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  »  New  Reviewing preamps by imbeciles...  More toilet reading about preamps......  Audio For Dummies ™  Forum     1  31604  06-25-2006
01-25-2007 Post does not mapped to Knowledge Tree
Dominic
Montreal, Canada
Posts 69
Joined on 08-23-2006

Post #: 1
Post ID: 3545
Reply to: 3545
Passive line level crossovers - re:pre amp
Is there any abstract value to going for a preamp with a stronger output if you're using a passive xo at line level?
I'd prefer to answer this question myself but i really don't have the budget to be swapping amps.
How does a PLLXO interact with a non-powered pre, like an autoformer volume control?
What i'm thinking about here is that the common problem with speaker level crossovers is power compression, and while you remove that problem as the amp sees it you move it to a location where you have less grunt to overcome the crossover and possibly you end up with more effect. If this view has some validity, how does the interaction change going from an active xo in a box, to a first order discrete compnent, to a digital version? I think i need something explained to me, but i'm not sure what.
01-26-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 2
Post ID: 3553
Reply to: 3545
Where to stick my filter?

Dominic,

I personally do not believe into nether non-powered preamps nor into autoformers volume controls. In my world as soon a any voltage dropper begin to drive any cable it calls trouble. A volume radiating voltage divider or transformer should be sitting right next to its load and I basically accept it as a rule.

Now we add another level of complexity – a passive filter. The subject of passive line-level filter is very complicated and it is very difficult to make any generalizations. It all will be hugely deepening form the type of the filter you intend to use, the design on the input circuit of your power amp, the topology of your power amps, type of the cables and how you plane to load them and the design of the output stage of your source that drive all this thing. Everything should be observed in its unity and the filterer should be implemented in the way that it does the less damage. Ideally, and it is perfectly achievable the filer it will not do damage at all.

“The first order discrete compnent, to a digital version”?  Perhaps, but it is not my religion.  It is fundamental facts fact that digital can not filter signal, digital can delay but no filter. A first order is a simple filter and it is always there is a place where to stick it inside of amplifiers or somewhere else…

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-26-2007 Post does not mapped to Knowledge Tree
Dominic
Montreal, Canada
Posts 69
Joined on 08-23-2006

Post #: 3
Post ID: 3562
Reply to: 3553
Well that's pretty much what i was getting at
I had pretty much the same impression and I was wondering if it would be corroborated. Perhaps another poster might have further insight?
01-26-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,143
Joined on 10-12-2006

Post #: 4
Post ID: 3563
Reply to: 3562
Crossing over

My own experience suggests that it is possible to do speaker-level passive crossovers, but I must qualify that by saying that although I have put a lot into the crossovers themselves, and the wire,etc., etc., it has only been since I got the ML2s tuned into the system that I have gotten this level of reproduction with this type of crossover.  Previously, this type of crossover has eaten dynamics to an unacceptable degree, and I went back and forth between throwing more power at it and just living with a better-sorted, range-restricted sound from "better" but less powerful amps.  I have never thought to try passive controls "driving" passive crossovers, and nothing I have heard to date has made me want to try digitally-processed "crossovers", either.  This is why I asked the follow up question of your other post about digital crossovers for multi-way horns, because I am still waiting for credible evidence that anyone gets music from such a set-up.

Every crossover has its own problems, however, and the active crossover, for all its potential, is actually more difficult to implement correctly, in my experience.  I am not sure why you would want a passive pre-amp, but if you insisted, still you might use active crossovers and limit the passive part to attenuation.

I still think that the most potential in terms of "crossovers" lies in the most difficult route of all, namely the narrow band/dedicated amp route.  There are two reasons why I have not gone this route myself: time and money.

Well, add a third reason: I got lucky, I guess, and I am getting very natural sound now, with my present "compromised" system.  I guess I'll revisit all this when I am overwhelmed by the need for comparable performance below 40 Hz.

Best regards,
Paul S

 

01-26-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,534
Joined on 05-28-2004

Post #: 5
Post ID: 3564
Reply to: 3563
Try converting a crossover from foe to a friend.

The line level crossovers have some advantaged: they loaded into higher impedance and therefore the values of caps are smaller. Also the line level crossovers loaded against fix impedance, contrary to the speaker level and this allow writing a very exact curve with very exact Q. Also the passive crossover; low passes do not talk with the inductance of the bass drivers. There are some other advantages… Still there is nothing wrong with properly implemented speaker-level crossovers and the line-level crossovers should not be considered as some kind of amassing benefit. I personally prefer to think about crossovers not as functional entries but rather as notes in a large musical score. Wherever you place them and however you impellent they will affect sound in one way or another. All together the playback should sound properly regardless what the crossovers used. The fine-tuning of crossover performance in multi-channels is a delicate and creative process, sometimes it has little technical merits and juts follow the exoteric rules of subjective perception.

Here is the rule that I sumized for myself: Badly done crossovers are fixing or masking some problem of playback. Properly done crossovers embrace positive aspects of installation. Do not think about crossovers as a masking tape but rather as a binocular….

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-31-2007 Post does not mapped to Knowledge Tree
Dominic
Montreal, Canada
Posts 69
Joined on 08-23-2006

Post #: 6
Post ID: 3603
Reply to: 3564
phono
I was just thinking.
Isn't an riaa filter just a line level crossover for one channel (times stereo)? So what you say makes total sense.
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