Buffered Pre-out? What is it?

I have a preamp that has a "normal" pre-out for short IC's and a "buffered" pre-out for long IC runs (not balanced). I assume the buffering is to keep noise down. What is the electronic or operational concept behind this type of buffering? Anyone know?

Thanks and Best Regards,
You don't say what make and model of preamp is involved. Buffering in an analog circuit is usually done to make a circuit more tolerant of difficult load situations. (This is different than digital buffering, where data is accumulated in a memory chip and then parceled out to a device or program as needed.)

In your case it sounds like the preferred circuit is the unbuffered one, but that it doesn't tolerate the added resistance or capacitance of a long interconnect. In that case, the extra stage of devices (the buffer circuit) may offer the better compromise in terms of sonic degradation.
Mlsstl, It is an Arcam C-30. And yes, you are correct, the unbuffered out is stated as prefered.

It was more of a general question than a problem with implementation. I am familiar with the concept of digital buffering in the manner you describe. How buffering is applied in the context of a pre-out just had me grasping at thin air (mentally ciruit challenged :>)).

Your thought makes good sense. Do you know what would be used in a buffer circuit that would degrade the sound? Just extra connections?

Just curious.

Thank You! - Jim S.
A buffer stage has a gain of 1 (or sometimes a slight attenuation). In general such a low gain circuit, either a tube (cathode follower) or a transistor, has virtually no distortion... certainly way less than the associated gain stages. A buffer output stage prevents signal deterioration due to loading of gain stages that have high impedance output, so it is puzling that the manufacturer says not to use it. Perhaps he is catering to those who believe that ANY additional circuitry is always bad. These folk ignore the loading effect on the "naked" gain stage.
Buffering lowers the output impedance of the source. Why? Well, sometimes the receiving component has a low input impedance, like some solid state amps. Long cable runs can also load the driving component excessively. So what does it sound like? Reduced dynamics and reduced high frequency extension. The broad rule is that the receiving component should be twenty times the impedance of the driving component. In other words, if your unbuffered preamp has an output impedance of two killaohms, then the amp must show a minimum impedance of 40K ohms. Lower impedance of the driving component and/or increased impedance of the receiveing component is considered better still. Again, there are combinations that sound good and are out of these parameters and there are some rare amps and preamps designed to have exactly the same impedance, but only when used with components from the same manufacturer. But why not then just design for a buffered output. Sometimes it requires more circuitry which adds another stage, some feel the shortest route is the best.
> Sometimes it requires more circuitry which adds another
> stage, some feel the shortest route is the best.

There are a number of equipment designers who believe that a simpler circuit design is better on the basis that the fewer components a signal must pass through, the better. This is the same reason that some electronics invert the phase of a signal. They could easily add one more stage to not invert, but feel the extra circuitry isn't worth the sonic cost.
Viridian, Eldartford, Mlsstl,

Thanks a lot for the explanations.

A pre-out buffer lowers the output impedance. In the case of Arcam they provide this optional output to make up for a long IC run that could add to the impedance the amplifier sees? Yes?

A buffered output stage doesn't necessarily add distortion because it does not add gain. It may deteriorate sound quality because of the added circuitry?

It all makes sense. Arcam markets to HT and multi-room implementations. Remote equipment placements, long IC's and/or speaker cable runs.

Thanks, it has been a good day at the office (I learned something today!). I am going to try the buffered output to see if I can hear a degradation in sound.

Just curious.

Really, thanks a bunch for taking the time!

Jim S.