Complete DIY LDR Passive Preamp Kit - LDR3.V25K

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tortugaranger

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Complete DIY LDR Passive Preamp Kit - LDR3.V25K
« on: 4 Nov 2014, 03:11 pm »
We're in the planning stage of a complete DIY LDR Preamp Kit that will include a LDR3x.V2 preamp controller board. The kit will only be for single-ended RCA.

If you're interested in such a product, please leave a comment or question here or drop me a PM. Now is the time to pipe up with your suggestions or "wish list" while the design is still fluid.

The kit will be comprehensive and include the following:

* LDR3x.V2 (V2.1) board fully populated & tested
* aluminum enclosure including black powder-coated extruded alum uni-body and black or clear anodized front/rear panels - approx 6.5" wide x 2.5" tall by 8" deep
* 3 RCA  inputs, 2 RCA outputs
* single display module
* 3 input relay board with parts - solder it yourself
* encoder with knob
* external wall-wart switching power supply
* silver coated stranded copper wire - enough to hook everything up.
* ribbon cable connectors as needed
* screws etc. as needed

You'll need to supply your own solder, iron, tools etc.

Cheers,  :thumb:
Morten
« Last Edit: Today at 02:00 am by tortugaranger »

point5028

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #1 on: 20 Nov 2014, 05:23 am »
Hi

There is a USB CABLE included in the kit.

1 – USB cable for connecting between the LDR3x board and the rear panel

But there is  no any USB port on the rear panel. Why?

 :D

DAVE

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #2 on: 20 Nov 2014, 12:11 pm »
Hi

There is a USB CABLE included in the kit.

1 – USB cable for connecting between the LDR3x board and the rear panel

But there is  no any USB port on the rear panel. Why?

 :D

DAVE

Thanks for scrutinizing the kit parts list. No, really, we intend for that list to be comprehensive and complete so requests for clarification are welcome.

The answer is this particular USB cable has a 5 pin socket on one end to connect to the board and the other end has an integral USB port that attaches to the rear panel with 2 screws.  :thumb:
« Last Edit: 20 Nov 2014, 01:28 pm by tortugaranger »

point5028

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #3 on: 20 Nov 2014, 02:25 pm »
Thanks for scrutinizing the kit parts list. No, really, we intend for that list to be comprehensive and complete so requests for clarification are welcome.

The answer is this particular USB cable has a 5 pin socket on one end to connect to the board and the other end has an integral USB port that attaches to the rear panel with 2 screws.  :thumb:

Do you sell USB cable separately?

 :)

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #4 on: 20 Nov 2014, 02:48 pm »
Do you sell USB cable separately?
 :)

Since several people have asked about this I will add it to our store. At $15 it's not cheap as 1 foot cables go but it serves the dual purpose of an internal board-to-panel connector plus as a robust type A USB port.

Here's the link to our website:  http://www.tortugaaudio.com/product/usb-cable-port/

Cheers,
Morten
« Last Edit: 20 Nov 2014, 05:00 pm by tortugaranger »

NachoTime

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #5 on: 20 Nov 2014, 06:14 pm »
Hello Morten,

Would you consider offering a balanced kit that doesn't include an enclosure?

Thanks,
Sten

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #6 on: 20 Nov 2014, 10:38 pm »
Hello Morten,

Would you consider offering a balanced kit that doesn't include an enclosure?

Thanks,
Sten

Hi Sten,

A kit without enclosure really boils down to a collection of our DIY parts that you'd need for a balanced system. I have numerous customers who have gone this route even though we haven't yet proposed this as a true kit.

The list boils down to:

* 2 - LDR3x passive preamp controller board
* 2 - IO3 modules (assuming you want to be able to handle more than 1 input)
* 1 - DM1 display module (& perhaps a 2nd slave module) - not required but highly recommended
* 1 - Encoder module - not required but highly recommended
* 1 - PS12.5 power supply board - not required but you'll need your own alternative 12 VDC supply which can be as simple as a 12 VDC wallwart
* 1 - Apple Remote
* all the ribbon cables etc. for the above (which come with the items anyway)

As you can see from the list you quickly get into a list of options but if we were to offer an "everything but the box" kit it would include all these items.

It would be very helpful to understand what your view of a kit might include that isn't included in the above items.


NachoTime

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #7 on: 21 Nov 2014, 03:11 am »
This is just what I was looking for.  Thanks for clarifying Morten.

How many balanced and/or RCA inputs and outputs are possible with this setup?
If it supports both balanced and RCA outputs, are they both active at the same time?

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #8 on: 21 Nov 2014, 03:41 am »
This is just what I was looking for.  Thanks for clarifying Morten.

How many balanced and/or RCA inputs and outputs are possible with this setup?
If it supports both balanced and RCA outputs, are they both active at the same time?

The LDR3x can switch between 3 inputs. However, if these 3 switching signals are used with a 3 digit binary decoder you can switch up to 8 inputs. We currently only offer a 3 input relay switching board. A pair  of relay switching boards are needed for balanced input. You can mix XLR or RCA inputs anyway you want but in my view since you're investing in a balanced preamp I suggest 1 RCA and 2 XLR. These are exclusive inputs. You only switch one input (RCA or XLR) at a time.

With mixed RCA/XLR it gets a bit messy. The RCA output while connected to a balanced input will be 6 dB lower in output than the balanced output since you're only taking one leg of the balanced signal for the RCA output. If you want an RCA input to be available as a balanced output, you'll need to run the RCA input through a transformer to convert it to a balanced signal before attenuating it and passing it out the XLR output. Clear as mud? Like I said, a bit messy.

NachoTime

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #9 on: 31 Dec 2014, 11:05 pm »
Hello again Morten,

I'll likely place an order for a standard preamp kit in the next couple of days and have a quick question for you.

The available upgrades for the kit lists a 2nd display and Cardas RCA jacks.  The 2nd display has a nice discount from retail, however the Cardas jacks appear to be more expensive than if purchased separately.  By my math the 5 pairs of jacks should be around $124, but the upgrade price is listed as $199.  Could you please clarify when you get a chance?

Thanks, and Happy New Year.

-Sten

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #10 on: 1 Jan 2015, 01:57 pm »
Hello again Morten,

I'll likely place an order for a standard preamp kit in the next couple of days and have a quick question for you.

The available upgrades for the kit lists a 2nd display and Cardas RCA jacks.  The 2nd display has a nice discount from retail, however the Cardas jacks appear to be more expensive than if purchased separately.  By my math the 5 pairs of jacks should be around $124, but the upgrade price is listed as $199.  Could you please clarify when you get a chance?

Thanks, and Happy New Year.

-Sten

Hi Sten,

Thanks for your note and for pointing out the pricing issue with the Cardas upgrade. The upgrade price was supposed to be $99 but it was mistakenly entered at $199. Thanks to your note it's now been corrected.

Best,  :thumb:
Morten

Magnatest

Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #11 on: 22 Jan 2015, 12:03 pm »
Morten,

  Would you please explain the adjustable input impedance ( 1K to 100K ) and how that changes the chart below found on your site?





 I ask the question, because ultimately I'd like to know how the LDR3.V2 Passive Preamp would pair with my Odyssey Audio Khartago mono block amps. The amps have an input impedance of 22K Ohms. From what I understand, we want at least a 10X ratio of amplifier input impedance to preamp output impedance.

Thanks,

Gregg


tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #12 on: 22 Jan 2015, 03:39 pm »
The key metric is the impedance "bridging" ratio which is the effective parallel impedance of the preamp/amp divided by the source output impedance. Usually a 50:1 or higher ratio is reliable indicator that things will work well with our passive preamps. This is general guidance and not some hard and fast rule. A lot depends on how robust the output stage is in your source. If you have a strong source able to deliver current into lower impedances you'll be ok with lower bridging ratios.

The best way I know how to get my head around this topic is by running the numbers in a spreadsheet with different assumptions regarding source output impedance, preamp input impedance and amp input impedance.

I've uploaded an Excel spreadsheet that you can download from our website which includes a version of the graph shown below.  Look for the "Impedance Spreadsheet" link on the right. http://www.tortugaaudio.com/downloads/


Morten,

  Would you please explain the adjustable input impedance ( 1K to 100K ) and how that changes the chart below found on your site?





 I ask the question, because ultimately I'd like to know how the LDR3.V2 Passive Preamp would pair with my Odyssey Audio Khartago mono block amps. The amps have an input impedance of 22K Ohms. From what I understand, we want at least a 10X ratio of amplifier input impedance to preamp output impedance.

Thanks,

Gregg

Magnatest

Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #13 on: 22 Jan 2015, 05:54 pm »
Morten,

  Thank you for the response. I'll review the information.

Gregg

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #14 on: 31 Jan 2015, 08:20 pm »
Thinking about getting an LDR passive preamp?
Want to keep the costs down?
Willing to go the DIY route?
But don't want to search high and low for all the parts plus enclosure?

Consider the LDR3.V2K Passive Preamp Kit - $695
http://www.tortugaaudio.com/product/ldr3-v2k-passive-preamp-kit/





jtwrace

Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #15 on: 31 Jan 2015, 11:03 pm »
Very cool Morten!  :thumb: 

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #16 on: 19 Aug 2015, 07:06 pm »
Initial customer feedback on having fired up his LDR3.V2k. I did not know it at the time he purchased the kit that he was already using a stepped passive attenuator.

Quote
Right from the start I was quite impressed by the sound performance. The Tortuga passive preamp replaced a passive preamp in my system equiped with Elma switches and Shinko tantalum resistors for shunt and series resitors. The Shinkos were until now the best resistors in this role and I was suprised that they were easily surpassed by the LDRs. The unit is now breaking in.

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #17 on: 1 Sep 2015, 05:33 pm »
The biggest problem with our LDR3x.V2K kit is a lack of comprehensive and easy to follow instructions. We are taking steps to correct this. In a couple of weeks we have 2 whole days scheduled with a videographer. We plan to document via video every step in assembling and testing this kit. Once we have the raw footage it will still take some time to edit it down and do the voice over. It will ultimately be published as a youtube video. We'll update you more on this as we progress.

tortugaranger

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #18 on: 16 Sep 2015, 12:36 pm »
Video filming day for the LDR3.V2K!  Roll'em!

Nick B

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Re: Complete DIY LDR Passive Preamp Kit - LDR3x.V2K
« Reply #19 on: 17 Sep 2015, 06:08 am »
Nice, Morton. Would like to buy within the year. How much for all the options?
Nick

PS   Great idea re the videos