Buffer, Line Stage, Preamp; What's the Difference?

I can't be the only one here that is confused by the different terminology to describe preamps. What is a buffer, a line stage, a passive preamp or an active preamp? What do the different ones do and why is one type preferred over another in your system?

Thanks,
Eric

 

Line stage: a preamp that does not include a phono preamp. It processes line-level signals only.

Passive preamp: a preamp that does not contain any active electronics, and usually does not supply any gain or buffering. It only provides volume attenuation and source selection (and maybe channel balance).

Active preamp: the "normal" preamp with active electronics, gain, buffering, volume attenuation, source selection, etc.

Buffer: circuitry which takes a higher impedance signal input and outputs a lower impedance signal. Useful for component matching.

 

Pre-amps

The normal integrated amp or pre-amp will have an active stage. This means that it has signal gain and buffering. This allows the use of longer signal cables and some models let you adjust levels between inputs so that one signal source (such as a CD player) is not louder than another signal source at the same volume setting.

Passive pre-amps are merely boxes with only a volume control, input switching, input/output jacks, and the internal wiring connecting it all. Why have an passive pre-amp? The lack of active circuitry and more direct in and direct out of your signal can result in greater detail. Why not have an active pre-amp? You absolutely need suitable matching equipment and cables. Long cable lengths are problematic with a passive pre-amp.

Hope that helps.

Scott

 

Line stage

I would call a line stage a pre-amp without a built in phono stage. The "line" in Line Stage means that it accepts any input from a device with an audio output. This means you can connect to your line stage devices such as CD players, external phono stages, FM tuners, tape players, SACD, DVD audio out, iPods, and I have used my XM satelite player on my integrated amp.

In a line stage the inputs are usually all the same. If your int. amp or pre-amp has inputs marked CD, Aux, Video, etc. these all mean nothing. Those markings are only marked with these names for convenience and corrspond to the associated jacks on the back of your equipment. My int. amp is marked 1, 2, 3 etc because those inputs are the same and any device can be connected to it and the circuitry underneath the hood is the same for all inputs.

The only exception in a line stage is the tape connection (marked 5 on my int. amp). The tape connection has an In pair of jacks and an Out pair of jacks for record and playback respectively.

Scott

 

So basically the more you break these things down the greater detail you will achieve in the playback?

 

I never cottoned onto the term "line stage".

 

I just acquired a Moscode Super IT phono/preamp from a friend. Anyone ever had one or have any ideas about it? I tried it direct to the amps (MC30) and then thru the preamp (Onyko P308) ...either way it seems to have added a lot of bass....is that possible?

 

Theoretically, yes but it depends on the quality of the seperates vs. the quality of the integrated. There are a number of very good (and somewhat expensive) integrateds out there that hold their own against the mid level seperates quite well.

What you get with a high quality integrated is both boxes on one chassis, which translates into one less power cord and interconnect to buy and not worrying about amp/preamp compatibility. (not to mention one less rack space...)

The downside to an integrated is always being locked into both amp and preamp...

But if you aren't a person predisposed to swapping gear a lot, a great integrated might just be your cup of tea!

 

Thanks Jeff. Helpful as usual

 

I've always dug a really high quality integrated. One less interconnect to buy!

 

That would be a negative for some audiophiles I know.

 

My preamp has a passive mode(with only the volume control) but I prefer it when active. Some may like the "passive" sound, to me it's just less ballsy, smeared, and smoothed out too much. It comes into good use for certain overbearing masterings, though.

 

I dig mine (Conrad-Johnson CAV-50)! Not sure if it is "really high quality," but I don't think anybody would doubt it is a "high quality" integrated! Heck, I think I can give it that faint praise--it is "really high quality!"

 

Anything from conrad-johnson is "really high quality."

I kinda got the hots for a McIntosh MA 2275, though.

 

Not enough gain?

A couple of you have made comments which seem to echo the common complaints against passive pre-amps. Passive setups can sound like there's less depth and drive than is possible with an active pre-amp or int. amp with passive pre section.

It can be difficult to build a system around passive gear.

Scott

 

I'd love this Line Stage! Looks cool!

 

One historical point to be made.
Preamplifiers all used to have a phonograph gain section.
They also usually had tone controls too.
The main things people conencted to them were AM FM tuners, phonographs. Later they started adding tape machines, then cassette tape decks.
When the Cd came along around 1983, it really became popular fast.
Soon, various preamp makers were beginning to build preamps without a phono section built in. THOSE were the ones called LINESTAGE.
And then they also started removingtone controls.
So finally a preamplifier now does almost nothing. it became a box with a bunch of connections, switches, and a volume control

 

Almost nothing? Well, I have certainly gotten some pretty great leaps of improvement to the sound of my system and/or changes to the overall character of my system by placing different "does almost nothing" boxes into my system.

In general, my experience with passives (even passive buffers that address impedance issues) mirrors what is said above. Drive and dynamics are a bit lacking. But detail retrieval is often excellent. So it will depend on what you value in your listening preferences as well as perhaps the type of music you prefer. Small ensemble jazz and classical can be divine with a passive pre. And you often need to spend some cash to find an active pre that can match a passive pre's level of detail retrieval and get the best of both worlds.

 

For many years I tried to match a power amp with the right preamp or the other way around and it was insane. Finally I moved to an integrated and I have not looked back ever since.

 

When building a system around a passive, and it needs to be a purpose built system, the main thing to remember is that the source then becomes the pre. IOW, the voltage coming out of the source needs to have enough voltage, gain, to drive the amp(s). Otherwise one gets the anemic dynamics described in this thread. For example, I have built my system around a Bryston BDA-1 DAC. This DAC has multiple digital inputs and both balanced and unbalanced outputs, 2.3V, 50 ohms and 4.6V, 100 ohms output respectively, discrete class A output stage. This is more than enough gain to drive most amps to full output. I chose the DAC carefully to make sure that the voltage was high enough and the impedance was low enough to work with a passive pre. Most DACs do not have this kind of drive capability. It should go without saying that my ICs are short and the capacitance is low. My system does not suffer from lack of dynamics.

 

I just found out the price for this preamp locally in China. A little over $10,000