Hi All,
Before shutting down all development and order fulfillment work prior to moving to Oregon, I managed to squeeze in a prototype of a future updated variation on my LDR300x.V3 Active/Passive Preamp. Even though I stopped building/selling new finished preamps as of a year ago, I haven't stopped working on the underlying tech or possible future limited production runs.
The photo below shows a potential prototype of what may become an LDR300LA.V4 Linear Active Preamp. The preamp shown here uses the current ePot.V3 Max preamp attenuator/controller board with the addition of a new plug-in solid state buffer/gain board that plugs directly into the V3 board socket where the LDR module would normally go. Instead the LDR module gets plugged into the solid state buffer/gain board. Thus the board on the right is actually a 3 tiered V3-buffer-LDR arrangement.
The board on the left is a new split voltage (+12/-12V) linear DC power supply which powers both the new solid state buffer/gain board as well as the V3 attenuator/controller board. The power supply board runs off AC mains and uses a low noise toroidal transformer. It's a 2 stage design with an unregulated stage followed by a regulated stage. After rectification it uses linear regulators together with high quality polypropylene as well as Elna silk caps bypass caps for high quality low noise split voltage power. The solid state buffer/gain board is direct coupled - no audio coupling caps in either the input or output audio signal path. It has trimmer pots for dialing in near zero DC offset.
The unit shown below actually belongs to a customer who was willing to to allow his existing LDR300x.V3 to be modified.
I confess I'm rightly impressed with sound quality from this LD300LA prototype. The sound is full and dynamic while retaining the inherent sweetness of LDR attenuation and without adding any noticeable coloration. The gain stage uses plug-in gain resistor modules - this one is set up with +6 dB gain. It can handle up to +12 dB gain but note that pumping up the gain if you don't need it only introduces more noise with no additional benefits. I found myself running this at around step 60 out of 100 whereas in unity passive mode I would normally listen to an LDR300x at around step 70-75.
I'm hoping to pick up work on this once I'm up and running in Oregon later this year. I've gone through several iterations on the new ePot.V4 as well and want to get that finished and released first and then integrate the V4 into the final configuration of this LDR300LA. Probably won't have that all ready by year's end but it's a goal of mine to give it a go.
Cheers,
Morten
