[robertopisa]

Hello Morten,

any news regarding pre-cal for owners of v2 boards?

P.S. Here is the info that I need. So my question is how bad is having just one display for pre-cal? Is it showing the first or the last two digits of the four digits info displayed?

http://www.tortugaaudio.com/product/precision-calibration-module-set/
http://www.tortugaaudio.com/documentation/#document-8

Thanks
Roberto

Sounds like we're confusing topics here. Auto-cal and pre-cal have nothing to do with the USB connection or uploading firmware.

I will provide additional info on pre-cal soon but I strongly caution owners to not mess with precalibration unless that are fully prepared to do so. If you fiddle with pre-cal and do it wrong there's no graceful exit and your board will probably not work right until you get through it correctly.

If you own a v2.1 board there's no need to rerun pre-cal. Owners of v2 boards can improve auto-cal accuracy by doing a one time pre-cal but pre-cal requires 2 different values of precision reference resistors be plugged into the board instead of the LDRs.

[tortugaranger]

Hello Morten,

any news regarding pre-cal for owners of v2 boards?

P.S. Here is the info that I need. So my question is how bad is having just one display for pre-cal? Is it showing the first or the last two digits of the four digits info displayed?

http://www.tortugaaudio.com/product/precision-calibration-module-set/
http://www.tortugaaudio.com/documentation/#document-8
Thanks
Roberto

With only a single (2 digit) display you will be able to see the last (right most) 2 digits only. This is enough to tell that the PreCal has stabilized and you are ready to go on to the next LDR.  However, you won't have any explicit confirmation as to which LDR the board is on. It's possible to get by with a single display but frankly I wouldn't advise it. This is a complicated enough process as some customers have learned who have tried it - and succeeded. Even though I do several of these each week I wouldn't attempt it without full display info. Too easy to get lost as to where you are (or more precisely where the LDR board is).

[robertopisa]

I agree that it would be better to use a dual display but I do not have it and do not have space to install one in my DIY pre So I must stick to a single display... so on each LDR socket, the two back pins are connected by the resistor at hand and the two front pins stay unconnected, right? Thanks.
-R

With only a single (2 digit) display you will be able to see the last (right most) 2 digits only. This is enough to tell that the PreCal has stabilized and you are ready to go on to the next LDR.  However, you won't have any explicit confirmation as to which LDR the board is on. It's possible to get by with a single display but frankly I wouldn't advise it. This is a complicated enough process as some customers have learned who have tried it - and succeeded. Even though I do several of these each week I wouldn't attempt it without full display info. Too easy to get lost as to where you are (or more precisely where the LDR board is).

[tortugaranger]

I agree that it would be better to use a dual display but I do not have it and do not have space to install one in my DIY pre So I must stick to a single display... so on each LDR socket, the two back pins are connected by the resistor at hand and the two front pins stay unconnected, right? Thanks.
-R

That is correct sir!

The pre-cal resistors take the place of the LDR resistance. The front 2 pins of each LDR socket normally control the LDR but are not involved/needed for pre-cal. The pre-cal resistors present a known fixed resistance (100 & 100k ohm) to the LDR3x board which allows the firmware to calibrate between these two limits.

The net result of pre-calibration is improved centering of the channel balance by overcoming variables in the board's hardware that otherwise make each channel slightly different from each other. Most of the time these differences aren't enough to be noticeable but sometimes they can be. Having commissioned many boards I've concluded it's due to random differences in the bits of hardware that participate in the auto-calibration circuit. This is something we started to do with the release of the V2.1 version of the LDR3x preamp controller board but can be retroactively applied to the V2 version boards once the firmware has been updated to the latest 2.X version.

All of our finished preamps shipped on or after Jan 1, 2015 were pre-cal'd as part of their commissioning as were all V2.1 boards.  No need to do it a second time in my view.

Pre-calibration arguably benefits dual board balanced and dual-mono configurations more so than single boards. Because with dual boards you have 4 different channels and thus a greater chance of random differences conspiring to degrade both the overall left/right channel balanced as well as the +/- phase balance within each balanced channel.

While I recommend pre-cal to V2 owners I caution that it's not for the technically faint of heart. There's a good chance you'll get lost in the weeds if not done correctly.    The good news is although you can screw up your V2 board temporarily you can't permanently damage ("brick") it. There's always a way back by doing it correctly.

Bon Chance! 
Morten

[robertopisa]

Great info, thanks Morten !
-Roberto

P.S. My new DAC Merging Hapi arrived. It is a reference DAC for DXD/DSD production (same company as Pyramix, the reference sw for DSD mastering). Sound is top level. It also has a good hw volume control inside but the Tortuga is better for this task, so I prefer Tortuga.