Tortuga Audio LDR3x DIY Preamp Controller w/ Remote

[CaptainWatt]

Now includes IR Remote & reduced price for Slave Board

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 - $295

2) If you're looking to build a balanced preamp, we've reduced the price of our optional Master Board - $150

 

[CaptainWatt]

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: LDR3x DIY Preamp Controller Board | Tortuga Audio
• We accept PayPal, credit cards, and also personal checks.

 

[CaptainWatt]

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

 

[kuribo]

Is it possible to use these after a multichannel dac in a biamping setup with computer based crossovers?

Is it possible to use one after a 2 channel dac, before an outboard active crossover in a 2 or 3 way bi/tri amp set up?

 

[CaptainWatt]

Is it possible to use these after a multichannel dac in a biamping setup with computer based crossovers?

Is it possible to use one after a 2 channel dac, before an outboard active crossover in a 2 or 3 way bi/tri amp set up?

This simple answer is a qualified yes.

It's helpful to use pics to talk about this so I've attached the diagram below.

The first configuration is your basic 2 channel DAC-preamp-amp with passive crossovers in the speakers.

The second shows the same 2 channel DAC-preamp but with an external active crossover feeding a tri-amp but could also be a bi-amp. This was the configuration of my personal rig for quite some time where I used our LDR6 Passive Preamp (same technology as the LDR3x). I've since gone to using full range speakers.

In both the first two configurations a single LDR3x preamp board handles the job just fine.

The third shows a bi-amped 4-channel DAC configuration where the crossover is done digitally upstream or integral with the DAC. Here we use an LDR3x in a master/slave configuration where the master handles the 2 left channels and the slave handles the 2 right channels. Please note that these are all unbalanced signals.

Where it gets even more interesting is in the last configuration which is a tri-amped 6 channel DAC again with the crossover done in the digital domain. Here we need 6 channels so a single LDR3x master/slave isn't enough. We could go with 2 pairs of LDR3x master/slave boards. How does this work with 2 masters? Actually this works quite well. We sold a pair of our LDR6 Passive Preamps to one customer who wanted mono-preamps. Using a single remote, the volume of both mono-preamps followed in lock-step even though they weren't actively slaved to each other. In the event they ever got out of synch (not at the same volume level) it's a simple matter of driving volume to zero via the remote to re-sync them.

I'm sure there are other possible variations on these scenarios but in most cases I can think of the LDR3x should be able to work quite well.

Cheers,
Morten

 

[kuribo]

Thank you for your detailed reply.

I should have mentioned that I am interested in balanced inputs and outputs. How would this change things?

Thanks again.

 

[CaptainWatt]

Thank you for your detailed reply.

I should have mentioned that I am interested in balanced inputs and outputs. How would this change things?

Thanks again.

Handling balanced I/O basically means that for each nominal signal you actually have two signals, a so called + and a - which are 180 degrees out of phase with other.

In terms of the diagram in the previous post, you would basically need twice the number of LDR3x boards since you'd have twice the signals. This gets back to the dual board LDR3x Master/Slave scenario which was designed for handling balanced inputs/outputs where the Master handles say the left channel +/- pair and the Slave board handles the right channel +/- pair. But with multiple channels the hardware count adds up.

And while it gets messier with multiple boards, we can easily match the attenuation curves off all the boards needed using our established LDR testing and curve correction protocols.

Alternatively, you could use transformers to briefly convert the signals to unbalanced at the input to the preamp and back to balanced at the output of the preamp. This would save you all the extra boards and prove to be a less costly approach. Edcor makes some nice transformers for this that run about $25 for a pair. You'd need 3 pairs for the tri-amped case in lieu of the extra LDR3x boards. I'm generally not in favor of all extra signal manipulation with transformers but they are quite quiet and introduce minimal signal loss.

Best,
Morten

 

[CaptainWatt]

We were just informed by one of our customers that if you're using Microsoft's Internet Explorer during purchase/checkout on our website/store that you might encounter a security warning page with the message..""This website's address doesn't match the address in the security certificate"

This is unique to IE and doesn't happen with either Chrome or Firefox. It's just our friends at Microsoft being more special again.

We have our hosting service looking into this but meanwhile be assured that our website is indeed secure and that we have all appropriate security certificates are in place. You can confidently bypass this warning message and purchase through our web store. LDR3x DIY Preamp Controller Board | Tortuga Audio

If you encounter this problem or have any related concerns or problems with our website please don't hesitate to PM me or contact me directly at morten@tortugaaudio.com

Enjoy!
Morten

 

[CaptainWatt]

We were just informed by one of our customers that if you're using Microsoft's Internet Explorer during purchase/checkout on our website/store that you might encounter a security warning page with the message..""This website's address doesn't match the address in the security certificate"

This is unique to IE and doesn't happen with either Chrome or Firefox. It's just our friends at Microsoft being more special again.

We have our hosting service looking into this but meanwhile be assured that our website is indeed secure and that we have all appropriate security certificates are in place. You can confidently bypass this warning message and purchase through our web store. LDR3x DIY Preamp Controller Board | Tortuga Audio

If you encounter this problem or have any related concerns or problems with our website please don't hesitate to PM me or contact me directly at morten@tortugaaudio.com

Enjoy!
Morten

Just a quick note to let everyone know we've resolved the above problem with Microsoft Internet Explorer. Turns out we didn't have a fixed IP address even though we ordered one and have been paying for one. We have one now! Trust yet verify indeed.

 

[CaptainWatt]

Thank you!

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

 

[CaptainWatt]

Customer feedback on the LDR3x

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

 

[CaptainWatt]

Greatly Improved Technical Manual

We just uploaded the latest LDR3x Technical Manual.

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

If you've 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

 

[CaptainWatt]

Sale on LDR3x Preamp Controller Board ends 9.1.13

Just a quick reminder that if you've been hesitating about ordering a LDR3x 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: LDR3x DIY Preamp Controller Board | Tortuga Audio

 

[CaptainWatt]

Just a quick reminder that if you've been hesitating about ordering a LDR3x 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: LDR3x DIY Preamp Controller Board | Tortuga Audio

In light of the extended Labor Day weekend here in the US, we're extending the sale price for the LDR3x up until midnight this Monday, Sept 2nd.

Enjoy the extended weekend!
Morten

 

[ErikdeBest]

I would like to pose a question, hope it is not a problem. Did you ever try to make a balanced LDR control with the LDR in place of the pot, as shown in the attached schematic? This would save 3 LDR's per channel.
What is the minimum resistance you have been able to achieve with these LDRs?
Many thanks! Erik

 

[CaptainWatt]

I would like to pose a question, hope it is not a problem. Did you ever try to make a balanced LDR control with the LDR in place of the pot, as shown in the attached schematic? This would save 3 LDR's per channel.
What is the minimum resistance you have been able to achieve with these LDRs?
Many thanks! Erik

Hi Erik,
No problem. Our current balanced LDR design approach looks something similar in that R1 and R2 are both LDRs (the series) and the RV1a is actually 2 LDRs (call them R3 and R4 - the shunts). Through testing and software we're able to shape the resistance curve of all 4 of these LDRs to achieve very decent channel to channel balance. Thus for unbalanced audio we use a total of 4 LDRs, 2 per channel and twice that for balanced.
Cheers,
Morten

 

[ErikdeBest]

Hi Morten,

thanks for your reply. That is indeed how I expected you would do it. I was just thinking that using fixed resistors for R1 and R2, and indeed just one LDR instead of two in series, could work as well - soundwise maybe worse, maybe better, don't know - but probably cheaper and easier (less LDR's, less matching issues). Downside is that impedances would vary more with this setup.

I was more curious if you have compared both ways of doing balanced volume control?

many thanks, Erik

 

[CaptainWatt]

Hi Morten,

thanks for your reply. That is indeed how I expected you would do it. I was just thinking that using fixed resistors for R1 and R2, and indeed just one LDR instead of two in series, could work as well - soundwise maybe worse, maybe better, don't know - but probably cheaper and easier (less LDR's, less matching issues). Downside is that impedances would vary more with this setup.

I was more curious if you have compared both ways of doing balanced volume control?

many thanks, Erik

For reasons I can't explain (because I don't know!) but that probably have to do with material properties, audio just sounds better having traveled through LD-resistors compared to conventional resistors. It would compromise sound quality to go back to using conventional resistors. Or else why not just use a stepped attenuator with say Vishay resistors...or a pot. The whole point of LDR based attenuation isn't merely to use less of them but to use only LDRs and just enough of them to get the job done.

 

[ErikdeBest]

Hi Morten,
I thought that the point was to avoid mechanical contact, but indeed the presence of more LD resistors may be the main factor influencing the sound. Well, from my side it was mostly curiosity, so maybe I will have to try it out myself. Many thanks for your replies, and succes with your business!
Erik

 

[Robert F]

Hi,

I received the kit, thanks. I have temporarily housed it in a plastic project box with very cheap and nasty phono sockets. I am delighted to report that it is clearly and unexpectedly better than my amorphous core TVC with its WBT "Next Gen" silver phono sockets. Thanks for the outstanding product!

Rob.