Preamp - what's the purpose?


Intentionally dumb question...

I've heard various 5-15W tube amps in my room. EL84, 300B, etc. They all have input stages and the output stage. I send them a line-level signal from a DAC.

Sitting a few meters away from my loudspeakers, the first watt alone gives me roughly 80db of volume. I think these amps are biased to expect the line level signal directly. Why wouldn't the designer do that?

So what's the point of adding a pre-amp? Why do people do it?

thanks in advance

 

clustrocasual

I liken my pre-amp to SS amp set-up as being something that burnishes the sound without any hint of foaminess that was the case when I was using pre and power tube amps simultaneously. I am, however, keeping the power tube amp and setting it up separately as a SS pre to tube power amp which can have its own hybrid sound advantages.

either is ok, modified sound with pre or pure sound with no pre.

once you feel pure taste with no sauce, you will remove the preamp!

@r27y8u92 I have LPs and CDs I recorded. I find that using a preamp gets me more neutral sound as the preamp is able to eliminate the coloration caused by the interconnect cables- if you've ever auditioned interconnect cables and heard a difference, you know what I mean.

I've also found that quite often if a passive control is used, when turned down from anywhere other than all the way up there is a loss of impact across the audio band- usually most noticeable in the bass. This is caused by the passive control being in series with the output impedance of the source (which might be a DAC). Active preamps do not have this problem.

I was a complete non believer in preamps. All the while, I was not getting satisfactory results from a Grimm Mu1/MMT front end, with the Tambaqui going directly into my Gryphon Essence amp. Sound was too gossamer, poor dynamics and bass, even bought a subwoofer. After two years of handwringing and tweaking, finally started auditioning pres. Fixed all of my issues. I was looking at moving up the amp chain, etc. Now, I have my subwoofer turned off. YMMV, but the Tambaqui going directly into the Essence, as much as logic should dictate, is not ok.

In my experience a pre is a clear improvement.  I assume there are situations where it isn't but the first time I put one in my system I was close to shocked.  I believe I was running a pair of Classe CA-200s bridged mono in addition to a pair of Infinity Intermezzo 1.2 subs.  All out of a Benchmark DAC1 with the balanced out to the amps and RCA to the subs.  This was around 2008.  I bought a Bryston BP25 used for a grand.  It made the overall presentation a ton more forceful and distinct.  Bass was more distinct and the mids gained a lot of texture.  I assume all the interconnects and multiple components were taxing the DAC output capability beyond what it could keep up with.  The system may have lost a trace of transparency but overall it was much better.