[jesserparker]

hi,
i've been thinking a lot lately about passive preamps and after reading just about anything i could find on them, or active versions, tubed and solid state, i think i may have found the ideal solution here.  check out this link, besides looking like one hell of a good idea, its a good read, make sure to read the mods section afterwards too.

http://www.stereophile.com/showarchives.cgi?54:0

anyhow, if anyone has built this, or knows anything about this design, or has any particular thoughts on it....  let me know,

jesse

[JohnR]

I still don't understand how people can call a preamp with an active circuit in it a "passive" preamp...  

That's a bit like calling my car a motorcycle... with two extra wheels  

Oops, sorry, I don't have anything actually useful to offer on this one

[jesserparker]

this is very true, its not so much passive, but i suppose it simply refers to the fact that it doesn't amplify the circuit in any way, which then begs the question "why call it a preamp?"
anyhow, on the plus side you can dumbfound all your friends when you show them your "passive" pre-amp that plugs into the wall.

[randytsuch]

I saw a post on this in the tweak section of AA a little while ago.  Someone was looking for parts for it, and someone else commented on how good it sounds.

Sometime this year, I may build a somewhat similiar circuit designed by Stan Warren, it's a simple FET buffer circuit which you can use as a preamp.

Randy

[jesserparker]

I still don't understand how people can call a preamp with an active circuit in it a "passive" preamp...  

That's a bit like calling my car a motorcycle... with two extra wheels  

hey look, a motorcycle with four wheels!  and right here on audiocircle

http://www.audiocircle.com/index.php?topic=1818&highlight=

ain't that some shit?

[Pez]

                 

[JohnR]

Darn....    

I'm speechless (for a change)  

[Vinnie R.]

this is very true, its not so much passive, but i suppose it simply refers to the fact that it doesn't amplify the circuit in any way, which then begs the question "why call it a preamp?"
anyhow, on the plus side you can dumbfound all your friends when you show them your "passive" pre-amp that plugs into the wall.

If this "passive" preamp is plugged into the wall or uses batteries, it is NOT passive at all, it is a 0dB gain preamp.  It IS a preamp.  It is a buffer, so while it doesn't have voltage amplification, it does have current amplification (ie, it can provide more current to the load than the source can by itself).  Therefore, it increased the signals power and has active devices, so it is a preamp.  

-Vinnie

[jesserparker]

yes, yes, yes
i know this.

the reason i refer to it as passive is that in the original article it referred to the design as a "buffered passive" design, and the reason they did this is because the article starts off with the author trying to improve upon a passive preamp's downsides, and then resulted in simply adding a buffer into the circuit, so the design is a passive design "in spirit".  really, i would call it neither.  the volume of the circuit isn't amplified, yet it does have electric circuitry.  however, all that does is modify the impedances to present a better electrical interface with the power amplifier.

jesse

[Vinnie R.]

the volume of the circuit isn't amplified, yet it does have electric circuitry.  jesse

Yes, the signal in is current amplified, but not voltage amplified.  
Power Out > Power In, so it  is active without a doubt.  

Dact makes a CT101 preamp that is the same type of idea.  

A passive preamp doesn't not contain any active components and does not provide any POWER gain.  

What may be confusing to some it that a passive preamp could provide voltage gain, or current gain, but NOT both    This is so by using a transformer.