as it is. Whether or not one can actually detect the differnce, with digital volume control, by definition it is not delivering every bit.

By having the PC on full and the amp turned down- wouldn't this be a risk.

No. Your PC sound card or DAC is a line-level-output device. You don't have any such worries about your CD player, so don't have them about your PC!

But... some cards/software may have the possibility to amplify the signal. I don't know how this works, but, for instance, in VLC, "100%" is only half-way on the software volume control. Do not use higher volumes! Stick to 0dB or 100% and you should be getting the best from your system whilst maintaining safety for both your speakers and your ears

 

[newtoaudio90]

Okay thank you very much. Your answer is very comprehensive. Last question, why is max volume called 0dB? I dont wuite understand the term " make sure its set at 0"When in reality this is inaudible? 0dB is no sound at all yer?

 

[Thad E Ginathom]

why is max volume called 0dB?

Ahhh... decibel scales and what they mean. Did I mention I hate numbers anyway?

If you use a sound-pressure meter to measure noise levels, 0dB would be absolute, deathly silence, and, as one might expect, as the volume increases, so does the number on the meter read out. There is no limit to how loud it can get, even way past the point where human brains have melted even with your hands over your ears.

With digital sound there is certainly a point beyond which it can get no louder, and that is when every bit is a one. Beyond this cannot be recorded, the tops of the wave forms get chopped off (this is also called "clipping") and a horrible noise results. I guess they decided to call this zero and measure down from it, as the variable in digital audio is not how loud can it get but how quiet can it get.

The numbers on your sound pressure meter are still not as simple as they look, because they can be weighted in different ways to give different readings, but they are akin to an actual measurement like a metre of cable or cloth. The numbers in your audio editor are not at all related to a fixed amount of volume --- as they have yet to be turned into sound and amplified.

This is my dumbo explanation. It may well include errors of fact: I'm working on understanding this stuff. Google may be more helpful But be warned, don't google deciBel unless you have plenty of time to spare :lol:

 

[newtoaudio90]

You also said clipping can not occur as your PC DAC is a 'line level output'- what exactly does this mean and how does it stop clipping?

Thanks for all you answers THAD- very helpful and very clear.

 

[Thad E Ginathom]

By clipping, I assume you mean the nasty noise that a speaker will make if you turn up the volume to a point where distortion occurs because the drivers are trying to move further than physically possible. Damage is the next step. This is a matter between you and your amplifier's volume control, not a matter of the source's line level, assuming, of course, that that is correct.

(It might happen also because the amplifier is not really capable of performing to max on its volume knob, and will then feed distortion to the speaker. Not being a deafening-level listener, I don't know much about this. It is often said that pushing a low-power amp too far is not good.)

Clipping in digital terms is something that occurs at the recording/mixing, rather than the playback, stage. Set the levels so that the wave needs to exceed 0dB: it can't, so the top of the wave is literally "clipped " flat loosing its top altogether. When this is played back, at whatever volume, it just gives a nasty noise.

as the variable in digital audio is not how loud can it get but how quiet can it get.

So, how quiet can it get?

In theory, it can go on getting quiet until it is quieter than the system's own noise (which is why we go on about a DAC with an SNR of 104 being "better" than one with an SNR of 100) but, in practice, you will reach the level of the environment noise around you a long, long time before coming anywhere near the noise floor which, itself, should be below human hearing. Try the Dynamic Range test on this page to find out how quiet can it get for your ears in your room.