LDR3x.V2 DIY Passive Preamp Controller Board w/ Remote

0 Members and 1 Guest are viewing this topic. Read 41656 times.

glynnw

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #80 on: 1 Mar 2014, 02:01 am »
Will the upcoming 3-input board accomodate unbalanced RCA connectors at all positions or are some of them required to be balanced?  I use all unbalanced RCAs.

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #81 on: 1 Mar 2014, 12:23 pm »
Will the upcoming 3-input board accommodate unbalanced RCA connectors at all positions or are some of them required to be balanced?  I use all unbalanced RCAs.

If you're asking about the version 2 LDR3x Preamp Controller Board, it will be similar to the version 1 board (actually version 0 but lets call it 1) in that it will interface with a 3 input relay switch board (as a current sink).

If you're asking about our upcoming input relay board, each board handles 3 singled ended (unbalanced) stereo inputs. To implement balanced inputs you will need a pair of LDR3x boards and a pair of input relay boards.

Unlike with the version 1 design where you had a normal master board and a dumb (no processor) slave board, with the V2 LDR3x the master/slave boards are identical smart boards except that the slave takes direction from the master which it knows to do by setting a couple of jumpers. Both boards will handle their own auto-calibration.

glynnw

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #82 on: 1 Mar 2014, 08:37 pm »
I have 2 LDR3X boards, both of which I believe are version 1.  Since version 2 will auto-calibrate, will the original boards eventually be out of calibration?

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #83 on: 2 Mar 2014, 01:03 pm »
I have 2 LDR3X boards, both of which I believe are version 1.  Since version 2 will auto-calibrate, will the original boards eventually be out of calibration?

There's no simple yes or no answer here. LDRs are made with an LED and a photoresistor and all LEDs slowly change their luminosity vs. current behavior over their nominal 50,000 hour life. Thus it is practically a given that any LDR based volume control will see the specific behavior of it's LDRs change over time. The key question is does it matter?

We go to great pains to use a matching set of 4 LDRs for each build. We then test each board with its specific LDRs and use that test data to derive a specific set of attenuation tables that are unique to that board and its LDR set. That all gets burned into the final software build for that board. The whole process is a time consuming PITA and involves quite a bit of custom programming and data processing. That's version 1 calibration.

As long as the calibrated matched set of LDRs continue to behave and age in a similar manner over time it won't matter. I've had a unit running more or less full time for almost 5 years and it works perfectly.

It's really not much different than a matched set of tubes aging over time. Who cares if they change (and they do) as long as they change together.

What version 2 auto calibration will do is move the initial calibration process from an external process to a repeatable internal one with improved precision. It will mitigate the degree of necessity for highly matched LDRs. And to some extent it will mitigate the effects of aging. It will also relieve us of maintaining a calibration database of every board we build.

And in the event a version 1 board was to drift out of calibration to the extent it became a problem, they can also be sent in for recalibration or swapped out for a version 2 board.

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
We are sold out of the original LDR3x and since release of the Version 2 board is in sight, we are no longer offering the Version 1 board. We will of course continue to support the version 1 board.

We are really pumped about the LDR3x.V2 board  :D  Here's the announcement and some more info on the LDR3x.V2:   http://www.tortugaaudio.com/ldr3x-v2-preamp-controller-board-coming-soon/

We are taking pre-orders for the LDR3x.V2. You can pre-order the LDR3x.V2 here: http://www.tortugaaudio.com/product/ldr3x-passive-preamp-controller-version-2/

Cheers,
Morten  :thumb:


tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Cardas RCA Jacks
« Reply #85 on: 13 Mar 2014, 08:15 pm »
We are pleased to announce that we are now using Cardas RCA jacks in builds of our LDR3 Passive Preamp.  :thumb:

These are gorgeous beefy brass jacks with rhodium over silver plate. These are their "long" jacks suitable for both thin and thicker rear panels. We plan on using Cardas jacks going forward in all our new product designs. Unfortunately, we can't use these with our LDR6 Passive Preamp due to space constraints.

We are also selling these to the DIY community but only in pairs. Pricing is per Cardas guidelines. Here's the link to our website:  http://www.tortugaaudio.com/product/cardas-rca-jacks-pair/


tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: Cardas RCA Jacks
« Reply #86 on: 14 Mar 2014, 05:08 pm »
We are pleased to announce that we are now using Cardas RCA jacks in builds of our LDR3 Passive Preamp.  :thumb:

These are gorgeous beefy brass jacks with rhodium over silver plate. These are their "long" jacks suitable for both thin and thicker rear panels. We plan on using Cardas jacks going forward in all our new product designs. Unfortunately, we can't use these with our LDR6 Passive Preamp due to space constraints.

We are also selling these to the DIY community but only in pairs. Pricing is per Cardas guidelines. Here's the link to our website:  http://www.tortugaaudio.com/product/cardas-rca-jacks-pair/



Just to clarify. These beautiful RCA jacks retail for $31.04 a pair and are semi-permanently on sale for only $24.83 - that's for 2 jacks.  :thumb:
http://www.tortugaaudio.com/product/cardas-rca-jacks-pair/

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #87 on: 19 Mar 2014, 09:48 pm »
We are pleased to announce that we are now taking pre-orders for  the new IO Relay Board.  :D
We expect to be shipping the IO Board on or before April 7th barring any glitches with  our suppliers.
The IO Board price is $59 which includes  the power/control connectors between the board and the LDR3x Preamp Controller Board.
It will work with both versions 1 & 2 of the LDR3x Preamp Controller Board or any other preamp control device that provides +5V and switching to ground.

You can find more info and pre-order the board here: http://www.tortugaaudio.com/product/io-relay-board/


tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
IO Board & Power Supply Board/Transformer
« Reply #88 on: 5 Apr 2014, 12:56 am »
We are pleased to announce that we are now taking pre-orders for  the new IO Relay Board.  :D
We expect to be shipping the IO Board on or before April 7th barring any glitches with  our suppliers.
The IO Board price is $59 which includes  the power/control connectors between the board and the LDR3x Preamp Controller Board.
It will work with both versions 1 & 2 of the LDR3x Preamp Controller Board or any other preamp control device that provides +5V and switching to ground.

You can find more info and pre-order the board here: http://www.tortugaaudio.com/product/io-relay-board/



The IO Boards are in. Still waiting on one back ordered component which was shipped but hasn't arrived yet. Should have them by Sat or Mon at the latest. The planned release date is this Monday, April 7th so it looks like we're going to hit the target on that one.

We also just received our Power Supply Boards. Haven't said anything about the PS Board yet so this will come as a surprise. It will include a small board together with a separate 10VA toroidal transformer that will be sold as a set. The board and the transformer each have to be mounted separately (they aren't packaged together).  The PS takes 115 or 230 VAC and produces 12 VDC. It uses full bridge rectification followed by an arguably overlarge 4700 uF filter capacitor followed by regulators. While is was designed to accommodate a conventional 7812 voltage regulator, we'll be using a 12 VDC version of our new SMPS dc-dc regulator instead. It accommodates 2 regulators in parallel so it can handle either a single ~400 ma output (more than plenty for the LDR3x), dual ~400 ma outputs,  or up to a single ~800 ma output with the dual outputs in parallel. The board is designed to land the transformer primary and secondary windings at clearly marked termination points on opposite ends of the board. There's also a provision for interfacing a 115/230 AC supply voltage select switch (or just using local jumper wires). Once the transformer is connected to the board all that's left is to connect is the main hot/neutral/ground. While all input/output connections will have screw terminals, everything can also be alternatively connected via solder pads. Lastly, there are ample solder pad connections to land multiple grounds to the board with the intent of using the board as a central star grounding point. More info on the Power Supply will be provided next week once we have all the components in, gets some photos taken and get it loaded up on our website. Pricing will be announced next week as well.

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
IO3 Board
« Reply #89 on: 5 Apr 2014, 08:33 pm »
Here's build #1 of the new IO3 Relay Board.
Officially released as of 4.5.14 (2 days early! )  :thumb:
Everything including grounds can be connected either via screw terminal blocks or solder pads.
Interfaces with the LDR3x as shown in our updated documentation here: http://www.tortugaaudio.com/documentation/#document-18
$59 - includes interface cabling etc. to the LDR3x

More info here: http://www.tortugaaudio.com/product/io-relay-board/

« Last Edit: 6 Apr 2014, 07:22 pm by tortugaranger »

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
PS12 Power Supply for the LDR3x
« Reply #90 on: 9 Apr 2014, 08:41 pm »
Fresh pics of the new PS12 Power Supply that uses switch mode dc power regulators and a 10VA toroidal transformer.

Comes in a few variations including:
1) 12 V - 400ma - single regulator
2) 12 V - 800ma (or 2 x 400ma) - dual regulators
3) 12 V - 400ma & 5 V - 400ma - dual regulators

More info can be found here: http://www.tortugaaudio.com/product/ps12-power-supply/




« Last Edit: 11 Apr 2014, 04:28 pm by tortugaranger »

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
PS12.5 Power Supply for the LDR3x
« Reply #91 on: 12 Apr 2014, 03:11 pm »
Fresh pics of the new PS12 Power Supply that uses switch mode dc power regulators and a 10VA toroidal transformer.

Comes in a few variations including:
1) 12 V - 400ma - single regulator
2) 12 V - 800ma (or 2 x 400ma) - dual regulators
3) 12 V - 400ma & 5 V - 400ma - dual regulators


Based on feedback we've tweaked the power supply offering and as a result are now calling it the "PS12.5" in recognition of the mix of 5 different 12V and 5V variations it comes in which are:

1) 5V-400ma - single regulator
2) 12V-400ma - single regulator
3) 2 x 5V-400ma (800 ma total) - dual regulator
4) 2 x 12V-400ma (800 ma total) - dual regulator
5) 5v-400ma & 12v-400ma - dual regulator

Also, note that we've added a pair of 47 uF caps to the ouput (positions C5 & C6) which further helps stabilize the supply and improve transient performance. These were intended all along but are missing in the build we used for the pics.

More info can be found here: http://www.tortugaaudio.com/product/ps12-power-supply/


tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Some Pics of the new LDR3x.V2 Preamp Controller Board
« Reply #92 on: 8 May 2014, 05:37 pm »
A few pics of the new LDR3x.V2 board.  :thumb:

* $259 - http://www.tortugaaudio.com/product/ldr3x-passive-preamp-controller-version-2/
* Handles up to 3 inputs via optional input relay board
* Controlled via Apple Remote and/or rotary encoder (not included)
* Auto-calibration of LDRs via 12 bit DAC/ADCs - always optimized - drift/aging a non-issue
* Replaceable LDR modules - like tubes, LDRs can go bad - just replace with a $20 module
* Attenuation between -60 and 0 dB via 70 attenuation steps
* Smooth ramp down/up muting
* Minimum 10k input impedance. See graph below and find our more about attenuation/impedance here: http://www.tortugaaudio.com/documentation/#document-18





« Last Edit: 9 May 2014, 01:18 pm by tortugaranger »

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
LDR3x.V2 input impedance spec changed from 10k to 20k
« Reply #93 on: 18 May 2014, 05:15 pm »
After some critical listening to the new ldr3x.V2 board, we've bumped the input impedance spec from 10k to 20k. At least on our test rig (SS amp with 20k input impedance), it resulted in noticeably improved sound. The sound stage got wider and more 3 dimensional and the stereo center moved further back and not as out in front as before. And the dynamics improved as well. I knew it was better because I blew through 3 hours of listening to one tune after another because it sounded so damn good.  :green:

This is very reminiscent of the improvements noted back when we introduced the HiZ upgrade last year. We really aren't doing anything different in that respect with the V2 but the Auto Calibration feature makes it much much easier to change the impedance and note the difference. It took about 10 minutes to run through the full calibration cycle for the 4 LDRs and after firing it back up again the benefits of 20k were quite obvious.

So, the ldr3x.V2 is now officially a 20k input impedance preamp controller board. The updated attenuation and impedance curves are shown below. A detailed explanation of these curves can be found in our online documentation here:  http://www.tortugaaudio.com/documentation/#document-19

The really cool thing (at least from a developer's perspective) is this change required editing one line of software code and changing the number 10000 to 20000. Cool beans.  :thumb:

Now, back to digging out from under our backlog of orders.

Cheers,
Morten



tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x.V2 input impedance spec changed from 10k to 20k
« Reply #94 on: 20 May 2014, 12:11 pm »
Regarding the impedance change to the V2, I received the following question on another site so I thought I'd post it and my response here.

Quote
Do you think the same benefit would be had by upping the input impedance in v1 boards? If so, is it possible?

I'm going to wait for feedback and consensus from V2 owners before deciding anything about further upgrades to the V1. When it comes to overall quality of sound it may prove to be a case of differences without distinction. Or not.

We went around the track a few times with the V1 last year trying 10k, 20k and even 50k impedance settings before settling on 10k. Even then, there were some who reported that 50k was superior.

Changing the impedance of the V1 is a PITA. We have to dig out their original test data for each individual unit, rerun the data through our modified program, burn a new chip, ship the chip, swap out the old with the new etc. If we added up all of our time and materials for all that, I doubt many would be happy with the price tag. I'd want to be very sure it was worth it before offering that up.

At least with the V2 design, we can email out software revisions or just post them on our website for owners to download and upload into their V2 boards.

We may end up posting 10k, 20k and 50k versions of the V2 software and let owners try all or none and decide what sounds best. I suspect the answer will be more system dependent than not. It would definitely be interesting.

Cheers,
Morten

glynnw

Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #95 on: 20 May 2014, 04:15 pm »
Can you test an amp and determine what impedence in the LDR3X will work best with it?

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #96 on: 28 May 2014, 01:25 pm »
Can you test an amp and determine what impedence in the LDR3X will work best with it?

Sorry for the slow response but was offline for a week of vacation.

The established guidance when connecting audio devices is to either match impedance (output impedance of source = input impedance of amp) or to have sufficiently high bridging impedance ratio (10:1 where amp input  impedance at least 10x greater than source output impedance). Matching impedance may be ideal but it's impractical so most sources have less than 1k output impedance and most amps have input impedances of 10k or greater.

When you place a preamp between a source and amp you now have 2 instances of impedance bridging: between the source (DAC, phono stage, CD etc. ) and preamp, and between the preamp and amp.

When we were able to raise the input impedance of our LDRx preamps to 10k last year (the HiZ upgrade), this improved matters between the source and preamp.

However, as the graph below shows, any passive attenuator employing voltage division (like pots or LDRs) has a varying output impedance that reaches a max of 25% of the input impedance at -6dB (loud!!!). In the case of a 10k unit, that's a max output impedance of 2.5k. For a 20k unit, it's 5k. This would then argue for amps having at least 25k input impedance for a 10k passive attenuator or 50k for a 20k passive attenuator.

Then again, as a practical matter few of us listen to music at -6dB attenuation. In the more likely range of -40 to -20 dB attenuation, the passive preamps output impedance is more likely to be in the 1-2k range which means that an amp with 20k input impedance of greater should suffice but arguably 40-50k or higher may be better (that's "may", not "will").

Beyond this level of general guidance you get into more subtle and equipment specific issues.

robertopisa

  • Jr. Member
  • Posts: 71
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #97 on: 28 May 2014, 08:32 pm »
So Morten, to make an example with my situation: I have a source DAC with balanced output impedance of 5 ohm, and my amp has >10kOhm of input impedance.

Using your 25% rule at -6dB, it seems that the optimal impedance for the above situation is 4kOhm, as 25% of it is 1kOhm and then 10 times is thus 10kOhm.

Is it so? In that case, it would be better to program your firmware with 4kOhm (great and flexible idea to have this V2 feature!)

Thanks
Roberto


Sorry for the slow response but was offline for a week of vacation.

The established guidance when connecting audio devices is to either match impedance (output impedance of source = input impedance of amp) or to have sufficiently high bridging impedance ratio (10:1 where amp input  impedance at least 10x greater than source output impedance). Matching impedance may be ideal but it's impractical so most sources have less than 1k output impedance and most amps have input impedances of 10k or greater.

When you place a preamp between a source and amp you now have 2 instances of impedance bridging: between the source (DAC, phono stage, CD etc. ) and preamp, and between the preamp and amp.

When we were able to raise the input impedance of our LDRx preamps to 10k last year (the HiZ upgrade), this improved matters between the source and preamp.

However, as the graph below shows, any passive attenuator employing voltage division (like pots or LDRs) has a varying output impedance that reaches a max of 25% of the input impedance at -6dB (loud!!!). In the case of a 10k unit, that's a max output impedance of 2.5k. For a 20k unit, it's 5k. This would then argue for amps having at least 25k input impedance for a 10k passive attenuator or 50k for a 20k passive attenuator.

Then again, as a practical matter few of us listen to music at -6dB attenuation. In the more likely range of -40 to -20 dB attenuation, the passive preamps output impedance is more likely to be in the 1-2k range which means that an amp with 20k input impedance of greater should suffice but arguably 40-50k or higher may be better (that's "may", not "will").

Beyond this level of general guidance you get into more subtle and equipment specific issues.

wilsynet

  • Full Member
  • Posts: 1233
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #98 on: 29 May 2014, 04:29 am »
So in summary, the rough guidance is less than 1K output Z for sources and greater than 20K input Z for amplifiers.  Is that right?

tortugaranger

  • Facilitator
  • Posts: 1160
  • Handcrafted high performance audio gear
    • Tortuga Audio
Re: LDR3x DIY Passive Preamp Controller Board w/ Remote
« Reply #99 on: 29 May 2014, 12:04 pm »
So in summary, the rough guidance is less than 1K output Z for sources and greater than 20K input Z for amplifiers.  Is that right?

The operative phrase being "rough guidance" but yes.