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What is a preamp and what does it do?

post #1 of 14
Thread Starter 

For example, take the two amps NuForce Icon HDP and Nuforce Icon HD. It's my understanding that the HD doesn't have a pre-amp; what does this mean? What can't it do?

post #2 of 14

I just googled "NuForce Icon HDP" and found this page of info at the NuForce website.

 

There it says the Icon HDP has a preamp output which makes sense to me. You question should be "What is a preamp output and what does it do?". :)

 

This will be what is often called a line level output. The signal level will not be altered by the gain (volume) control on the NuForce amplifier.

 

This is there so that you can connect the NuForce Icon HDP to, maybe, a Hi Fi system, something like that. That "preamp output" is a standard-ish level that is the same as the output from a source like a CD player or a Tuner or a DAC.

 

Historically those sources in a regular Hi Fi would be plugged into a preamp and then that would be connected to a power-amp which would drive your loudspeakers.

 

That separation of preamp and power amp has sort of been disappearing a bit. Often now you have amplifiers that simply do both tasks in one box, and in fact there is no separation in their circuitry between a preamp and a power amp.

 

The advantage of having that "preamp output" as Nuforce describe it is that you could use the DAC in the Icon HDP with a regular Hi Fi amp or a different headphone amp. I think that is useful and personally if I were getting the Icon I would get the HDP one.

 

I think that Nuforce might be better if they used the more commonly used "line out" description for that output.

post #3 of 14
Quote:
Originally Posted by p a t r i c k View Post

I just googled "NuForce Icon HDP" and found this page of info at the NuForce website.

 

There it says the Icon HDP has a preamp output which makes sense to me. You question should be "What is a preamp output and what does it do?". :)

 

This will be what is often called a line level output. The signal level will not be altered by the gain (volume) control on the NuForce amplifier.

 

This is there so that you can connect the NuForce Icon HDP to, maybe, a Hi Fi system, something like that. That "preamp output" is a standard-ish level that is the same as the output from a source like a CD player or a Tuner or a DAC.

 

Historically those sources in a regular Hi Fi would be plugged into a preamp and then that would be connected to a power-amp which would drive your loudspeakers.

 

That separation of preamp and power amp has sort of been disappearing a bit. Often now you have amplifiers that simply do both tasks in one box, and in fact there is no separation in their circuitry between a preamp and a power amp.

 

The advantage of having that "preamp output" as Nuforce describe it is that you could use the DAC in the Icon HDP with a regular Hi Fi amp or a different headphone amp. I think that is useful and personally if I were getting the Icon I would get the HDP one.

 

I think that Nuforce might be better if they used the more commonly used "line out" description for that output.


i dont understand this,.. it only makes sense to me if youv got a combo - a dac and amp in the same box, then i can understand why youd want a "pre-amp output", if indeed its just a line out for using just the dac. but why would anyone need it otherwise? whats the point of connecting a dac, into a pre-amp and from there to the power amp? why would i connect a line-out, into a different box, that also outputs a line-out?

post #4 of 14
Quote:
Originally Posted by adamlr View Post


i dont understand this,.. it only makes sense to me if youv got a combo - a dac and amp in the same box, then i can understand why youd want a "pre-amp output", if indeed its just a line out for using just the dac. but why would anyone need it otherwise? whats the point of connecting a dac, into a pre-amp and from there to the power amp? why would i connect a line-out, into a different box, that also outputs a line-out?

 

 

What NuForce describe as "pre-amp out" is I think possibly one of two things. It could be a "line out". This is standard-ish output level that is the same as the output from a CD player or a Tuner. The headphone volume control will not change the level of that output so you can plug it into an amplifier the same as you would a CD player. This means that you could use it as a DAC.

 

The standard setup in the olden times was:

 

CD player -> preamp -> power amp -> speakers

 

In this, the preamp will have a gain control. So, it takes a line level in, and outputs a variable level to the power amp.

 

So if you wanted to use the NuForce as a DAC it would go:

 

NuForce HDP -> preamp -> power amp -> speakers

 

Here you would use the "preamp out" connection if it is the standardised line level suitable for inputing to a preamp.

 

The other thing that NuForce HDP could mean by "preamp out" is not a line level output, instead the level is adjusted by the gain (volume knob) on the NuForce HDP, in which case they would intend it to drive a power amp directly. In that case the NuForce HDP would be behaving as a preamp.

 

Since my earlier post I am increasingly thinking it might be this second option because "preamp out" makes more sense as a name for that.

 

Which it is I don't know as I have no experience of the NuForce HDP.

 
 
 

Edited by p a t r i c k - 1/19/13 at 2:06pm
post #5 of 14
Quote:
Originally Posted by p a t r i c k View Post

 

 

What NuForce describe as "pre-amp out" is I think possibly one of two things. It could be a "line out". This is standard-ish output level that is the same as the output from a CD player or a Tuner. The headphone volume control will not change the level of that output so you can plug it into an amplifier the same as you would a CD player. This means that you could use it as a DAC.

 

The standard setup in the olden times was:

 

CD player -> preamp -> power amp -> speakers

 

In this, the preamp will have a gain control. So, it takes a line level in, and outputs a variable level to the power amp.

 

So if you wanted to use the NuForce as a DAC it would go:

 

NuForce HDP -> preamp -> power amp -> speakers

 

Here you would use the "preamp out" connection if it is the standardised line level suitable for inputing to a preamp.

 

The other thing that NuForce HDP could mean by "preamp out" is not a line level output, instead the level is adjusted by the gain (volume knob) on the NuForce HDP, in which case they would intend it to drive a power amp directly. In that case the NuForce HDP would be behaving as a preamp.

 

Since my earlier post I am increasingly thinking it might be this second option because "preamp out" makes more sense as a name for that.

 

Which it is I don't know as I have no experience of the NuForce HDP.

 
 
 


but outside the hdp. why would i need a pre amp? whats the difference between the olden days, and today? if i had gain control anywhere but the amp, id put it at 100% and let the amp be my volume control. i dont get it... is a preamp just a way of getting more gain for speakers or something? is it like double amping?

post #6 of 14
Quote:
Originally Posted by adamlr View Post


but outside the hdp. why would i need a pre amp? whats the difference between the olden days, and today? if i had gain control anywhere but the amp, id put it at 100% and let the amp be my volume control. i dont get it... is a preamp just a way of getting more gain for speakers or something? is it like double amping?

 

In the olden days and still today I think, power amps don't have gain controls. If they have a gain control and input selector then they are usually called "integrated amplifiers".

 

The power amp is a box with one button for on and off. The gain control is in the preamplifier, along with a selector for input. Two descriptions would often be used for preamps, passive and active.

 

Passive Preamp

 

This is a box with a gain control and an input switching control. This needed no power at all. The passive preamp adjusted gain with a variable resistor, so it always went down.

 

Active Preamp

 

Active preamp manages gain using a circuit. This type of amp does have a power supply. Active preamps often contain an RIAA stage for a record player.

 

 

If you go to this webpage you will see a preamplifier and a power amplifier:

 

http://www.musicalfidelity.com/products/m8series/

post #7 of 14
Quote:
Originally Posted by p a t r i c k View Post

 

In the olden days and still today I think, power amps don't have gain controls. If they have a gain control and input selector then they are usually called "integrated amplifiers".

 

The power amp is a box with one button for on and off. The gain control is in the preamplifier, along with a selector for input. Two descriptions would often be used for preamps, passive and active.

 

Passive Preamp

 

This is a box with a gain control and an input switching control. This needed no power at all. The passive preamp adjusted gain with a variable resistor, so it always went down.

 

Active Preamp

 

Active preamp manages gain using a circuit. This type of amp does have a power supply. Active preamps often contain an RIAA stage for a record player.

 

 

If you go to this webpage you will see a preamplifier and a power amplifier:

 

http://www.musicalfidelity.com/products/m8series/


well that cleared it up entirely, cheers! thanks for the explanation =]

post #8 of 14

This cleared up the basics for me, however I'm left with one question. 
Could you use either a preamp or a poweramp alone, without the other? Or would that just be silly?

post #9 of 14
If the preamp added gain, what is the role of the amp?
post #10 of 14

I would say the old type set up was an integrated amp. This included both preamp and power amp in the same box. The preamp part accepted various line level inputs, such as cassette deck, CD player, tuner, plus a special input for a turntable. A knob would enable selection of one of the input's signal to be sent to the power amp section, and then out of the box to the speakers. Volume control was also from this box. I had an Audiolab 8000A integrated amp - look for pictures on the net.

 

Higher end products would separate the pre amp and power amp to reduce electrical noise, I believe.

 

Power amps don't usually have a volume control so if you didn't have a preamp you would need some method of doing this.

 

You could not use a preamp to power speakers as there won't be a strong enough signal.

 

In my speaker set up I have a separate CD Transport and DAC. The DAC has a volume control. This is then connected to a power amp. It is said that my DAC can act as a preamp but it doesn't have to. I could send the signal from my DAC to a preamp and then to a power amp.

 

If you only have one source you probably don't need a full blown preamp, but if you have a range of sources and often flit between them, a preamp is a good idea. Of course with separate preamp and power amp you require more cables and space - and probably money!

post #11 of 14

To separate the preamp from power (likein intergated amp)....that for better power supply / preamp tend to have better design implement reject noise etc / connect more input / you can connect the preamp from company A to power from company B and also try interconnect etc....that should be for fun (oh i mean for finding better synergy)

 

Even the preamp added gain....you need the power amp to driver your loudspeaker. Loudspeaker is not like an dynamic headphone that can run from few mw..


Edited by conheo - 10/16/13 at 5:53pm
post #12 of 14
Thanks for clarification. So basically preamp tells the amp what is the desired gain and amp takes over from there to drive the speakers/headphone to that level. Preamp also allows for switching of the inputs.
post #13 of 14

Yes.

post #14 of 14
Quote:
Originally Posted by adamlr View Post
 


i dont understand this,.. it only makes sense to me if youv got a combo - a dac and amp in the same box, then i can understand why youd want a "pre-amp output", if indeed its just a line out for using just the dac. but why would anyone need it otherwise? whats the point of connecting a dac, into a pre-amp and from there to the power amp? why would i connect a line-out, into a different box, that also outputs a line-out?*

 

If you have your headphone and speakers system in the same room, it's useful. For example, I might equal quality of headphone and speaker listening from one source, say in one case a dedicated digital audio transport (disc or HDD) and in another case a desktop system built around a small computer. On the first case, I can feed the signal from the digital audio transport into the HDP using SPDIF, which is standard on these. HDP drives headphones connected to it for night listening, then I connect the preamp output into a dedicated power amp (no volume control) that powers my speakers. Alternately, if I have a desktop system, this makes a lot of sense. Say I have the HDP hooked up to a laptop or small computer where I listen and browse the web, or maybe work on it too. In that case the HDP drives headphones, while at the same time it can feed a preamp signal into active monitors, making your system function much like a studio monitoring/mixing console (except you don't necessarily have actual inputs to record anything).

 

As to why anyone would need a headphone and speaker system, it depends on their needs - if you're fine wearing headphones all day, then you don't. I don't like wearing headphones all day for a number of reasons: humidity, heat, sweat or loud A/C, wearing out the pads, itchy cheeks, open back headphone lets me hear my neighbors' loud cars (or this lady screaming at her brat who I think should just be allowed to lose a few fingers on the lawnmower or something to learn the lesson permanently), etc, and I sometimes sit there all day going through several academic journals on weekends. By day I use speakers; then by night there isn't enough noise to get through into my headphones and I can't rock the house with the speakers either.

 

 

 

 

*You might be confused as to what "preamp output" means. It does not mean you hook up a preamp there (not that it's impossible, but see above), it means the signal that comes out of there is the same output you can get out of a dedicated preamp, meaning it takes a line level fixed level signal from a CDP or in this case the DAC section of the HDP, then feed it into a power amplifier.

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