Experts: Why is preamp important?

Tomcy6, for termination of a balanced line 600 ohms is the standard. By preamp standards, this is a very low impedance and many preamps can't drive that without a loss of bass, loss of signal level or both. Even though the termination is often not used, its a good idea to be able to drive it so as to be able to control the interconnect cable.

Atmasphere, What do you consider a low impedance?

I am by no means an expert, but the importance of a preamplifier can be essential or superfluous -depending on the system configuration. Here’s some reviewer comments-

“Conceptually, the preamplifier is the bottleneck in an audio system. All sources pass through it, and it influences every sound you hear... surely a preamplifier, more than any other component, should be able to approximate the late Peter Walker's "straight wire with gain…. The acid test of a preamplifier, of course, is to compare it with no preamplifier at all." (John Atkinson; Mark Levinson No.326S…Stereophile - January 2006)

“Should a preamplifier be merely a traffic director, controlling the rate of signal flow and routing signals along chosen pathways while remaining neutral about what’s passing through the pipeline. Or should it also impart a pleasing flavor to the proceedings? These questions, long debated among audiophiles, are a waste of time, in my opinion. Anything inserted into the signal path will change the sound, even a passive volume control – especially if it’s unbuffered. Those who seek some mythical sonic purity should give up audio and join a monastery. Any audiophile who’s bought a tube preamplifier has decided to impart a particular sonic flavor to the proceedings. However, the same can be said of those who prefer solid state preamplifiers.” (Michael Fremer;Dartzeel nhb-18ns Stereophile - June 2007)

“I hate preamplifiers. The stupid things are the only links in the audio chain that are designed (italic) from the get-go to restrict, impede, and otherwise diminish the audio signal. Audiophiles can and will spend all sorts of money …in an effort to increase information retrieval…And then you stick a fancy electronic bottleneck in the pipeline to throw away much of what has been "gained". What's so hard about "Turn that damn thing down!" anyway? (Bruce Kinch; Bent TAP…Positive Feedback - September 2006)

“Some may think that the best preamp is no preamp at all. At some point, every audiophile I know has entertained this possibility; I certainly have - more than once. Some have been persuaded of its truth. For what it's worth, I gave up on pursuing this approach when I realized that even though reproducing music requires amplifying a signal sufficiently to drive a loudspeaker, producing music is not equivalent to merely amplifying a signal sufficiently to drive a loudspeaker. “ (Jules Coleman; Shindo Monbrison; 6Moons)

“What role does an active preamp really play in a 21st-century digital system outside of input switching and volume control? Clearly not gain. Most modern digital sources drive most modern amps to full output directly. Nor resolution enhancements. Or do you find the argument persuasive that -- lots of -- additional analog circuitry could increase resolution? Not. Common sense suggests that the best any active circuitry could hope for in that regard is utter transparency. Let's thus tally up our compelling reasons for adding an active preamp to a standard 2V-out CD player and 0.5V input sensitivity amplifier. Redundant gain. And resolution that's at best equal to -- but more likely, subtly diminished over -- no preamp at all. Bitter blimey. That certainly couldn't be all of it. Could it?” (Srajan Ebaen; "Pick your world view" - 6Moons)

“A superior and expensive linestage thus needs to justify its existence far less on practical grounds than any amp (can it drive the speakers without distortion is its foremost concern) or any source component for that matter (which is simply indispensable). A preamp becomes far more of an *artistic rather than essential proposition. … It's perhaps here where an electronics designer can imprint his personal vision of 'musicality' the most…Because interpretative freedom is greatest here, it's also where a designer's personal vision and yours need to overlap the most to be relevant.” (Srajan Ebaen; - 6Moons)

Pinkus, in fact our preamps are designed to support the balanced line standard- in effect dramatically reducing the effect of the interconnect cable to the point that it is no longer important. This is not to say that you can't hear differences, but they cease to be the make-or-break sort of thing that you hear of so commonly. The reviewers are not wrong- they are simply not working with preamps that attend to this issue.

Honest1, the answer to your question is 'yes'. For that reason, you want to keep the length between the sources and the preamp inputs as short as possible. Anytime the source or preamp cannot control the cable, you will want to keep the cable as short as possible to reduce interaction. It won't eliminate it but it will help.

HI MR. JEFFKAD, i didn't want to recommend any specific manufacturers- i can only go by what i have seen and auditioned in person. my personal biases lean towards krell, levinson, rowland, etc., iow, "you know who i mean".
a nice rowland concentra-2 would, imho, make you a very happy audiophile. perhaps you would prefer a levinson-383. or you could pick up a rowland consonance preamp with a surprisingly good phono stage built in for $1200. after a few hours/days of listening you will be so happy you bought something at this level that the whole discussion above will be rendered moot.

Yeah, I-don't-know-who either.
I would say that running the signal through 2 budget priced preamps is going to do more harm than good. I would even say that running the signal through 2 high end pre-amps will probalby detract noticably fromthe sound, compared to just 1 preamp. (Althogh I have not tried an Atma-Sphere pre-amp)
Ralph - Does the interconnect between the source and the pre-amp run into the same problem as if you were to run the interconnect directly to the amp?

Jeffkad,

Yes, the Pioneer did affect my 2-channel is a positive way as it did my 5.1 Magnepan set up. Mid and low bass was much improved and the highs were not as harsh. In regards to the "Direct Mode", I think you mean the Pure Direct mode which doesn't take in account the MCACC equalization. Direct mode still uses the receiver's processing.

Atmasphere,

I assume your preamps are correctly designed to render interconnect differences moot. I can assure you that there are reviewers out there who will let you know that interconnects do indeed make a difference with your preamps. Now who do I trust....reviewers with golden ears, or the manufacturer....hmmm :)

French fries: I'm a little slow on the uptick. Who do you mean by "you know who"?
Slbenz: your preamp improvement seems to be relative to a HT environment. Did you see equal improvement in 2 chnl sound? I didn't think the MCACC system (and it's equalization) impacted 2 chnl listening much, and not at all in "direct" mode.
To all: the question remains - am I "double processing" the signal using pre-outs to an integrated, and how much negative imapct will this have? Would I be better off with an amp switcher instead?

Having just recently going from an Outlaw Model 990 home theater processor to a Pioneer VSX-74TXVi which is similar to your Pioneer receiver which I am using as a home theater processor, I would say the preamp is very important. At first I didn't think going from a separate processor back to a receiver would be a big upgrade but in my case it was. Most of the upgrade in sound was probably due to the more sophisticated acoustic measurements with the Pioneer vs. the basic speaker level adjustments with the Outlaw. But also having the iLink ability with my Marantz DV-9600 to capitalize on the jitter-free transfer system helped as well. I am using a Parasound 5 channel amp to power my Magnepan speakers and I can say that the separate power amp helps with the sound as well. Wider soundstage, more detail and better dynamics vs. the Pioneer's power amps. If you ask me which has the greater impact in the sound quality, I would say the preamp in my case. Using the Pioneer's MCACC mic system is several levels higher than the Outlaw's basic mic system. But there are positive audible differences going to a separate power amp with your Pioneer as well.

Don_s, If a preamp has a low output impedance, many of the differences you are accustomed to hearing in interconnect cables go away.

In fact the balanced line system used for decades in the recording studio and broadcast was conceived to eliminate (quite successfully) interconnect cable interactions.

Many sources do not have particularly low output impedances. For that reason it is useful to have a preamp line stage to buffer those impedances from the interconnect cable. This prevents the cable to the amp from having any significant effect on the sound.

Quite a few preamp manufacturers do not recognize this function of preamps, so there are many preamps out there wherein the interconnect cable between the amp and preamp is quite audible. So if you hear big effects between interconnect cables between the preamp and amp, then your preamp does not support this function.

the B&W's require very competent amplification. given your $3k budget it would seem that you would want an integrated amp from "you know who"- check the listings under int.amp-SS.
$3500 would get you a component that you could be happy with for quite a long time- powerful and solidly built. OTOH, a separate preamp and pwr amp would require a very good pair of (balanced) interconnects between them- perhaps costing $500 or more.

"and least understood- control the interconnect cable between amp and preamp to minimize the effect of the cable. Most sources cannot do this BTW."

I know this isn't to topic but Atmasphere's #4 purpose is so intriguing that, like Don_s, I would appreciate it if (with Jeffkad's indulgence) someone could expand on this point.

I'm running a somewhat parallel thread in this forum under another heading, but the same issue has now arisen. Am I wrong in my assumption that the pre-outs will contain the rcvr's processed signal? If I run that into another preamp, am I not getting essentially a "double processed" signal ultimately going to amp? Or does the last preamp clean up and control the ultimate signal to the amp? Dave: don't lose sight of my 2-3k budget. Assuming what I asked above is not a problem, is it worth splitting the budget to get lesser preamp and amp combo, or use it all on a really good amp now and maybe next year get a good preamp?

Atmasphere, Would you please elaborate on point 4. I would like to understand that function better. In some applications I have found "source direct to amplifier" less than satisfying.

"4) and least understood- control the interconnect cable between amp and preamp to minimize the effect of the cable. Most sources cannot do this BTW."

Thank you.

Others have covered what a preamp does so let's turn to what you might do with your system.

In higher end systems the preamp becomes a more dominant component in determining the ultimate sound quality. Recievers and surround processors are not very good sounding when compared with good analog two channel preamps. Besides being designed and optimized for "theater" rather than music, they are loaded with RF producing digital components that negatively affect the analog signals. Even the best digital surround preamps from companies like Meridian do not equal the sound of many dedicated two channel analog preamps.

Your best bet would be to get a high quality analog preamp and run the pre-outs from your receiver to a processor input (or any unused input- it's not that complicated at all).

Next, purchase either a very good multichannel amp that is capable of being an impressive two channel amp for your mains, or get a separate dedicated two channel amp for your mains and use the receiver's built-in amplification to drive the center and rear speakers.

All of this assumes that you really value listening to music in two channel and want to make a major upgrade to that part of your system.

preamp functions:

1) provide volume control
2) input switching
3) provide any needed gain or attenuation
4) and least understood- control the interconnect cable between amp and preamp to minimize the effect of the cable. Most sources cannot do this BTW.

Kthomas, you are right, I am asking several questions. I am generally interested in what exactly a preamp does, then I'm more specifically interested in how important it is in my upgrade path. I now have speakers in my HT system that will do justice to my critical music listening needs, so I'm trying to figure out whether I should get an integrated amp, just an amp, or possibly separates. I have some space constraints that I may have to work around as well. My amp budget is probably $2k-2.5k (maybe 3k if value is there) and I will buy used to increase value proposition. I have listened to some integrateds that I love (Mac MA6500 and the Cayin H80a), but they are quite large and neither have HT bypass. I know there are workarounds to this, but it gets more complicated. Then I started to think that maybe spending the same money on just the amplification might render bigger improvement and also simplify the process (just going pre-out to the amp and that's it). That's why I asked the preamp question.

I may also consider upgrading source, currently Pioneer dv47a universal player. I will also be upgrading my Sonos unit, probably with a Cullen mod and mayber also a standalone dac, although the dac in the Pioneer rcvr is excellent, and compares favorably to what I'm getting out of a Sonos/BelCanto DAC2 setup in my upstairs system (older B&W matrix 803s2 pwrd by Acurus DIA100 passive integrated). So I'm tackling numerous issues and trying to manage budget as well. Hopefully this gives you a little more insight into what I'm trying to accomplish.

It seems like you're asking a couple questions at once. The issue of why a preamp is important is a pretty broad question, and the answer is dependent on very many variables.

The more tactical question of how do you go from your Pioneer HT receiver to the "next level" and spend your dollars most wisely also depends on a few variables, but is easier to answer. IMO, no question, buying a good amp and using the pre-outs on your Pioneer will be a substantial upgrade. You don't give a budget, either immediate or longer term, but there are any number of two-channel amps that are very affordable used, that would be a substantial upgrade, and if you can spend more, the benefit would just increase. Then, at a later date, buying a higher-end pre/pro to replace the pre/pro functions of the Pioneer would again be a substantial improvement.

Charting the path, especially in a dual-use system, requires really understanding your parameters and your priorities, but, in general, replacing the functions of a HT receiver with dedicated, higher-end separates is going to be a substantial upgrade.

My experience has been that pre-amps can make a big difference to the sound of a system, although it seems like it should have afairly easy job. Very few systems really need the additional gain provided by the preamp; in most cases, teh preamp reduces, not amplifies, the signal. This would be obvious if you ever tried to connect your source (CD player for example) directly to your power amp without the preamp in between. The sound would be terribly loud, perhaps even damaging your speakers (I really wouldn't recommend trying this, unless you use a CD that starts softly and builds gradually, like Ravel' Bolero.) For this reason, in a budget system, a passive preamp might be a good choice. My experience was that inexpensive preamps did way more harm thatn good, because they were passing the signal through a cheap gain stage that wasn't necessary. My friend has a Mod Wright passive pre, and I had it in my system for a couple days. I was surprised at how good it sounded.

This is where your signal starts. If your preamp is the weakest link, it doesn't
matter how good everything down the chain is, you won't get the best sound.
In all the systems I have had, I found the preamp was most important . Just
my opinion.
Joe

The pre-amp is as the name implies the first step in amplification. It takes a very low power signal for a source component and steps it up so that it can then be further amplified by the power amplifier. The reason a good pre-amp is important is that a bad one can add noise or "color" the source signal and then those unwanted additions are passed on to your ear through the amplified signal that comes out of your speakers. Today however, the output signals from numerous high quality sources are strong enough to not need pre-amplification hence the advent of the passive preamp which does a number of things such as allow you to switch sources and adjust channel balance but it performs no pre-amplification rather it just passes the source signal on to the amplifier to do its job.

I don't know much about the Pioneer receiver you have but typically receivers are a set of compromises to deliver a lot of functions in one box and at reasonable price. Some receivers have the reputation for strong amplification sections, others their tuners or decoders. The conventional wisdom is that separate components provide better performance but a number of high end integrated amps have been very favorably reviewed. So I think the test is in the listening, you have some good front speakers and hopefully an equally good center I wouldn't be surprised if you could do better than the sound from your receiver.

I don't know about your particular HT receiver, but, most of the HT processors and receivers I've heard, including those pushing $10k are very disappointing -- brittle, unnatural and unpleasant. If you are serious about good audio (not primarily home theater), you will need either a good linestage/amp or an integrated amp and then switch out the speakers when not doing the home theater thing. That is what a friend of mine does.