[tortugaranger]

For those who have already placed pre-orders (thank you!) and for those who are otherwise waiting on the release of the LDR3x.V2 Preamp Controller Board, you may have noticed we've already slipped a couple of weeks on the release date (it's currently April 16th).

Rather than keeping everyone in the dark wondering what's the hold-up, I've decided to provide some more timely info on the product development process as we approach the release date. Just like "sausage making", the end product might be satisfying but seeing it being made may well put you off your feed. So be it. 

The V2 board has a smaller piggy-back board attached to the main board. The piggy-back board with handle the switching/routing of the audio signals to to ADC inputs during auto-calibration. We had the piggy-back board all finished including a complete production run of boards (unpopulated). Only then did we discover an impedance problem with the auto-cal ADC inputs which meant we needed to put a quad op amp buffer between the audio signals and the ADC inputs.     Goodbye auto-cal piggy back boards - all 200 of them - in the dumper. Sigh!    That set us back roughly 2 weeks. Now we're waiting on latest prototype boards which we should have by Monday. If we're lucky, that should be the last iteration of prototype boards for both the main and piggy-back boards which means we can release both for production runs by the end of next week. If we encounter another problem....we'll be...slip slip slip'n along.

And just in case any of you audio design hawks are freak'n out about the audio signals going into op amps and ADC's etc. fear not. When auto-cal is disabled, the audio signals are physically disconnected from the auto-cal circuitry and only go through the LDRs.  We may not be that bright, but we're not stupid. 

Cheers!
Morten

"Designing The Sausage - it's all alligators in there".

[tortugaranger]

We recently took a closer look at our 5 VDC power supply regulators and compared our original 7805 regulator to our new SMPS regulator. I knew the SMPS was better but I wasn't prepared to see how badly the linear regulator performed by comparison. Wowzer!

I invite you to take a look at what we saw. See links below: 

Google Doc Format: https://docs.google.com/presentation/d/11kYcaSOxeeUNpl19Ypdr5U6pTNl7VOfDcMWcz_36-uk/edit?usp=sharing

PDF Version: https://drive.google.com/file/d/0BzkBmU5mW70WaURvcUQ2c0VmdUk/edit?usp=sharing

[tortugaranger]

We are waiting on delivery of what we hope is THE final version of our PCB design for the LDR3x.V2. Should have those by Wednesday this week. "Those" meaning both the main board and the piggy-back calibration board. By this weekend we should know whether the board designs are ready for a production run. Production boards will take another 7-10 days so best updated estimate on release of the LDR3x.V2 is now around April 23rd. Everything takes twice as long and costs twice as much.

[tortugaranger]

The "final" LDR3x.V2 prototype boards are in-house and we're flailing away with testing and tweaking. So far so good. Only a couple of minor corrections needed for the production board but nothing that warrants another round of prototype boards and testing. With a little luck we just might get the version 2 board ready for release this month (this year!).

[tortugaranger]

Note that we sent out to our pre-order customers yesterday.
___________________
Dear Pre-Order Customers,

Despite our best efforts to release the LDR3x Version 2 board this week we are going to need a bit more time. Work is progressing nicely and we are now working with our final prototype board which so far is holding up nicely. The version 2 board is a very ambitious project and we’re committed to getting it right before we lock in the design and order production boards.

There are actually 3 separate printed circuit boards for the Version 2: the main board, the smaller calibration piggyback board, and the very small removeable LDR module board. The LDR module board is done and we have production units already in hand. We are just now testing the final main/calibration board prototypes to make sure that the hardware end of things are good to go. Given where we are in that process I expect to be able to order production boards within the next 5-7 days.

Software being software we’ll be tweaking that up until the last minute and then keep on tweaking it even after the release date. The core of the software is built on the version 1 board foundation which is very solid at this point. The key additions are auto-calibration, usb communications and board-to-board spi communications for balanced audio coordination between master/slave boards. Of those, the auto-calibration is the big deal addition and continues to be our primary focus.

Cheers!
Morten

[tortugaranger]

A preview of our replaceable LDR Module that will be used in our upcoming Version 2 LDR3x. Each LDR3x uses 4 of these. If needed, it's a simple matter of unplugging an LDR Module and popping in a new one in. Not unlike a tube.

In some ways, LDRs and tubes are similar even though they do very different things. Some tubes fail early on. Some tubes drift to the point they become out of spec and need to be replaced. All tubes have finite, albeit long, lives and eventually need to be replaced. Newer, better, and even older/better tubes come along that warrant replacing the original tube for improved performance. LDRs are similar in these respects.

So, introducing the replaceable LDR Module. Boom!

Will we see "LDR Rolling" in the future? Don't know. But it's good to stay flexible. 

[tortugaranger]

There comes a time in the design of all things where you finally have to shoot the engineer and build the damn thing. 
The deed is done and production boards have been ordered for the Version 2 LDR3x Preamp Controller.
Shipment of boards out to our shop is promised 4.28.14 so figure release of the LDR3x.V2 the week of May 5-9. 

[tortugaranger]

While waiting on the LDR3x.V2 production boards to arrive from our fabricator we've been working like mad on tuning up the auto-calibration software.

I can now say without a doubt that auto-calibration has exceeded all expectations with channel balance within +/- 0.1 dB over the full attenuation range of -60 to 0 dB.  For LDRs that's darn tight balance and sounds fantastic. And that's hands off with no help from external test/calibration equipment. It's taking roughly 10 minutes to run through a full auto-calibration cycle for all 4 LDRs with each LDR going through 70 attenuation steps.

One decision that's yet to be made is how often to run the auto-calibration routine when the unit is turned off. During development, we've just let it run continuously when off. There's no harm in this as far as the LDRs go but the EEPROM memory we write the results to will eventually fail. Assuming a life of 1,000,000 erase/write cycles this translates into something like 16 years of auto-calibration every 10 minutes. If we put in a timer to only run auto-cal every 60 minutes than the life of the EEPROM becomes something like 97+ years. Good enough, ya think!!? 

Of course this also assumes the unit is never turned on....which would be sad indeed. 

Check out this recent article we posted on the evolution of LDR volume control: http://www.tortugaaudio.com/evolution-of-ldr-volume-control/

Cheers,
Morten