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Thread: LDR Preamp Single and 3 Input Kit

  1. #1
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Smile LDR Preamp Single and 3 Input Kit

    Hi
    We have our Light Dependant Resistor Single and 3 Input Kits available at:
    http://stores.ebay.com.au/stereo-coffee

    We looked at LDR products, and Kits seemed to be missing, certainly there were single input models and others using relays to switch audio outputs, but to our thinking not many strangely were building these to get the best audio from an LDR. We were excited with the wonderful audio LDR's can produce. and filed a patent for the control board as it achieves low voltage between 1.9v and 1.4v with sufficient current, whilst operating as a L pad potentiometer.

    We listen carefully with the ESL57's to get the best sound. Before shipping a Kit we then tailor 3 parts on each control board to refine further still.

    The kits comprise a assembled Control Board, a assembled LDR Output Board, a Bourns potentiometer, and switch for the 3 input edition. There is NO signal switching, rather the anode of the LDR simply switches on or off, to select or deselect that input. Dorothy and I carefully select NSL32SR2 or NSL32SR2S LDR's to individually match a Series and Shunt pair so you achieve matched pairs of devices. This makes a big difference to stereo balance. Eight LDR's are used for 3 inputs, six for the series and two for the shunt elements.

    To get our kits up and running you will need, cable, a 12v regulated power supply, or 12v battery and charger, casework, a few hours, a screwdriver, a soldering iron and ideally a multimeter to check DC polarity. Optional is an additional capacitor for the power supply once polarity is confirmed and if soldering is difficult we can supply a 5mm pitch connector to get you going with 1 input, until soldering gear can be obtained.

    Thank you for your support. We look forward to answering any questions you may have.

    Chris and Dorothy
    Attached Images Attached Images

  2. #2
    Join Date: May 2008

    Location: Surrey

    Posts: 7,103
    I'm Rob.

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    Interesting product. I made several LDR pre-amps when George released the details some years ago. Some for me and some for other people. The original one I made is still in my system and still going strong. Cost me about £15, plus power supply. These are very underrated IMO.

    Good luck with these.

    Rob.
    Buy Bose...And get your parking validated!.

    https://youtu.be/ZCBe7-6rw4M

    No Highs...No Lows....It Must Be Bose!

  3. #3
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Smile

    Hi Rob
    Thanks,

    We hope the efforts we put into the control circuitry is a step above what occurred a few years ago, without diminishing the prior accomplishments of others.

    Yes LDR's are very special when it comes to listening.

    Cheers Chris and Dorothy

  4. #4
    Join Date: Feb 2008

    Location: http://www.homehifi.co.uk

    Posts: 6,288

    Default

    Good luck with your venture Chris. But be careful when applying for a patent on an application like this.
    I myself have considered many patent applications on some of my ideas, but once I had seen what was involved to fight cases I left things as they are.
    One major obstacle is when you have to rely on an already patented component from a different company. They can file for a cut of your sales. The Apple/Samsung patent war is a recent example of how messy and expensive things can get.

  5. #5
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Smile

    Hi Stanley
    Thanks for your advices, patents and their processes are certainly not something i enjoy either.
    Cheers / Chris

  6. #6
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Smile

    Hi
    We have received a number of questions concerning directly wiring to our LDR output board. The advantage we see to not using RCA's is removing another connection point. Our board accommodates generous room for soldering your own wires, so please let us know at checkout if you do not need the RCA block. We will provide a modest refund if the RCA block is not required.

    We have received very encouraging feedback on sales so far and with all of our LDR kits we very carefully match the NSL32SR2S , so you get the very best stereo presentation.

    Regards / Chris

  7. #7
    Join Date: May 2008

    Location: Lancaster(-ish), UK

    Posts: 16,937
    I'm ChrisB.

    Default

    Chris,
    I hope you don't mind if I make a constructive suggestion?
    A common theme that I notice on sales related threads on hi-fi fora is that the person pitching their wares writes the first post while presupposing that the reader has prior knowledge of the item on offer.
    I'd think there are an awful lot of people who could make good use of your kit, but don't know it because they haven't got a clue what an LDR is, why it's different from other approaches etc.
    Spill the beans on the basics mate! It can only help your cause.

  8. #8
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default

    Hi
    Thanks Chris.

    What is a light Dependant Resistor ? and how does it benefit audio reproduction
    Imagine a world of audio without switches... Hmm that takes some imagination as switches take many forms. But it is possible when we use a unique device called a Light Dependant Resistor (LDR)

    Why are switches bad for audio ? A vast question but easily answered when we start to visualize one contact on another,slipping with different metal types. Up the food chain of switches is the relay, but its still a switch. subject to one contact on another.

    An LDR though is quite different on one side a resistor that varies resistance between two leads, and on the other a LED, between the two mediums is just light. We have a device then which has no contacts and acts as a variable resistor. Arranged as a L pad circuit we then have a attenuator that varies with light.

    Ideally the LDR should approximate a potentiometer in use, our circuitry achieves this, which greatly assists impedance matching.

  9. #9
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Smile

    Here is a build of the 3 input LDR board without the RCA block. Its in a recycled Audio Synthesis PAS02.chassis.
    Image shows 3 inputs ,the series LDR pair for the 4th input in this build will be added, I will post another image once this is done.

    It shows how the boards can be mounted to suit existing rear plate RCA's with the result of a big improvement to a prior switched attenuator type passive pre amp.

    Cheers / Chris
    Attached Images Attached Images
    Last edited by Light Dependant Resistor; 06-10-2013 at 11:33.

  10. #10
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,779
    I'm Martin.

    Default

    I've just ordered the single input version, will report in due course.
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

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