2. amps-preamps
  3. 136322-2546

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
tweak1 OP
3,680 posts
 
George Hi tweak1 I am not sure if you referred to my review of the Nord Class D and Hattor preamp. I

Yes, that review is where I first learned of you, it motivated me to get the Hattor.

I thought I had posted this but, I decided against the Nord Two because of the monster power. Sometimes I change discs and the output is crazy different: than the new disc BLASTS out so loud it scares me, and I run for the remote//mute. 

Then I got a deal on the AA amp for about half the price of the Nord, which you said is an even worse impedance match than my prior EP 100.2SEs, which sounded glassy in my system. Prior to the Hattor I had a Parasound P5 and was not thrilled

FYI: I went all in on XLR decades ago.

I asked Arek about the OpAmp you suggested, but he is on holiday. He suggested sending me the board with OpAmp, which I hesitate to do, but...

Then an AA DAC//Pre came up at a price I couldn't resist. Better not be an impedance mismatch there. I should have it Thursday. I  will use until I get the Hattor sorted out.

Thanks again
tweak1 OP
3,680 posts
 
FYI, Oppo 105 output impedance is 100 ohms. Is the Hattor still a mismatch with the AA amp?
georgehifi's avatar
georgehifi
10,312 posts
 


tweak1 OP622 posts07-26-2018 3:09amFYI, Oppo 105 output impedance is 100 ohms. Is the Hattor still a mismatch with the AA amp?


Now we’re looking at what the Oppo can drive

I don’t know the impedance of your Hattor or is attenuation method, series, ladder or shunt.

For simplicity let’s say it’s ladder (the best one), And is say it’s a 17kohm ladder passive this impedance combined (paralleled) with the 17kohm impedance of your AA becomes half, at 8.5kohm that the Oppo will see, this to me a still good impedance for it to looking at.
You can see "if" the Oppo is 100ohms from 20hz to 20khz then the ratio into the 8.5kohm combination Hattor/AA is 1:85.
BUT!!! see that "if" the Oppo could have an output coupling cap, an if not large enough will make that 100ohm impedance rise in the bass and then your 1:85 ratio quickly diminishes which could roll off the bass to early.

Cheers George
mitch2
4,086 posts
 
@atmasphere 
FWIW dept: our MP-3 preamp can be ordered as a balanced tube buffer with no active gain stage.
That is interesting Ralph, I wish I had heard the no-gain version back when - I may not have sold my MP-3.   Now I have a great sounding SS unity-gain buffer by Steve McCormack so don’t have the need for another.  You should get the word out.  With today’s high output DACs, that might be just the ticket for many.

mrdecibel
3,065 posts
 
I might be missing something, but for as long as I can remember, the dacs I have owned, the cd players I have owned, the tuners I have owned ( and some tape machines ), have all been 2 volts output, or more. I also remember early passive units from way back. So none of this is new, with maybe the buffer circuit being new. Of my hundreds of amplifiers passing through my doors, all could be driven to full output with 2 volts in ( I am not talking about the impedance here, just the output voltage ). I do understand the importance of impedance matching. Enjoy ! MrD.
More to discover