Adjustable Impedance

0 Members and 1 Guest are viewing this topic. Read 18804 times.

justubes

  • Jr. Member
  • Posts: 35
Re: Adjustable Impedance
« Reply #60 on: 7 Nov 2016, 04:50 pm »
 Have changed out previously all ldrs with new one, same issue.

Seems that my autocal is not completing the whole cycle which i wrote to you before and havent since  tried to touch in fear it become unusable meaning no more music  and dont want the downtime.

I have not gathered courage to do the firmware update as it means i have to run autocal all over again?

tortugaranger

  • Facilitator
  • Posts: 1180
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Adjustable Impedance
« Reply #61 on: 7 Nov 2016, 05:41 pm »
Have changed out previously all ldrs with new one, same issue.

Seems that my autocal is not completing the whole cycle which i wrote to you before and havent since  tried to touch in fear it become unusable meaning no more music  and dont want the downtime.

I have not gathered courage to do the firmware update as it means i have to run autocal all over again?

LOL. I never thought updating firmware would require courage! I realize I have a different perspective on this given my familiarity with the inner workings of everything but I literally load/update firmware into our boards on almost a daily basis. It's a highly mature process which just works once you have everything set up.

More recent firmware update work specifically addressed a few lingering issues when using our controller boards in a balanced (master/slave) configuration. For this reason I would encourage updating the firmware on balanced setups especially.

Moreover, running autocal isn't some kind of iffy process that anyone should be afraid of. As long as your LDRs are healthy it just works. If they're not healthy...well, you should find that out and replace them accordingly. Autocal helps in this process. Again, if you have noticeable channel imbalance after changing impedance settings, you definitely need to rerun autocal. My recommendation is   - just do it!  :thumb:

tortugaranger

  • Facilitator
  • Posts: 1180
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Adjustable Impedance
« Reply #62 on: 13 Sep 2017, 07:29 pm »
Upcoming Changes to Adjustable Impedance in V25 Based Preamps

Appreciate any inputs from users on this topic.

The Problem: The adjustable impedance feature currently allows users to unwittingly select an impedance setting (1 thru 5) and level (1k  thru 99k) which has not been properly initialized (has not been through a calibration cycle). This will result in no audio output because the user will have selected an impedance setting/level which has an empty attenuation table. The classic symptom is no audio output or very low audio output that doesn't respond to volume changes. Users get justifiably confused/concerned and wonder why their preamp isn't working. I get emails and phone calls.

The Fix: Firmware update/change which:
a) Will cause the displayed impedance setting/level to blink indicating that the setting/level has not been initialized (has not been run through calibration).
b) Will not allow preamp to switch to a setting/level that is not initialized as evidence by blinking display. 
c) Will leave setting #1 fixed @ 20k as the permanent default. User can rerun calibration of this default setting/level at any time but can't change the impedance level of #1.
d) Will revert to default #1 @ 20k, or, to last known valid initialized setting #/level if user makes a change to impedance setting #/level and does not then immediately thereafter initialize this change by running the preamp through a calibration cycle. 

To summarize this in as simple language as possible, after this firmware change, when you scroll through impedance settings #2 thru 5, if the display blinks those settings are not initialized and therefore the preamp won't switch to any blinking setting. Setting #1 at 20k will never blink because it's the default and user can't change its level. If you do want to use settings 2 thru 5 or change the level of any of these setting #'s you have to run autocal immediately after selecting/changing them or else they will remain un-initialized.
« Last Edit: 14 Sep 2017, 04:49 pm by tortugaranger »

kernelbob

  • Full Member
  • Posts: 341
Re: Adjustable Impedance
« Reply #63 on: 13 Sep 2017, 11:18 pm »
Hi Morten,

I'm so glad your back, safe and sound.

Regarding setting impedance setting #1 permanently to 20k, I really hope you can avoid this.  I use all five of the available saved settings and 20k isn't even in the ballpark.  I'm using the Lampizator Golden Gate DAC.  I'm able to fine tune the voicing of the DAC for different recordings by selecting between my various saved impedance settings.

Currently, I have my LDRxB's five impedance settings at 85, 88, 91, 94, 97k.  Those are of course per phase on each leg of a balanced input.  Even at that, it would be great to have more available saved settings.  Now that you have more available memory in your logic system, could you have 10 settings identified as 0 through 9 with 0 being a fixed value?

Best,
Robert

kernelbob

  • Full Member
  • Posts: 341
Re: Adjustable Impedance
« Reply #64 on: 13 Sep 2017, 11:23 pm »
justubes, if you have the feature where the display goes dark after a period of time, make sure that you disable that (set the delay time to 0) before setting an impedance level.  I occasionally forget to do that and run an impedance change.  The first time that I did that, I thought the calibration cycle had finished and brought the system back up.  Just a thought.

Best,
Robert

tortugaranger

  • Facilitator
  • Posts: 1180
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Adjustable Impedance
« Reply #65 on: 14 Sep 2017, 05:06 pm »
....it would be great to have more available saved settings.  Now that you have more available memory in your logic system, could you have 10 settings identified as 0 through 9 with 0 being a fixed value?

Since I'm modifying this code right now anyway expanding from 5 to 10 settings is fairly straightforward. Setting #1 will remain fixed at 20k and the other 2-10 are all adjustable. Once these changes have been tested all new V25 units will shipped with the changes outlined.

kernelbob

  • Full Member
  • Posts: 341
Re: Adjustable Impedance
« Reply #66 on: 14 Sep 2017, 08:24 pm »
Hi Morten,

It's like you've got a magic wand.  More than once, when I've suggested something, it just happens!  I did want to reiterate to anyone shopping for a controller that I've come to really value the adjustable input impedance feature.  Having lived with three DACs with the LDRxB-V2 (and tried others with it), I would not want to use any other controller that lacked this feature.  The Lampizator Golden Gate was especially responsive to different input impedances which I now use to voice the sound for specific recordings.  Even a change of a few kohms is audible.

Now, if there were just some way to move/copy an impedance setting from one saved slot number to another to avoid having to do recalibrations to reorder the impedance slots...

Best,
Robert

tortugaranger

  • Facilitator
  • Posts: 1180
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Adjustable Impedance
« Reply #67 on: 15 Sep 2017, 12:54 pm »
Now, if there were just some way to move/copy an impedance setting from one saved slot number to another to avoid having to do recalibrations to reorder the impedance slots...


That's doable but would add a level of additional complexity to the code that would take a fair bit of additional time to implement and test. I simply don't have the time for that right now but will put it on the wish list.  :thumb:

tortugaranger

  • Facilitator
  • Posts: 1180
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Adjustable Impedance
« Reply #68 on: 16 Sep 2017, 10:09 pm »
Upcoming Changes to Adjustable Impedance in V25 Based Preamps

I've completed the software mods and will be posting an updated V25 firmware file soon for those interested in uploading this change to their V25 based preamp. 

Here's an update on how things turned out.

The Problem: The adjustable impedance feature currently allows users to unwittingly select an impedance setting (1 thru 5) and level (1k  thru 99k) which has not been properly initialized (has not been through a calibration cycle). This will result in no audio output because the user will have selected an impedance setting/level which has an empty attenuation table. The classic symptom is no audio output or very low audio output that doesn't respond to volume changes. Users get justifiably confused/concerned and wonder why their preamp isn't working. I get emails and phone calls.

The Fix: Firmware update (rev 1012) as follows:
a) Possible impedance settings has been increased from 5 to 10.
b) Each setting 2 thru 10 can be adjusted by user to be between 1k and 99k.
c) Setting #1 is now fixed at the level of 20k and this level cannot be changed by user.
d) In the event user makes a change to an impedance setting level and forgets to subsequently run autocal to build the attenuation table for that setting/level the preamp will not ignore that setting/level and next time the unit is turned on it will use either the default setting #1/20k or the most recent other valid impedance setting/level if there is one.
e) If the user switches the preamp to an impedance setting/level that has not been initialized (run through autocal) the display will blink and there won't be any audio output.
f) If the user becomes confused, just turn the preamp off and back on again and it will resume operating at the last known valid impedance setting/level.

All preamps shipped on/after Sept 16, 2017 will already incorporate this firmware change.

It's worth noting that the adjustable impedance feature of the V25 is entirely optional. If you never make a change the preamp will use the default setting #1 fixed at 20k input impedance.