? about passive preamps

leftwinger57

Firstly I did do a search on this but found no best answer as to if one is better than the other.My Onkyo P-301 pre
dropped a chnl. and it's deffinately not a cable issuse.Now I use the pre outs of my Yamaha RX-v665 but since I do
have an Adcom gfa 555 I was thinking of going w/ the same brand pre. Cruising e-bay I did notice a few of their
their models and was wondering what exactly is the difference going to be in the simplest terms.Right now there's no
problem both set/ups are in the same stack. If I were to seperate the units then it would be problematic keeping the Yamaha as the pre.

steveinaz

I'm not really sure what you're asking? Are you looking for a passive linestage?

leftwinger57

I don't know.What's the difference between the active and passive Adcom models and is there an appreciable difference?

steveinaz

Passive means there is no preamplification. Since most sources these days put out 2v, they can drive most power amplifiers to full output without the need of preamplification. Some believe that the signal is purer by not going thru the extra stages of an active preamplifier.

Passive linestages (as opposed to "preamps" linestage is more correct since no preamplification is happening) are basically just a volume control, and possibly multiple inputs, depending on brand/model. Some very simple passives don't even require power.

Active preamps, preamplify the signal first--then send it to the amplifier to ensure enough input level to fully drive the power amp.

As to which is better? Like anything, which is better Chevy or Dodge? I personally love my passive linestage, but they aren't for everyone.

heiney9

Not sure it's "more correct" as there are many more factors involved. Passive has it's drawbacks like anything else. It comes down to design and components, etc as well, but one will only know for sure if it works in their system by trying it.

I can run either and for some material it works well and for others it doesn't.

Just my .02c

H9

mhardy6647

with a passive, one loses the ability to correct for impedance mismatches (buffer) between the source and destination. This may have zero sonic consequence, or it could be detrimental. If nothing else, the length of interconnecting cables between the passive device and its input sources and output to the amp should all be as short as possible to minimize "insertion loss".



NB I am currently using a passive (autoformer volume control with a source selector switch) - works well for me but it did require me to move to a higher gain phono preamp. That wasn't a bad thing, as my new phono preamp is considerably better sounding than my old one :-)

zingo

I've really enjoyed the Luminous Audio Axiom and Stereo Knight Silverstone passive linestages. The first is about 1/10 the price of the second, but both are great for their price points. Usually you loose remote control and other electronic functions, but good passives still include them if that is a must. The Stereo Knight units use transformers instead of resistors for volume attenuation, so they can have a different effect on impedance matches. Also, the Luminous Audio Axiom is a special order unit that Tim matchs to the specs of your system to minimize effects of impedance mismatches and low gain.

audiocr381ve

I'm using a Pass DCB1 (direct coupled) unity gain buffer and it is every bit as good as my Adcom GFP-750's passive section was, if not better.

Not an expensive build if you're into DIY.

steveinaz

Placette RVC $1000:

The Remote Volume Control has the Placette Audio 125 step attenuator that uses only Vishay resistors. The input impedance is a constant 9k ohms at every volume setting. The remote control allows for easy operation while at the same time placing it close to the power amp for the shortest possible output interconnects.

Although passive, these units do not suffer the usual loss of dynamics or bass response associated with other passive designs because of the non-inductive load offered by the Vishay S-102 resistors that are use throughout the volume control circuits. These controls will allow the sound of your sources to come through in full without the grain and brightness caused by typical volume controls including the "variable out" that is available on some source components.

SolidSqual

steveinaz wrote: »

Passive means there is no preamplification. Since most sources these days put out 2v, they can drive most power amplifiers to full output without the need of preamplification. Some believe that the signal is purer by not going thru the extra stages of an active preamplifier.

Passive linestages (as opposed to "preamps" linestage is more correct since no preamplification is happening) are basically just a volume control, and possibly multiple inputs, depending on brand/model. Some very simple passives don't even require power.

Active preamps, preamplify the signal first--then send it to the amplifier to ensure enough input level to fully drive the power amp.

As to which is better? Like anything, which is better Chevy or Dodge? I personally love my passive linestage, but they aren't for everyone.

Passive Pres and Active Pres can all sound equally awesome in the right system put together with synergy in mind. I owned a Wyred4Sound Pre for a while which is a passive hybrid of sorts. It is amazing in my opinion. Excellent pre for any money.

leftwinger57

Thanks ,all very concise answers. I will still most likely go w/ an Adcom pwrd pre of the GTP 400/555 class.

tonyb

Just my opinion, but any of the Adcom pre's, aside from the 750, aren't going to sound better than your Onkyo 301. I'd be looking elsewhere and since budget is of concern maybe an older Parasound pre, B&K pre especially. Just my .02 LW.

heiney9

Those Adcom's are OK, but not great. I'd look elsewhere or expand your budget. Probably won't sound any better than what you have. Of the two the 555 is slightly better.

H9