Have Passive Preamps Finally Come of Age?


Back in the late 90s (eons ago) I tried a variety of passive preamps (PPs). The most musical was an autoformer, but back then my system was not balanced. For the last decade I have been using active preamps, both tube and solid state, but finding a quality balanced preamp under $4K is damn near impossible. Enter the Parasound P5 (2.1), which in addition to having balanced I/Os, it has a separate bass management circuit (MSRP $1095), and I was hoping it would provide better control over the built in class D plates incorporated into my 2 SVS powered subs, whose volume controls are STUPIDLY sensitive: when barely cracked from zero they overwhelm. Alas, no bueno. 

Recently i watched a PS Audio YT video that was emphatic about NOT connecting powered subs with interconnects; instead he recommends speaker cables piggybacked off the main systems amp/s. I had a spare set of DIY flat copper cables, and was shocked how much better they sounded, but doing so did not change the  volume control problem and unfortunately this id not bypass the SVS amps whose class D chips are now ancient. Thinking there could be an impedance problem led me to revisit PPs.

I sold my P5 and was using the XLR outs from my Oppo 105 (upgraded power supply and IEC/wiring to the power supply) direct to my Emerald Physics 100.2SEs (class D). The noise floor dropped tremendously, allowing me a much better view into the music. My Core Power Technologies 1800 PLC had more than a little to do with this, but...  

Days of PP research later, I came across LDRs, which seem like the ultimate PP option, but XLR versions are ~ $2K and up, with the Tortuga coming in at $2700, seems like a true SOTA bargain, just not in my current budget. Scouring the' for sale' sites I came across a Hattor XLR (MSRP $995) which was in my price range. Hattor's www had links to 2 reviews both were extremely positive: one used it in combination with a class D amp. Bingo! I snapped it up.

It arrived late yesterday, although Hattor's www pictures look awesome, they do not compare to seeing and touching it. The metal carrying case was an indication of the designer's dedication. This is an etremely well made piece of kit, but how does it sound? Alas it came with no manual and Hattor's site does not have a PDF. How hard can it be to hook up? Well, after a couple scary minutes, I discovered that it would not light up until I connected the 105. 

Stone cold, the first thing that shocked me was a further reduction in noise floor and an incredibly wide and deep sound stage, but as can be expected, it was dry. Fingers crossed, in about a half hour I began to be rewarded with texture as well. Tis only got better as the night wore on

I hope somebody chimes in with their Tortuga experience, or any other high quality PP information.that goes under the reporting radar. 
tweak1
it may explain why good active line stages can easily outperform passive devices in some cases.
"In some cases" Very few.
With 10k passives only if output to input impedance matching is below 1:10 ratio, which in most cases it’s not, unless the amp is 25k or lower.


Some preamps are designed to have very large s/n ratios and very large voltage swing range capacity. This results in a far higher level of signal quality on the output, with regard to preserving micro differentials in the signal
An active preamps gain stage after the volume control cannot give micro detail a "leg up" compared to the original, as the gain stage amplifies everything up, so it remains the same. But it does include it’s own noise and distortions on top of the original, which may give the illusion of detail.

Nelson Pass on passives pres:
"What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection."

"Just musical perfection" Which means "true to the source" nothing added or taken away.

Cheers George
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Well, it seems to me the gain issue ( voltage ) has just be proven by kosst's last post, taken from Nelson Pass himself. Take care of the impedance issue, using buffers ( 0 gain ) and the source can drive most power amps quite well. Enjoy ! MrD.
Well, it seems to me the gain issue ( voltage ) has just be proven by kosst's last post, taken from Nelson Pass himself. Take care of the impedance issue, using buffers ( 0 gain ) and the source can drive most power amps quite well. Enjoy ! MrD.
This is certainly true- if your only source is digital. If other sources are involved (such as a tuner, tape or phono) then it won't be the case. We've built buffer-only preamps for some of our customers that are digital only, but at least one of those shipped his preamp back after about 5 years and had us install the active gain circuitry as well, despite all his sources being digital. If you have more than one source, occasionally you run into the issue that not all digital sources actually conform to RedBook output standards. These sources will need additional gain. 

The thing is, if you do your design homework, the distortion and bandwidth limits of the active line stage can be much better than those of the source itself and if you do your engineering homework, its possible to insure that the kinds of distortion it does make are of the type to which the ear isn't particularly sensitive.