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Thread: LDR Preamp Single and 3 Input Kit

  1. #21
    Join Date: Mar 2008

    Location: Halifax, UK

    Posts: 1,399
    I'm Nick.

    Default

    It involves blending the hot and cold
    More like blending the hot and not hot, but I know what you mean :-)
    Nick.

  2. #22
    Join Date: Feb 2013

    Location: Switerland

    Posts: 1,199
    I'm rupert.

    Default LDR Preamp Single and 3 Input Kit

    Quote Originally Posted by nat8808 View Post
    With the right circuit, you can implement a balanced version with just a stereo pair.. It involves blending the hot and cold in order to attenuate the levels on both at the same time.

    With a matched quad control, you need to have that quad absolutely perfect else when the balanced signal is converted to single ended at the final stage, you'll have a signal with spurious parts of the signal removed via slight mismatching of the hot and cold attenuation and dependant on volume level too. But hey, I guess that applies to how the balanced signal is made in the first place - really need a transformer or digital 180' phase difference.
    i think they (tortuga) got the matching sorted with software.. which imho is the differentiating characteristic of the tortuga vs other LDR pre's... of course the totrtuga is more expensive too

    I'm writing this from a phone so please excuse the typos

    http://www.tortugaaudio.com/ldr3b-ba...preamp-update/

  3. #23
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default Balanced stereo coffee

    Hi
    A balanced version of our stereo coffee can be done. We have done two of these. We use a double L pad , one pad does Hot, the other does Cold. Matching of 8 LDR's is required for one stereo input as you want hot and cold to be the same. The double L pad configuration requires 2 of our control boards, and a dual gang pot, ... er and many patient hours.

    Cheers / Chris

  4. #24
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default

    Hi
    We have reduced our prices on both our 3 input and single input kits http://stores.ebay.com.au/stereo-coffee

    Stereo coffee LDR kits do not use relays, rather we provide for our 3 input model, 6 matched Series LDRs and 2 matched Shunt LDR's, To switch inputs we simply turn the anodes of the series pair of LDR's off, the input you were listening fades out to silence and the next commences.

    There are very good reasons not to use any switching of signal paths at all, including relays or conventional switches as one contact on another causes audio degradation, and is the very reason why LDR's are used in our kits to overcome any switching of signal paths. We offer our kits with or without the RCA connector block, if you want to direct wire your audio system or choose to use cable of your choice.

    Cheers / Chris

  5. #25
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default A Review of the Stereo Coffee LDR 3 input kit

    Hi
    A review of our Stereo Coffee LDR 3 input kit here: https://lencomotion.wordpress.com/20...-preamplifier/

    Cheers / Chris

  6. #26
    Join Date: Sep 2010

    Location: Macclesfield, UK

    Posts: 360
    I'm Jason.

    Default

    Interesting review Chris, and especially relevant here that he compared it to a Khozmo with z-foils.
    Jason™

    Built by Hand, Tuned by Life

  7. #27
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default Stereocoffee Website

    Hi
    We have our new website up and running http://www.stereocoffee.com

    Cheers / Chris

  8. #28
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default Stand alone LDR preamp Kit *Note Local Sourcing of LDR's needed

    Hi
    In response to the unsure present supply to EU markets we have adapted our kit so you get everything less the LDR's. As we all know matching LDR's takes a certain skill set to get resistances close. So this kit is for the more experienced, We will supply you with every bit of assistance. There are many suppliers with overnight or same day delivery of the NSL32SR2S and NSL32SR3 the latter also suitable for this kit.

    *** Update, we have now adapted the stand alone kit, with a BIG thanks to NRG Neal's suggestion , so we supply you with matched LDR's which we will have as a separate item available shortly, but with the stand alone you will need to
    carefully solder these in. We will do all the matching and labeling ie 1234 for a single input kit and update our instructions with lots of images so you can't make any errors, and you end up with a great sounding kit.***

    The stand alone kit is now available at our website http://www.stereocoffee.com and includes in the price an assembled control board, a prepared LDR board for 3 inputs if and when you wish to expand or use them, a 500k potentiometer, and a switch for the anodes.Also flat rate shipping price is included from New Zealand. Separate listing will show matched LDRs as components suiting exact board placement

    We will keep you advised when there is clearer indication of our assembled matched LDR provided boards returning to normal supply.

    Cheers / Chris

    Stand Alone Stereo Coffee Kit.jpg

    So as we are on the same page the attached schematic shows a diagram of what we first use for getting LDR's close. The diagram shows connection to our control board and to relative points on the LDR board for series and shunt LDR's , so you will need a 250k 1/4 watt and a 56k 1/4 watt resistor, a small breadboard and some wire to attach.

    Test LDR.jpg
    Last edited by Light Dependant Resistor; 26-06-2014 at 12:11.

  9. #29
    Join Date: Feb 2008

    Location: Down South

    Posts: 2,413
    I'm Neal.

    Default

    Chris, I don't see anything stopping you from supplying matched NSL32SR2S and NSL32SR3 separately as 'parts'...
    Listening in a Foo free Zone...

    Only a Sith deals in absolutes.

  10. #30
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,757
    I'm Chris.

    Default

    Quote Originally Posted by NRG View Post
    Chris, I don't see anything stopping you from supplying matched NSL32SR2S and NSL32SR3 separately as 'parts'...
    Thanks Neal, thats a good suggestion !

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