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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
celander's avatar
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celander
1,036 posts
 
About designers/manufacturers nixing the website content of other designers/manufacturers, there is a lot of puffery to go around. To wit, take the following quote about the specifications of an attenuator from an Australian website:

“Frequency response: 0hz – to almost Infinity. (Lightspeed) (interconnects are the determining factor here)”

Notwithstanding the hilarious frequency response claim, I’m pretty sure the internal wiring to and from the internal portions of the RCA input and output jacks of the attenuator is likely going to be more bandwidth limiting than any external RCA interconnect(s).

Reminds me of glass house owners being stone throwers.
georgehifi's avatar
georgehifi
4,966 posts
 
Notwithstanding the hilarious frequency response claim,

Did you or your kids ever term the phrase?????? Or maybe you don't get out enough???
It was meant as a bit of a joke, Infinity and beyond (Buzz Lightyear/Lightspeed!!)
I think everyone here can see it’s a "exaggeration" in reference to the name Lightspeed v Infinity, except for you maybe.

As for it’s actual "measured HF speed", when you can’t detect not even 1/10th of a dB drop with a 500mhz Tektronix scope, I think that can give me the "exaggerated" use of "infinity" in reference to the name Lightspeed, even if it is in jest.

Cheers George
kosst_amojan
2,095 posts
 
@georgehifi 

There's no "likely" about resistors having an effect. They absolutely do. And usually their physical size is a strongly determining factor. Those optos you like probably have a few pF of capacitance. 
geoffkait's avatar
geoffkait
14,147 posts
 
I’m waiting for the passive aggressive preamp, myself.
almarg's avatar
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almarg
8,673 posts
 
Notwithstanding the hilarious frequency response claim, I’m pretty sure the internal wiring to and from the internal portions of the RCA input and output jacks of the attenuator is likely going to be more bandwidth limiting than any external RCA interconnect(s).

While I’m not familiar with the internal construction of George’s Lightspeed attenuator, I would expect that what limits high frequency bandwidth is the low pass filter formed by the interaction of the impedance "looking back" from the junction between the series and shunt LDRs and the capacitance "looking forward" from that point.

Given the far greater length of an interconnect that would be usually be connected to the output of the Lightspeed, compared to the length of the wiring between the LDRs and the output of the device, that capacitance will almost invariably be dominated by the capacitance of the interconnect. Hence the statement I quoted above appears to me to be incorrect, and George’s statement that "interconnects are the determining factor here" is likely to be correct.

Perhaps, though, the statement I quoted above was intended to refer to the bandwidth of the interconnect in itself. If so, under any reasonable circumstances involving a home audio system I would expect that number to be so high as to be irrelevant to the bandwidth limitation imposed by the interaction of the capacitance of the interconnect and the Lightspeed’s impedance that I referred to.

Regards,
-- Al


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