[WireNut]

Do we need a preamp that increases gain?

 
 

[Davey]

Maybe, maybe not.  Your question is meaningless without knowing the particulars of the system said preamp will be used in.

Dave.

[WireNut]

Maybe, maybe not.  Your question is meaningless without knowing the particulars of the system said preamp will be used in.

Dave.

It's just a general question to get a feel of how folks feel about the need for gain in a preamp.

[avahifi]

Well, if it does not have the capability to increase gain, then its not a preamplifier at all, because it cannot amplify.

If that is the case, it might be better called "a volume control in a box". 

Frank Van Alstine

[Davey]

Well the "gain" could be current gain and not voltage gain.  Also, gain could be negative and still considered voltage gain. 

Regardless, the original query is still impossible to answer.  Sometime you want/need gain in a preamp and sometimes you don't.

Dave.

[G Georgopoulos]

Well the "gain" could be current gain and not voltage gain.  Also, gain could be negative and still considered voltage gain. 

Regardless, the original query is still impossible to answer.  Sometime you want/need gain in a preamp and sometimes you don't.

Dave.

Davey man your post is impossible to follow,negative gain,current gain,impossible to answer,tell us more!!!
gain in a preamp is not bad at all!!!

[G Georgopoulos]

Well the "gain" could be current gain and not voltage gain.

Dave.

Actually is both!!!,current gain into a resistor translates into voltage gain!!!

[Davey]

Davey man your post is impossible to follow,negative gain,current gain,impossible to answer,tell us more!!!
gain in a preamp is not bad at all!!!

If you have speakers that are 100db efficient and a power amp with 32db voltage gain, is voltage gain in the preamp "not bad at all?" 

Dave.

[G Georgopoulos]

If you have speakers that are 100db efficient and a power amp with 32db voltage gain, is voltage gain in the preamp "not bad at all?" 

Dave.

There is always a volume control to play with!!!
It also depends on the input sensitivity of the pwr amplifier!!!

[Davey]

My point is the volume control becomes a hair-trigger switch in that instance.  The useability of the preamp becomes pretty tedious in that case. 

I mentioned a 32db voltage gain amplifier.  Sensitivity is a rather meaningless specification since it refers to rated output......which might be anything.  Voltage gain defines accurately the power amp's contribution to the gain structure of the system.

Cheers,

Dave.

[*Scotty*]

I have the potential"Hair Trigger Switch" Davey refers to. I have a second preamp with 14dB of gain and an amplifier with 26dB of gain with a input sensitivity of 1 volt in for 110 watts/8ohms at full power out. This combined with speakers having a sensitivity of 1 Watt for 96dB output equals an unusable system. The "preamp" that is actually used in the system is a buffer with zero gain.
 The preamp with 14dB of gain would be usable in a system with speakers in the sensitivity range of 86dB to 88dB. With the aforementioned speakers of lower sensitivity another 6dB of available power would also be useful to avoid clipping.
Scotty   

[G Georgopoulos]

Actually, you need a preamp to increase line level from (ie vinyl) to cd level nowadays...

[Davey]

Obviously vinyl requires a preamp/EQ to achieve line-level.  That's not (I believe) what the OP was referring to. 

He's referring to the line-level portion of a typical preamp unit.  Much depends upon the voltage gain of the power amp, source level, and speaker sensitivity, but I find a line-level preamp voltage gain of about 6db is usually optimum.  This gets the volume control in a good position for most playback yielding better volume fine-tuning and (usually) more accurate tracking between left/right channels.

An example of a poorly conceived preamp is an Audible Illusions Modulus 2 I recently repaired for a fella.  This preamp has too much gain in the line-amp section and not enough gain in the phono section.  (It also has dual-mono volume controls.)  It works okay when playing vinyl but is horrible when using the CD player.  Settings above 9 o'clock are never needed and it's nearly impossible to match left and right channels.  A real engineering masterpiece. 

Cheers,

Dave.

[G Georgopoulos]

A preamp with gain will do miracle in the pwr amp nfb factor...

Saved the best one for last...

[Davey]

Saved the best one for last...

You certainly did.  I have no response to that. 

Dave.

[Quiet Earth]

It's just a general question to get a feel of how folks feel about the need for gain in a preamp.

I think in general, music has become louder within the recording, and preamp design has not changed very much to accomodate that. A preamp that was designed before 1985 (like the Audible Illusions mentioned) was not ill-conceived. It was designed with phono as the primary source, and then tape and tuner. CD was still auxiliary and most of your CDs were recorded no louder than -20dBfs peak anyway. So it didn't really matter if your CD player could put out high line level voltage. You could use CD with your preamp and still have some useable range on the volume control.

This is not the case today. We use digital source components with high gain stages and strong output voltage capacity, which in turn play hot recordings (always at 0dBfs peak and often compressed). Most of these dacs are robust enough to drive a power amp on their own. There is no need for more gain in this scenario (an active preamp). Yet put on an original CD of Livin' on the Fault Line or Joshua Judges Ruth and maybe you wish you had just a few dB of gain from your passive volume control. Or put in a cassette on the old tape deck or play the old phono stage and there you go, you need some gain. (Not much though.)

I think we have increased the span of dynamic range in our source components but we still haven't decided if we need too much or not enough gain from the preamp. There was a mention of 6dB of gain being perfect for an active line stage. That sounds nice, but all I ever see is 12 to 18 dB. Even from companies that use step down transformers. There is no standard and the sources keep changing.

[mrlittlejeans]

+1

[Davey]

Qe,

Yes, good points.  I didn't realize the Audible Illusions Modulus 2 vintage was that far back.
However, looking at their newer units, it appears the same gain structure remains.  The line amp stage is 30db and the phono section is 28db!  I just don't see the wisdom of that unless the mated power amplifier is really low gain.  The Modulus 3B must be horribly user unfriendly when volume setting for sources on the high-level inputs.  Maybe they've changed the taper on the potentiometers to make it better?

http://www.audibleillusions.com/products/modulus-3b-full-function-stereo-preamplifier/m3b-specifications/

Cheers,

Dave.

[mrlittlejeans]

The L3 linestage has dual attenuators that allow you to set channel balance very well and cut down some source gain.  The volume control is a single volume knob.  I have found it very useful for giving me decent volume range on various recordings.  I also had a Modulus 3A and didn't have problems with having limited use of the volume controls though I prefer a remote controlled single volume control.  In the old days before I had all of my music streaming from a server, I could get up and adjust the volume when I changed a cd. Now, I'm sitting in my chair and controlling the playlist via a tablet or phone and switching rapidly between artists and albums so I need to change the volume more frequently and dislike manual dual volume controls.

[bummrush]

Well hope i have this correct. Im using mine at unity gain so as i know it is essentially using it with no gain.Speakers are 6 ohms and 87 sensitivity.Also i can add gain if i feel i need it but rarely use i can use up to 18 db as i understand.Works very well this way.