Passive Preamp?

[Reverend]

There are many variations of litz wiring, the stuff I used was a bit of an overkill.  You really don't need that thick of wire (I used 16 gauge, 20 or 22 would be fine) but I really recommend using it or silver.  You can get a 6' piece of silver wire for around $25, that might be another option. 

I got the knob I ordered in but it's a little big.  I kind of like it but will look at smaller ones.  (sorry for the crappy pic).

[RuralTom]

I dunno, Ryan, that looks pretty cool.. kinda in the same ballpark as the amp bmw posted.

[Reverend]

I just ordered this one, it's about .75" smaller in diameter.  I dig that amp, very cool design.

[OldiesButGoodies]

I hear good feedback on Rev's passive and look forward to listening to it first hand. 

For anyone considering cooking their own as well:  the pot that Rev used is 100 Kohms,  not 10 Ks (Rev - maybe update the diagram to include that spec?)

[schwarcw]

Rev, you've got a great looking knob! 

[schwarcw]

That pot Pepe gave you looks excellent!  I was surprised that it was only around $35.  My buddy replaced his volume pot on a Krell preamp.  It was crazy how many steps it had, cost around $150 or so if I recall.

[OldiesButGoodies]

I was able to audition Rev's passive preamp this weekend.   It is possibly the best pre I have listened to so far. The cleanliness of the sound,  tight imaging,  soundstage - etc.  [I know all those sound like cliche terms - but in this case they actually apply without reservation] are vastly improved. 

This almost makes the case for having a passive pre [like this one] in the path to the power amps after your "regular" pre. As Rev & I discussed - you can almost leave the volume pot out and just have a switch box wired w Litz to switch in the right output (probably your DAC) to the power amps,  since most software control volume digitally anyway. Rev has the Melos going into the passive as an input to use the phono pre,  so in a way he is doing that.

The sound was great - I could have listened to that setup for several hours.  This also speaks to the potential of the Carver ribbon paired with a decent woofer in a cabinet,  and the cleanliness of the ECS-U holography processor,  assuming that it was online while auditioning.

Pepe

[bearjew]

I was able to audition Rev's passive preamp this weekend.   It is possibly the best pre I have listened to so far. The cleanliness of the sound,  tight imaging,  soundstage - etc.  [I know all those sound like cliche terms - but in this case they actually apply without reservation] are vastly improved.

Agreed; it really brought the sound to life.  It's cool because with an invisible pre, you can get a feel for how the amps actually sound, uncolored by anything after the source before the amps.  The sound stage was so much bigger than it was with the melos; I didn't feel like I needed to sit in the "sweet spot" in order to get a feel for the sound.  i am kind of compelled to make a passive pre, but it isn't feasible in my current setup, so that'll maintain being on the backburner for a while.

[Anders]

Passive preamps don't work well if you have long interconnects.
The capacitance of the interconnects rolls off the highs.
Thats why I use a tube preamp with a cathode follower output which lowers impedance  so it can drive the long wire without rolloff.

[rgpit]

Passive "preamp" is kind of a misnomer. It actually is not a preamp but an input selector with an attenuator. There is no amplification.

[ataudio]

Hehe...."Pre"amp......as in "before" the amp. 

 But I certainly understand the conventional nomenclature and what people
expect when someone says preamp.  But it is surprising how good they can perform
for such a small investment.  Everyone should try one at least once. Properly executed
they excel in openess , zero floor noise, etc.  Short of pushing long interconnects they easily
beat most mid-fi preamps. IMO anyway. 

[rgpit]

You're right.....my bad

[MacGeek]

When my last preamp crapped out on me, I temporarily connected my CD player, which has a volume control, directly to the power amps while I shopped and waited for a replacement.  That's when I realized what a pre-amp can do to or for the signal path (this comparison convinced me I should be happy with the replacement pre, by the way)

Why not simply connect source components with an output level control (my R2R, cassette deck, tuner and CD player have variable outs) directly to a switch box to eliminate the attenuator and achieve the same, or even better result? 

A Niles TSB3 used as a switcher adds tape loop functionality.  Some DATs have a variable out.  I imagine finding a phono pre with a variable out may be a challenge, but a standard preamp with phono can serve the purpose for LP playback.

[OldiesButGoodies]

Ron was pawned on this one  . 

I would have never imagined the difference to be that great between a regular pre and a passive.  but take note - the passive requires a bad ass power amp.  Ryan has the Carver 305s -  that gives him enough power to be fine with the lack of gain in the pre. You cannot get away with that with lesser amps.  And still he does not get crazy volumes - at 90% throttle he is getting decent but not crazy volume levels.  Your results may vary depending on the efficiency of the speakers.

Still, what volume he is getting is pretty dang good sound.

[MacGeek]

OBG-good point.  The ability to max the power amp will depend on the source voltage.  I find, however, that I seldom get above unity gain (0db) when adjusting the pre amp volume, and I do occasionally like to play it loud.