Help me understand Passive preamps ?

[Audio Al]

:scratch: Come on guys what am I missing :scratch:

You buy a box with nothing inside it , Some stepped rotary volume control knobs , A line select rotory knob

some rca ins and outs , then you take out the std wiring and put in some silver wires :scratch:

And have spent £600 :eek:

Help :)

[narabdela]

:scratch: Come on guys what am I missing :scratch:

You buy a box with nothing inside it , Some stepped rotary volume control knobs , A line select rotory knob

some rica ins and outs , then you take out the std wiring and put in some silver wires :scratch:

And have spent £600 :eek:

Help :)

Yep, that's pretty much it. :exactly:

[Light Dependant Resistor]

What you are missing is that stepped attenuators and switches are not
the only forms of passive. To name a few, passives are also represented by Transformers, Fets and LDRs

From the source component to the signal being delivered at the power amp input, start seeing audio being
changed by every component that is attenuating. Not just accepting that its a box with a few parts inside

You then will start to appreciate that a signal side switch or volume control changes the audio often very
much for the worse, and cannot be recovered.

It is far better if accurate audio is needed to have the attenuation done by a medium that does not involve rearranging the audio signal.
Whilst that sounds like a conundrum - thinking clearly it is not at all.

Rather all you need to do is create a variable resistor by using a medium that couples, without physically touching.
because you are removing straight away the mechanical interface. Crudely one surface passing an audio signal
grinding on another explains a stepped attenuator or potentiometer type.

Coupling is not perfect either, but it is very close indeed when done properly.

The very best attenuation involves a coupling medium separating the audio signal from the mechanical medium and that has properties
preserving the audio signal and allowing the audio signal to pass untouched other than attenuating.

Impossible ? not at all..

Cheers / Chris

[Macca]

:And have spent £600 :eek:


....But got the sonic equivalent of an active pre-amp that would cost you several thousands...

[ReggieB]

Is that Chris talking or is it the devil's work ... look at the post number (https://goo.gl/photos/rYbFnsBXtPsYvnsCA)

[Macca]

Is that Chris talking or is it the devil's work ... ]

A little from column A, a little from column B...

[Light Dependant Resistor]

Is that Chris talking or is it the devil's work ... look at the post number (https://goo.gl/photos/rYbFnsBXtPsYvnsCA)

Just me, trying to be as good as I can

Cheers / Chris

[RothwellAudio]

You buy a box with nothing inside it , Some stepped rotary volume control knobs , A line select rotory knob
some rca ins and outs,
And have spent £600


To put the cost into perspective you have to compare/contrast passive and active pre-amps. Both have to have a case, both have to have a front panel with lettering, both have to have in/out connectors, both have to have knobs... etc etc. In fact, there's essentially no difference in build costs between passive and active preamps except for the mains transformer (if there is one) and a collection of transistors/resistors/capacitors. True enough, a mains transformer can be quite expensive, but transistors and resistors and capacitors are (or can be) very cheap. So the idea that a passive pre-amp "has nothing inside" and therefore "should cost nothing" is a false one which doesn't stand scrutiny.

What about performance? It's another marmite thing. Some people love passives, some people hate them.

[Audio Al]

What about performance? It's another marmite thing. Some people love passives, some people hate them.


OK I see now :)

[Arkless Electronics]

To put the cost into perspective you have to compare/contrast passive and active pre-amps. Both have to have a case, both have to have a front panel with lettering, both have to have in/out connectors, both have to have knobs... etc etc. In fact, there's essentially no difference in build costs between passive and active preamps except for the mains transformer (if there is one) and a collection of transistors/resistors/capacitors. True enough, a mains transformer can be quite expensive, but transistors and resistors and capacitors are (or can be) very cheap. So the idea that a passive pre-amp "has nothing inside" and therefore "should cost nothing" is a false one which doesn't stand scrutiny.

What about performance? It's another marmite thing. Some people love passives, some people hate them.

Spot on yes. £60 for the case and lettering and £10 for the electronics (cost price) for a basic SS active pre would be in the right ballpark.