[tortugaranger]

We are coming out with an LDR based passive/active preamp controller board (the LDR3x) for the DIY community hopefully before the end of April. This is a result of development work we're doing on our line of LDR based passive preamps including the development of a balanced LDR passive pre.

With the LDR3X board you'll be able to build either a passive or active preamp that provides exceptional LDR attenuation, remote selection from 3 input signals, and be controllable via IR remote as well as manually via a pot, encoder, buttons etc.

Also, by using a pair of these in a master/slave configuration, you'll also be able to configure a balanced LDR based preamp.

More info can be found in a recent post on our website: Tortuga Audio Plans LDR3X Preamplifier Controller for DIY Community | Tortuga Audio

The LDR3X preamp controller board will likely be viewed as pricey when compared to typical dirt cheap Chinese made audio boards. This board will be made in relative small quantities here in the US. Also, quite a bit of testing and custom tuning goes into each board given the unique characteristics and variability of LDRs. By its nature, this doesn't lend itself to mass production and low cost. As least not yet. I'm trying to keep it under $300.

I value your inputs and suggestions. In fact, every member on AudioCircle who provides constructive input, comments, suggestions or questions via this thread will be entered into a drawing from which I'll randomly choose 1 winner to receive a free board (including shipping) once they become available. So have at it and thanks.

Cheers,
Morten

[tortugaranger]

Good news! Orders were placed earlier this week for production boards and parts for the LDR3x Preamp Controller Board. http://www.tortugaaudio.com/product/ldr3x-diy-preamp-controller-board/

Barring any last minute glitches we expect to have finished boards ready to ship starting June 24th if not sooner!

If you're interested in the LDR3x Preamp Controller Board, you can still pre-order one at a 20% discount off the regular price via the following link. http://www.tortugaaudio.com/product/ldr3x-diy-preamp-controller-board/

The pre-release discount ends once we have finished boards ready to ship.

Cheers!
Morten

[tortugaranger]

It's taken a bit longer than planned but we're pleased to announce that the LDR3x DIY Preamp Controller Board has been released and pre-release orders are shipping!



The LDR3x allows you to build your own high performance LDR based passive (or active if you include a buffer) preamp that can be controlled remotely and also locally via rotary encoder/switch or discrete pushbutton inputs and a simple potentiometer.

Built around precisely matched digitally controlled LDRs, the LDR3x offers the DIY'er the ability to build preamp that will rival the audio performance of even the best high end preamps.

We'll be posting more pics next week and tweaking the technical manual which has been updated as of today (6.29.13) to reflect the final design/build. We still need to include more detailed artwork describing the board and the interfaces.

You'll notice from the pic that the board isn't fully populated. The board has certain functionality that isn't available to the DIY'er and thus those relavant parts are not included. We also plan on using these boards in  future iterations of our own preamp products.

You can find more information and purchase the LDR3x via the website/store at: LDR3x DIY Preamp Controller Board | Tortuga Audio

You can also find a recent review of our LDR6 Passive Preamp at 6moons.com via this link http://www.6moons.com/audioreviews/tortuga/1.html to get a feel of what to expect by way of sound quality with the LDR3x. Expect quite a lot actually.

Final pricing is:
Master Board for unbalanced inputs - $295
Matched Master & Slave Boards for balanced inputs - $495
Tortuga Audio IR Remote - $49

All questions, comments and inquiries welcome.

Cheers,
Morten

[jtwrace]

The board has certain functionality that isn't available to the DIY'er

Such as?

[tortugaranger]

The board has certain functionality that isn't available to the DIY'er.

Such as?

Such as the J4 header which allows the LDR3x to interface with a particular NewHaven graphical display module. This is still in development and may one day become available to the DIY'er but would require a software upgrade via a replacement CPU if/when that day arrives. No specific plans on that at this time. We plan on including a graphical display in our next iteration of our LDR passive preamp products which will supercede our current LDR1/LDR6 line.

Such as the J7 header and the 3 rows of diode/resistors which will allow the LDR3x to interface with a future 3 input switch board wherein LDR's are used in lieu of electro-mechanical relays. This is the same design approach we use in our LDR1/LDR6 passive preamp products. We are planning to eventually release a 3 input switch board for the LDR3x. It would include an upgrade kit to populate these components and would interface via a 2-5 IDC cable to header J7. We don't have any timing on this yet.

That's all of the "such as's" I can think of.

Best!
Morten

[tortugaranger]

We've made some changes!

1) Our LDR DIY Preamp Controller Master Board now also includes our custom IR remote. All you need to supply is your own 12 VDC power supply and you'll have a fully functional state-of-the-art LDR attenuator/preamp controller

2) If you're looking to build a balanced preamp, we've reduced the price of our optional Master Board by $50



The LDR3x - What Is It?

• Digitally controlled, analog audio preamp controller in the form of a populated 2.5 inches wide by 4.7 inches long printed circuit board
• Comes with a handheld IR remote
• Allows the DIY audio enthusiast to build their own exceptionally transparent and articulate balanced or unbalanced audio preamplifer
• Rivals the performance of even the best high end preamp costing 10-100 times more than the LDR3x
• By itself is an unrivaled passive preamp/controller but can also be incorporated into any DIY active preamp design
• Utilizes light dependent resistors (“LDR”) in lieu of conventional potentiometers or stepped resistive attenuators for volume control
• Precision control of the LDRs and all other functionality of the LDR3x is done via a software driven on-board microcontroller (microprocessor)

What's Included?

• Tortuga Audio 2.5 by 4.7 inch printed circuit Master Board populated with components
• Vishay TSOP1138 38kHz high performance IR Receiver which can be inserted/soldered into the board or located external to the board
• Tortuga Audio IR remote with full functionality
• Optional - matching Tortuga Audio Slave Board to enable balanced inputs - $150 additional (must be purchased with matching Master Board)

Functionality

• Smooth custom attenuation curve from -60 to 0 dB
• Accepts one (1) single ended unbalanced stereo input
• Accepts one (1) balanced stereo input when mated with the LDR3x Slave Board
• Can switch between 3 inputs (unbalanced or balanced) when mated with an appropriate external relay/input board
• Fully controllable via infrared remote
• Fully controllable via an encoder with integral switch
• Alternatively controllable via discrete user inputs including a conventional volume control pot
• Output muting with smooth ramp down and ramp up
• Status output than can drive a status LED
• Provides traditional left/right channel balance for fine tuning
• By itself, is an LDR based passive preamp/controller
• Mated with a buffer output stage, can be an active LDR preamp/controller
• Electrical and optical isolation between audio and power/control signals
• Provides a 12 VDC trigger out to turn other audio system components on/off
• Runs off  of any 5 VDC or 12 VDC power supply (12 VDC trigger out feature requires 12 VDC supply)

How Much Does One Cost?

• Master Board including IR Remote - $295
• Optional Slave Board for balanced inputs - $150

How Do I Buy One?

• Go to our website: http://www.tortugaaudio.com/product/ldr3x-diy-preamp-controller-board/
• We accept PayPal, credit cards, and also personal checks.

[tortugaranger]

We're running a whopping 33% off summer sale on our DIY LDR preamp controller board.

• Master Board w/ remote - normally $295 - sale price $195!!!
• Master & Slave Boards w/ remote (for balanced signals) - normally $445 - sale price $295!!!

We accept all major credit cards plus PayPal.

PM me or email me at morten@tortugaaudio.com with any questions. Or just post you questions and comments here.

Here's the link to our website/store for more info: LDR3x DIY Preamp Controller Board | Tortuga Audio

Enjoy!
Morten 

[tortugaranger]

A quick shout out to our new friends in Singapore, Portugal and New Zealand!

[tortugaranger]

Received the following unsolicited feedback in an email from a recent LDR3x customer. Had to share.

"Today I received the LDR3 board and I am FLOORED by the sound quality.  I've been using a TVC [transformer volume control] for several years and was very happy, but the LDR simply blows it away.  I am hearing detail I never knew existed in recordings I have listened to hundreds of time before. Bass is better, treble is clearer, etc....the sound is killer.  I am retired and have been pursuing this hobby seriously for 40 years.  The last 20 years of my career was as a music wholesale salesperson - I worked for Telarc for 7 years and then for an indie distributor where I sold several audiophile labels, so I have some serious experience listening.  This volume control is fabulous." - Glynn Wilson

[J Payton]

I may be interested in a balanced version of your DIY kits.

Do you supply literature on how to wire and hook the unit up.

Specifically I like to see how to wire for manual volume control as this would be used at my desk system so remote control isn't really necessary. Also what is needed (a potentiometer, momentary push buttons, etc).

I've made quite a few projects (Dac, Ncore Amps, Misc Class D amps) but typically need some good instructions or schematics to put a together.

JP

[tortugaranger]

I may be interested in a balanced version of your DIY kits.

Do you supply literature on how to wire and hook the unit up.

Specifically I like to see how to wire for manual volume control as this would be used at my desk system so remote control isn't really necessary. Also what is needed (a potentiometer, momentary push buttons, etc).

I've made quite a few projects (Dac, Ncore Amps, Misc Class D amps) but typically need some good instructions or schematics to put a together.

JP

Good point and I'm working on that. Expect to have something available in another day or so.

Cheers,
Morten

[tortugaranger]

I may be interested in a balanced version of your DIY kits.

Do you supply literature on how to wire and hook the unit up.

Specifically I like to see how to wire for manual volume control as this would be used at my desk system so remote control isn't really necessary. Also what is needed (a potentiometer, momentary push buttons, etc).

I've made quite a few projects (Dac, Ncore Amps, Misc Class D amps) but typically need some good instructions or schematics to put a together.

JP

We just uploaded the latest LDR3x Technical Manual which should now provide what you're looking for.

This latest revision is a big improvement in that it provides much more detailed info on how to wire up the LDR3x to unbalanced and balanced audio signals and also how to connect the optional manual control inputs and outputs. 

You can view/download the latest manual by going to the following link and scrolling down to the bottom the page. LDR3x DIY Preamp Controller Board | Tortuga Audio

For those who have already purchased an LDR3x you'll be getting an email with this updated manual attached.

As always, if you see something that's just plain wrong, doesn't make sense or needs additional clarification, give me a shout here, via PM or via morten@tortugaaudio.com

Enjoy!
Morten

[tortugaranger]

Just a quick reminder that if you've been hesitating about ordering a LDR3x Passive Preamp Controller Board w/ Remote, the current sale on the LDR3x ends at midnight next Sunday (9.1.13).

Right now the LDR3x goes for $195 including remote ($295 for the balanced Master/Slave board combo).

Visit our website/store to find out more: http://www.tortugaaudio.com/product/ldr3x-diy-preamp-controller-board/

[JohnR]

Hi Morten, I'm wondering if it's possible to separate the analog grounds for the two channels (by cutting a track on the board if necessary)?

[tortugaranger]

Hi Morten, I'm wondering if it's possible to separate the analog grounds for the two channels (by cutting a track on the board if necessary)?

As currently designed, separating the left/right channel grounds would require cutting the ground trace and somehow effecting a new connection to the now dangling ground trace. Doable but ugly and all to easy to bugger the board in the process.

I realize there's a school of though that takes a dim view of a common audio ground as implemented here.     In the end, we took the common ground approach because we felt it was more important to achieve the best possible left/right channel attenuation balance with reference to the same ground. At least with single ended systems. As a practical matter, we've not found this to be a problem with our passive preamps and so far the proof is in the listening. 


 

[JohnR]

Hi Morten, thanks for the info, actually the reason I asked was because I'm trying to figure out if the LDR can go between a balanced output DAC and a Broskie cathode follower:

http://www.tubecad.com/2006/08/blog0075.htm



The thought was that if the grounds were not common then an extra pair of coupling caps would not be needed. However, I've realized since then that if using the boards in balanced mode/one per channel, then it should work if the ground were simply not connected. I'm assuming the analog ground is not connected anywhere else?

It also occurs to me as I write this that I'm making it too complicated...! It would be simpler and easier to put the LDR after the CF output and use it "passive",  built into its own box it can be used with any other equipment as well.

[tortugaranger]

The thought was that if the grounds were not common then an extra pair of coupling caps would not be needed. However, I've realized since then that if using the boards in balanced mode/one per channel, then it should work if the ground were simply not connected. I'm assuming the analog ground is not connected anywhere else?

It also occurs to me as I write this that I'm making it too complicated...! It would be simpler and easier to put the LDR after the CF output and use it "passive",  built into its own box it can be used with any other equipment as well.

While you could go with a Master/Slave dual board balanced approach on the input to the follower, I agree that putting a single passive on the downstream end is both simpler and cleaner all around.

Yes, with balanced you could leave out the ground connection.  And yes, the analog ground on the LDR3x is isolated from the power ground.

[rklein]

I just spent some time talking with Morten on the phone about various possibilities regarding his product line.  He was certainly very open to some of the ideas that I posed to him concerning both his DIY products and finished retail product line.    I respectfully, will defer that conversation and let him post on what ideas he would like to implement here on AC. 

I plan on ordering the LDR3x Master & Slave Boards w/ remote (for balanced signals).  For me and my system and for the price of admission (current promotion), I have to see for myself and listen with my own ears, how the LDR based passive preamp differs from the passive pre I am currently using.

Regards,

Randy

[C17FXR]

Morten
I like what you've done with your LDR volume control. It fits right into the requirements I have for a remote control.
I'm looking to implement this into my buffered preamp that consists of a stepped attenuator built around a Shallco with Audio Note resistors.
Quite pricey I must say but very transparent, my only complain being the lack of remote control.
I have been looking into possibly implementing a LDR control into the mix but just haven't found one the suits my needs until I seen your offerings.

But I have a question concerning the LDR3x DIY. Is the circuit board made with the same material as the LDR1 and LDR6?
"Cool blue nickel immersion gold printed circuit boards. Premium materials. Lead-free board & solder. No corrosion."

 

[tortugaranger]

But I have a question concerning the LDR3x DIY. Is the circuit board made with the same material as the LDR1 and LDR6?
"Cool blue nickel immersion gold printed circuit boards. Premium materials. Lead-free board & solder. No corrosion."

In a word....yup! Same style/specs and same US fabricator. Been very pleased with the quality.

And I would think that with proper planning and attention to detail that the LDR3x would make for a very nice retrofit attenuator/controller for any existing active preamp - especially if you're looking to add remote control capability.

Retrofitting into an active preamp is something several people have mentioned they're thinking about or going ahead with. Based on my own experience with conventional resistive attenuator vs. LDR, I'd would expect a noticeable improvement in sound quality.

If you do this, please let us know what you think of the results.

Best,
Morten