2. amps-preamps
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How important is the pre-amp?

Hello all,

Genuine request here for other's experiences.

I get how power amps can make really significant changes to the sound of a system. And of course speakers have an even bigger effect. And then there is the complicated relationship between the speaker and power amp. But I wonder about pre-amps.

In theory a well designed preamp should just act as a source switch and volume control. But does it add (or ruin) magic? Can a pre-amp color the sound? Alter pace and timing? Could you take a great sounding system and spoil it with the wrong preamp? Stereophile once gushed (while reviewing a preamp that cost as much as a car) that the preamp was the heart of the system, setting the tone of everything. Really? Some people don't even bother with a preamp, feeding their DACs straight into the power amp. Others favor passive devices, things without power. If one can get a perfectly good $2K preamp, why bother with 20K?

What your experiences been?
128x128rols
atmasphere's avatar
atmasphere
11,979 posts
 
The one that sounds closest to a piece of wire is the best, that’s the "direct" next best is the "passive", then the "active".
As we all know from the existence of the high end cable industry, sounding like a 'piece of wire' might not be the way to go- since obviously different pieces of wire sound different- hence the cable industry.

The solution to preventing wires from sounding different, and getting rid of their artifact, is a technology that was originally developed for the telephone industry, but was rapidly adopted by the recording and broadcast industries in the early 1950s- the balanced line system, which is implemented with a set of standards. A passive volume control cannot support the balanced line standard, and so is less capable of being neutral.
roxy54's avatar
roxy54
8,098 posts
 
Check mate Ralph!
unsound
7,336 posts
 
As far as “standards” go; it would seem to me that if amplifier manufacturers would adapt a standard for single ended input sensitivity of say between 2 V (CD) and 2.2 V (HDCD) and a balanced input of between 4 V and 4.4 V for full power output, it would go a long way towards making direct connection from digital sources, more accessible. This would permit full range of the volume controls and reduce the risk of bit stripping, especially with the now ubiquitous digital sources with extra bits that can be applied for this very function. Doing so would reduce the amount of cables and the corresponding concerns being attributed to them.
unsound
7,336 posts
 
Addendum; Another consideration would be to include volume controls at the input of the amplifiers (this would probably require remote control) so that full output would be driving the full length of the cables.
And yet another consideration would be, at least for Class D amplifiers, to have digital inputs. From which a conversion of PCM to PWM would take place, and thus eliminating the traditional DAC altogether.
georgehifi's avatar
georgehifi
10,312 posts
 

Many amps are 1.5v or less input sensitivty for full output, and most dacs today are well over 2v output these days, so there's no problem with being able to voltage drive.
And most dacs today have very low output impedance output stages, that are equal to or better than many solid state preamps to drive any capacitive interconnects with, essecially bettering most tube preamps.
So it's a furphy to say a preamps drive better than dacs can direct.
 And like I said if a passive pre has no voltage or impedance issues then it is the next best way. 

Sure balanced has it's place in over 3mt interconnect runs, for noise cancelation only, below that there is no need for it. As single ended is just as good, and better in many cases better, as the balanced inputs of many poweramps are just a "balanced opamp" then leading the into the real single ended input of the amp which will sound better.

Cheers George
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