LDR300.V25 Buffered Preamp

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tortugaranger

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LDR300.V25 Buffered Preamp
« on: 9 Jul 2018, 02:40 pm »
We are pleased to announce that Tortuga Audio will soon be releasing a new LDR preamp model, the LDR300.V25. 

The LDR300 is a 3 input, dual output, unity gain (no gain stage!) buffered preamp with a low impedance solid state JFET ouput buffer stage mated with our high performance V25 LDR attenuator. The absense of a gain stage combines the best aspects of a passive preamp together with the elegant simplicity of a robust output buffer to deliver outstanding sonic performance. For those who don't happen to have source components with highly robust output stages and thus can't derive the full benefit of a passive preamp, the LDR300 provides the muscular punch and dynamics to bring out the very best in our LDR attenuator.

A specific release date has not been set but we currently expect to start shipping in the latter half of August.

Pricing has not been finalized but will be incremental to the existing base price of $1195 for the existing LDR3.V25 passive preamp without  the buffer.

The LDR300.V25 will be available soon for pre-order at a discount off the to-be-announced LDR300 base price.

Please note that the LDR300 is a single-ended model. Due to space constraints within our standard LDR1B.V25 enclosure a comparable self-contained buffered balanced model is not practical, however, we do plan on offering a standalone balanced solid state buffer which when mated with our LDR1B.V25 will yield comparable performacne to the LDR300.  Full kits including possibly a parts-in-a-bag buffer board only kit are being considered. Buffer retrofits to existing LDR3 preamps will also be offered.

Last but not least we'll be organzing a AudioCircle tour for the LDR300 so let me know if you're interested in participating.

More info on the LDR300 will be available soon.

Cheers,   :thumb:
Morten

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #1 on: 26 Jul 2018, 07:07 pm »
The LDR300 product page has now been stood up on our website via the link below.
https://www.tortugaaudio.com/products/buffered-preamps/ldr300-v25-buffered-preamp/

The base price for the LDR300 is $1495 but prior to being released on August 28, it's availble for preorder at a 20% discount for $1195 which is the same as our existing LDR3.V25 Passive Preamp.

We're organizing a tour for the LDR300. More info on the tour can be found via the thread below:
https://www.audiocircle.com/index.php?topic=158982.0

Externally, the LDR300.V25 is essentially identical to our LDR3.V25 model but unlike the passive LDR3, the LDR300 sports an active buffer output stage.






tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #2 on: 27 Jul 2018, 03:50 pm »
Here's an article I just posted that discusses our new LDR300.V25 Buffered Preamp that's set for release on August 28th.

Cheers,  :thumb:
Morten

https://www.tortugaaudio.com/tortuga-audio-to-release-new-ldr300-v25-buffered-preamp/

CKKeung

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Re: LDR300.V25 Buffered Preamp
« Reply #3 on: 8 Aug 2018, 08:10 am »
... Please note that the LDR300 is a single-ended model. Due to space constraints within our standard LDR1B.V25 enclosure a comparable self-contained buffered balanced model is not practical, however, we do plan on offering a standalone balanced solid state buffer which when mated with our LDR1B.V25 will yield comparable performacne to the LDR300.  Full kits including possibly a parts-in-a-bag buffer board only kit are being considered. Buffer retrofits to existing LDR3 preamps will also be offered. ...

Hello Morten,

I am very interest in the "standalone balanced solid state buffer kit" you mentioned on #1.
May I know the progress of its development?
Any photos of it and any tentative price?

Many thanks!

CK

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #4 on: 8 Aug 2018, 01:14 pm »
Hello Morten,

I am very interest in the "standalone balanced solid state buffer kit" you mentioned on #1.
May I know the progress of its development?
Any photos of it and any tentative price?

Many thanks!

CK

Hi CK,

Our focus right now is finalizing the buffer design which is in its 5th prototype iteration. The basic design concept is done and we're refining the controls that prevent transient bumps/pops during power up and shutdown. I expect we'll finish that work over the next few days and will be ordering production boards soon thereafter to meet our August 28th release date for the LDR300.V25

Once the LDR300 is released and we get production rolling smoothly in September we'll begin working on the details of a stand-alone solid state buffer including a balanced version. I don't expect we'll get that done until some time in the 4th quarter and don't want to get ahead of ourselves with timing or pricing until we do that work.

What I can say is that any stand-alone buffer will utilize the same enclosure design as most of our preamps including the LDR300 as well as our TPB.V1 Tube Preamp Buffer.

CKKeung

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Re: LDR300.V25 Buffered Preamp
« Reply #5 on: 9 Aug 2018, 03:58 am »
Dear Morten,

Many thanks for your detailed reply!

I am particularly interested in the coming "parts-in-a-bag buffer board only kit" of this solid-state balanced buffer amp.

Please keep us updated on the progress.

Thank you again!

CK

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #6 on: 14 Aug 2018, 02:35 pm »
Yesterday we did some critical listening to the next to last (hopefully) prototype buffer board. The buffer stage itself is actually a separate 4-pin plug-in module so we can quickly try different FETs. We compared 2 different FET modules, one with a low noise pricey JFET transistor and the other with a more common low power and way lower cost MOSFET transistor. It was no contest.

While the JFET had remarkable clarity and definition it just wasn't very warm or musical. Precise yes, fun to listen to not so much. The MOSFET on the other hand was warmer and more analog sounding and the highs were not as pronounced and forward but still very much present. Very enjoyable.

As things stand now we'll probably be going with the MOSFET although we still want to evaluate a couple more specific MOSFET models to see if one sounds better than our current pick. These are low power MOSFETs running Class A with idle currents typically running in the 10-30 ma range.

The final LDR300.V25 production buffer board will have socketed buffer modules so they can be swapped out down the road if we find something better. Or if someone wants to try something themselves.

Cheers,
Morten

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #7 on: 16 Aug 2018, 05:39 pm »
Very interesting and enjoyable bake-off listening sessions yesterday comparing 2 different MOSFET transistors in the LDR300.V25 buffer stage. The most recent transistor we tried out clearly outperformed the prior model. These are both small signal MOSFETs with remarkably similar specs yet with clearly audible differences with the one beating out the other.

To be clear these were subjective evaluations that involved 2 people swapping buffer modules randomly while the other person listened not knowing which transistor type was installed. Measurements suggest they should sound the same but active listening demonstrated they do not.

At this point we are freezing the buffer module design and going with our most recent MOSFET which is the ZVN3310. It beat out the VN10K we'd been using in our TPB.V1 Tube Preamp Buffer which we will soon also be testing with the ZVN3310 with expectations that we'll adopt it for the tube buffer as well.

I still have plans to revisit and test out some more JFETs down the road but for now MOSFETs +2, JFETS 0.

Cheers,
Morten 

Yesterday we did some critical listening to the next to last (hopefully) prototype buffer board. The buffer stage itself is actually a separate 4-pin plug-in module so we can quickly try different FETs. We compared 2 different FET modules, one with a low noise pricey JFET transistor and the other with a more common low power and way lower cost MOSFET transistor. It was no contest.

While the JFET had remarkable clarity and definition it just wasn't very warm or musical. Precise yes, fun to listen to not so much. The MOSFET on the other hand was warmer and more analog sounding and the highs were not as pronounced and forward but still very much present. Very enjoyable.

As things stand now we'll probably be going with the MOSFET although we still want to evaluate a couple more specific MOSFET models to see if one sounds better than our current pick. These are low power MOSFETs running Class A with idle currents typically running in the 10-30 ma range.

The final LDR300.V25 production buffer board will have socketed buffer modules so they can be swapped out down the road if we find something better. Or if someone wants to try something themselves.

Cheers,
Morten

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #8 on: 27 Aug 2018, 02:33 pm »
Release week is here and so of course we're still making a last minute decision on which FET to go with. I've tried numerous JFETs and MOSFETs but to date have NOT tried the LSK170 which is the current production model equivalent of the famous Toshiba 2SK170 made popular by Nelson Pass and the DIY community as being the final word on discrete audio JFETs. You may well ask why didn't we start with the LSK170? Pure stubborness is probably the most honest answer. If we end up using the LSK170 after testing it later today/tomorrow it will be because we ended up there after taking a journey through the land of alternatives. In the end I want to be convinced we picked the best part and didn't just go with the herd.

Cheers,  :thumb:
Morten
« Last Edit: 27 Aug 2018, 05:29 pm by tortugaranger »

MttBsh

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Re: LDR300.V25 Buffered Preamp
« Reply #9 on: 27 Aug 2018, 03:38 pm »
I think there's wisdom in trying out the "alternative" FETS first, today when you test/hear the LSK170 you'll have an unbiased picture of where it stands among its competitors. I'm really looking forward to hearing the LDR300V25.

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #10 on: 27 Aug 2018, 08:20 pm »
Ok.
We did it.
We tried LSK170 JFETs in the buffer.
They're great.
No contest.
Sweeter, fuller, more musical, more fun to listen to.
We're going with LSK170's.
Done!  :thumb:

RDavidson

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Re: LDR300.V25 Buffered Preamp
« Reply #11 on: 28 Aug 2018, 02:24 am »
I think there's wisdom in trying out the "alternative" FETS first, today when you test/hear the LSK170 you'll have an unbiased picture of where it stands among its competitors. I'm really looking forward to hearing the LDR300V25.

Agree 100%. And that’s why I always urge people if they’re curious to try a new piece of audio gear to just do it (assuming they can afford the risk). If anything, you’ll learn from the experience and understand more about what you like and what you don’t. :thumb:

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #12 on: 14 Sep 2018, 07:04 pm »
First production pics of the LDR300.V25. Internals with rear panel but without the front panel.



tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #13 on: 15 Nov 2018, 09:48 pm »
** LDL300.V25 Design/Configuration Change **

When we finalized the design of the LDR300.V25 Buffered Preamp we made a couple of arguably minor changes from the fully tested prototype version to the production version. Then we went into production and shipped out a bunch of units that had been pre-ordered. All those units had their input impedance set at 20k which has been the default impedance level for our LDR attenuators for the past several years.

As it turns out the 20k default impedance setting is far from optimal for the LDR300 and could result in poor sound quality depending on the source device connected to the preamp. By "poor sound quality" I mean the mid-range would sound like it was missing or had been sucked out of the music.

The correct impedance setting for the LDR300 turns out to be 75k and it makes a world of difference. Fortunately, it's a fairly straightforward matter to adjust the input impedance of the LDR300 using the interactive menu and selecting "Imped", then selecting impedance setting #2 (or whichever you want), raising the impedance to 75k, and then pressing Enter to run the unit through a calibration cycle. After completing one cycle you should repeat the cycle one more time at 75k to improve the accuracy. That's it!

On new builds we have changed the default impedance setting #1 from 20k to 75k. Future release of the firmware will have this built-in so existing customers can update their firmware if they wish but this isn't really necessary since the impedance can be changed by the user with the existing firmware.

Cheers,
Morten

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #14 on: 17 Dec 2018, 03:46 pm »
We are already on RevB of our LDR300 Solid State Buffer board having made several  "under the hood" changes that have further improved on the great sound from this simple yet highly effective JFET buffer.

You can check out the LDR300 Buffered Preamp here:  https://www.tortugaaudio.com/products/buffered-preamps/ldr300-v25-buffered-preamp/






tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #15 on: 22 Feb 2019, 08:42 pm »
I'm pleased to announce that we've made some changes for the better to the LDR300. These changes were initially prompted by feedback we received from the LD300 tour unit but as we looked into the original design we decided to also make several additional changes. The net net of all this is an even better sounding preamp.

Here's the summary of the design changes:

1) Deleted the input coupling capacitor - it's now direct DC coupled
2) Added 2-stage internal split voltage power supply with SMPS 1st stage and linear 2nd stage (was previously a 10 V single linear supply)
3) Changed from 12 V to 24 V - 500 ma external power supply input
4) Additional power supply bypass capacitors - Elna Silmac II plus Vishay Polypropylene

We actually went through several iterations before settling on this approach. The output DC offset is almost zero but we kept the output coupling caps to avoid the complications of DC offset protection. The sound is more natural and relaxed and not quite as solid state dry as before. Overall a more pleasing listening experience.

By going with split voltage the PSRR is now huge (meaning VERY quiet) since any noise on the +/- voltage supply will be next to invisible at the near zero volt DC buffer output signal half way between the power rails.

We're waiting for updated production circuit boards at this point.

Once we have production boards we'll  be sending out the tour unit for its last few stops and anyone else who may be interested in giving the LDR300 a try - just let me know.

Cheers,
Morten  :thumb:

tortugaranger

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Re: LDR300.V25 Buffered Preamp
« Reply #16 on: 22 Mar 2019, 01:46 pm »
The LDR300.V25 Buffered Preamp has now been updated with a substantially redesigned SSB.V2 (RevA) solid state buffer board. The result is a combined LDR attenuator plus minimalist JFET split voltage buffer that is a delight to listen to and takes the LDR300 to a new level. I'm very very pleased with the results and do not anticipate any change to the LDR300.V25 going forward after this design update. At least not for a very long time.

All back-ordered and new LDR300.V25 orders will be built with the new SSB.V2 buffer design.

More info on the LDR300.V25 can be found here:  https://www.tortugaaudio.com/products/buffered-preamps/ldr300-v25-buffered-preamp/

The rough bench pic below shows the new SSB.V2 buffer board in the foreground and the LDR.V25 preamp controller board in the background. The buffer board is roughly 45% power supply & controls, 45% output coupling caps and 10% actual buffer signal components.


paul79

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Re: LDR300.V25 Buffered Preamp
« Reply #17 on: 22 Mar 2019, 06:47 pm »
Very nice. Sounds like a very exciting update to an already great sounding unit!