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-   -   Pré amplifier is not needed!.... thread to discussion (http://www.diyaudio.com/forums/solid-state/151197-google-page-rankinge-amplifier-not-needed-thread-discussion.html)

destroyer X 5th September 2009 08:10 PM

Pré amplifier is not needed!.... thread to discussion
 
Do you agree?

We will need for phono...for sure...but all other audio sources are strong enougth to drive a power amplifier.

Theorical folks.... this is for you....have fun!

http://www.youtube.com/watch?v=VOJ4S9aTCPY&NR=1

regards,

Carlos

AndrewT 5th September 2009 09:03 PM

A pre-amp is required to interface the source to the receiver.
It can have gain or pass on the signal substantially unaltered.
It can have an attenuator.
It can have some form/s of EQ and/or filters.
It can receive and distribute many signals.
It should send on the signal irrespective of the loading of the receiver and connecting cables.

coloradosound 5th September 2009 09:22 PM

May not need a preamp with modern sources for gain per se, but a flexible, high
quality control unit is always helpful. (Switching, any other imaginative signal routing
options, volume, balance control. But at least some form of electronic buffering
helps with impedence/load interface problems presented by the volume controls.
And as Andrew mentions, other so called "non-audiophile" approved functions.
(I like some tone and loudness compensation, myself!)

farjon 5th September 2009 09:57 PM

I agree with AndrewT and Colorado's viewpoints. Pre-amp is a matter of personal taste, too. I'm used with loudness compensation, too, and you can have (or build) a unit with bypass options.

destroyer X 5th September 2009 10:22 PM

Interesting points of view about pré amplifiers...all respectable guys with
 
respectable ideas... despite have not my agreement, i love to have you here.

Don't you think we can survive without them, or to use some passive thing having switches and connectors?

regards,

Carlos

Ragnwald 6th September 2009 01:54 AM

That small voltage coming from any modern audiosource opamp TV, CD, DVD, Blu-ray player, etc, does certainly not need any extra-amplification to drive any modern poweramp to full output power.

Anyone worried of impedance missmatch, can use a constant impedance attenuator. Now we are speaking nonballanced home hifi and short cables.

Perhaps it´s time to rename preamp to just controllbox. The pickup-amplifier can ofcourse be integrated.;)

destroyer X 6th September 2009 08:57 AM

Thank you Rangwald.... that's my point of view too.
 
Farjo..... really the loudness is something not easy to have without a pré amplifier.

But.... we use loudness contour when we want to play low volume, to compensate audibility losses into deep bass and high treble.... we can also increase volume...this way loudness control will not be needed anymore.

A passive pre amplifier, or a "control box" may be more interesting....not having extra stages we will avoid the disturbances created/produced by those circuits.... one or two less circuits inside the audio chain can help you to reproduce a better audio... a more realistic thing.

Thank you Farjon, by your contribution to this thread.

It is interesting as non needed things, or, something we can avoid, is so widely used, and example is the AC voltage regulator, the step down voltage regulator we use together our computers.... only in Brasil people use that...absolutelly not needed ... the computer switching power supply is many times better than the AC stabilizer to face voltage variations and mains noises..also the computer can work into 220VAC and 110VAC.... a non needed thing those autotranformers we use, with plus and minus 20 percent regulations...and we brazilians, feel afraid not to use that not needed thing.

I have abandoned that use 15 monthes ago, and everything is working fine here...no more clicking relays while switching auto transformer taps...the computer's switching power supply is doing all the job without complain, and the fan second stage that enters when the supply is overheated is not beeing called to work..so..the computer's supply is working cool.

This stupid thing is our invention Farjon....only in brazil (i think) such kind of thing is used... around the world, people is plugging their computers directly ito the mains outlet.

In the reality i have one used...but i have removed all internal circuits and transformers..i am using the case and the output plugs.... it is now just and extension cable with a male and several female plugs..and the switch is used... a case with an input cable and output plugs to feed monitor, CPU and audio amplifier only.... the mains ground and plug polarity is guaranteed this way.

regards,

Carlos

Andre Visser 6th September 2009 09:27 AM

Quote:

Originally Posted by destroyer X (Post 1916910)
A passive pre amplifier, or a "control box" may be more interesting....not having extra stages we will avoid the disturbances created/produced by those circuits.... one or two less circuits inside the audio chain can help you to reproduce a better audio... a more realistic thing.

In theory, I agree with you but I've tried a few times to connect a CD player directly to an amplifier and each time I lost some dynamics and detail compared to using a good pre-amp. Of course one can argue that you can build the same driver stage into a CDP but that doesn't seem to be the case in normal commercial equipment.

Calvin 6th September 2009 10:13 AM

Hi,

amplification is the last thing You need with modern highlevel outputs.
You just have to care for a lowish and constant output impedance of Your volume control circuitry (which discludes the use of a simple pot as prime solution). I use active circuitry only (it can be switched into the signal path via IR-remote) to symmetrize a signal and/or if a bit of gain (+6dB) is needed with older signal sources and of course for phono.
So You can compare realtime and with exact the same volume what happens when switching from passive to active ---> passive always won :p
(with only 2-3 first class resistors in the signalpath at normal listening levels----how could You get any closer to a piece of wire??)

jauu
Calvin

destroyer X 6th September 2009 10:16 AM

Interesting....so...you have lost dinamics.
 
1 Attachment(s)
It seems your CD output is high..and the power amplifier sensitivity has compressed the audio level..this way peaks does not appear.

Maybe a better adjustment into the power amplifier sensitivity can avoid that.

I suggest you to increase your gain adjustment resistance and to give another try..double your gain resistance value and check if you have this effect/deffect.

The increase in the gain resistance ohmic value will decrease the sensitivity..this way the amplifier will be able to face 1.5 to 2 volts rms....or..will need 1.5 to 2 volts rms to drive the power amplifier full power without compress/control audio level.

Another way is to produce a voltage divider.... for instance, loading the CD output using two 27K ohms resistance in series..from the live output wire to ground..then you pick the audio to the power amplifier between those two resistances and ground...this way you gonna insert half voltage into the power amplifier.... sometimes reducing the CD player output volume can fix that..sometimes not because of dinamics.

regards,

Carlos


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