Solid State Preamp Reviews

They could come up with a designer version and sell it for $20k :-) ........

Same disc.
https://www.steinway.com/music-and-artists/label/mussorgksy-hersch-natasha-paremski

According to JA1's measurements LA4 can pass through up to 20 to 21 bits of dynamic range signals, without any interference ....... In other words, LA4 doesn't 'editorialize' the passing signal :-) .......

Like KR said, it is 'super transparent' :-) .......

Let's start a petition!

In a perfect world, there would be no need for Any "active circuitry in an analog preamp".

The manufacturer (Benchmark) talks about using 'active buffering', actually to reduce the noise levels ...... See, manufacturer's comments in the print edition of January 2020 Stereophile ........ JA1's measurements show 20 to 21 bits of SNR (dynamic range) ........ It would be nice to see manufacturer's comments included in the web postings of the reviews, BTW :-) .......

from an Application Note. I doubt they'll mind my quoting it here at significant length:

THE "FULLY PASSIVE" MYTH
Most people understand that active buffers create some noise and distortion. But many people falsely assume that these active components are the only source of noise and distortion in an audio circuit. The truth is that passive components are usually the primary source of noise and distortion in an audio circuit!

In a search for perfection, many audiophiles have bought into the "fully passive" myth. I suspect that this explains why most relay attenuators are fully passive. On the surface, "fully passive" sounds like a good idea.

LOW NOISE REQUIRES LOW IMPEDANCES
What many audiophiles don't realize is that a single resistor can create far more noise than a good active buffer. For example, an LME49860 opamp produces about the same noise as a 440-Ohm resistor. This means that the LME49860 is 13.6 dB quieter than the thermal noise produced by a single 10 k resistor! Buffers can allow the use of much lower impedances in an attenuator's resistor ladder network. When the impedances are reduced, an active design can be far quieter than a fully-passive design. Low-noise can only be achieved when resistors have very low impedances and signal levels are kept high.

PASSIVE DESIGNS FORCE A TRADE OFF BETWEEN NOISE AND DISTORTION
If the impedances are reduced in an fully-passive attenuator design, the noise can be reduced but distortion will increase. This distortion is caused by an overloading of the upstream device. When an audio output is overloaded, distortion increases. Contrary to popular myth, distortion can be reduced by adding high-quality active buffers.

PASSIVE DESIGNS CAN CAUSE FREQUENCY RESPONSE PROBLEMS
A third problem with passive attenuators is that they may not provide enough drive for downstream devices. Cable capacitance and input capacitance can cause a high-frequency roll off. Worse yet, the frequency response may change as the volume is adjusted with a passive attenuator. Low output impedance is important for maintaining a wide bandwidth. Output buffers are essential for delivering a predictable frequency response.

https://benchmarkmedia.com/blogs/application_notes/benchmarks-256-step-r...

Jim Austin, Editor
Stereophile

I ordered them with only one end terminated because I wanted an unusual termination on the other end. They supplement/complement a pair of Benchmark NL2 TO BANANA - 2 POLE cables which can be used only with the Benchmark amp. Both sets use the same bananas and the same cable (Canare 4S11) and, not surprisingly, they sound identical.

I stopped using the AQs only because their stiffness and their bulky connectors make them inconvenient with my new Revel Studio2 speakers which have a cover/door over the speaker terminals that I'd like to close for cosmetic reasons.

I will say that I do not hear any change but I am a cable (difference) denier. At audio frequencies, any competent cable should sound the same, imho. You might consider it a bias. I do not.

32 bits, which is SNR of 192 :-) .......

To answer your question straight off, no.

Would it be good enough for you? Very possibly.

If you listen to music regularly at 110dB, your hearing will suffer in a few years or less.

A 100dB is actually pretty loud, but not deafening. It still may cause hearing damage, but will take much longer.

Most speakers (not horn-loaded), start to achieve their maximum output level around 104-110dB. This is a broad generalization, but, for the most part true.

If you are listening to music and the octaves around 1kHz are hovering at 100dB, then there is a really good chance that the bass one decade lower (100Hz) is about 10-12dB higher.

After looking at this for a decade (time, not frequency), I've come to the conclusion that music, live or recorded, sounds best when it has equal energy per octave... like pink noise. This again is a generalization, but it seems to work almost all the time for me.

In a really great listening room or recording studio, the background noise is going to be between 10 to 20dB. That does seem like a lot, given that the standard threshold for audibility in humans is 0dB, but trying to achieve that in the real world is very difficult. Cars, busses, over-flying planes & helicopters, dogs, cats, squirrels and people walking by with those animals make noise. And that's just outside your place.

Inside, you have a refrigerator, water heater and house heaters to deal with. Not to mention air conditioning when it's really hot and, when not, you'll have windows open somewhere.

My main audio system is in my basement. Generally, the quiescent noise in it is around 25-30dB when nothing is running.

Unless you are going to create a purpose-built room with no windows, incredibly expensive air-driven HVAC and have it inside something akin to a concrete bunker inside a larger concrete bunker, you won't get significantly better than my basement when nothing is running.

So, looking at all of this, why do you need a pre-amp better than the Project Audio or Parasound?

Perhaps, you personally, do not. This is not a cut on you, but not everyone has the same hearing acuity and, if you are living in the city, the background drone is going to be pretty high regardless of how many floors your apartment is from the street.

When it comes just to noise, that is usually (and should be) a steady state for any component. I'm pretty sure this Benchmark unit crushes the units you mentioned. It should given its price.

What you should really be looking at, though, is its distortion measurements. Those will give you the idea about how this unit sounds. I think that JA already stated that better than me.

Distortion is not steady state. It's dynamic and, unlike noise (which you can accommodate and then ignore somewhat in your brain), distortion of all types is undesirable in a h-fi component. It is coloration. While it can be benign, sometimes it's not.

Given what I know about the two pre-amps you mentioned, I'm sure that, until you build your bunker in a bunker, they would be fine.

With 110dB being the loudest you will play your system, the dynamic range of the average dwelling might only be, optimally, 85dB.

This, then, is where it gets very hairy. The noise in your place is not a stream of pink noise. It is also dynamic and generally centered around various, random frequencies below 1kHz. So the mids and highs have less noise intruding upon them.

Humans also can distinguish sounds way below the current noise of standard life. Sometimes up to 30dB into and below the background noise.

So, a pre-amp with 120dB dynamic range is actually what you need if you have the listening room to allow it to give you the best performance.

That does not mean that you can't enjoy music in noisier environments with equipment that has more noise. I did that for a few decades.

This is a great time to be an audiophile if you buy stuff like that made by Benchmark.

As Don Fagen sang, "What a beautiful world it will be, what glorious time to be free."

The people who have bought Benchmark products based upon their belief structure in measurements have largely been bored by the result.

Dunno where the data for that statement comes from but it seems to imply that there is an inverse relationship between good measurements and satisfying sound and that is unreasonable.

I urge all of you hell-bent on buying this preamp based upon JA's measurements to borrow one first and listen for a month.

Always good advice for any significant purchase. I will note that I reviewed it before JA measured it and would certainly buy one if I did not need 4 of them!

... hold your music together?

Is there some optimal level of noise below which, to your ear, the notes fall apart and above which the musical message is obscured or impaired?

Don't certain equipment reviews extol the virtues of those products that exhibit a "blacker background" - or, in other words, generate less intrinsic noise and distortion?

As a headphone amp borrowing tech from the AHB2 power amp, the unit is incredibly resolving. THX developed a different approach for all of their new amplification line. The collateral information on their website is comprehensive and convincing from many perspectives.

It would seem that the implementation of feedback here has been handled very differently as the measurements suggest. Noise of a superfluous nature is bad, if it's not needed in a design to achieve the design goals.

Other amps sound fantastic with other approaches towards the use of feedback. They usually measure well, too.

After a week of ownership of the HPA4 (THX-88 headphone amp + LA4), I concur that this preamp is quite transparent to sources. If I add a tubed phone preamp or perhaps the PS Audio Stellar as a source, I can more effectively tailor the sound to my preference, combining a transparent line and hp stage with a luscious or straight phonostage, dac or whatever.

I am looking at the AHB2 for amps in the next few months, but what stops me from auditioning (or purchasing to audition) a Rogue Audio Stereo 100 tubed power amp and see how that integrates with my system, both in front of my MG 1.6's or in back of the HPA4? It's the same risk invested to auditioning at a dealer and then purchasing and re-auditioning in one's home.

JA1 was never relegated to anything. It's up to us to determine where a given measurement and a given component applies to one's preference in shaping a stereo system.