Can I drive a power amp without a pre?

[nowwhat?]

From Sean Adams, founder of Slim Devices (now Logitech Squeezebox):

Digital Volume Control and SNR - SqueezeboxWiki

He suggests running at full volume to DAC and from there on to an analog volume control.

Whether this affects clarity or not I do not know as I neither have a DAC nor a preamp at this time.

 

[Thad E Ginathom]

Which theory will explain it?

A parable might

Two facts about volume and music are very well established. One of those is what I call "the first rule of psychoacoustics". I have no idea whether it is the first or the millionth, it just seems to me to be the most relevant to most listening and all listening tests and comparisons:

Unless already too loud, louder is always better

The second fact is the loudness curve of human hearing: that our hearing is optimised in the midrange, and falls away towards the higher and lower ends of the spectrum, and that, as overall volume is decreased, this causes us to hear progressively less bass and treble. Maybe this is the reason for the first fact: not sure, but it certainly contributes to louder-is-better.

Let us now take one audiophile. It is only necessary that this audiophile has heard something about digital volume control being done by bit reduction, but does not have an engineering-level grasp of digital sound. My fictional audiophile is certainly not any one of us here --- but it could be quite a few of us. It certainly could be me.

Let us sit our volunteer in front of the speakers and play him some music. First, we will reduce the volume using an analogue knob. Next we will restore it to its previous level and reduce it using digital means. We won't bother to do anything like setting the original levels accurately (SPL meters and all that) and, of course, we will make sure that our audiophile knows whether he is listening to analogue or digital volume control.

Which will our audiophile prefer, and why?

Of course, it could go either way --- but let him amongst us who is free of bias and expectation cast the first, erm... bit

It is just a parable, a story, a fiction ...about how we think.

My PC listening set up has analogue volume control, both of the speakers and of the headphones. I'd need reminding that there even is a volume control on my player! I've listened to a demonstration of bit levels, quantisation error and dithering, and I've played, briefly, with the effect of bit reduction to the point where it does cause the sound to become distorted. But I haven't tried a side-by-side comparison of simple volume control. Even if I did, I'd still probably recommend the analogue volume control. It's the way I think

From Sean Adams, founder of Slim Devices (now Logitech Squeezebox):

Digital Volume Control and SNR - SqueezeboxWiki

He suggests running at full volume to DAC and from there on to an analog volume control.

Whether this affects clarity or not I do not know as I neither have a DAC nor a preamp at this time.

Yes, that's a great explanation to explain the basis of our preference: analogue control reduces noise as well as signal, digital control does not reduce noise, but only signal.

So... (this test I have done )... record some "silence" using whatever recording/editing software is available to your PC. Audacity is free, if you do not have one yet. Play it back, and it should be silent, and if it is not, then something is seriously wrong with your PC. Now select all or part of the wave until you just begin to see that there is stuff there. You probably still can't hear it. Amplify it until you can hear it. I think it was something over +85dB on my system at that time.

 

[ranjeetrain]

i can say the same thing about a pot based analog volume control.

That's fair. So, if the difference is so hard to perceive, why get bought into such gimmick. We can certainly leave certain things for "ultra audiophiles", isn't it

When we are wanting to save money, by going pre-less or using iPod, we are certainly not talking about that region. And unless it goes into that region, the difference is so so subtle, most people cant perceive it.

My question is - why the BIAS against the digital? hyeah:

 

[ranjeetrain]

Unless already too loud, louder is always better

Spot on!

I'd just change that last better to sounds better.

 

[Thad E Ginathom]

Well, yes ... but fewer words is more punch . Higher SNR! :lol:

My question is - why the BIAS against the digital?

Because in theory it could be said to be true. At which point I guess we need a GOTO in the thread :lol:

 

[ranjeetrain]

Well yes then :lol:

 

[ynotbubba]

We can certainly leave certain things for "ultra audiophiles", isn't it

Well said.

Here is an example of the so called "ultra" ones:

 

[Thad E Ginathom]

:clapping: hyeah: :yahoo:

... That is superb. Thank you!

As to our GOTO, I think we should make it a loop:

while(audiophile) ...

GOTOs are deprecated. They sound terrible

 

[ranjeetrain]

Speechless :indifferent14:

 

[gans]

I think that the previous posts have by and large covered most of it but let me summarise.

As per my understanding, a preamplifier does the following tasks: -

1. Provide impedance matching between the source and the power amp.

Different types of music would load the amp differently. Some like Western Classical and Hard rock put more load while some like Jazz are easy on the amp.

To be able to play all kinds of music without putting undue strain on either the source or the amp, the thumb rule is, 1:10 i.e. the output impedance of the source must be 1/10th of the input impedance of the Amp or lower.

2. Provide volume control

Traditionally this is done through a potentiometer which is nothing but a carbon based variable resistor. Due to the moving parts involved, this is bound to induce noise into the system the quantum of which is inversely proportional to its cost.

Newer (at least for me) ways of volume control have now come up using 'Light Dependent Resistors' 'Transformers' and the digital ones.

3. Source Selection

Since majority of people use several sources like CDs, TTs, Media players, DVD/BD players, STBs, it provides a convenience of switching between several sources without one having to take the trouble of swapping I/Cs

Can the preamp be eliminated? Yes it can be but subject to above.

Superbly explained sir.:clapping: