What is preamplifier? How important it is in the stereo music system?

[ukjeyaraj]

I think you are getting impression that at certain volume level you will get equal sound level for all sources. This is incorrect. Rather than you will headroom for increasing input for power amp, thanks to preamp. For TT phono stage adds extra but fixed gain to cartridge output.

In the post by venkatcr, he has mentioned pre-amp will add necessary gain to increase the signal from 200mV or 400mV or 500mV to give a steady 2V. If I understand you correctly, just by making the different input signals gained to steady 2V, it does not make the volume level same for all sources.

 

[venkatcr]

Its a forum and not the argument to justify, Hence please correct me if am wrong

I agree it is a forum. At the same time, the law of physics does not change for anyone. At least as we know it today.

Please go back and read your first post and see what all you have said. Add this to your last post, and you are confusing yourself and others by adding terms that are not needed to explain a pre-amplifier. 'Frequency', DB, etc. None of that is relevant here.

A pre-amplifier is actually a very simple device - it takes an input signal, adds a gain to it, and sends the resultant signal out for further processing. That is all there is to it. The input and gain added are all simple electrical signals that can be measured and quantified.

Cheers

 

[omishra]

In the post by venkatcr, he has mentioned pre-amp will add necessary gain to increase the signal from 200mV or 400mV or 500mV to give a steady 2V. If I understand you correctly, just by making the different input signals gained to steady 2V, it does not make the volume level same for all sources.

IMO there is a concept called ALC (Automatoc Level Control). That mean whatever input is - 200mV, 400mV and .7V, output will be 2V. But doesn't this mean output of preamp will be constant and defeat purpose of volume control? What if some power amp goes to max full output power with 1V input? (for example only).

So ALC is good for recording output, surely for amp you need level set by you as an user. Volume controls as a help. I don't want to open can of worm but there are variable as well as constant(levelled) output.

So output of preamp will be treated as input X gain. But controlled by volume control.
E.g. If gain is 30 (not dB) then
For 200 mV input output will be 200 X 30 = 6000mV = 6V.
Calculate so on.
And then volume controller acts on, (please take this as vague explanation as volume controller can be beforehand also). At perticular selected volume level preamp output will vary wrt input from source. So you can match output wrt each source input as your preamp add headroom by amplification and volume control for adjustment or correction.

 

[Audio_Freek]

I agree it is a forum. At the same time, the law of physics does not change for anyone. At least as we know it today.

Please go back and read your first post and see what all you have said. Add this to your last post, and you are confusing yourself and others by adding terms that are not needed to explain a pre-amplifier. 'Frequency', DB, etc. None of that is relevant here.

A pre-amplifier is actually a very simple device - it takes an input signal, adds a gain to it, and sends the resultant signal out for further processing. That is all there is to it. The input and gain added are all simple electrical signals that can be measured and quantified.

Cheers

Venkatcr,
I do agree with the word "it takes simple input signal and adds gain to it",But i understand that the discussion is "what is Signal? or wat is passed into pre-amp and Wat is gain\wat is added..

We can even compromise UKjey in simple terms as "Pre-amplifier get something and adds something"

I would be very happy if you could explain the terms Gain and signal info on it Pls.. Other than giving a link to Wikipedia

Also the terms Frequency or DB might not be considered in pre-amplification, but its required to complete the purpose of the Amplification

 

[ukjeyaraj]

Like the quest to find matching speaker for amp(or the other way), pairing of pre-amp and power amp also looks to be critical, if someone takes the route of separate pre-amp and power amp. Is it always safe bet to go with manufacturer paired pre-power combo?

@omishra --> From your signature, it is evident that you are avid DIYer. Is there a decent DIY pre-amp with multiple inputs and TT-Phono Stage. Another question is how will one find a matching power amp for DIY pre-amp? Is it again DIY power amp.

 

[Thad E Ginathom]

In practical terms, and leaving theory and levels and volts out of it, this is what a preamp does...

1. Allows switching between multiple sources.

2. Allows adjustment of volume.

3. Outputs to a power amp.

Given a number of boxes called "amplifier" in a domestic hifi, the preamp is the one with the knobs on.

There. Hows that for pre-amps for dummies? :lol:

 

[venkatcr]

I would be very happy if you could explain the terms Gain and signal info on it Pls.. Other than giving a link to Wikipedia

If you would care to search, I have already explained gain, signal, SNR - the whole gamut of pre-amplification extensively in many threads. Not only me. but many people have done that.

Also the terms Frequency or DB might not be considered in pre-amplification, but its required to complete the purpose of the Amplification

We are talking about pre-amplification. Why talk about amplification here? That is a different subject matter, again explained in many threads nauseum.

Cheers

 

[mbhangui]

In practical terms, and leaving theory and levels and volts out of it, this is what a preamp does...

1. Allows switching between multiple sources.

2. Allows adjustment of volume.

3. Outputs to a power amp.

Given a number of boxes called "amplifier" in a domestic hifi, the preamp is the one with the knobs on.

There. Hows that for pre-amps for dummies? :lol:

That's perfect. Sums everything spoken in previous threads in just 3 points.

 

[omishra]

Like the quest to find matching speaker for amp(or the other way), pairing of pre-amp and power amp also looks to be critical, if someone takes the route of separate pre-amp and power amp. Is it always safe bet to go with manufacturer paired pre-power combo?

@omishra --> From your signature, it is evident that you are avid DIYer. Is there a decent DIY pre-amp with multiple inputs and TT-Phono Stage. Another question is how will one find a matching power amp for DIY pre-amp? Is it again DIY power amp.

There is alway match required as output of preamp need to be matched to input of power amp interms of impedance, output levels. But generic preamps can do better if they are near to ideal impedances - infinite input impedance and zero output impedance. Practically 47K input impedance and 50 ohm as output impedance works well with nearly all source and power amplifiers except few tube amps.

For DIY you need to buy component and assemble one. I have build one with CNC phono, source selector and two preamp modules, one at either side of volume control.
Pics are here http://www.hifivision.com/diy/21036-pass-b1-84.html#post398331
description is here http://www.hifivision.com/diy/21036-pass-b1-86.html#post401615
I used Pass B1 and also tried op amp based SSP as buffer/gain stages. It has 1Mohm input impedance and 50 ohm output impedance. You can search DIY section for both of them.

Even any buffer of your choice, volume control and suitable PS could be used. Preamp is simple device but it handles delicate audio signal with low levels which could be easily damaged by equipment, interconnect and environment noise. So it needs careful implementation and it's serious affair.
If not confident about DIY then you can buy ready made. I saw few good one at good prices selling here in HFV itself. Btw sorry, I am not turning this thread into marketing, it was unintentional.

 

[ukjeyaraj]

^^
Amazing info. Thanks for making a lot of things clearer.

 

[Thad E Ginathom]

That's perfect. Sums everything spoken in previous threads in just 3 points.

The control aspect is prime. Without a pre-amp, one would have to plug/unplug to select different sources, and would be condemned to listen to them at just one volume level.

...Well, theoretically, at least. I believe that there are people who, for instance, connect a CD player direct to a power amp, and use the volume control on the CD player, but that only goes to show that there always going to be exceptions and different ways of doing things.

 

[Thad E Ginathom]

...These days cd players can drive an amp directly, about 200 milliamps, giving good power output.... [/url]

But no control, source-switching, tape loop etc etc. The facilities of the pre-amp (or integrated, of course) are still needed by most people.

 

[asliarun]

^^
Amazing info. Thanks for making a lot of things clearer.

Yes, Thad summed it up quite nicely.

I had the exact same question a few months ago when I bought my power amp and didn't have a pre-amp. It turns out that my power amp ran quite happily when connected directly to the source (Squeezebox Classic). Since I only had one source, I didn't really need a pre-amp. The SB Classic also has a digital volume control that I was able to use to control the volume.

It turns out that I was losing quite a bit of audio quality with this setup however. Digital volume control apparently drops bits (again, rightly pointed out by Thad and other forum members) - i.e. the sound quality degrades significantly as you keep decreasing the volume. Since my power amp was quite powerful, I was running it at near minimum volume so I was losing quite a bit of audio quality due to my setup! In fact, it turns out that the right setup is always max out the volume at the source and control the volume only from the discrete pre-amp or the integrated amp.

I then decided to go for a pre-amp. I had two options - passive or active. The way I understand it is a passive preamp controls volume by decreasing the amplitude or power of the input source signal, and an active preamp has a separate mini amplifier that controls volume by amplifying the source input signal. The other way to think about it is that a passive preamp is like applying brakes to a car to control speed, and an active preamp is like using the accelerator to control speed.

Many of the discerning audiophiles prefer a passive preamp as it does the minimum amount of manipulation or interference to the source audio signal. As you can imagine, the amplification that an active preamp provides will inevitably modify the sound in doing so. In fact, square_wave once posted about a preamp being sold on DIY Audio that uses a light dependant resistor to control volume - i.e. this type of a preamp even prevents the volume control mechanism (pot) from introducing additional noise. That's as pure as it gets.

On the flip side, many people prefer the way the pre-amp colors or modifies the sound. I guess that's why a tube (or Class A) pre-amp is preferred by many along with a solid state power amp - the tube provides warmth to the sound, and the solid state power amp provides decent power levels. In the Pune HFV meet, from what I read, the Nelson Pass preamp got extremely good reviews.

Anyway, long story short, I just wanted to share my personal experiences with you regarding preamps. In my case, I chose an active preamp as I didn't want to lose signal quality. Adding an Emotiva preamp was a night and day difference - it hugely increased the audio quality, and in many Floyd songs, I could hear levels of detail I didn't even know existed! It is a highly detailed and resolving preamp, especially for its price. It is also built really well.

 

[kneo]

Extremely informative thread about the various aspects of the stereo chain. Even though it has some information about Pass B1, can someone explain 'buffer' in simple terms?

 

[heliumflight]

I like to keep the chain simple as possible and have opted to connect HTPC directly to Luxman power amp M-06A which have L and R attenuator controls. I agree with this kind of setup, I have to increase the volume knob a notch higher.

helium= HTPC Asus Xonar ST + Sansui Au-317 + Luxman M-06a + Magnepan

*For sale: Polk Audio LSi9/ Vintage B&W Dm4/ Cdp-CA 640c V2

 

[vijwilso]

I have a integrated amplifier with the passive pre-amp stage , just a volume attentuator .
Amplifier spec :
Input Sensitivity : 250mV
Input Impedance : >14K Ohms, line input

Source ( DAC )Spec : Not published , the data below is from Sterophile measurement for 1 Khz tone
Ouput level : 1.86V
Output impedance : 0.65 ohm

Is the pairing ok ? Sorry if this was covered already.