Stupid preamp question

[d-ray657]

How does your preamp control the volume of your power amp?

I just recently started using a power amp. I am using a NAD receiver's pre out as the preamp. The power amp has no volume control. What doesn't make sense to me, is that when there is nothing feeding back from the power amp to the pre, how does the preamp control amount of power the amp puts out?

I am confused, because if seems that, if a component (other than a phono) were to be directly connected to the power amp, the line out would be played at the amp's full volume. I have previously been under the impression that the preamp did not add to the strength of the signal, and if that is the case my assumption about the line out would be correct. Is it a misunderstanding of that portion of the preamp's operation that causes my confusion. I am not really inclined to run an experiment with a line in for fear of blowing a speaker. Can anyone cure this bit of ignorance?

Regards,

D-ray

 

[Jon_Logan]

The power amp provides a fixed gain. Whatever goes into the power amp gets amplified. Your preamp adjust what signal level gets into you power amp. from nothing to a signal large enough to clip your power amp.

 

[d-ray657]

The power amp provides a fixed gain. Whatever goes into the power amp gets amplified. Your preamp adjust what signal level gets into you power amp. from nothing to a signal large enough to clip your power amp.

What I am wondering is whether the preamp at top volume sends the same level signal as the line out of a component, or does it amplify or otherwise enhance that signal.

Regards,

D-Ray

 

[cdfac]

I am confused, because if seems that, if a component (other than a phono) were to be directly connected to the power amp, the line out would be played at the amp's full volume.

depends on what you mean by "full volume." as Jon says, an amp with no attenuators (which is true for most amps) has a fixed amount of gain. if your source puts out, say, 1V RMS and it only takes 1V RMS of input signal to reach your amp's peak RMS power (which is true for some amps with high sensitivity), then your quote above is true. but the amp only knows how take an input signal of _V and turn it into an output signal of A*_V, where A can be calculated if you know the dB gain of the amp.

it might be that A*_V is large enough that your amp is clipping, depending on how large the input _V is, or you might still have some headroom left, so you may or may not be at full volume without the preamp in the chain. but the preamp knows (virtually) nothing at all about the amp that comes after it, so does not determine the power output of the amp or volume you hear by itself -- you turn the volume dial, which adjusts the size of _V that the amp will see, and the amp takes it from there.

make sense?

 

[donberry]

depends on the preamp and the component. Without a preamp, hooking a source directly to the power amp, each may be different as far as loudness.
With preamps, each one may also have a different effect on the loudness as one preamp may have a different "gain" then another. Simply, gain in a preamp is just the voltage it supplies to the power amp, which in turn controls the loudness.

In my experience, a preamp is what makes or breaks my system. A good preamp is going to give you much better imaging, sound stage etc, which is why some are more expensive then others.

(sorry, I posted this at same time as above post which explains it all)

 

[cdfac]

What I am wondering is whether the preamp at top volume sends the same level signal as the line out of a component, or does it amplify or otherwise enhance that signal.

Regards,

D-Ray

this depends on your preamp. most preamps have gain, and some have a LOT of gain (over 20dB). this would mean that at full volume you'd be heaving clipping the amp on a high-level source like CD. with a low-gain preamp (3dB or so), you will increase the size of the signal but it might not be enough to clip the amp at full volume. passive preamps and buffer preamps (like the Pass B1) at full volume put out basically the same size signal that they get in from the source.

 

[FreeOrange]

You may want to look into the difference between passive and active pre-amps too. A passive pre-amp provides no additional applification, just signal attenuation. An active pre-amp does provide some gain in the signal path. (I think, perhaps some of the better versed members can add to this topic)

 

[FreeOrange]

EDIT: Beat to it!

 

[d-ray657]

Thanks folks, it is making making more sense. If I get it right, although there is a difference between gain and volume, increase in gain results in an increase in volume. Except with a passive preamp, the preamp will provide some gain in voltage to the amp.

I would also suppose, then, that a passive preamp would need to be used in conjunction with a phono preamp.

Regards,

D-Ray

 

[ev13wt]

^^ Correct.

 

[cdfac]

I would also suppose, then, that a passive preamp would need to be used in conjunction with a phono preamp.

only necessary if you insist on being able to crank the volume knob wide open. and in fact, many phono preamps will output a lower signal than a digital source, so you may actually want some gain from the preamp.

 

[d-ray657]

only necessary if you insist on being able to crank the volume knob wide open. and in fact, many phono preamps will output a lower signal than a digital source, so you may actually want some gain from the preamp.

I didn't state that very clearly. I was suggesting that if someone wanted to use a passive preamp, he would most likely need a phono preamp for the amp to even detect the turntable.

Regards,

D-Ray

 

[whoaru99]

Thanks folks, it is making making more sense. If I get it right, although there is a difference between gain and volume, increase in gain results in an increase in volume. Except with a passive preamp, the preamp will provide some gain in voltage to the amp.

I would also suppose, then, that a passive preamp would need to be used in conjunction with a phono preamp.

Regards,

D-Ray

A preamp can (and usually does) provide either attenuation or gain depending on position of the volume control. A passive is typically an attenuation-only device.

About the TT, yes, a phono gain stage before the passive would almost certainly be necessary to get any honestly usable volume (and the RIAA eq).

 

[donberry]

from wikipedia as they say it more succinctly then I could

A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for further amplification or processing. A preamplifier is often placed close to the sensor to reduce the effects of noise and interference. It is used to boost the signal strength to drive the cable to the main instrument without significantly degrading the signal-to-noise ratio (SNR). The noise performance of a preamplifier is critical; according to Friss' formula, when the gain of the preamplifier is high, the SNR of the final signal is determined by the SNR of the input signal and the noise figure of the preamplifier.

The preamplifier provides voltage gain (e.g. from 10 millivolts to 1 volt) but no significant current gain. The power amplifier provides the higher current necessary to drive loudspeakers.

 

[HighTopFade]

I'm new and have somewhat of a similar question. Other than looks, are there other cons to using a DJ mixer as a preamp? The mixer I plan to use is a 1985 Numark PPD DM-1900. If I remember correctly, Numark's PPD line is supposed to have better sound quality. Back it in the day, it just meant more expensive. Thanks.

*EDIT* New thread started as suggested.

http://www.audiokarma.org/forums/showthread.php?t=370608

 

[hesson11]

"Stupid Preamp Question"

There is no such thing as a stupid preamp.
-Bob

 

[whoaru99]

I'm new and have somewhat of a similar question. Other than looks, are there other cons to using a DJ mixer as a preamp? The mixer I plan to use is a 1985 Numark PPD DM-1900. If I remember correctly, Numark's PPD line is supposed to have better sound quality. Back it in the day, it just meant more expensive. Thanks.

Probably better to start a new thread, but most mixers I've seen have not had as good as signal to noise ratio or frequency response specs as a typical, good quality, stereo preamp. That said, I use a Yamaha MG16/4 mixer in my garage system where previously a Yamaha C-40 was used. I think the C-40 was quieter (bit less hiss, etc.) but in terms of basic sound quality the MG16/4 does a good job.

 

[JJJimmy]

Sorry for any highjack, but...

what, in general, is the best setting for your amp volume levels when paired with a preamp? In particular; I keep my B-2 speaker level pots straight up (half volume), which means my C-2a volume rarely goes over 10 o'clock. should the amp pots be set higher?

 

[Renzor213]

I've been running seperate's for year's, and really never looked back. A pre-amplifier is just that. Really the control center of your system, bringing low level input's, switching, tone control function's to a level the power amp can deal with. Reciever's can be broken down into three component's, pre-amp, power amp, tuner, just all in one case. Reciever's are o.k, just lot's of stuff jammed into a single case, so can be comprimises. No such thing as passive pre-amp's, just switch boxes with level control's adding load impeadance to the power amp input's. Nothing I'd ever use.

 

[rjag46]

pwr amp.

How does your preamp control the volume of your power amp? Just curious, Got a mitsubishi pwr. amp that does not have a volume controll. When i power her up the vu,s peg out? If i added the pre amp would the vu needles go back down?????

I just recently started using a power amp. I am using a NAD receiver's pre out as the preamp. The power amp has no volume control. What doesn't make sense to me, is that when there is nothing feeding back from the power amp to the pre, how does the preamp control amount of power the amp puts out?

I am confused, because if seems that, if a component (other than a phono) were to be directly connected to the power amp, the line out would be played at the amp's full volume. I have previously been under the impression that the preamp did not add to the strength of the signal, and if that is the case my assumption about the line out would be correct. Is it a misunderstanding of that portion of the preamp's operation that causes my confusion. I am not really inclined to run an experiment with a line in for fear of blowing a speaker. Can anyone cure this bit of ignorance?

Regards,

D-ray

Have a mitsubishi pwr. amp that has no volume controll. When powering up by itself the vu,s peg out?? Would adding a preamp take care of the problem of the vu,s pegging out?????:scratch2: