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
These are two Hattor’s.
Passive, which I believe you have, which what looks to be Kozmho switched volume control, which I believe is a fixed series resistor and variable ones to ground, which will vary it’s i/o impedance’s at different volume levels, best to me is ladder ones, where the series and shunt resistors work in opposites to each other to give a more constant I/O impedance
https://www.audiocircle.com/index.php?topic=145833.0

And the active buffered Hattor which used an opamp.
http://mockingbirddistribution.mockingbirddistr.netdna-cdn.com/wp-content/uploads/2018/03/Hattor-Min...

Here are some different ways of doing a volume control, quad matched ldr is a ladder
https://www.stereo.net.au/forums/uploads/monthly_2018_06/Capture.JPG.93bbd2ce49060300b06abfd1a62ce8f...

Cheers George

Just found their site, they have an extensive range, of what looks to be well made products, including a tube one
http://www.hattor.com/index2.html#ultimate

Cheers George
It is really well built, all shiny stuff is real metal, too, including the remote

Mine is near the top of their product page. MSRP $995
Its an active (buffered) control. Shouldn't this thread have a different title?

"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.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp."

George always leaves out the rest of Nelson's words, as if they don't exist. Here they are, as you can see Nelson does not think passives are the last word by any means:

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.

There are lots of different possibilities for buffers, but we are going to pick my favorite:





Question is not which pre-amp but why there is floor noise:
a) bad or wrong wiring?
b) one element Is damaged.

so to rebuilt piece by piece the system and everything will go in the right way. Could be the pre-amp but also something else. 

Personally i I use an “AM Audio PRE 04F”.. pure art of electronic building. No noise, no distortion, no bass nor high adjustments.. just volume and selector knobs... price below 2k
.
regards