Preamp - what's the purpose?

These days you don’t really need one IMO unless you have analog sources and still like records or tapes. I run my dac directly to my amp and it sounds great. I have tried two different preamps in my system and I keep going back to running straight from the dac. It’s not that it sounds like crap with a preamp in the chain but I find I lose a little bit of that air and transparency if going through the preamp. It’s that much more electronics and cables added to the signal chain that you don’t possibly need. Paul McGowan from PS Audio was always saying “the best preamp is no preamp” and I tend to agree with him. Although he did admit that once in a while a really good preamp could improve the sound sometimes but also said if you are not going to use a real high end preamp, you are still better off going direct from dac and I agree.  Then again it all comes down to personal preference and taste. 

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?

In a smaller system you might not need a preamp. If you have multiple sources (tuner, tape, phono, TV, etc) you might. Most sources cannot drive long cables very well; if you want the best you have to use monoblock amps so they can sit by the speakers, allowing you to keep the speaker cables as short as possible.

A good preamp can drive long interconnects without the interconnects imposing a 'sound'- so it can be more neutral. You don't need to sacrifice any transparency or 'air' with a good preamp.

The purpose of a preamp?

There are multiple reasons, depending on your setup.

1. Selecting between multiple sources.
2. Some sources don't have their own volume control and most power amps don't have one either.
3. Some power amps don't have enough internal gain to put out full power from a line level source and/or not all line level sources output 2 volts.
4. Gain can also be an issue with some recordings. LPs are a classic example where records with 15 minute long sides could be recorded louder than those with 20 or 25 minutes on a side.  I've also seen CDs recorded at unusually low average levels.  For those recordings you may need more gain than the power amp along provides.
5. The output impedance of a source and the input impedence of a power amp may not be a good match. Or, as already noted in a prior reply, interconnecting cables, particularly if longer, can adversely affect the sound quality.
6. A preamp can also imprint its own sonic signature on the sound quality. You may like the way a particular preamp sounds versus no preamp.

Even if your particular setup doesn't have any of the above issues, the only way you will know what you like best is to experiment.

@mlsstl Nailed it!

@mlsstl

+1

It puts the magic and bloom into the sound. While direct DAC to amp components are getting better, except in rare instances a great preamp is requirement for really good compelling musical sound. Lots of folks have connected DACs directly to amps only later realizing got all the detail and dynamics of recordings but lost its soul. I am sure a few haven’t discovered this an don’t know what they are missing.

Coming to this "hobby" from receivers and being on the lower tier, I need a preamp to connect all the sources I use. Turntable, T.V. and CD/DVD player. There is also a USB in for smart phone or laptop if I want. For streaming, I use a Bluesound node.

@arnold_h 

Paul McGowan from PS Audio was always saying “the best preamp is no preamp” and I tend to agree with him.

I ran my DSD DAC directly to my BHK250 power amp.  It sounded kinda flat, and by no means as good as when I ran the DAC through my BHK preamp.  Since I have a turntable and a R2R, I certainly need a preamp, but I just had to try it.  

It is all about system matching.  BUT IMO, preamps do more that what has been already stated above.  A good preamp will add dynamics, loud to soft to loud contract, speed, soundstage dimension - front to back - side to side, tone, separation of vocals and instruments, flow of music, definition, details, clarity, float high frequencies, provide a more beautiful mid-range especially with female vocals, woodwinds, and strings, a more realistic sound, etc.

Happy Listening.

@viridian 

Now that was funny!

I removed my ARC Ref 6SE and put my DCS Rossini APEX straight into my amp…. The loss of dynamics and soundstage was dramatic. I promptly but that experiment to bed.

Been without a pre for over a decade now without withdrawal symptoms, so you might say I’ve survived....sorry ’bout that...Not. *g*

One analog 6x6 matrix, one digital 6x6 includes video & optical, 2 digital eq’s (one for the space, other for whatever)....that’s most of a pre, anyway.

Was gifted with a nice older one ’while back, but looping it in ’proper’ calls for a major physical re-arrange and some more IC spaghetti....

Only been asked once "Why isn’t this up against the wall?"

😒 "C’mere...look...."

"Oh...."

’Puters and amp have their own line cords. all else is low watts & amps on a 3rd line. You can guess the rest...;)

to manage and organize sources
to send source signals to a power amp


by using gain, impedance matching & whatever im leaving out

 

To control multiple sources.

I have tried it both ways- in my case a PS Audio Direct Stream DAC to an Audio Research SP 15, an Audio Research Ref 6SE and direct to amp.

My experience is this: If I don't mind having lower volume recordings preventing me from getting the DBs I want (I like 80-96DB) DAC to amp is just fine.

Alternatively my SP 15 added a certain brightness to the mid/highs which I wasn't satisfied with. 

My Ref 6 SE was a big volume booster- and nearly neutral. Zero added shades. It did add discernable separation of string instruments (airness?) and the feeling I could "see" behind the cello as it played. I thought that was really cool and worth the price of admission. 

I no longer use phono and CD so switching between sources was not important to me. 

There is also the budget issue. DAC to amp saves you the costs of buying and maintaining a preamp. At least for me having great music and a small budget when I got back into the hobby made DAC to amp a great deal. 

I hope my "eye witness" experience helps you with your decision. 

Functionally: Volume Control is the most common need. Thus a Preamp is an attenuator, most combined with a gain stage. Passive is a switcher, attenuator with no gain stage, perhaps other features.

Pre-Amp, (the pre) (ignoring features, switching, tone/filter/modes/etc) are needed to pre-amplify low level signals up to Line Level, then off to the amp., i.e. Moving Magnet Cartridge’s low signal strength

Any Line Level Strength signal can go straight to the amp, BUT, where is the volume control?

’Back in the Day’: Amps were/are designed to receive ’line level’. Original Sources, i.e. Mono FM produced/sent 1 volt to an amp.

Stereo: you need another amp, stereo source like Stereo FM. Now two 1 volt out to two amps to two speakers.

Vinyl: original ceramic cartridges were strong signal, (remember RIAA EQ had to occur somewhere), originally within the preamp, now often a separate component: then Line Level Signal to Amp. MM cartridge signal strength, stronger than Ceramic, into MM Phono for RIAA EQ, and boosted to line level.

Pre-Pre Amp. MC cartridges, lower signal strength, in order to use existing MM RIAA circuits, needed to be pre-amplified up to MM signal strength, then to MM Phono EQ input, then out at line level. SUTs, i.e. Step Up Transformers are pre-preamp solutions.

Modern sources, i.e. CD Players, digital output ... can send much more than the old 1 volt line level.

Some Preamps, like my current and past McIntosh preamps, and prior Tandberg Receiver, let you ’level’ the various signals to each other, so there is no need to alter the volume control when switching sources, i.e. Phono 1; Phono Two; Tape: matched level controls, then off to the Primary Attenuator.

I have been using a Decware amp fed by a DAC and phono preamp for more than a year.  I decided a remote control was needed and ordered an Erhard Audio Aretha preamp.   It made my system sound better.  Soundstage was the largest benefit.  Instant gratification!

A preamp is primarily a switching center. If you don't need it don't worry about it. 

a preamp has MANY benefits.

Input source selection.
Volume and balance controls.
Tone controls, YES, tone controls. They are invaluable in my opinion, especially if the source music is not perfect, also room layout, speaker placement, so much can affect the sound and tone controls can go a long way to 'compensate' for any short comings.
I use Baxandall tone controls in my custom builds, one the best tone control circuits out there. I also offer a tone defeat switch, very handy when a 'pure' line preamp is desired for certain listening sessions.

@heartwoodcorp

glad to hear that you are enjoying your Aretha!

Many preamps have subwoofer circuitry with high pass filters and gain control too. The switching ability, volume control, remote control and multiple analog and digital inputs/outputs are very important to me.  The pleasure of a tube preamp allows for a different dimension in sound quality too.  

That’s the thing these days, most dac sources have subwoofer circuitry with high pass filters and gain control.  My Oppo 205 has all these features plus many more including surround 7.1. I run it direct to my power amp through balanced XLR connection.

Some people have multiple sources and need a switch.  I have 2 inputs but have an amp with 2 inputs.  My new amp I ordered custom has 3 inputs, one for a spare.  

Some DACs don't have volume control, so they use the pre for that.

Some people think a preamp improves the quality of the sound.  I say it can only color it.  

And I do it just like you--DAC into my tube amp.  

Jerry

Fair question. Obviously, you need a preamp if your amp has no volume control and you want to use more than one source and want to conveniently select between them with a switch. With some sources, you might need amplification to get to line level. Phono, for vinyl and MC or MM cartridges and no phono preamp, some digital sources (I remember an Apple Airport I used as a streamer some years ago needing quite a bit of volume addition from my Rotel Receiver.) If you want to use headphones but don't want to have a dedicated headphone amp, a preamp can provide. These days, other devices have assumed some of the preamp functions, so you could make do without a separate preamp. Many streamers have DACs and preamp volume, bass, treble and balance functions of classic preamps in their phone apps, some even have phono preamps and headphone amps with headphone jacks, functions which duplicate or replace those typically on a preamp. Depending on your use case, the need for a preamp could range from not at all to essential.

Thanks for the replies. The obvious answer is regarding sources and level control. I wondered about people who use it to color the sound, as some salespeople have said "it just sounds _better_ with the ($5-15k) preamp!" and based on the gear they were talking about, it seemed kinda BS. But I know there are power amps which the designer biased on the low or high side.

I think if I needed input selection or attenuation, I would try to build or look into buying a passive pre-amp... 

@clustrocasual -- "I wondered about people who use it [a preamp] to color the sound..."

Its been explained that "colored sound" can also happen when there is a mismatch between the source's output and the power amp's input. 

You can't just assume that all line level sources are capable of optimally driving a power amp. Sometimes that's true, and sometimes its not.

The BEST sound comes from a TUBE PRE and a SS amp....PERIOD !

Never been a fan of preamps. The main course is the amp, preamp is like adding salt n pepper.

Viridian, is your sound system outside?

The signal coming from your source and being fed into your power amplifier needs to be in the sweet spot of your amplifier's sensitivity.  Meaning that you are well above the noise floor of your amplifier, but not approaching the output clipping level of your preamp or DAC device.  Here is an interesting paper on the topic:   Gain Structure 101
If you wish to have a streamer with a built-in DAC you need to choose one that has an excellent analog output stage, offering sufficient gain and low noise. A good example of this is the  miniDSP SHD.  Many of our customers who have adopted the SHD to gain the benefits of Dirac Live initially had very expensive preamplifiers in their systems. Given some time, in most cases we've seen these preamplifiers removed with improved results. 
 

Funny no one seems to remark/notice that if your DAC has sub circuitry, gain, etc it IS a preamp too! 

@mbmi   The BEST  sound  comes from. TUBE PRE and a SS amp. BS. I had a SS amp. A Krell FPB 600 and an ARC Ref  6se . Now I have the ARC Ref 750s mono blocks  with the ARC Ref 6se. Can’t compare. 

I find it somewhat ironic that those purists who eschew the use of a preamp because it "colors" the sound will then seek out amps, cartridges, wires or speakers to achieve the tone color they seek. 

If you only have one source, no preamp is okay. As long as the source or amp has a volume control it will work. But some prefer the dynamics and/or coloration a preamp adds.

there was once a description of sound. American sound and British sound.

am. sound = big scale, br. sound = detailed.

americans like exaggerated sound such as boomy, more bass.

this is not true to the original music. 

cooked fish with no sauce at all = you can feel the pure taste of fish.

cooked with lots of sauce = you can feel the variety of tastes

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 

Yes, this is basically my attitude about it...

raw fish with NO cooking = ultimate purity. 🍣

A Primaluna EVO 400 pre-amp feeding into the AGD Audion Mk3 is the best of both worlds. Granted, many customers have probably embraced GanFET amps with the idea that this would do away with some of the inconveniences of tubes and yet still sound like tubes. That is partially true but not true enough. With the tube pre in the chain it is finally enough.

The pre-amp warms up faster, creates less heat and does not contain so many tubes to keep track of. This works fine for me.

I run my AGD Audions from Cary SLP 05 and am also very happy.  

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.

@ricky64

Very interesting

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.  

One day I expect I will have a combination DAC/Preamp form factor from MSB or DCS and do away with the separate pre, dac, streamer, etc.