Discussion:
My Review of the Tortuga Audio Passive Pre
konut
2013-11-19 23:51:13 UTC
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This is part 1 of a review of the Tortuga Audio LDR1 passive volume
control, or passive preamp, as some like to call it.

http://www.tortugaaudio.com/

There was a delay in getting a newly implemented control software
chip due to refinements that were required after beta testing. Part 2
will consist of a comparison between the original chip and the new chip.
I felt compelled to post my thoughts while they were fresh in, what
little is left of, my mind.
My system consists of a Sony BDP S580 BluRay player hooked up via a
15ft length of DH Labs SilverSonic D75 coax BNC/RCA adapter->BNC to a
Bryston BDA-1 DAC(Mojo Audio PC). The single ended out then goes to
Creek OBH-12 passive pre via a 26" pair of Sweet Spot Reveal "Silver"
interconnects then from the Creek to a pair of W4S SX500 mono amps(W4S
P-1 PCs) via a 3ft pair of Grover Huffman ICs. A 3ft pair of Anti-Cables
go from the amps to Aether Audio Black Boxes, Aether Audio Timepiece
Minis and VMPS Super tweeters(facing backwards). The amps are plugged
into the wall, and eveything else in plugged into an APC S15 power
conditioner and Belkin PureAV PF60.The LDR1 replaces the Creek.
I have not used an active pre in almost 20 years. My system is
optimized for use with a passive pre. The Bryston DAC was selected
because of its 2.3V, 50ohm, discrete analog output, and reliability. The
W4S amps were chosen for their high gain, low noise and distortion, and
relatively high, for ICE power type amps, input impedance of 60k ohms.
ICs are short and low capacitance. No accommodations were made to
substitute the Creek with the Tortuga.
I've been on the hunt for a replacement for the Creek for some
time. To be sure, the Creek is an entry level passive but offers 3 input
switching and remote so it met my needs. The replacements that I have
considered over the years all have some perceived weakness. Mostly they
offered no, to me, significant increase in sound quality commensurate
with their price. AFAIK, there are only 3 methods of implementing
passive pres; resisters, transformers, and light dependent resisters.
Each method has its assets and liabilities. It wasn't until the Tortuga
came along that I felt there was something that minimized the minuses
and maximized the pluses and justified the asking price. I jumped at the
opportunity to secure a spot on the audition tour that was offered.
I received the unit on Halloween. Trick or treat? It is housed in a
nondescript black case with a window for the infrared remote receiver,
blue lettering, a black knurled knob, and an on/off blue LED that some
might find too bright. After substituting the LDR1 for the Creek I got
no sound. I called Morten to see what could possibly be wrong. He
indicated that there was not much that could go wrong. When installing
the unit I had double checked that I had made the correct input/output
connections, as I have made that mistake in the past. While on the phone
it occurred to me that maybe I had forgotten to turn my amps back on.
That, indeed, was the case. How embarrassing. I had a nice chat with
Morten, indicated all was well, and he could not have been more cordial.
I had tricked myself and now for the treat.
It became immediately apparent that the LDR1 was a more
transparent component than the Creek. At 3 times the price, one should
expect that. What they had in common was the black background, low/no
distortion, and wide sound stage. The LDR1 improves on the Creek in a
number of different areas.
Leading edge attack transients are more delineated throughout
the frequency range. This was most noticeable with all types of
percussion. Snare, cymbals, toms, and kick had much more snap and
precision.
The mid-bass on down seemed to gain a few extra db of authority.
Not lumpy mind you, but a smooth fullness contributing a sense of
realism to whatever instrument was in that range. The extra degree of
sub 40hz info gave an increased sense of acoustic space.
Low level detail increased to a great degree. Previously obscured
detail was laid bare. Each instrument and voice gained, not only an
extra dimension in space but, resolution giving a sense of the artists
emotional intent.
It seemed like the LDR1 was letting more signal through. I was
listening at levels above my usual, 85db-95db, to levels of 100bd+ as
everything just sounded so good. Some discs which I had been able to
turn up all the way with the Creek, and in theory should be the same as
a bypass, were needed to be restrained a bit as not to push the amps,
and/or speakers, past their limits.
There was a greater sense of dynamics, compered to the Creek, at
all volume levels. Greatly anticipating the new chip to see if this is
expanded.
If I were to change anything I would give some sense of the volume
going up and down other than just the aural evidence. As it is the blue
LED flashes slowly when either the volume is all the way up, or all the
way down. There is an enter button on the remote which causes the LED to
flash rapidly and I would prefer this sense of feedback when raising and
lowering the volume. This is the way the Creek works but this is by no
means a deal breaker for me. I would also like a less bright LED, but,
again, not a deal breaker.
I listen to a wide variety of music. I pulled out discs that I had
not listened to in years and probably listened to more music, since
receiving the LDR1, than I had listened to in the past 6 months. I was
given a renewed sense of excitement that I had been missing for a long
time. I can't think of higher praise. As a casualty of the part-time
economy I shall have to find a way to acquire one of these.


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konut
2013-12-10 01:31:31 UTC
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This is part 2 of a review for the Tortuga Audio LDR1 passive preamp. I
was able to audition the LDR1 for a full month before receiving the
updated software chip. There had been a delay in sending out the chip as
it was discovered there were certain anomalies with Class D amps. Once
those were resolved the chip was sent out. Since I have W4S Class D
amps, it was reassuring that this was checked out. Having the LDR1 for
so long made it easy to hear the difference between the old software and
the new software.
The only difference in actual operation of the pre was that now when
the volume was raised or lowered, the LED fast flickers. Tortuga had
incorporated my suggestion. Nice!
The purpose of the new software was to increase and optimize the
input impedance thus resulting in better dynamics especially at lower
volumes. In actual practice it did much more than that. Dynamically
there was a sense of increased transient response though not nearly as
significant as the difference between my old passive and the old
software. At lower volumes it was difficult for me to detect a
significant increase in dynamics across the board. What was significant
was a marked increase in low level detail, even at lower volumes. But
the most improvement came in rendition of sound stage. At all volumes
there was an expansion of width and depth as well as a greater
perception of space. There was a smoothness to the presentation that
gives a greater sense of reality, especially in live recordings.
My GUESS as to whats going on is that the precision of the channel
balance that the original software pioneered is further enhanced and
made more apparent by the impedance optimization. Those spacial cues
that are embedded in the phase relationships are made more precise by
the channel matching and brought to the fore by the impedance
refinement. Again, just a guess on my part.
Having sent the unit on to the next participant on the tour, and
going back to my previous pre, I noticed that the texture of instruments
and voices are less refined. The subtle emotional nuances are less.
There is a flattening of the sound stage and the sound sticking more to
the speakers. Harrumph.
Having worked in live sound for a few years and maintaining an
interest in audio as a hobby for 40 years, I have come to appreciate
that everyone comes to different conclusions as to what they hear and
thus how they want their audio to be reproduced. Its a trial and error
process hopefully with correlations between what is heard and what can
be measured. That has been my experience anyway. What I have found is
that low distortion, high signal to noise ratio, and flat frequency
response are the preeminent determinants as to whether I will like a
certain component. Others have come to different conclusions.
The very nature of the recording process manipulates the sound
running it through various circuits with all kinds of deleterious as
well as beneficial effects, some recordings more than others. Some are
of the opinion that since this is the case why not use every means at
our disposal to manipulate the sound, when reproducing, to achieve
pleasing results. Those that use passive preamps take an opposing view.
The last thing we want to do is use anything that will obscure the
waveform as its delivered by the source medium. The fewer circuits the
better. While I have not personally auditioned a lot of passive pres, I
can say that the LDR1 is as a transparent component as I have ever
encountered. I will be curious of the findings of the rest of the tour
participants as to how the LDR1 performs with their systems. Thanks to
Tortuga for sponsoring the tour.
The LDR1 tour is a being conducted for members of the Audiocircle
forum who responded to a thread in the Tortuga Audio sub-forum. You can
follow it here.

http://www.audiocircle.com/index.php?topic=119915.0


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konut
2014-05-06 02:05:46 UTC
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The tour has been completed. Reviews in a wide variety of systems have
been posted accessible via the link in the previous post.. I have
purchased the tour component.


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