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
georgehifi's avatar
georgehifi
10,312 posts
 

If you have 2v from the source and your amp clips at 1v there is absolutely NO ADVANTAGE in having 4v from the source.
Don't let anyone no matter who they are tell you the 4v or 6v will give extra headroom or dynamics, it is a falsehood.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 
Now you confuse me by saying (7/25): Now we’re looking at what the Oppo can drive
We were before just taking about just about match between passives and amps.

Now we are talking with the Oppo and what it is able to drive, and in a (non active) but passive situation that will be the paralleled combination of the passives input impedance and the amps input impedance together.

As all the Oppo sees, is "like" two paralleled resistors to ground, one being the passive the other being the amp. Throw and active preamp into the mix and forget about the amps impedance, all the Oppo sees is the input resistance of the active, it can’t see the amp impedance.

Cheers George
mrdecibel
3,062 posts
 
Many amplifiers overloaded with 2 volts ? Are we talking about power amplifiers being overloaded, or preamplifier sections being overloaded ? 30 volts output ? Now I am confused. But, Enjoy ! MrD.
Post removed 
almarg's avatar
Ag insider logo xs@2x
almarg
9,670 posts
 
Many amplifiers overloaded with 2 volts ? Are we talking about power amplifiers being overloaded, or preamplifier sections being overloaded ? 30 volts output ? Now I am confused.
I haven’t read most of this thread, but regarding your comment I’ve seen preamp output voltage specs confuse a number of people here in the past. The 30 volt number Ralph referred to, and other preamp output voltage specs that are greater than a few volts, represent their maximum output voltage **capability.** Everything else being equal, the higher that number is the better (within reason of course), as a higher number will provide more margin relative to the output voltages that are actually required from the preamp in normal use.

Actual output voltages higher than a few volts (in many cases something like 2 volts) will not occur in normal use, as they would drive nearly all amplifiers into clipping, and perhaps damage the speakers as well. Not to mention driving the listener out of his or her chair and toward either the volume control or the nearest exit :-)

The actual output voltage provided by a preamp will correspond to the input voltage the source provides to it at any instant of time (which will vary with the volume of the music, of course), multiplied by the gain of the preamp (expressed as the ratio of output voltage to input voltage), and reduced by the amount of attenuation the volume control provides at the setting being used (relative to its maximum possible setting).

Regards,
-- Al
More to discover