AudioNervosa
Systemic Development => Amplification and Preamplification => Topic started by: miklorsmith on March 14, 2007, 07:49:52 AM
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First Watt's new F4, an amp with less than 1 db of gain:
http://www.6moons.com/industryfeatures/f4/f4.html
My setup with an active preamp can be Very high on gain. The Definitions are so efficient that my old setup with Modwright preamp and Clari-T amp (average "typical" gain) couldn't get to 9:00 on the volume dial.
Does anyone understand how an amp could be zero gain? My caveman understanding is that amplifier means gain by definition. Obviously, that's wrong.
Is this concept interesting to anyone but me?
Mike
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I was thinking exactly the same thing when I read the thread title. By definition, and amp's JOB is to provide gain.
Bryan
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Sure. Nelson Pass is no fool though. I may not understand what he's doing but the idea is really cool.
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What other things does an amp do to a low level signal besides boost signal voltage?
>Buffer, lower impedence
>Improve dynamic resolution, which is not visible on 1kHz tone measurement
>Add lovin and excitement to the sound
>A CDplayer PS cannot drive a speaker, but it would be nice if it could. F4 allows high sensitivity speaker to be driven "directly" by a linesource with up to 100watts of power.
The manual has more info:
http://www.passlabs.com/np/F4%20Power%20Amplifier.pdf
I have written about the zeroformers that I use on my speakers. They convert voltage from tube output to current for speakers, making both work much better together. They can be used in reverse, and until this post I never could figure why? They could take some of that 100W output and increase the voltage so the speakers with naturally high impedence play a little louder with F4.
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For an easy-to-understand discussion of gain, some of you may wish to read this:
www.transcendentsound.com/amp_input_sensitivity_and_gain.htm
(yeah, I know, it seems that's all I talk about these days... :lol:)
WEEZ
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Hi Guys,
I do not understand his point about lowering the gain of the preamp. By lowering the gain of the preamp, the same gain in the amp, so the same total number of stages in the system. Seems to me that if the preamp stage has more gain, with the same bandwidth, one could eliminate a gainstage in the amplifier and get better fidelity. One would still have the same, or near the same overall voltage gain.
Nice idea.
Otherwise it is a clear, easy to understand explanation. Good job.
Just a thought.
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Yup, that's probably what Pass had in mind with the F4, gainless power amplifier. Just provides current for mechanical load of the speakers. Leave voltage gain to upstream devices.
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Yup, that's probably what Pass had in mind with the F4, gainless power amplifier. Just provides current for mechanical load of the speakers. Leave voltage gain to upstream devices.
Yep, Nelson has a brilliant idea.
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Agreed. My contention all along is that most systems have more gain than is needed.
I'm no designer, but noise is inherent where there is gain...so having more than is needed is wasted in noise...no matter how little there might be.
But I'm prolly wrong.. :?
WEEZ
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Agreed. My contention all along is that most systems have more gain than is needed.
I'm no designer, but noise is inherent where there is gain...so having more than is needed is wasted in noise...no matter how little there might be.
But I'm prolly wrong.. :?
WEEZ
You are right on Weez. But there is more. It also has to do with u, transconductance, Rp, equivalent noise resistance as well.
A tube can have lower u, lower transconductance, higher Rp, and higher equivalent noise resistance,
and be much noisier than a tube with a higher u, higher transconductance, lower Rp, and lower equivalent noise resistance. So in that case, the higher gain tube has more gain and lower noise than the lower gain tube.
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I oughta know better than to get in technical discussions. You just went w-a-y over my head.
But I get your drift..
WEEZ
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I oughta know better than to get in technical discussions. You just went w-a-y over my head.
But I get your drift..
WEEZ
Sorry about that. Didn't mean to.
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I wish we had a smiley that had his head spinning off and flying away.
Hey WEEZ, on the bright side, we have 4 new vocabulary words to learn this week (month? year?). But when I google "u" I don't get very far. :lol:
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I wish we had a smiley that had his head spinning off and flying away.
Hey WEEZ, on the bright side, we have 4 new vocabulary words to learn this week (month? year?). But when I google "u" I don't get very far. :lol:
Hi Rich,
u, the "amplification factor". It is the ratio of a change in plate voltage divided by the change in negative grid voltage, effecting the same change in plate current. Most of the time authors will state, keeping the plate current unchanged. u = a greek letter. Most of the time I see Mu used.
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OK, now I get it. u, as in mu (pronunciation), as in something I once heard in math class, as in strike fear into my heart! If it wasn't related to tubes I would be in pure denial. Thanks Steve!!
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a, e, i, o, u! .....and sometimes y. (I remember that from school :shock:)
mu...not to be confused with yew...or is it mooo...I forget.
(sorry for the poor attempt at humor...I just got back from my wifes' family reuion picnic lunch :rofl:)*
WEEZ
*and no, there wasn't any booze