[tortugaranger]

Here's where things stand regarding expressed interest in an V2.1 group buy. We're at 8. Absolute minimum is 10 with goal of 20. I'm reiterating the first post below so others don't have to wade through to find out what's going on.

The board has gone from 6 layer to 4. Although there are 3 separate voltage regulators only the +5 analog is pervasive while the +9 and +5 digital have very limited reach and so can coexist on a single power plane without undue compromise. The board cost jumps considerably going from 4 to 6 layers.

Input voltage might be able to go as high as 35 VDC although I still have to check whether that may cause thermal issues. Overall current load is still relatively low with the V2 so should be ok; want to avoid heat sinks.

1 - 33na3rd
1 - glynnw
2 - clefchef
1 - jtwrace (maybe)
1 - markn
1 - mikebarney
1 - golfrod

I'm planning a revised version of the LDR3x.V2 Passive Preamp Controller Board. This is a refinement of the V2 versus a new design. Think of it as the V2.1. The driver for this is to improve performance while also driving down the cost of a finished board.

The key refinements include:

1) Integration of simplified auto-calibration circuitry on to the main board - no more separate piggy-back auto-cal board.
2) Separate digital and analog power supplies
3) No direct use of external power source - everything gets regulated/filtered on the board
4) Related to 3), the V2.1 can accept a wider range of external supply voltages from 12-24 VDC (perhaps even higher) including unregulated.
5) 6 layer PCB board with 3 power planes in addition to ground plane
6) No audio signals passing through relay connections (on our LDRx/LDRxB preamps we already do this but it's done with a special version of our IO board).
7) Use of multiple low drop out, low noise linear regulators vs. existing single switch mode regulator.

All of that translates into a better overall design with quieter power supply that will hopefully yield improved performance. Getting everything on to a single board will go a long way to offsetting some of the cost increases related to items 1-7) such that the overall fully assembled cost of the board will still be less.

If you've been planning a DIY passive preamp around the LDR3x.V2, I'm extending a group volume price of $199 for the V2.1 version (vs. current V2 price of $259).  To get this off the ground I need a group buy of at least 10 units but want to target 20+.

If you are interested please chime in here or send me a PM. And let your DIY audio buddies know.  At this point I'm only looking to gauge interest and not a firm commitment. At some later point I may set  this up as a pre-order on our website.

Enjoy! 
Morten

[TrungT]

Please add 2 more. 

[krikor]

I'm interested! Thinking about incorporating into my Bottlehead Crack that is in the process of being built

[tortugaranger]

Ok. We are up to 11 here and I think I've got +2 on diyAudio & +2 via email so lets call it 15. Need 5 more to hit the 20 mark.

A little more inside ball on the 2.1 design. Both the V1 and V2 designs took a simplified approach to power using only single 5 V supply and 2 layer boards. The V2 added 12 volts but again only single supply. That has limited the use of which type of opamp to use for both the control circuit and the auto-cal circuit. In the latter case we had to go with a relatively expensive rail-to-rail opamp that could operate well between 0-12 volts especially when near 0 volts. Also the V2 used whatever 12 volt supply was provided by the user with no regulation/filtering while providing on-board regulation etc of the 5 V supply.

The V2.1 will have a split +9/-9 volt supply for the op amps which will allow the use of much better (less noisy) op amps that will generally work more predictably. It will also continue to have a single 0-5 VDC supply needed by the microcontroller, DACs and EEPROM. That's 3 different voltages. Add in the ground and that makes 4 power/reference planes. After some back and forth I had to bite the bullet and so we're back to a 6 layer board 4 of which are power/ground planes. This will further ensure low noise. FYI, none of these power/ground planes extend out to where the audio signal traces run. 

As I mentioned earlier the the supply voltage to the board will be able to be between 12-35 VDC although I still have to test if there will be thermal issues at the upper voltage range. However, the "12 Volt Trigger Out" feature of the V2.1 will run off the board's supply voltage so if you plan to use this feature limit the supply voltage to ~12 VDC. 

1 - 33na3rd
1 - glynnw
2 - clefchef
1 - jtwrace (maybe)
1 - markn
1 - mikebarney
1 - golfrod
1 - krikor
2 - TrungT

[markn]

Please add one more for me, a total of 2...

Thanks,

Mark

[sfox7076]

Will there be a group buy for the kit? 

[justubes]

Please add one more for me, a total of 2...

Thanks,

Mark

Hi Morten,

My post might be slow as i'm a newbie.

Please add me in for 2 (Balanced connection)

When will this version be ready?

Thanks

[tortugaranger]

As of this AM we are at 19 so I'm going to assume we'll add a few more soon enough. Good enough to kick this off.

Timing & next steps.

I'll set this up on the website and let you know when that's done so you can go there and formally place and pay for your order. I figure another week or so of tweaking and double-checking the design before ordering the boards. Turn-around on board fabrication will be roughly 2-3 weeks. Getting them faster just drives up the cost. Once we have the boards we'll start stuffing boards and shipping. Adding that all up plus a little room for slippage and figure release/shipping starting mid December.

One additional feature of the V2.1 is the op amps will be socketed. The V2 uses 3 14 pin quad op amps with standard quad op amp pin out; 2 are used for controlling the LDRs and the 3rd only comes into play during auto-calibration otherwise is isolated from the audio signals. This opens up the possibility of exploring whether alternative op amps might improve performance. I'm agnostic on this topic. Specs like slew rates and bandwidth etc. shouldn't be relevant since we are only putting DC through the op amps. The only AC they see should be noise from the power supply. Yet every op amp contributes its own noise. Even though the audio signals are optically isolated, noise present on the control signals to the LDR's LED will be seen by the photoresistor and thus the audio signal. Response of the LDR's photoresistor is not instantaneous so they do act as natural filters. At what point such filtering renders any further improvement in control signal noise moot is something I'm curious about but have not had time to fully explore.

AudioCircle
1 - 33na3rd
1 - glynnw
2 - clefchef
1 - jtwrace (maybe)
2 - markn
1 - mikebarney
1 - golfrod
1 - krikor
2 - TrungT
2 - Mas
diyAudio
1 - Quirepace
1 - Do
1 - nilsjnesse
2 - justubes

[sfox7076]

I will take one.  Hope you can do a kit with it though.  Or at least make a case available.

Shawn

[tortugaranger]

I will take one.  Hope you can do a kit with it though.  Or at least make a case available.

Shawn

We are working on a kit offering that will likely have options for: a) complete kit (V2.1 & enclosure etc.), b) kit minus the V2 board (for those who already have the V2 board), and c) enclosure only. More on all that soon. 

[eparson]

Put me down for one...

[rklein]

Hi Morten:

I also would also appreciate being have my name added to the list.

Regards,

Randy

[tortugaranger]

Group buy tally as of 11.7.14 AM - 22.  We have liftoff!

AudioCircle
1 - 33na3rd
1 - glynnw
2 - clefchef
1 - jtwrace (maybe)
2 - markn
1 - mikebarney
1 - golfrod
1 - krikor
2 - TrungT
2 - Mas
1 - sfox7076
1- eparson
1- rklein
diyAudio
1 - Quirepace
1 - Do
1 - nilsjnesse
2 - justubes

[ClefChef]

Would it be possible to add a simple clock feature to the dual display units? Just an idea.

[tortugaranger]

Would it be possible to add a simple clock feature to the dual display units? Just an idea.

Although the V2 microcontroller has numerous timers etc. I think that in order to display an accurate digital clock you'd need a precision clock reference with battery backup for when the unit is disconnected from power. I'm sure this is doable but not without adding more "stuff" to the design hardware/software. Such added cost is hard to justify for what is arguably a non-essential feature.

[tortugaranger]

I wanted to give everyone a brief update on the V2.1 and related product evolution so here goes.

1) The V2.1 board design is complete but waiting on arrival of 2 new components for final fit-up check and functional test. I expect to have that done by Nov 19th or so at which time I will proceed to order the boards.

2) We are going ahead with the DIY preamp kit - the LDR3.V2K. This will be available for pre-order at the same time the $199 V2.1 board special becomes available for pre-order. So you can choose whether to go with just the board or a complete kit. More to follow on that.

3) In addition to the LDR3.V2K kit, we are also going to offer an upgraded variant of the kit as a finished product - the LDR3.V2 (without the "K"). There will be a few differences between the kit and the finished product, both cosmetic and probably internally. However, both will utilize the same extruded aluminum box as our original LDR1/3/6 passive preamps at 6" wide x 3" tall x 8"deep but with new and different front/rear panels. More to follow on that as well.

4) Lastly there will be a price increase of our LDRx and LDR3xB Passive Preamps effective Jan 1st. If you've been jones'n for one of those, you still have time but the price will go up several $100 each starting in 2015.

None of this is on our website yet. An announcement with more details with be forthcoming via our Newsletter soon. If you're interested in the newsletter you can sign up here. http://www.tortugaaudio.com/newsletter-subscription-signup/

Cheers,
Morten

[VincentH]

Hi Morten

Please add me to the list. Thanks

[Alfi]

Hi,
I'm interested in your $199 V2.1 group buy.

thanks,
Alfred

[tortugaranger]

Updated group buy list. As soon as I get the V2.1 set up on the website/store I'll let you know.

AudioCircle
1 - 33na3rd
1 - glynnw
2 - clefchef
1 - jtwrace (maybe)
2 - markn
1 - mikebarney
1 - golfrod
1 - krikor
2 - TrungT
2 - Mas
1 - sfox7076
1- eparson
1- rklein
1- VincentH
1- Alfi
diyAudio
1 - Quirepace
1 - Do
1 - nilsjnesse
2 - justubes

[tortugaranger]

Ok. We have pulled the trigger on both the latest version of the V2 board, the V2.1....and...we are also announcing the new LDR3.V2K comprehensive passive preamp kit including enclosure. 

The $199 pre-order special on the V2.1 runs out on Jan 5th after which the price goes back up to @259
More details on the V2.1 including pre-order purchase are available here: http://www.tortugaaudio.com/product/ldr3x-v2-1/

In case you're looking for a complete kit rather than just the V2.1 board, the new V2K passive preamp kit is also available for pre-order purchase for $695 also until Jan 5th after which it goes up to $795.
More details on the V2K kit including pre-order purchase are available here: http://www.tortugaaudio.com/product/ldr3-v2k-passive-preamp-kit/

Cheers,
Morten