Tortuga Audio LDR3x DIY Preamp Controller w/ Remote - Page 16 - diyAudio
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View Poll Results: What type remote do you prefer to control your preamp?
Use a dedicated custom remote? 2 10.53%
Use the Apple Remote? 5 26.32%
Use an app on my iPhone, iPad or Android? 9 47.37%
Custom plus apps? 2 10.53%
Apple plus apps? 1 5.26%
Voters: 19. You may not vote on this poll

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Old 19th June 2014, 01:41 PM   #151
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Default Some Perspective on Designing with LDRs

1/ they are impracticable for stereo use as they cannot make matching pair.
2/ if you do spend loads of time matching pairs then they drift with age and **** it all up again
3/ they are prone to failure

These 3 points were mentioned on another audio forum as good reasons to avoid LDRs. Since I've personally gone through several LDR design iterations, I thought I'd share my perspective on working with LDRs.

In brief, designing with LDRs is a PITA. There's considerable variability between each individual LDR even of the same make/model. They are highly nonlinear especially over a wider resistance range. Given a choice, it's a rare bird that would willingly choose to work with highly variable nonlinear components in audio equipment design. So why do it? Because it's worth it if you're seeking the best possible audio experience. If you've spent some time around LDR preamps you get the joke pretty quickly. For example, I just had a customer tell me he's selling his $10k tube preamp after auditioning our LDR passive.

As with all analog components, LDRs will drift. LDRs are actually 2 analog components (photoresistor & LED) in an integral package. Most drift just a little. Some quite a lot. If you start with a decently matched set, a little drift isn't a big deal, especially if they all more or less drift similarly. Iv'e had an LDR preamp unit running for several years with no discernible drift that matters. But as I've found out, you can't count on that.

The first version of our LDR passive pre-amp design was entirely dependent on starting with matched sets of LDRs. We had to characterize every LDR over the full resistance range we needed. These tests results went into a database. We'd test 50-100 LDRs at a time. Then we would take that data and run it through a sorting algorithm to select the 4 or 8 best matched LDRs and use those in our next build. A lot of effort went into test rigs, data acquisition, and post-test data processing. We had to store each tested LDR with its own ID tag. Did I mention PITA?

In our second generation design, we still tested each LDR but applied a very different approach where we no longer needed perfectly matched LDRs. Instead, we simply picked pairs of test data points from each LDR that yielded the necessary dB attenuation setting for each volume step for each channel and placed those settings into a table used to drive each LDR at each volume step. Of course this was only possible because our design utilizes a software based digital microcontroller that drives the analog circuitry which regulates each individual LDR. But even with this approach, we had to custom test and calibrate each pre-amp build and store the resulting test data in our IT system. If any software changes needed to made to a customer's unit we had to utilize that original test data. If the LDRs drifted too much, the unit would need to be sent back for retesting and recalibration. This didn't happen very often but once in a while is frankly once too often.

With our third and most recent generation design ("V2"), we got ambitious and made the leap to self-contained auto-calibration where the preamp continuously recalibrates each LDR against a programmed dB attenuation schedule. No pre-matching or testing. Just plug in 4 LDRs and less than 10 minutes later it's ready to go. If one LDR happens to be too far out of spec to calibrate properly or just fails, you pop it out and plug in a replacement, wait 10 minutes and you're back in business. This is a more complex design, involves 12 bit DACs and ADCs, and consequently costs more, but it's completely software driven and the software can be updated via a USB port and a PC. We plan on selling high end finished units and want our customers to know they're getting a great long-term value.

To sum it up, I generally agree with the first 2 points but they can be successfully mitigated if not totally overcome. It's called engineering.

On the last point, I have to disagree. My own experience suggests maybe 1% of the LDRs we use are prone to infant mortality and there are ways of culling those out. The rest will likely live for several 10's of thousands of hours. Kind of like tubes only better.

Cheers,
Morten
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Old 2nd July 2014, 12:41 PM   #152
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Default New LDRx & LDRxB (balanced) Passive Preamps

As of 7.1.14 we are announcing the upcoming release of our new line of finished LDRx & LDRxB Passive Preamp products. As things stand now, the official release date is July 31, 2014. Despite the epic delay is getting this product ready, this is the real deal. It's really going to happen. Soon. No, really!

When released, the LDRx will replace our existing LDR3 and LDR6 offerings and can be ordered with 3-6 inputs. The LDRxB is our first balanced passive preamp with a blend of 3 balanced plus 1 alternative unbalanced input, 2 balanced outputs plus also an unbalanced output. Both versions will be housed in our new attractive enclosure design and utilize our latest LDR3x.V2 preamp controller board featuring auto-calibration.

As of today, we are accepting pre-orders. Details on the LDRx & LDRxB Passive Preamps can be found on our website via this link: LDRx & LDRxB | Tortuga Audio

Here is our latest CAD renderings. Actual pics to follow when they're available.

Cheers,
Morten

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Old 13th July 2014, 01:16 PM   #153
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Default Discontinuing Sales of the LDR3 and LDR6

A brief note to advise that with the imminent release of the new LDRx and LDRxB Passive Preamp models, that we have suspended sales of the LDR3 and LDR6.

Info on the new LDRx and LDRxB can be found here: LDRx & LDRxB Passive Preamps | Tortuga Audio

These new models are currently available for pre-order at a 10% discount. The discount period ends they're released. Plus with pre-orders you don't make any payments until such time as the new models are released and begin to ship.

Cheers,
Morten
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Old 22nd July 2014, 04:57 PM   #154
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Default See you at 2014 RMAF!

Tortuga Audio is planning to be at the 2014 Rocky Mountain Audio Fest in October.

In addition to Tortuga Audio's LDRx/LDRxB Passive Preamp, we'll be co-showing one of Volti Audio's (Volti Audio - Hi-Efficiency Horn Speakers) remarkable hand crafted horn speakers.

If you're attending the RMAF please plan to stop by and see us.

Cheers,
Morten
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Old 30th July 2014, 02:31 PM   #155
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Default LDRx/LDRxB Passive Preamps

We sent a notice out around 10 days ago to everyone with pre-orders that the release date for the LDRx/LDRxB has been pushed out to mid-August. Everything is done and ready except for fabrication of the enclosures which is well underway. We are doing the enclosure fab work in-house except for the anodizing. Milling the parts and the turnaround on the anodizing is the key reason for the pushing out the release date.

The 10% pre-order discount is still available until the release date. More info here: LDRx & LDRxB Passive Preamps | Tortuga Audio

The pic below is a set of front panels fresh off the CNC mill before brushing/anodizing. Note the milled out center stripe is for the dark acrylic inlay which will cover up the "window".

Here is a link to a youtube video showing one of these front panels being milled on our CNC machine. We removed the dust/vacuum cover so the cutting would be visible for the video which is why there are cuttings everywhere. Cutting Front Panels for New LDRx/LDRxB Passive Preamps - YouTube

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Old 4th August 2014, 05:32 PM   #156
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Default Tour for the LDRxB Balanced Passive Preamp

We're organizing a tour for our soon to be released LDRxB Balanced Passive Preamp. Hope to kick it off later in September.

If you're interested in participating, follow this link to our forum on AudioCircle for more info. LDRx/LDRxB Passive Preamp Tour - 2014/2015

Cheers,
Morten
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Old 25th August 2014, 12:38 PM   #157
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Default Pic of LDRxB Rear Panel - Final Fitup

Here's a pic of the rear panel of the LDRxB Balanced Passive Preamp showing final fitup of parts. The XLR jacks are heavy duty cast Neutriks with gold connections. The RCA jacks are Cardas. As shown here the panel (3.25" by 12.5") is raw brushed aluminum prior to being black anodized which happens later this week. The XLR socket in the lower right is standing in for a dual USB socket which uses the same XLR form factor and should arrive from our supplier in a few days. To the left of the power entry module is the 115/230AC selector switch. Above that is the 12V Trigger Out.

We are on track for release at the end of the month at which time we'll start building and shipping units beginning the first week of September starting with existing pre-orders. There is still time to place pre-orders for at 10% discount through Sunday August 31st. LDRx & LDRxB Passive Preamps | Tortuga Audio

Cheers!
Morten

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Old 31st August 2014, 12:47 PM   #158
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Default 10% Discount on LDRx & LDRxB Extended Through Sept 1st

In recognition of this Labor Day Weekend holiday and the release of our new LDRx and LDRxB Passive Preamps, we are extending the 10% pre-release discount through midnight tomorrow (Monday - September 1st).

We commence building and shipping LDRx and LDRxB units on Tuesday! Woot woot!

LDRx - 10% off at $1346 - LDRx Passive Preamp | Tortuga Audio

LDRxB (balanced) - 10% off at $2156 - LDRxB Balanced Passive Preamp | Tortuga Audio

Cheers!
Morten
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Old 9th September 2014, 03:05 PM   #159
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Default First pics of our new LDRx & LDRxB Passive Preamps

As we were shooting these pics I commented that these looked like audio porn shots. When we have more time I'll get some lower temperature shots against neutral/white background. These were the best we could do at the end of a crazy busy day. Enjoy!

The rear panel is for the LDRxB Balanced unit with the optional Cardas Gold XLR jacks. Bling bling!

More info here:
Single-ended: LDRx Passive Preamp | Tortuga Audio
Balanced: LDRxB Balanced Passive Preamp | Tortuga Audio


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Old 9th September 2014, 11:38 PM   #160
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Default New York Audio Show

If you're planning on attending the upcoming New York Audio Show later this month (Sept/2014), I invite you to stop in and meet our partners at Bright Audio who will be exhibiting our new LDRx Passive Preamp along with some very nice gear from other manufacturers.

Located in the dynamic East Village area of Manhattan, Bright Audio has a unique showroom and offers full service high end audio including installation services to the New York City market.

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New York Audio Show 2014 | Home Audio Show | Chester Group


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Home Theater, Home Audio, Stereo, New York | Bright Home Theater
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