The Sonic Role of a Preamplifier
 

For most of my audiophile life, I viewed preamplifiers as complex switching devices that allowed easy selection of source components with minimal degradation of the source's signal. About a decade ago, my belief in this principle led me to develop an interest in passive preamplifiers that by design had minimal impact on the sonic character of the source components. I bought a Placette passive preamp which did an excellent job save for its susceptibility to EMI. The noise of this particular passive preamp led me to buy an active one - a Classe CP-800, which seemed about as neutral as any preamp I've ever heard in that it added nothing and subtracted nothing. In recent years, I noted with interest as reviewers observed that better preamplifiers over the last decade not only avoided degrading the source signal, but somehow improved the sonic qualities where tonality, soundstaging, and even resolution were unambiguously improved. Examples of such preamps I read about include Ayre's KX-R and KX-R Twenty, PS Audio's BHK Preamp, and Audio Research's Ref 6. Based on my own experience in recent days, I would describe the Rogue Audio RP-7 as having this quality as well.

There is a running debate about how a preamp improves on a source's signal. How is such an effect possible? Does the preamp add something that wasn't in the recording? Does it somehow unpack the source's signal in a way that an amplifier can't? Are tubes especially good at this? Perhaps not with Ayre and PassLabs preamps as examples.

My Totaldac d1-twelve SE DAC is regarded as one of the best digital sources in the world. Without a preamp, it's sound is musical and extremely well detailed. It has a buffered output which can drive my system without a preamp. But with the RP-7 in place, the soundstage depth is improved and individual instruments and voices have a greater sense of dimensionality/body. Because of this, individual voices and instruments are somehow easier to follow in the midst of complex counterpoint, which symphonic and operatic music have plenty of. As good as my system sounds without a preamp, it sounds even better with the RP-7.

Perhaps engineers will be able to explain just what good preamps do to enhance a hi-fi system’s sound quality. There may be definitive explanations about this phenomenon already and I’m simply unaware of it. But this topic to me is one of the more fascinating aspects of our hobby that I would love to see explained in engineering (measurement) terms.

Great topic! I have no idea why, but a quality preamp is essential to getting top quality sound in my opinion, even above the SAME digital source when used as a pre. I tried this with my old k03 and there was no contest.

Don't forget about Conrad-Johnson's preamps...they have some "street cred", too! ;)

I've participated in a number of experiments with DACs or passive preamps that can drive amps vs. active preamps, and in every case, every person preferred the sound of having an active preamp in the system.

I think the simplest explanation is that they increase signal to noise, and in ways that our brains find that creates an experience that sounds more like what we perceive to be real music.

I'm not sure that the reasons can be entirely explained simply by engineers and/or measurements. The reason I say this is that I don't think we fully understand the nature of perception of hearing, of our brian's deconvolving these auditory signals into what we know as music, and music reproduction etc. Therefore, I don't think we know all the various parameters of what constitutes an engaging and beguiling msuical experience and therefore what to measure, or how to measure them.

An example: how does one measure the way a Stradivarius violin sounds different than a Guanerius playing the same notes or piece of music? They sound different, and we can hear that, but we don't know how to measure to show how they sound differently.

And at the end of the day, I don't think it matters; both are beautiful instruments to listen to.

So, I posit some thoughts for consideration: does it really matter how active preamps do this and what measurements may or may not explain why we prefer them, or should we just settle back with our active preamps, knowing that they make the experience more engaging, and enjoy the music? ;)

Just sayin'! :D

A preamp can not improve sound beyond what is coming into it. What a great preamplifier does is preserves the signal in its fragile low level state and passes it on to an amplifier with minimal corruption. I still feel a reference level solid state preamp will excel at this task.

Back in day I owned an Ayre KX-R and that was truly a great example. The way the KX-R spot lit the soundstage and made all the instruments take their proper space on the soundstage, left to right, front to back in a virtually holographic way and brought forth clarity, dimensionality and tonal accuracy was mesmerizing. It did not achieve this with gimmickry or electronic trickery but preserved every tiny electron in the signal and guided it safely through to the amp.

I strongly believe tubes will have a different effect on that low level signal but if the design is great, it adds euphony, color, harmonic bloom and body to the sound without making mush and marshmallows out of it but we often perceive this as a positive and I’ll be the first to agree it can be very enjoyable.

Perhaps passive preamps just are not able to support the low level signal without active circuitry and the result is not quite as good, to my ears at least.

I ultimately sold the KX-R and kept my Lamm LL2.1 preamp because of the delicious tone and harmonic richness, liquid and seductive midrange but knowing damn well it was not even close to the accuracy of the KX-R which was OK for me.
We all have our taste and preference.

Taking a close look at what build quality, component selection and design that actually goes into a reference grade preamplifier like the KX-R and some others and what effort must be made to achieve a performance of that level, it becomes clear that we may not ever be able to measure and document such phenomenon in audio but our ears can certainly appreciate the effort even if our wallets can not...

I think like many things in audio, it is what it just is.

I also suspect that some time in the future all the things we discuss and wonder about today, those that can not be measured or explained but certainly heard, with trained ears that most audiophiles posess after decades of daily dedicated and focused listening sessions, will be very simply explained by quantum physics. :yes: That mysterious electron cloud with all the electrons somewhere yet everywhere at the same time, moving through the system, bringing life to speakers shall be solved. :D

And don't forget about Schrödinger's cat! :D

Based on some of the recent theories that we create our own reality, I'd be inclined to believe that we hear what we want to hear and therefore the elusion becomes our reality.. hence all the arguments, especially over cables. :D

As for the cat, he had no knowledge of the situation as in his reality he was simply curled up next to Dr.Schrodinger as he was cranking away at his gramophone handle, sipping whisky and pondering over the experiment in which the cat is both alive and dead at the same time. Life is good thought the cat... :smoking:

:D:music:

I've always believed that a great tube preamp will increase satisfaction over no-preamp or passive alternatives, though I've never seriously done comparisons. Also, my 2ch rig is turntable sourced only, with a low-output MC, so I do kinda need the extra gain (though my current preamp gives even more gain than I need).

Not at all a fair comparison, but my turntable setup and tube preamp driving a balanced headphone amp and Sennheiser HD650 headphones clobbers the same headphone setup driven by a Schiit Yggdrasil without preamp. So the preamp certainly can't be doing much wrong, if anything.

And dammit - now I've got to get an RP-7 to try in my system! Though the Hera has knocked off the Ref 6 in my system, so it's going to have a heck of tough job. If it sounds like the Hera but with lower noise I'd be in heaven.

Interesting topic.

The idea that a quality PreAmp better preserves every electron of the low level, and presumably fragile, output makes the most sense to me. That would be my hypothesis.

Now I have to go read up on Schrödinger’s cat and learn if he ever found that single particle in a box.