LDR Active Preamp - does it exist?

It's not LDR, but I think a preamp like the W4S STP-SE is what you're looking for. If it isn't everything you hoped for, well, they take returns.

Maybe use the Burson Buffer?

http://bursonaudio.com/Burson_AB160.html

6db of gain, or about 2V. Not ideal, although it solves potential future impedance mismatch problems too.

The Burson has a 6db gain, although it isn't obvious from the literature. It also has no volume control, so you would continue to use the Lightspeed LDR.

It's called out here:

http://www.partsconnexion.com/t/Index/bur_buf160.html

And also implied by looking at the specs for maximum input voltage and maximum output voltage. Somehow it got more out than in, so it has to add it in between.

It is different than the Dodd Buffer Preamp which has no gain, does buffer, and has a volume control.

Great idea, except gain is exactly what he's looking for.

The Lightspeed LDR is wonderful provided your source and amplifier are appropriate for a zero gain, zero buffering preamp.

Either find a source that outputs closer to 4V, find an amp whose sensitivity is closer to whatever output voltage of your source, find another way to either add gain or lower sensitivity, or get an active.

I happen to think the Burson Buffer is a reasonable try to add gain to your system. It's actually what you're looking for, isn't it? An active, with gain and LDR volume control. The Burson Buffer adds 6db gain, and your Lightspeed LDR acts as volume control.

Having said that, an LDR is not the only means to deliver great sound, I happen to think the Coincident Statement Linestage and TRL Dude are better than the Lightspeed. But if your source and amplifiers are appropriate, I'd agree that there may be nothing better at the price point of the Lightspeed LDR.

Burson Buffer is $550, not $700.

http://www.partsconnexion.com/t/Index/bur_buf160.html

I have not much to say about the Decware. At the risk of being impolite, when people talk about buffers, Burson usually comes up first. I'd go with the more well known manufacturer in this case.