[tortugaranger]

As a manufacturer I am obviously biased towards our products - LDR Passive Preamps. That said, I'm also a life-long audiophile looking for what works best together, sounds better, and along the way trying to separate the hype from the reality.   

I got into the business of designing and manufacturing LDR Passive Preamps because I was blown away by the sound quality relative to all other options and thought we could do a better engineering job of taming the wild LDR - which I think we've done!

Now that we have a few years of business under our belt and have accumulated a decent size customer base there's little doubt (in our minds at least) that LDR passive preamps are the best sounding volume control (attenuation) devices available today. This isn't just our opinion it's the overwhelming conclusion of our customer base. Several of our customers owned exceptional tube and SS preamps costing upward of $10k and after auditioning the Tortuga pre, sold off their hi-end active preamps and stayed with the Tortuga. Customers tell us we bested their stepped attenuators and even their transformer based volume controls costing way more than our models.

Yet even a casual exploration of online audio forums reveals a fairly consistent picture where passives are generally viewed as inferior to conventional active preamps. The active vs. passive debate may rear it head now and get rehashed but the prevailing view remains that actives trump passives - generally speaking. And since LDR based passive preamps are a subset of passive preamps they get painted with the same inferior brush - however unfair and inaccurate that might be.

The case for LDR passives is both simple and compelling:

• Excellent overall sound quality including remarkable bass - open, articulate, uncolored, transparent
• Great dynamics - punch, slam & pluck
• The vast majority of audio systems do not need preamp gain (a.k.a. "active" amplification of the audio signal prior to the amp)
• Lowest possible noise floor (no power supply interaction with audio signal)
• Lower cost
• Adjustable input impedance to optimize bridging impedance and performance between source and amp.

And yet, if you lined up any 10 audiophiles and read off this list of  substantiated audio goodness I would argue that most (8 out of 10? ) would assume this was questionable marketing hype and refer you to the assumption that you need a quality conventional active (powered) preamp to get the best sounding audio system. And of course none of them will have actually tried (listened to) an LDR passive yet be firm in their convictions.

So my collection of interrelated questions for the audiophile community at large are as follows:

1) How do you change the minds of informed audiophiles with information contrary to their prevailing views?
2) Is framing this as a passive vs. active debate even useful or effective?
3) What are the key issues with preamps and does the LDR preamp address these or not?

[steve f]

My questions about passive devices. I need, or rather like, a remote for volume and sources.  I'd like a balance control too.

That said, the one thing I require that is non existent in passive devices is very low output impedance.

I've tried passive devices, not yours, and found them lacking. These were older devices. For comparison, my favorite preamps to date are the Horn Shoppe Naked Truth, Morrison ELAD (discontinued) and for tubes and just a step lower in my opinion only Transcendent Sound Grounded Grid.

I do agree that most devices have enough gain to drive a power amp. I am also convinced that those devices need a buffer too.

steve

[Shakeydeal]

I have owned many high dollar preamps, and several types of passive devices. I think if your system is suited for a passive, the LDR just can't be beat. That said, there are some systems that just have to have additional gain. For the most part, I think these are systems that weren't well planned from the start. But hey, that's just me.

However, there will always be the guys that have passive friendly systems that won't even consider a passive of any pedigree. They are fully wed to active preamps and there's no changing their minds. Added to that are the guys that would never consider any device in their systems that cost so little, no matter how good the performance.

Lastly, there are people who don't realize how bad their systems are because the preamp is masking the flaws. Put a truly transparent preamp in the system and it's a wake up call they aren't willing to receive.

So that's  my take on why passive devices, LDR or othewise, will never suit everyone.

Shakey

[RDavidson]

1. The only way to change minds is to have people try them risk free ; The audio equivalent of The Pepsi Challenge.

2. No, it doesn't. If anything, the whole passive vs active debate will only fuel preconceived notions or experiences based on lesser passives. Perhaps a better discussion should revolve around this question : Should a preamp color the signal or not, and why?

3. Passive or active, the key issue with preamps is coloration (in my opinion). Ideally, a preamp should just pass the signal and provide attenuation  (and perhaps other conveniences like source selection) and provide the best electrical signal (impedance) to the amp. Because all systems are different, it seems that without a buffer of some sort, performance of a pure passive will always vary.

So, with anything, there are tradeoffs. A buffer will make things simpler / easier and more universal, but will color the sound (more than a pure passive). A pure passive can be the most transparent, but this assumes factors of voltage, impedance, cable length etc are always accounted for by the user. Even some seasoned audiophiles don't quite grasp all of the latter. We all want the best sound, but not all of us care to have to consider or even know to consider all the factors involved with passive preamp implementation.

[steve f]

RD, I tend to agree with most of your post.
Point of difference. A good buffer is absolutely transparent, and will avoid many problems with interconnects.

If you need long interconnects, you need very low impedance, 50 Ohms or less works well. You also need some drive current. In some systems a passive can work very well. Short, decent quality interconnects, and an easy to drive amp. I think we're pretty much in agreement.

How about a passive pre tour? I'm all in for that. It doesn't have to be a top of the line new unit. It doesn't have to be pretty either. It just has to show Tortuga's ability.

steve

[RDavidson]

Well....having nothing in the signal path is more transparent than having something in the signal path, which is why I don't think a buffer is absolutely transparent regardless of how good it is.

[tortugaranger]

My questions about passive devices. I need, or rather like, a remote for volume and sources.  I'd like a balance control too.

The Tortuga pres have both of those.

That said, the one thing I require that is non existent in passive devices is very low output impedance.

The output impedance of any passive attenuator (voltage divider) will vary as you run it from 0 (zero voltage/volume) to 100% (full voltage/volume). This is a matter of physics really - the law of resistors in parallel. This is exactly what happens with any potentiometer. An LDR passive more or less emulates a potentiometer so it behaves the same way. If you want fully resistive/passive, you don't get low/fixed output impedance. 

However, the assumption that a low (or fixed) output impedance is a requirement for an effective passive preamp is generally not the case. To make it an absolute requirement is to effectively close off the possibility of using any resistive passive. Such a requirement is synonymous with requiring a buffer stage on the output of the "passive" and the moment you do this it ain't no passive no more - it's an active preamp with no gain. So we are back full circle with the "you don't need a conventional active preamp to have excellent audio when an LDR passive can more often than not to a better job of it."
 

I've tried passive devices, not yours, and found them lacking. 

I've tried a few myself and agree with you. And others have had similar experiences. It's really tough convincing someone who's already tried something and didn't like it to try it again. What became clear to me when I first started working with LDR attenuation is the simple fact that LDR's just sound different. Or perhaps more correctly - they don't sound like anything at all! 

I do agree that most devices have enough gain to drive a power amp.

Most but not all. We did run across a couple of instances where the customer had a low wattage SET tube amp connected to relatively low efficiency speakers and concluded after trying our preamps that they simply needed a little upstream gain to get the volume level up. But most of our customers running Tortuga preamp into tube amps have found there's no need for additional gain. We've been slowly developing an output buffer option for just such a situation but release of that is still a ways off.

I am also convinced that those devices need a buffer too.

We've found that as long as long as your amp has sufficiently high input impedance relative to the output impedance of your source, that LDR passives do a fantastic job without a  buffer. Of course there will always be exceptions but based on our experience and that of our customer base those exceptions have turned out to be quite rare.

[tortugaranger]

However, there will always be the guys that have passive friendly systems that won't even consider a passive of any pedigree. They are fully wed to active preamps and there's no changing their minds. Added to that are the guys that would never consider any device in their systems that cost so little, no matter how good the performance.

Such is life. A friend of the family where I grew up when asked what he wanted would always answer..."I don't care. Just make it big, heavy and expensive." He owned a car dealership, had the cash, and had a philosophy. Worked for him.

Lastly, there are people who don't realize how bad their systems are because the preamp is masking the flaws. Put a truly transparent preamp in the system and it's a wake up call they aren't willing to receive.

I'm of the view that most are in that boat. I know I was. It was a revelation when I first started working with LDRs. I could hardly believe my ears. I hauled in family members and did some blind A/B testing. These were not audiophiles. The results were black and white. I wasn't imagining it. The fact that a preamp/attenuator could make such a difference changed my whole outlook on the relative importance of various audio gear. But you have to be at least open to the idea of trying it.

[steve f]

Just a couple of quick comments. And posted with friendly intent.

Yes a well designed passive can be excellent with most equipment. Agreed.

The very best buffer type preamps have noise measurements at the residual noise of the test equipment used to measure them. A passive can't sound more quiet. Disagree.

So how about a tour unit? Here's a chance to prove that a passive device can equal/exceed the best active devices. It might generate some sales too. I keep a tube, a solid state, a photo optic, and soon a buffer only unit. ( I keep a variety of pre and power amps as I design speakers ) If you can convince me, I'll sing your praises, and buy one too.

[Shakeydeal]

So how about a tour unit?

I thought this was something that was already happening?

Shakey

[steve f]

You are correct. I'm a newcomer to Tortuga, and I missed that. Too late to join in?

steve

[tortugaranger]

You are correct. I'm a newcomer to Tortuga, and I missed that. Too late to join in?
steve

That tour has left the station and is full up - with a long delay - but is getting rolling again. And is only for our LDRxB - Balanced Passive Preamp.

I'm willing to start a separate tour for our LDR3.V2 singled ended unit and will set that up outside of this thread.

[steve f]

Thank you. I would love to join that one.

steve

[33na3rd]

After I got my LDR3.V2, I sold my $3750 tubed preamp. It sounded "thick & fuzzy" in comparison. I like "warm", but who needs "thick & fuzzy"?

I don't know how you're going to convince someone that it's better, until they've heard it themselves.

For me, the "LDR" may be a bigger aspect than the "passive".
I used the original LDR3X.V1 to fix my broken Melos SHA Gold. That Preamp has both passive & active outputs. Switching between those two outputs showed subtle differences in my system. The differences between the LDR and conventional volume controls though, is huge!

You've got a great product Morten!

I don't know how you get the word out. I would be afraid of the mainstream audio press, so many politics at some of those places.

[Shakeydeal]

Steve,

I don't want to hijack this thread, but I just want you to know what other active preamps I have owned.

BAT VK3i
BAT VK30
Audible Illusions Modulus 3a
Cary SLP-98
CJ Premier 17LS
deHavilland Ultraverve
Art Audio DPS
Audio Research SP9 II
Antique Sound Labs Flora
JJ Electronics 234

There were others, but those are the heavy hitters. What took me away from all of them were transformer/autoformer preamps, of which I've owned a few. All of these were better than any of the active preamps by a fair margin. I settled on the Sonic Euphoria AVC and nothing seemed to be able to best it. Until I heard an LDR.

I just wanted to put things in perspective for you and encourage you to try an LDR if you get the chance. You'd be welcome to come listen to mine if you were close enough.

Shakey

[tortugaranger]

Thought I'd mention this just in case folks don't pick up on this from our website.

We have a 30 day buy-try-decide audition policy. What this means in practical terms is you have 3-4 weeks to try out our preamps at home in your own system. If things don't work out, you ship the unit back and we refund you 100% of the cost of the unit - no restocking fee. You pay the return shipping cost.

So at least in the US, for somewhere in the range of $20-35 net worst case (return shipping), you get to try out our preamps. Sure, you do have to lay out the cash up front but you get that back if you don't keep it. About as risk free as it gets.

It's a bit costlier for international buyers due to higher shipping costs plus duties/taxes etc.

Here's the audition policy details but it's basically as outlined above: http://www.tortugaaudio.com/policies/30-day-audition/

[Shakeydeal]

Thought I'd mention this just in case folks don't pick up on this from our website.

We have a 30 day buy-try-decide audition policy. What this means in practical terms is you have 3-4 weeks to try out our preamps at home in your own system. If things don't work out, you ship the unit back and we refund you 100% of the cost of the unit - no restocking fee. You pay the return shipping cost.

So at least in the US, for somewhere in the range of $20-35 net worst case (return shipping), you get to try out our preamps. Sure, you do have to lay out the cash up front but you get that back if you don't keep it. About as risk free as it gets.

It's a bit costlier for international buyers due to higher shipping costs plus duties/taxes etc.

You can't get more fair than that.

Shakey

[barrows]

Because you are asking:

1) How do you change the minds of informed audiophiles with information contrary to their prevailing views?

If I knew the answer to this!  Audiophile dogma dies hard, I think you are already doing what you can, allowing for fairly painless home auditions.  Very precise, clear, measurements can help (see 3 below).

2) Is framing this as a passive vs. active debate even useful or effective?

This depends on what you want to make/sell.  Of course LDR does not have to mean passive.  I suspect that you would find a very good market for an LDR preamp with a really good, discrete, MOSFET unity gain buffer at its output (some might be OK with a diamond buffer IC).  There is no question that some source/amp combos need additional current drive (not gain though) to achieve good dynamics.  The problem is a passive will not suit all systems.  I prefer to view gain as a separate issue, too many audiophiles do not address proper gain matching in their systems and are throwing away performance.
 
3) What are the key issues with preamps and does the LDR preamp address these or not?

Inserting any component results in losses.  I prefer source-amp direct connection as long as the source has enough current drive to achieve good dynamics.  As I DIY, I just make sure my DAC has a robust enough output stage, and good gain matching, and I can then use digital volume control and eliminate a box and interconnect.  I also prefer single source systems, eliminating any switches from the signal path, as switches can be heard, as can an extra interconnect.
Volume control implementation is a critical design element of preamps, no question.  So, if LDR really is better, than say, Shallco switch stepped attenuators with 0.1% TX2575 resistors, then you have a benefit-but without publishing very precise measurements from an AP sys 2 of a passive with the above two volume controls there is little evidence to prove that the LDR is better.  Let's see a comparison of noise and distortion spectra at: 0 dB, -4 dB, -8 dB, -16 dB, -32 dB, -64 dB.
In the best preamps, active or not is not really the question, as the best active stages can be so close to fully transparent (distortion levels below the threshold of audability) that there is no downside to having an active circuit.  Implementaion of PCB layout, input switches, and volume control are going to be the defining aspects of preamp "sound".

[barrows]

Well....having nothing in the signal path is more transparent than having something in the signal path, which is why I don't think a buffer is absolutely transparent regardless of how good it is.

R: the above is only true as a thought experiment, or technically.  From the standpoint of audability, it is entirely possible to design and implement a buffer circuit which will be below the threshold of audability, and hence, be transparent.

[rajacat]

barrows,

Why don't you participate in the Tortuga LDR tour? Do your tests if you want, listen to how  it sounds compared to your "fully transparent" active pre and come to your conclusions first hand.