LDR300x.V3 Preamp Tour

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tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #80 on: 21 Dec 2020, 09:48 pm »

Interesting update on the LDR3000x.V3 Active version

https://www.audiocircle.com/index.php?topic=168215.msg1836816#msg1836816

jriggy

Re: LDR300x.V3 Preamp Tour
« Reply #81 on: 29 Dec 2020, 06:19 pm »
Hey guys,

The preamp did not get rerouted, landed here yesterday, and I turned it around to Michigan via USPS today, with a prepaid label from Morten.

Was a bummer having it here and sending it off right away. Really wish I could participate.

Have fun

Jason

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Re: LDR300x.V3 Preamp Tour
« Reply #82 on: 5 Jan 2021, 06:50 pm »
Hi All,

The tour preamp has suffered some damage due to having been shipped multiple times where the shaking/vibration has broken loose one of the CuTf coupling caps. This doesn't surprise me given that those caps are about as big and heavy as a roll of quarters and we do not have provisions for strapping down these caps in the current board design.

The good news is Bob2 has agreed to put on his repairman hat and have at it. However, rather than simply reattaching the CuTf VCap I've instructed Bob2 to remove them both altogether. Instead we are converting the active gain/buffer board over to direct coupled output.

Some background. The SSPB.V2 gain/buffer board is a second gen design where we changed to a split voltage power supply (+/- 12V), added an input stage (op amp), and added the ability to adjust the bias current of the JFET output buffer using trim pots (the 2 blue cubes with a screw on top). The split voltage PS together with the adjustable output bias current was intended to allow for the elimination of the output coupling caps (AC coupling) and thus run DC coupled instead. This follows the philosophy of "the best coupling cap is no coupling cap". DC coupling works well provided the DC offset can be kept to a minimum - typically 50 millivolt or less - ideally zero MV.

The SSPB.V2 provided for the use of coupling caps as an initial default. Meanwhile we've had some time to explore running the board without the caps while monitoring the behavior of the DC offset. What we've determined is that once adjusted to near zero DC offset, the offset remains very stable and typically can be held under +/- 5 MV which is more than acceptable. Also, there's no power-on or power-off bump or pop because the SSPB.V2 board has its own muting relay with a delayed unmute when power is first applied. And when power is dropped, the muting relay shunts all output to ground.

Once Bob2 has made the modifications including adjusting the JFET bias current to yield ~0 DC offset, he'll keep the unit for up to a week of listening and then it's back on the road again to the next person but with a direct coupled output.

uncola

Re: LDR300x.V3 Preamp Tour
« Reply #83 on: 5 Jan 2021, 10:43 pm »
Not to mention direct coupled is cheaper because it doesn't need those fancy capacitors!

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #84 on: 6 Jan 2021, 12:25 am »
Not to mention direct coupled is cheaper because it doesn't need those fancy capacitors!


Indeed!

LarryD56

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Re: LDR300x.V3 Preamp Tour
« Reply #85 on: 6 Jan 2021, 01:02 am »
    When I was preparing the preamp's box to be shipped out the cardboard was already getting rather loose, so I removed all the loose tape and tightly re-taped the entire box. It was looking a bit beat up when I got it. Glad the preamp's case didn't get damaged. Looks like FedEx charged me an additional $5 for their botched re-routing to Bob2. I will be speaking with their billing dept. this week about a refund.  I usually don't have any problems with them.

   Yeah, I'd prefer a stable direct coupled design. Now I'm even more interested in the preamp. Wanting to hear what Bob2 thinks of the LDR300x.V3 after he fixes it.

  Larry D.

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #86 on: 7 Jan 2021, 06:43 pm »

Success! Bob made the modifications removing the VCaps, installing direct links, and adjusting the DC offset to ~zero.  Says it's sounding great. Looking forward to reading his review.



Hi All,

The tour preamp has suffered some damage due to having been shipped multiple times where the shaking/vibration has broken loose one of the CuTf coupling caps. This doesn't surprise me given that those caps are about as big and heavy as a roll of quarters and we do not have provisions for strapping down these caps in the current board design.

The good news is Bob2 has agreed to put on his repairman hat and have at it. However, rather than simply reattaching the CuTf VCap I've instructed Bob2 to remove them both altogether. Instead we are converting the active gain/buffer board over to direct coupled output.

Some background. The SSPB.V2 gain/buffer board is a second gen design where we changed to a split voltage power supply (+/- 12V), added an input stage (op amp), and added the ability to adjust the bias current of the JFET output buffer using trim pots (the 2 blue cubes with a screw on top). The split voltage PS together with the adjustable output bias current was intended to allow for the elimination of the output coupling caps (AC coupling) and thus run DC coupled instead. This follows the philosophy of "the best coupling cap is no coupling cap". DC coupling works well provided the DC offset can be kept to a minimum - typically 50 millivolt or less - ideally zero MV.

The SSPB.V2 provided for the use of coupling caps as an initial default. Meanwhile we've had some time to explore running the board without the caps while monitoring the behavior of the DC offset. What we've determined is that once adjusted to near zero DC offset, the offset remains very stable and typically can be held under +/- 5 MV which is more than acceptable. Also, there's no power-on or power-off bump or pop because the SSPB.V2 board has its own muting relay with a delayed unmute when power is first applied. And when power is dropped, the muting relay shunts all output to ground.

Once Bob2 has made the modifications including adjusting the JFET bias current to yield ~0 DC offset, he'll keep the unit for up to a week of listening and then it's back on the road again to the next person but with a direct coupled output.

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #87 on: 13 Jan 2021, 02:15 pm »
Hi All,
A quick update on the tour. Had the typical holiday slow down but we are moving forward now.
sruffle is up next.

1) uncola - HI
2) MttBsh - WA
3) Delta77 - CA
4) Emiel - AZ
5) LarryD56 - ID
6) Bob2 - MI

7) sruffle - NJ (up next)
8') krustykat - NC
9) GentleBender - FL
10) Mollydog

Standby List
1) ** open **

Bob2

Re: LDR300x.V3 Preamp Tour
« Reply #88 on: 14 Jan 2021, 04:44 pm »
The 300 preamp has been here and is on it's way to the next person.

Let me preface this post. I'm not an Audiophile. I'm an enthusiast so no Fancy Pants verbiage, plots or charts.

I use a tone control tube preamp to drive my amp. When Morten started collecting names to try his LDR300x.V3 I thought it was a good time to see how a SS preamp would handle my Stratos Extreme. I signed up and away we go!

Morten has explained what happened with the preamp so no need to get into that.

With the 300 working again I hooked it up for my first listening session. I use a PC that plays music ripped to a hard drive. The PC utilizes an Asus Essence STX II sound card to send the analog signal.
I also use an Azur 851N streaming from various sources.

I spent about 7 hours over two evenings going through a collection of music.
Sound was different than my preamp of course but very good never the less.
I did find that bass was less than I am accustomed to. Mids were a bit more present.
Sound stage was wide and reasonably deep. The 300 presented itself very well.

I planned to listen to vinyl for the next session. That unfortunately did not happen.
I started the session with Brubeck's Take Five Lp cued up. As soon as the needle starting sending a signal the preamp froze. The volume control as well as the remote became unresponsive then the preamp shut down.
I checked to make sure everything was connected properly and tried the album again. Same thing.
I tried with my second tt only to have the same results.

Contacted Morten and he offered up a couple of suggestions for me to try. Sadly those did not rectify the issue.
After some e-mails and phone conversation with Morten there was not much that could be done. The 300 is working in active and passive modes when connected to my PC and the Azur.

I went back through this thread but didn't see any that stated they had listened to vinyl.
So I'm not sure if the stated issue was there prior to the vcap ricocheting around the enclosure.

I did spend a couple of hours listening in passive mode. I feel that active mode is a bit better.
If you are looking for a preamp on a budget it is worth checking it out.

I want to thank Morten for giving us an opportunity to try it out. I have to say that Morten is a brave man for turning me lose making repairs.
Also thanks to Audio Circle for creating a great forum that makes this possible.

Equipment used:
Speakers, Focal Aria 948
Digital Sources, PC, Azur 851N
Analog Sources, Specific Dynamics tt, Sony 3000tt
Phono preamps, Goldnote PH-10, Creek OBH-15 mk2
Amplification, Odyssey Stratos Extreme
Interconnects, Wireworld



tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #89 on: 14 Jan 2021, 06:42 pm »
I want to thank Bob for participating and especially for his help in converting the preamp over to active direct coupled.

Bob encountered a problem when he connected his phono preamp(s) to the LDR300x. When he dropped the needle on his turntable the LDR300x would either freeze or shut down. We've not had reports of anything similar ever happening to any of our earlier preamps so this is new. I told Bob I didn't have a simple fix from afar. We were able to determine that this has nothing to do with the active part of the LDR300x - it also happened when running passive with the active gain/buffer board literally removed from the unit. While I don't have a specific explanation it's highly likely that the phono preamp linestage signal ground is inducing sufficient ground current to cause the power internal to the LDR300x to fluctuate and trip the microcontroller. We will be looking into this here at our shop with our phono rig which we usually don't use during development or commissioning.

The 300 preamp has been here and is on it's way to the next person.

Let me preface this post. I'm not an Audiophile. I'm an enthusiast so no Fancy Pants verbiage, plots or charts.

I use a tone control tube preamp to drive my amp. When Morten started collecting names to try his LDR300x.V3 I thought it was a good time to see how a SS preamp would handle my Stratos Extreme. I signed up and away we go!

Morten has explained what happened with the preamp so no need to get into that.

With the 300 working again I hooked it up for my first listening session. I use a PC that plays music ripped to a hard drive. The PC utilizes an Asus Essence STX II sound card to send the analog signal.
I also use an Azur 851N streaming from various sources.

I spent about 7 hours over two evenings going through a collection of music.
Sound was different than my preamp of course but very good never the less.
I did find that bass was less than I am accustomed to. Mids were a bit more present.
Sound stage was wide and reasonably deep. The 300 presented itself very well.

I planned to listen to vinyl for the next session. That unfortunately did not happen.
I started the session with Brubeck's Take Five Lp cued up. As soon as the needle starting sending a signal the preamp froze. The volume control as well as the remote became unresponsive then the preamp shut down.
I checked to make sure everything was connected properly and tried the album again. Same thing.
I tried with my second tt only to have the same results.

Contacted Morten and he offered up a couple of suggestions for me to try. Sadly those did not rectify the issue.
After some e-mails and phone conversation with Morten there was not much that could be done. The 300 is working in active and passive modes when connected to my PC and the Azur.

I went back through this thread but didn't see any that stated they had listened to vinyl.
So I'm not sure if the stated issue was there prior to the vcap ricocheting around the enclosure.

I did spend a couple of hours listening in passive mode. I feel that active mode is a bit better.
If you are looking for a preamp on a budget it is worth checking it out.

I want to thank Morten for giving us an opportunity to try it out. I have to say that Morten is a brave man for turning me lose making repairs.
Also thanks to Audio Circle for creating a great forum that makes this possible.

Equipment used:
Speakers, Focal Aria 948
Digital Sources, PC, Azur 851N
Analog Sources, Specific Dynamics tt, Sony 3000tt
Phono preamps, Goldnote PH-10, Creek OBH-15 mk2
Amplification, Odyssey Stratos Extreme
Interconnects, Wireworld



sruffle

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Re: LDR300x.V3 Preamp Tour
« Reply #90 on: 16 Jan 2021, 10:22 pm »
Hello all.  I had a pleasant surprise today when the pre-amp arrived earlier than expected.  I will be setting it up this weekend and will give a report within the next week.

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #91 on: 28 Jan 2021, 08:51 pm »
Hi All,

After enduring multiple high-G shipments and physical modifications at my behest, I'm having sruffle send the tour unit back to the barn for a checkup and updating. I'll be sending it back out ASAP to krustykat who is up next.

1) uncola - HI
2) MttBsh - WA
3) Delta77 - CA
4) Emiel - AZ
5) LarryD56 - ID
6) Bob2 - MI
7) sruffle - NJ (up next)

8') krustykat - NC
9) GentleBender - FL
10) Mollydog
11) Audiosaurusrex - MA

Standby List
1) ** open **
« Last Edit: 29 Jan 2021, 01:42 pm by tortugaranger »

sruffle

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Re: LDR300x.V3 Preamp Tour
« Reply #92 on: 29 Jan 2021, 01:51 pm »
I had the pleasure of auditioning the tour preamp over the last week.   The audition got off to a rough start as I had trouble with one of my RCA cables making a connection and was only getting sound out of one channel.  After diagnosing the problem on the phone with Morten, we were able to get the preamp running with no issue.  (Note - Morten was extremely helpful and patient)

To provide some background, my system consists of:

- MacMini (Roon/HQPlayer DSD upsampling)
- Holo Audio Spring DAC
- DIY Tortuga preamp
- Deware Zen 25thAnniversary SET amp
- DIY open baffle speakers

My current preamp uses the Tortuga kit and has upgraded components (silver wire, Furutech RCA jacks, linear power supply).   This preamp sounds absolutely terrific.  The primary drawback is that the display is an older one that only shows one number.  It works for me but makes me nervous that the wrong push of a button on the remote could send me down a difficult path of trying to recover my original settings.   

I wanted to see if the new preamp can sound as good as my current one and also wanted to test the active mode.  Unfortunately, I couldn't get the active mode to work so listened in passive.  General conclusions were that this version is close to my modded version.  The new display and remote control functionality are leagues ahead of the older versions that only show one window.  That alone is a major selling point. 

In terms of the sound, I made the following notes on my standard demo playlist:

- Bass comes through as clear and articulate.  There is no issue producing a very satisfying texture as well as going low
- Soundstage is what you would hope for. 
- Detail is excellent.  I usually listen to live Grateful Dead and Duke Ellington big band songs.  I was able to pick out every instrument without the detail feeling etched. 
- Tones are pure.  Vocals and guitar solos sound like you are in the room.

I would have liked to try the active mode but very much enjoyed listening to this.  I have tried running direct from DAC to amplifier with several DACs but the sound was never satisfactory.  I haven't used a ton of different preamps but compared to the ones I have used (modded Acurus RL-11 and RedWine Audio tube preamp, the Tortuga produces the most clarity and provides the biggest soundstage.  On the whole, I am very happy with the sound quality of the Tortuga preamp and do not have any itch to try another type of preamp.

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #93 on: 1 Feb 2021, 01:50 pm »
Thank you for posting your review, for participating in the tour, and especially for taking the time to make the modifications we discussed.

Best,
Morten

I had the pleasure of auditioning the tour preamp over the last week.   The audition got off to a rough start as I had trouble with one of my RCA cables making a connection and was only getting sound out of one channel.  After diagnosing the problem on the phone with Morten, we were able to get the preamp running with no issue.  (Note - Morten was extremely helpful and patient)

To provide some background, my system consists of:

- MacMini (Roon/HQPlayer DSD upsampling)
- Holo Audio Spring DAC
- DIY Tortuga preamp
- Deware Zen 25thAnniversary SET amp
- DIY open baffle speakers

My current preamp uses the Tortuga kit and has upgraded components (silver wire, Furutech RCA jacks, linear power supply).   This preamp sounds absolutely terrific.  The primary drawback is that the display is an older one that only shows one number.  It works for me but makes me nervous that the wrong push of a button on the remote could send me down a difficult path of trying to recover my original settings.   

I wanted to see if the new preamp can sound as good as my current one and also wanted to test the active mode.  Unfortunately, I couldn't get the active mode to work so listened in passive.  General conclusions were that this version is close to my modded version.  The new display and remote control functionality are leagues ahead of the older versions that only show one window.  That alone is a major selling point. 

In terms of the sound, I made the following notes on my standard demo playlist:

- Bass comes through as clear and articulate.  There is no issue producing a very satisfying texture as well as going low
- Soundstage is what you would hope for. 
- Detail is excellent.  I usually listen to live Grateful Dead and Duke Ellington big band songs.  I was able to pick out every instrument without the detail feeling etched. 
- Tones are pure.  Vocals and guitar solos sound like you are in the room.

I would have liked to try the active mode but very much enjoyed listening to this.  I have tried running direct from DAC to amplifier with several DACs but the sound was never satisfactory.  I haven't used a ton of different preamps but compared to the ones I have used (modded Acurus RL-11 and RedWine Audio tube preamp, the Tortuga produces the most clarity and provides the biggest soundstage.  On the whole, I am very happy with the sound quality of the Tortuga preamp and do not have any itch to try another type of preamp.

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #94 on: 3 Feb 2021, 06:28 pm »
Hi All,

The tour unit is back on the road after a pit stop. I decided the replace the gain/buffer board since the original got a good beating when one of the Copper Teflon coupling caps broke loose during a prior shipment and thrashed the board but good. I also updated the firmware in the V3 controller board which will have no impact on the sonics but cleans up a couple of minor bugs.

Just a reminder that the preamp is configured by default as an active preamp set at unity gain (meaning no gain/amplification). I popped in a TL072 JFET op amp which replaces the original LME49720 which we've determined was marginally stable at unity gain.

Also, if you're curious don't hesitate to open up the preamp to swap the discrete attenuator board for the LDR attenuator board. You can also move the jumpers JPL and JPR from the "A" (active) position to the "P" (passive) position if you're curious to hear the preamp in passive mode. This bypasses the gain/buffer board completely.

The preamp in now on its way to krustykat in North Carolina.

Enjoy and stay safe!

Bob2

Re: LDR300x.V3 Preamp Tour
« Reply #95 on: 3 Feb 2021, 07:29 pm »
Morten. did you try it out with a TT?

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #96 on: 3 Feb 2021, 07:39 pm »
Morten. did you try it out with a TT?

No specifically with the tour unit but am setting up a turntable in our shop to test generally. Waiting on some cables and will have that up and running soon. We have a modest phono preamp that can handle both MM and MC cartridges. Our TT currently has a MC.

For those reading this, the question relates to Bob2's experience running his turntable into the LDR300x and seeing the LDR300x turn off and/or freeze the moment the needle hit the vinyl. My guess is that's a ground loop problem but so far it's just a guess. Will report findings once we have our rig up and running.

Our current source is a Schitt Yggdrasil DAC which I really like. 

Hikmer

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Re: LDR300x.V3 Preamp Tour
« Reply #97 on: 5 Feb 2021, 03:49 am »
I'm running a Manley Chinook into the LDR300x without any issue of needle drop problems.  Sounds amazing. 

krustykat

Re: LDR300x.V3 Preamp Tour
« Reply #98 on: 9 Feb 2021, 03:42 pm »
The LDR300x.v3 arrived this weekend and I had a chance to try it for a bit on Sun and Monday.  I'm using a VPI Classic w/ a Transfiguration Phoenix MC cartridge through a K&K Maxxed-Out phono preamp for my analog source and a Innuos Zenith MK3 to a Border Patrol DAC for my digital.  Output to a Pass XA30.8 amp and Selah Tempesta Extreme speakers.

The timing was fortuitous as my normal preamp developed a slight problem that required me to send it in for repair.  The appearance of the LDR300x.v3 is very subdued - it eschews bling for an appearance that just blends into the background.  The bamboo front on my LDR3.v25is a bit more stylish, which unfortunately is not available anymore.  The apple remote is a nice touch as they are easily obtainable just in case your dog decides to chew on it. 

My initial tests with the turntable showed none of the problems earlier reported with crashing on needle drops.  The user interface is well laid out and very intuitive, much easier to use than the old non OLED interface on the LDR3.v25. The sound is clear, bass extension is tight and deep.   Treble extension is very good, with only the slightest touch of grain on some vocals.  Soundstaging is very wide too, it's not as deep front to back as I've heard, but it is still very good.  I do wonder if a good linear power supply might help, but unfortunately I don't have one of the right voltage to test.  In active mode, the gain is too low for me, I had to go up to 75 (out of 100) or higher to achieve my normal listening volume and it never pushed my amp out of class A mode.   Morten, is this adjustable?
 
I'll be listening more over the coming week and will post more detailed impressions, but I can say that my quibbles are minor and I am quite impressed by the quality of this unit!  It appears to be a steal for the price that Morten is asking for it!  I'll be testing it in passive mode and also comparing directly against my LDR3.v25.   Stay Tuned.
  :popcorn:

tortugaranger

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Re: LDR300x.V3 Preamp Tour
« Reply #99 on: 9 Feb 2021, 11:29 pm »
In active mode, the gain is too low for me, I had to go up to 75 (out of 100) or higher to achieve my normal listening volume and it never pushed my amp out of class A mode.   Morten, is this adjustable?

Interesting comment.

First, the active gain in the LDR300x is set at unity (1x) meaning no amplification (or a gain of 1.0). This is deliberate and is the default gain setting. What does that mean? It means the input stage of the active board isn't trying to increase the voltage of the incoming signal (i.e. it's not amplifying it to make it louder). It's simply acting as a unity gain input buffer (an active impedance fire wall). This is no different than running the preamp in passive mode from a volume standpoint. However, the active board also has an active output JFET stage which acts as a current amplifier. A current amplifier boosts the available power of the audio signal without making it louder. This translates into better overall dynamics of the audio signal (better punch, slam, pluck etc.). Do you need that? Depends on your source components (which should be more than capable of delivering that power without having to lean on an active preamp, but many are not).


Secondly, let's examine the volume setting. You note that you had to go up to 75 out of 100...or higher. That's entirely expected and in keeping with normal volume settings when operating the LDR300x. I typically run my system at around 75-90. For me, that's "normal" when running with a unity gain preamp (both active or passive).

Yes, you can increase the actual gain. You can replace the plug-in gain modules with +6 or +12 dB gain modules which are resistor pairs that increase the gain of the input op amp. But to what end? What's the point of doing that?  Let's say you install +12 dB gain modules. Now you can run the volume setting at 20 steps lower (each attenuation step being ~0.6 dB). But what have you accomplished? You will have punched up the potential volume by +12db only to crank it down again by 12 dB to achieve the same effective loudness.

In my view, the only justification for boosting the actual gain of the LDR300x (or any preamp) is if you're running out of volume control headroom. Which means you just can't get the system to play loud enough.

So what if you run the unity gain LDR300x at 75, or 85 or 90 (out of 100) - active or passive. Is it loud enough or not? If it's not loud enough, add some gain. If it's loud enough, carry on.  :thumb:

Cheers,
Morten