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

Showing 15 responses by kosst_amojan

@georgehifi You're over here totally mischaracterizing Pass too? Do I need to quote and cite the article for his active pre-amp that you're cherry picking his words from? And why can't you understand impedance isn't the only factor? Why do you keep selling the myth 90% of system only need a passive? If it was true, they'd be in 90% of systems. They obviously aren't! Just give it up!
@georgehifi 
Nonsense. Active pre-amps aren't going anywhere. They're an unusual fetish that'll never become mainstream because of their unavoidable failings. 5000 ohm of impedance to the input of 90% of amps is never going to sound as good as 50 ohm. 
@georgehifi 
I believe facts. Facts like Nelson Pass explaining the superiority of a buffer to a passive. Facts like measured performance. Facts like subjective performance. Facts like the rarity of passives. 
@tweak1 
A buffer is an active stage that does give gain. Because it's assumed everything in an audio chain are voltage sources, voltage gain is all that gets labeled gain. Building pure current gain circuits is totally possible. That's what a buffer is. The output stage of a power amp is typically a massive current gain stage, i.e., a buffer, to the loudspeakers. Input stages to power amps are reactive loads. They have some inductance, impedance, and capacitance. That's why their behavior drifts around depending on the signal frequency. Flatly assuming a 10:1 impedance match is all that needs considered is simplistic to say the least. All reactive loads will induce some nonlinearity in the driving gain devices. If those devices aren't in the pre-amp, then they're in the source. 
Hope that makes some sense. 
@mrdecibel 

He doesn't know what he's talking about. No good amp designer builds an amp that really peters out at it's rated power. You overbuild the amp, set the gain conservatively, and then brag how your amp gets .00X% distortion at "rated power" with 1.5V input. That's what Nelson Pass does all the time! It takes WAY more than 2 volts to break down a typical small signal audio JFET. 
Huh.... looks like the Aleph L runs runs 30 volt rails to get upwards of 10 volts output. With...... MOSFETs!

If no amp ever made required more than 2 volts to utilize it's full power, why's Nelson Pass build nothing but pre-amps that give you at least 9.5 dB and at least 5 volts output? He certainly isn't the only one. All kinds of reasons why, too. 
@georgehifi 
It's just a fact that operating gain devices deep into their linear region yields better performance. It's a byproduct of that fact that they also have the ability to output high power. 
Yet every single Pass pre-amp has at least about 10dB of gain... It's like he doesn't even take his own advice!
@analogluvr 
I'd say the answer is clearly no.. No reason to believe they ever will. 
Could somebody remind me what a resistor is? Oh yeah! They're usually windings of long, thin conductor! 
Resistors have all that stuff too! Especially the giant piles of them in resistor ladders! I'm not stalking you. You say silly things that are clearly incorrect again and again and again and propose flawed solutions as if they're perfect while making mountains out of the ant hill sized issues with other solutions. 
@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. 
Practically nobody is running an impedance converting amplifier like the F4. It is, for all intents and purposes, a gigantic buffer that allows high impedance sources to drive low impedance loads. It's designed on the premise that the best place to get voltage gain is in the line stage/pre-amp where noise, heat, and power are much better controlled. I'm pretty sure I pointed that out when somebody suggested that the only place worthy of applying gain was in the power amp. 

Go ahead now... Flag away. I'm sure the mods are waiting for you to make my point.