LDR300x Preamp | Passive & Active Versions

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Hikmer

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #20 on: 19 Aug 2020, 06:08 pm »
Good news, is the pre-order discounted?  I also see options for capacitor upgrades.  Can those be done at a later time?  Finally, is a remote included?  Don't see a TA option either.

tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #21 on: 19 Aug 2020, 06:23 pm »
Good news, is the pre-order discounted?  I also see options for capacitor upgrades.  Can those be done at a later time?  Finally, is a remote included?  Don't see a TA option either.

Pre-order discount - Given the relative aggressive pricing there's really no room for discounting these preamps. I did consider this since it's been customary to offer pre-order discounts.

Capacitor upgrades - Yes, these can be done down the road. It does require carefully removing and reinstalling soldered components but quite doable.

Remote control - Yes, all of our preamps are always remote control. We are, after all, civilized  ;)

TA Option - By this I assume you mean the discrete attenuator option in lieu of the LDR. After much back and forth on this I won't mince words. The LDR approach remains the better sonic option. I'd expected less of a difference and I'm actually quite agnostic as to which is better but so far the LDR wins so we are leading with what sounds better until something else comes along that beats it. I'm looking into an alternative discrete attenuator topology which may sound better than the logarithmic/ladder approach we currently have. We'll have to see how that goes.

Hikmer

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #22 on: 19 Aug 2020, 06:39 pm »
Alright, appreciate the response.  Purchase made, glad you reduced the level of options :)  Now I need to find a new phono stage!
« Last Edit: 19 Aug 2020, 11:50 pm by Hikmer »

tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #23 on: 19 Sep 2020, 03:30 pm »
Here's our first batch of product pics for the LDR300x.V3 Preamp.
Still need to get one made with the unit powered on with the OLED display showing.
We've started shipping these.  :thumb:

LDR300x.V3 Preamp | Active or Passive | https://tortugaaudio.com/products/passive-preamps/ldr300x-v3-preamp/









 
« Last Edit: 19 Sep 2020, 05:52 pm by tortugaranger »

tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #24 on: 23 Sep 2020, 08:46 pm »
Here's a decent pic of the LDR300x.V3 Active Preamp internals all dressed with VCAP reference series copper teflon output coupling caps. Amazing natural detailed sound.

https://tortugaaudio.com/products/passive-preamps/ldr300x-v3-preamp/


tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #25 on: 25 Sep 2020, 02:15 pm »
A musical interlude (click on youtube video link) for our Tortuga Audio mascot hard at work keeping our OLED display healthy.
The screensaver kicks in automatically after 15 minutes of no control activity when the unit is on.
The slight flicker seen in this video is an artifact of fluorescent lighting interacting with the camera.
It actually doesn't flicker at all. 

Enjoy!
Morten

https://youtu.be/eGbH_h8wd5w



GentleBender

Re: LDR300x Preamp | Passive & Active Versions
« Reply #26 on: 26 Sep 2020, 01:37 pm »
Looking good Morten.

uncola

Re: LDR300x Preamp | Passive & Active Versions
« Reply #27 on: 3 Oct 2020, 02:05 am »
Sign me up for the west coast leg of the tour!  If hawaii counts as west coast.  Great job on keeping price low and your programming of the settings is impressive.  What's next, software tone controls?  ;)

Hikmer

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #28 on: 3 Oct 2020, 04:46 pm »
I've had mine for about a week now and can say this pre-amp is an amazing little device.  While I can use it in pure passive mode, the active buffer really gives the music some weight and body.  It is three preamps in one if you consider all the settings (assuming you purchase the active model - pure passive, active buffered, active with 6 db gain).   Need to fine tune my setup as it is very revealing and I have found a number of areas in my system that needed tweaking or correcting.   I'm giving it a little more time to burn in before a proper review but it replaced a preamp that was 4 times the cost with very expensive tubes and I am not missing it. 

MttBsh

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #29 on: 3 Oct 2020, 08:03 pm »
I've had mine for about a week now and can say this pre-amp is an amazing little device.  While I can use it in pure passive mode, the active buffer really gives the music some weight and body.  It is three preamps in one if you consider all the settings (assuming you purchase the active model - pure passive, active buffered, active with 6 db gain).   Need to fine tune my setup as it is very revealing and I have found a number of areas in my system that needed tweaking or correcting.   I'm giving it a little more time to burn in before a proper review but it replaced a preamp that was 4 times the cost with very expensive tubes and I am not missing it.

This is great to hear! I'm looking forward to auditioning the LDR300x in the coming weeks to determine if it's enough of an upgrade to displace my 6 year old Tortuga passive...

uncola

Re: LDR300x Preamp | Passive & Active Versions
« Reply #30 on: 4 Oct 2020, 08:41 am »
I just noticed I missed out on the tour again for yet another generation of preamps  :cry:
Morten you're so good at programming the settings through the screen did you ever think of adding a DAC module to the preamp?  Like I know soekris has a small oem dac module board.. and the orchard audio guy has his pecan pi dac boards available

tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #31 on: 4 Oct 2020, 12:27 pm »
I just noticed I missed out on the tour again for yet another generation of preamps  :cry:
Morten you're so good at programming the settings through the screen did you ever think of adding a DAC module to the preamp?  Like I know soekris has a small oem dac module board.. and the orchard audio guy has his pecan pi dac boards available


There's room on the tour. No worries. As for DACs I'm biased towards DACs being standalone components and am unclear on whether there would be demand for an integrated DAC/preamp. I'm broadly aware of the soekris DAC and believe ladder types are the way to go. Do you believe a visual front end for an OEM DAC board would be of interest and if so what functionality should it have?

tortugaranger

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LDR300x Preamp | Active Version Design Improvements
« Reply #32 on: 21 Dec 2020, 09:46 pm »
As we gain more runtime on the new LDR300x we've been refining not only the control firmware but have also been tweaking the SSPB.V2 gain/buffer board used in the active version of the preamp. One thing we've noted from day 1 is that the LDR300x has a noticeable bass boost especially in the active configuration. It's pleasant and not boomy but I've wondered about it. We've been using the LME49720 audio op amp in the active LDR300x all along and until recently haven't really taken the time to explore alternatives. Fortunately, the dual channel op amp is a plug-in PDIP8 type so it's easy enough to swap out the LME49720 for alternatives.

Today we swapped out the LME49720 and tried a good old TL072 JFET op amp. To our pleasant surprise the change was an overall positive mode. The base boost was dialed back while everything continued to sound marvelous if not actually a tad bit better. My tech thought so right away. Moreover, the TL072 exhibited very stable unity-gain operation - arguably better than the LM49720 which tended towards some low level motor-boating with low/zero gain.

Based on the success with the TL072, which was first released back in 1978 believe it or not, we are going to try a few other alternatives op amps and report back on results. As things stand this moment I'm going to switch over production units to the TL072 unless we find something better after trying a few others.

I'll report back on findings after we've tried some others.

The other tweak we've been testing is running the LDR300x with direct coupled output. Direct coupled means we don't use output coupled capacitors ..... at all!! For this to work we have to ensure that the DC offset on the output signals are near zero (just a few millivolts). We baked this capability into the design of the SSPB.V2 board but until recently haven't focused on it. The use of a split voltage power supply together with adjustable JFET buffer current allows us to literally dial in zero DC offset using trim pots. What we're finding is that once trimmed out, the DC offset remains quite stable and resumes near zero levels after power up each time. Running without output/blocking caps yields the best possible sound quality since the best coupling capacitor is no capacitor at all provided the DC offset is small and stable. Anyone with an existing unit can implement this themselves using jumper wires, a volt-ohm meter, and a thin bladed screwdriver.

Between the op amp optimization and the direct coupled output, the active version of the LDR300x is evolving into a truly great sounding preamp.

Cheers,
Morten

uncola

Re: LDR300x Preamp | Passive & Active Versions
« Reply #33 on: 21 Dec 2020, 10:00 pm »
nice to see active development!  I love when these tweaks come stock.  what next, power supply regulator rolling or mumetal shielding and vibration damping?  :)

LarryD56

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #34 on: 22 Dec 2020, 02:31 am »
   Is there room within the preamp enclosure to use a Burson V6 Vivid or Classic opamp? Those are supposed to be the cat's meow for opamps and they would be a direct substitute for the ones you are using.

   L.D.

tortugaranger

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #35 on: 22 Dec 2020, 02:01 pm »
   Is there room within the preamp enclosure to use a Burson V6 Vivid or Classic opamp? Those are supposed to be the cat's meow for opamps and they would be a direct substitute for the ones you are using.

   L.D.

I'm reasonably sure a Burson would fit width-wise.  I did a quick measurement and the distance from top of current chip to top of enclosure is almost 1 inch whereas the Burson needs 1.14 inches. If I subtract the thickness of the existing chip we are probably right at the 1.14 inch height. Worst case scenario remove the plastic case from around the Burson op amp and I'm sure that the discrete boards would fit. I'm going to give this a try as well and report on the results. Good suggestion!

tortugaranger

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Re: LDR300x Preamp | Active Version Design Improvements
« Reply #36 on: 23 Dec 2020, 07:33 pm »
We tried several alternative op amps today. We agreed the OPA2134 stood out. All the others sounded good/similar while the OPA2134 was more refined. That's not a big surprise as the OPA2134 has a great reputation. We may still try some others but for now will likely stay with the OPA2134 going forward. The OPA2134 is rock solid at unity gain while the LME49720 would sometimes exhibit some low level motor boating (oscillation).

The others we tried included:
LME49720 (our original choice during the design and initial production)
NE5532 - considered a more modern replacement for TL072
TL072
TLE2072 - a modern version of the TL072

As we gain more runtime on the new LDR300x we've been refining not only the control firmware but have also been tweaking the SSPB.V2 gain/buffer board used in the active version of the preamp. One thing we've noted from day 1 is that the LDR300x has a noticeable bass boost especially in the active configuration. It's pleasant and not boomy but I've wondered about it. We've been using the LME49720 audio op amp in the active LDR300x all along and until recently haven't really taken the time to explore alternatives. Fortunately, the dual channel op amp is a plug-in PDIP8 type so it's easy enough to swap out the LME49720 for alternatives.

Today we swapped out the LME49720 and tried a good old TL072 JFET op amp. To our pleasant surprise the change was an overall positive mode. The base boost was dialed back while everything continued to sound marvelous if not actually a tad bit better. My tech thought so right away. Moreover, the TL072 exhibited very stable unity-gain operation - arguably better than the LM49720 which tended towards some low level motor-boating with low/zero gain.

Based on the success with the TL072, which was first released back in 1978 believe it or not, we are going to try a few other alternatives op amps and report back on results. As things stand this moment I'm going to switch over production units to the TL072 unless we find something better after trying a few others.

I'll report back on findings after we've tried some others.

The other tweak we've been testing is running the LDR300x with direct coupled output. Direct coupled means we don't use output coupled capacitors ..... at all!! For this to work we have to ensure that the DC offset on the output signals are near zero (just a few millivolts). We baked this capability into the design of the SSPB.V2 board but until recently haven't focused on it. The use of a split voltage power supply together with adjustable JFET buffer current allows us to literally dial in zero DC offset using trim pots. What we're finding is that once trimmed out, the DC offset remains quite stable and resumes near zero levels after power up each time. Running without output/blocking caps yields the best possible sound quality since the best coupling capacitor is no capacitor at all provided the DC offset is small and stable. Anyone with an existing unit can implement this themselves using jumper wires, a volt-ohm meter, and a thin bladed screwdriver.

Between the op amp optimization and the direct coupled output, the active version of the LDR300x is evolving into a truly great sounding preamp.

Cheers,
Morten

Hikmer

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Re: LDR300x Preamp | Active Version Design Improvements
« Reply #37 on: 21 Jan 2021, 08:21 pm »
As we gain more runtime on the new LDR300x we've been refining not only the control firmware but have also been tweaking the SSPB.V2 gain/buffer board used in the active version of the preamp. One thing we've noted from day 1 is that the LDR300x has a noticeable bass boost especially in the active configuration. It's pleasant and not boomy but I've wondered about it. We've been using the LME49720 audio op amp in the active LDR300x all along and until recently haven't really taken the time to explore alternatives. Fortunately, the dual channel op amp is a plug-in PDIP8 type so it's easy enough to swap out the LME49720 for alternatives.

Today we swapped out the LME49720 and tried a good old TL072 JFET op amp. To our pleasant surprise the change was an overall positive mode. The base boost was dialed back while everything continued to sound marvelous if not actually a tad bit better. My tech thought so right away. Moreover, the TL072 exhibited very stable unity-gain operation - arguably better than the LM49720 which tended towards some low level motor-boating with low/zero gain.

Based on the success with the TL072, which was first released back in 1978 believe it or not, we are going to try a few other alternatives op amps and report back on results. As things stand this moment I'm going to switch over production units to the TL072 unless we find something better after trying a few others.

I'll report back on findings after we've tried some others.

The other tweak we've been testing is running the LDR300x with direct coupled output. Direct coupled means we don't use output coupled capacitors ..... at all!! For this to work we have to ensure that the DC offset on the output signals are near zero (just a few millivolts). We baked this capability into the design of the SSPB.V2 board but until recently haven't focused on it. The use of a split voltage power supply together with adjustable JFET buffer current allows us to literally dial in zero DC offset using trim pots. What we're finding is that once trimmed out, the DC offset remains quite stable and resumes near zero levels after power up each time. Running without output/blocking caps yields the best possible sound quality since the best coupling capacitor is no capacitor at all provided the DC offset is small and stable. Anyone with an existing unit can implement this themselves using jumper wires, a volt-ohm meter, and a thin bladed screwdriver.

Between the op amp optimization and the direct coupled output, the active version of the LDR300x is evolving into a truly great sounding preamp.

Cheers,
Morten

So are the expensive capacitors no longer needed in Active mode?  Just wondering as I am still enjoying the unit and waiting for the chassis upgrade.

tortugaranger

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Re: LDR300x Preamp | Active Version Design Improvements
« Reply #38 on: 21 Jan 2021, 10:12 pm »
So are the expensive capacitors no longer needed in Active mode?  Just wondering as I am still enjoying the unit and waiting for the chassis upgrade.

From what we've been observing it looks like the design can maintain a stable low DC offset which allows running the active/buffer board without coupling capacitors - cheap or expensive. It's up for debate whether there's a discernable sound quality difference between running without any cap vs. running with a high quality cap but I submit "no cap" is better than the "best cap" provided you can maintain a low DC offset at the output.

Swapping out different input/gain op amps has a more noticeable impact on sound quality. Not so much better vs. worse as in different where it comes down to preferences as much as anything. After going back and forth I'm currently liking the TL072 the best. Vivid mid range with plenty of high frequency "air". In systems that already tend towards bright, the TL072 may not be ideal and the more laid back BurrBrown OPA2134 may work better. These are 8 pin DIP plug-in dual op amps so it's easy enough to try alternatives to see which you prefer. The biggest challenge is patiently inserting the 8 pin DIP into the socket without bending the pins.

Hikmer

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Re: LDR300x Preamp | Passive & Active Versions
« Reply #39 on: 28 Jan 2021, 07:56 pm »
I ordered a pair of Burr Brown OPA2134, I haven't opened up my preamp but is there one or two that need to be replaced?