Are your running a passive pre

heiney9

I recently aquired a pre-amp that can run in both active and passive mode. While both modes (except for a difference in gain) are strikingly similar but I do notice a slight collapse of the SDA soundstage when running in passive mode.

For those of you with SDA's that have run both active and passive have you noticed this?

It seems all the musical information has close to the same amount of depth in passive as active except it's all pretty much contained between the speakers. Very little of the same information in active, which extends beyound the outer edges, seem to be as prominent in passive mode.

H9

Face

I'm currently running a passive in my den with a pair of Tannoys and the soundstage is wall to wall. I had a pair of SRS2's in my living room and with a passive there were no soundstage issues, but they sounded a little thin.

heiney9

I'm still experimenting but these are just my first initial impressions. All the reviews state the actve vs. passive there are only very slight differences with many of the hardcore reviewers stating they prefer the passive w/ the active being very close.

The 750 is the typical Nelson Pass design all discrete, no opamps, single stage, class A, straight forward design and in both active and passive is about as close as you can get to no pre-amp at all. I was just noticing some of the slight differences between the 2 stages and wondering if since I had SDA's if that might be why I notice a difference.

Again more listening to a variety of music is needed.

H9

steveinaz

I hesitate to say this, but:

Not trying to hock my goods H9, but you should BUY my Placette---or buy a Placette. Seriously. I would love for you to hear this thing, and at my price you could turn it around quickly with no loss if you found it didn't fit your needs.

gdb

Newb here:D Whatsa passive pre, and how does it differ from an "active" one? Does it just pass the info w/out going thru tone controls and other features that modify the signal ?? (except volume)

steveinaz

Close. A passive has no gain. It simply runs the line level signal (via your source) thru a volume control (typically) and out to the amplifier. The idea is less electronics = purer signal.

Active preamps amplify the signal before passing on to the amp.

heiney9

steveinaz wrote: »

I hesitate to say this, but:

Not trying to hock my goods H9, but you should BUY my Placette---or buy a Placette. Seriously. I would love for you to hear this thing, and at my price you could turn it around quickly with no loss if you found it didn't fit your needs.

Steve, it's tempting but with the purchase of the Aleph 30 and the GFP-750 I've exhausted my current budget. Plus, the remote and balanced in's/out's on the 750 are a huge plus.

This pre is the closest I've come so far to not having a pre at all. Perhaps after I recover a bit financially the Placette could be an option if for no other reason than to hear it perform.

This GFP-750 is everything and more everyone has said about it over the years. Both it and the Pass Aleph 30 have given me a whole new level of pleasure.

H9

gdb

steveinaz wrote: »

Close. A passive has no gain. It simply runs the line level signal (via your source) thru a volume control (typically) and out to the amplifier. The idea is less electronics = purer signal.

Active preamps amplify the signal before passing on to the amp.

Gotcha,thanks for explaining that and for your kind patience with a troublesome newbie !!

steveinaz

heiney9 wrote: »

This GFP-750 is everything and more everyone has said about it over the years. Both it and the Pass Aleph 30 have given me a whole new level of pleasure.

H9

No problem at all, just thought I'd throw it out there. I've never heard the 750, but I'd bet it's a CLASS ACT; that piece gets excellent reviews.

steveinaz

gdb wrote: »

Gotcha,thanks for explaining that and for your kind patience with a troublesome newbie !!

No problem home biscuit.

Face

A passive is basically a volume controls, sometimes with a source selector and/or buffer stage. As Steve stated, it doesn't add any gain, less coloration, and less distortion.

Here is a passive pre with a stepped attenuator volume control.





Sorry for the derail Brock.

tcrossma

I don't have SDA's so I can't comment on your question specifically, but I have run my 750 in both active and passive extensively, and honestly both sound almost identical. Soundstage, depth, and imaging don't really seem to change between them. I think maybe that the midrange is a little more forward in active mode, but not by much.

The one issue I have with active on this pre is that the gain is just too high for the remote to be usable. In other words, one click UP on the volume on the remote turns the volume up a ton. In passive it does this to an extent too, but it's much more usable. I run mine balanced to a Pass X-150 amp, but using single-ended from my CD player (at least until I can upgrade my CD)

Still though, I sometimes flip back and forth between active/passive for experimentation. But both sound good.

heiney9

Face wrote: »

Sorry for the derail Brock.

Not a problem . The GFP 750 basically routes the signal from input to selector (via realys) to vol control, no buffer, no balance, etc.

When active there is just one gain stage which is class A. The selectors are actually run by relays (20 of them) not switching I/C's and no muting transistors either. The Adcom has a potentiometer for volume instead of stepped attenuator, and has a balance control which is an elegent modifier of gain, meaning it never quite mutes the L or R channel when at the max position for either side.

This unit is very, very similar to the Pass Aleph P in design, with just a few minor changes (DC blcoking caps added in a couple areas). I don't believe the Alpeh P can be run in passive.....not sure though.

So far I'm loving it!!!

H9

heiney9

tcrossma wrote: »

The one issue I have with active on this pre is that the gain is just too high for the remote to be usable. In other words, one click UP on the volume on the remote turns the volume up a ton. In passive it does this to an extent too, but it's much more usable. I run mine balanced to a Pass X-150 amp, but using single-ended from my CD player (at least until I can upgrade my CD)

Still though, I sometimes flip back and forth between active/passive for experimentation. But both sound good.

I found that to be true also. I'm running my Pass Aleph 30 balanced but I also have an Adcom GDA700 DAC which can be run balanced. Both running balanced the gain is very high in active.........too much so. It's great for passive however.

I'm considering not running balanced at all. Nelson said something to me about running balanced being prefered by audiophiles because it cancels 2nd order harmonics..........I'm still trying to figure out why/how that is and how it affects the sound.

H9

strider

heiney9 wrote: »

I'm considering not running balanced at all. Nelson said something to me about running balanced being prefered by audiophiles because it cancels 2nd order harmonics..........I'm still trying to figure out why/how that is and how it affects the sound.

H9

Interesting. I have been under the impression that one of the reasons people enjoy tube amplification over solid state is because the harmonics are second order.

Personally, I didn't notice an issue with the soundstage when I had my passive in the mix with the 2B's. That shouldn't hold a great deal of weight, however, because it was just for a short time when I was demoing the MIT ICs and speaker cables awhile back.

heiney9

strider wrote: »

Interesting. I have been under the impression that one of the reasons people enjoy tube amplification over solid state is because the harmonics are second order.

Personally, I didn't notice an issue with the soundstage when I had my passive in the mix with the 2B's. That shouldn't hold a great deal of weight, however, because it was just for a short time when I was demoing the MIT ICs and speaker cables awhile back.

That's what I thought too. Actually he was sort of saying it tongue in cheek. That's why I may stay single ended because I like the presentation of the 2nd order harmonics. I still have lots of experimenting to do with cables, passive/active or balanced/un-balanced.

H9

Systems

wrote:

Nelson said something to me about running balanced being prefered by audiophiles because it cancels 2nd order harmonics..........I'm still trying to figure out why/how that is and how it affects the sound.

Being as it's single ended the THD will be mostly of the even order variety and running balanced will cancel much of this.Balanced single ended will result in both less even and odd order harmonic distortion.

heiney9

I can say that for some things it sounds great in Passive but others need the "help" of active. It ALL has to do with the recording. In passive mode you are basically hearing it as close to the recording as you can get. In active there is a bit of "sparkle" added as well as s slight, very slight broadening of the soundstage as well as bringing some of the vocals a wee bit forward in the soundstage.

It's nice to be able to choose between active and passive as it opens up a whole new listening experience for many recordings.

This is a REALLY nice pre-amp.........if you like things dead neutral and pretty much don't like having a pre-amp in the circuit at all......it's that transparent. Which is good and bad depending on the recording quality of what your are listening to.

H9