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Light Dependant Resistor 3 Input Preamp Kit

What is reasonable to pay for a LDR 3 input Kit

  • $150.00

    Votes: 33 80.5%

  • $180.00

    Votes: 5 12.2%

  • $300.00

    Votes: 3 7.3%
  • Total voters
    41
Jump to Latest
C

Chris Daly

Member
Joined 2004
#1

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#4
Sale Pricing on my 3 input LDR passive preamp kit until midnight 20/09/13
just $155.00 Au and shipping $30.00 Au with NZ Tracked postage.

8 matched NSL32SR2 optocouplers,with RCA outlets, Patent Applied for Control Board, 50k High quality Bourns Potentiometer and Switch.

Some technical specifications: LDR's measure and maintain between 1.4 and 2.00 volts making this design the best I know of for low distortion available. My own listening through ESL57 and Quad 303 confirms very high audio quality.

items in stereo coffee store on eBay!

Happy to assist with any questions. / Chris
 
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#5
Hi
Just letting you know, there is NO signal switching on my LDR preamp. The 3 stereo inputs utilise 6 series LDR's and 2 Shunt LDR's for that reason.

The anode of the Series LDR's for each stereo input (on the DC side NOT on the signal side ) is switched.

In practice one input fades out whilst another comes in. Due to the extreme resistance of a off state LDR, this method is far better than relays or any switching of signal path.

My board also achieves direct wiring to the RCA socket and a short path circuit track for the other half of signal.

Also here are separate ground paths for DC cathode series, shunt , and signal

Cheers / Chris
 
#6
We have added a Single Input Light Dependant resistor Kit to our eBay shop. Just $95.00 and $30 tracked shipping during our SALE

The single Input version allows you to expand to 3 inputs later with our Expansion Kit, some soldering skills needed.

It is supplied with our Patent applied for Control Board and high quality Bourns Potentiometer
stereo coffee items - Get great deals on items on eBay Stores!

I look forward to answering any questions you might have.
Cheers / Chris
 
#8
This is my first attempt at any type of amp build. Very much a beginner when it comes to electronics, but I was able to follow Chris instruction and dont think I made any major mistakes. Works any way. I did add a 12 Led on light not sure if that affects anything.

BTY let me know if anything is wrong or can be improved.🙂
 

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#16
tabarddn said:
Hi Chris, quite interested in this little unit of yours, but i do not know the pot you are using, can it be sustituted for a 50K stepped Dales Resitor pot.😀
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Hi Tabarddn
The pot we use is a bourns 50k single type, it has proved itself over many years of development to be an excellent part for this task. with no failures of any kind.

Yes it can be substituted with other switched type resistor pots, the pot is of course processing DC. In our circuit we use the pot wiper to deliver to each anode LDR pair that then is seeking ground with its cathode- note the pot, as normally occurs is not grounded on one side. So low resistance near 5 ohms or less is ideally needed at each resistance end, because we need to deliver to the LDR

A few years back I converted with much success a Audio Synthesis Passion to be a 4 input LDR. I recall I had to parallel the hubs normally used for each channel to get sufficiently low resistance, rather than any de soldering of Vishay's from the exceptionally nice Shallco switch.

Cheers / Chris
 
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#17
Chris Daly said:
Hi Paul
Have you had a chance to listen to it ? If so can you comment how it compares with other pre amps you might have used.

Cheers / Chris
Click to expand...

Chris I built your LDR to be used with a future kit amp I'm going to build and its just temporarily connected to SS amp built by Richard McDonald in Adelaide which already has volume control, not sure how its configured, but as Richard hand wires everything point to point and is a minimalist , I'd assume it is passive. Amp only has one pair of RCA connectors.
Been busy with work and haven't had a great deal of time to listen to music. I haven't got much to compare with either. Give me some time and I probably can give a better opinion.
But I will say for now, it certainly doesn't seem to detract from the sound of the amp. Volume is even and continuous, balance seems to be spot on (I've heard that balance can be a problem with LDR's) everything is clear and precise, plenty of wide open soundstage, its quiet.....Tiss good am happy🙂. Cant wait to hear it coupled to its own amp.

BTW is there a shelf life with LDR's?
 
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#18
tabarddn said:
Hi, thanks, Hum I am an electronic Luddite, are you saying that the pot does not add or distract from the sound. Your Ebay add seems to me anyway only to suggest that your units are in/out put controllers.🙄
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Hi tabarddn
You are comparing I think, a conventional L Pad potentiometer with an LDR, they are quite different.

Light Dependant Resistor circuits use the potentiometer simply to alter DC current and voltage delivered to the LED half of the LDR. after that just Light causes a variable resistor to change its resistance inside the LDR's encapsulated space .

Advanced Photonix Canada, Inc.: Products: Audiohm Optocouplers: Principles of Operation

This is the wonderful and special thing about LDR's there are no switches or contacts. In my circuit we take this further still removing any signal switching, and we solder the signal wire on one side with a short circuit board trace, and the other directly to the RCA to give you the best listening experience.



Cheers / Chris
 
#19
awty said:
Chris I built your LDR to be used with a future kit amp I'm going to build and its just temporarily connected to SS amp built by Richard McDonald in Adelaide which already has volume control, not sure how its configured, but as Richard hand wires everything point to point and is a minimalist , I'd assume it is passive. Amp only has one pair of RCA connectors.
Been busy with work and haven't had a great deal of time to listen to music. I haven't got much to compare with either. Give me some time and I probably can give a better opinion.
But I will say for now, it certainly doesn't seem to detract from the sound of the amp. Volume is even and continuous, balance seems to be spot on (I've heard that balance can be a problem with LDR's) everything is clear and precise, plenty of wide open soundstage, its quiet.....Tiss good am happy🙂. Cant wait to hear it coupled to its own amp.

BTW is there a shelf life with LDR's?
Click to expand...

Hi Paul
Thats a very promising review, and i look forward to when its coupled to your new amps.

Shelf life is very long 25-30 yrs and of no real concern particularly if you leave the volume control slightly on when not in use rather than fully off ie at position two or three compared to a normal volume setting. The preamp will provide a very long life of music enjoyment, probably longer than any other component in your audio system.

Cheers / Chris
 
#20
We have had a few questions and sales from customers wanting their 3 input and single input preamp matched LDR kits, to be made without the RCA block, so that wire can be soldered directly onto the board.

There is good provision on the board for this,and we are happy to do this,at slightly reduced cost, providing a modest refund via paypal following sale. Simply message when checking out if this is required, 🙂

Cheers / Chris
 
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