Passive/Active preamps: pros and cons....


New to preamps...what are the advantages/disadvantages of passive or active designs? I will be only connecting one source (CD) to the pre...any thoughts? passive/active switch like the highly reviewed Adcom piece? any others come to mind? Also...in an active design...how much emphasis does the pre have in regard to the main amp signal?
0af4f876 eb83 4323 a292 3564f9bafea1phasecorrect
There's a certain group that advocates passive pre's because they do not "color" the sound - it's like the pre is a volume control and that's it. I've read good things here about the McCormack TLC-1 (see http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1081433013&openfrom&1&4#1 for a discussion of McCormack's gear). There seems to be a consensus that you cannot use long cables with passive pre's. Those who do not like passive pre's usually claim they lack the dynamics of an active pre. I've read several threads that indecate passive preamps don't even have to be plugged in to work. I've never heard a passive pre, so I can't say much about them.

Active preamps act as a buffer and tend to be more lively and dynamic, but most add or subtract something as all electric components seem to do.

I tried to find resources on the web that directly compared the two, but wasn't successful. Others here will be able to explain the differences in detail though.

Good luck!
If your system is passive friendly (amp with high gain, low input sens., appropriate source, and reasonably efficient speakers) then there are absolutely no drawbacks at all to my ears in using a transformer based passive attenuator. I have a custom preamp using S&B trannies and it has bettered many other preamps, mostly tubed and a couple of passives, in my system. It has the body and weight of a tubed device, but the transparency you expect of a passive. And hands down the best bass of any active preamp I have heard.

Oz
Passive preamps have some sonical benefits compared with active ones butat a cost, passive designs are very transparent, clean midrange reproduction units and closer to the thrith as for impact and attack of solo instruments (cymbals, woods and most of acoustic music foundation) BUT there is unfortunalty a lack of dynamics, continuity and exceptions of the above virtues when not properly matched thatmade me go back to GOOD active designs preamps.

My commetn would be, get a passive preamp (inexpensive) and don´t invest on an active until you are ready to go up in the dollar value.

Hope this helps

Fernando
I think the previous response has it nailed.
One option though, when faced with the same question I picked up the channel island $250 list passive and gave it a try. If you don't like it you shouldn't lose much on resale. I found it a quality component and playing with it was a good learning experience.
FWIW, my system ended up in the 'mostly sounds better but lost dynamics' catagory and I went looking for an active that otherwise sounded like a passive.
Good luck! (And no I ain't in cahoots with Channel Island.)
If you are going the passive route, I highly recommend the Placette RVC for you. If you need more inputs, then get the 3 input version (PLC). I went from an Audiolab 8000C which is an active pre to the Placette PLC and the Placette was by far better than the Audiolab. It sounded better and didn't lose dynamics. With the Placette, you don't have to worry about the whole impedence matching as much just a long as you have a solid state source and a decent amp. I've tried a Belles Hot Rod and Audiolab amp and haven't any problems yet. If you are concerned about if you are source and amp are good match, give Guy Hammel a call. He is very helpful and knowledgable. He has a 30-day trial period so if you don't like the RVC, you can return it to him.
HI.
I'VE USED THE PLACETTE PASSIVE, BENT AUDIO W/SILVER S&B TRANSFORMERS, EVS ATTENUATORS AND TWO ACTIVE PREAMPS, THE ARC SP 10 & FIRST SOUND DELUXE MKII.
BETWEEN THE TWO PASSIVES, THE BENT AUDIO PROVIDED FULL & IMPACTFUL BASS-THE PLACETTE WAS WHERE DID IT GO. THE PLACETTE WAS A LITTLE BETTER ON THE TOP END. THE BENT AUDIO WAS BETTER IN LAYERING.
WHEN COMRING THE BENT AUDIO TO THE FIRST SOUND, MOST AREAS WERE REMARKABLY CLOSE, DETAIL RETRIEVAL WAS BY FAR BETTER WITH THE BENT AUDIO. DETAILS THAT WERE OBSCURED BY THE FIRST SOUND WERE CLEARLY HEARD WITH THE BENT AUDIO.
I FELT BASS RESPONSE WAS EQUAL.
AT FIRST, I FELT THE BENT AUDIO WAS COMPRESSING THE SOUND,
SOMEWHAT RESTRICTING IT WHEN COMPARING TO THE FIRST SOUND, BUT LATER I REAILZED THAT THE FIRST SOUND HAD A FINE GRAIN RIDING ON THE SIGNAL THAT MADE IT SOUND MORE LIVELY (SOME WOULD CALL MORE DYNAMIC).
ALL COMPARISONS WERE MADE USING SAME RCA TYPE IC'S.
WHEN I WENT BALANCED, THERE WERE SMALL "BUT I WOULDN'T GO BACK TO RCA" IMPROVEMENTS.
Agree with Ozzy, passive in a system that takes advantage of it's (passive) advantages is very hard to beat.

I had a passive (using S&B trannies) also and the sound quality was steller in every area.

A system/room change led to much less than ideal conditions for the passive so I sold it and moved back to active.

I wound up going to my first tubed active pre-amp (Audioprism Mantissa) as I could not find an active SS design I could afford... or listen to for very long...outstanding mid-range quality will spoil you and is something the passive brought to my system...much like the almost passive Mantissa does.

Dave
I have a S&B TVC, agree with Ozzy62, and find the passives “lack of” perception is more like passives “don’t add” dynamics, colorations, etc. of active pres.

Compared to running direct - the TVC adds a tube like liquid, warm feeling in the mids, the highs smoother or slightly rounded, and pace more relaxed. The alteration are very, very slight, and much less than the actives I’ve tried, but not absolutely invisable either. Everything else seems untouched.

I haven’t compared it to many actives and would be interested in comparisons from others – like Ramses.
If you are a candidate for a passive then by all means get one. If your CDP has enough output at a low impedence and your amp is sensative with a high input impedence it should be fine. I connected my CDP direct to my amp and it has too much output and would have overdriven my amp on all CD's (no two CD's are recorded at the same level) What this means is my former active tube preamp (now retired) was really acting as an attenuator. Everything got better with it out of the loop. It was a very nice modded CJ pre. My CDP is also nice an MF Trivista which has a very hefty low impedence output. In my opnion many CD players do not qualify for passives. Try connecting yours to your amp direct first and see. Have a CD that starts out quiet and your remote in hand ready to push the stop button if it overdrives your amp. If it does not overdrive at anytime and say only produces a moderate volume level you are not a candidate for a passive. I use the Placette and love it. It sounds no different than with my CDP connected directly. I reburned some CD's @ -10db to do lengthy testing before switching to passive. I like Placette and the company is really great. I have tried a few other passives and did not like them as well. I would like to try a Bent which is TX-102 transformer based compared to Placette's Vishay resistor ladder. I think I would not like the high end but am open to anyone who wants to lend me theirs for evaluation. The Bent and other transformer based passives actually have about 6db gain, so I have read, the TX-102 is a step up X-former. Good luck!

ET
Electroid, it is precisely because most cd players are capable of driving amplifiers to full output that the Placette Passive was made. Unless it was simply a typo, I'm wondering why you think that most CDPs are not "qualified for passive". There's a reason why Placette decided to put in finer volume steps in the lower volume ranges. In most systems and sources, the Placette passive has more than enough gain.
Howie -- maybe he means that the volume controls contained in the cdps are not very good?
There seem to be many S&B users here. BTW, the 102 is NOT a step up, it ust has a +6 output tap on the secondary that one may or may not use (I, for one, don't).

The basic premise is simple: IF the source (cdp) has a reasonably low output impedance (mine has 22-50 max ohms) and the load is sufficiently benign (10kOhm or higher), then you're set for a wonderful musical journey. If the load is lower than ~7kOhm and the source impedance is high, then dynamics suffer... i.e. you;re losing energy across the "transmission line".

There's really no reason for an active line level device unless you need the buffer effect. Things are different when it comes to a phono (there, you need the extra amplification)!