Benchmark LA4 line preamplifier Page 2

Benchmark sent along a DAC3 B (footnote 2), which I connected to the Balanced 1 inputs of the LA4. I connected the front L/R outputs of my exaSound e38 Mk.III DAC to the Balanced 2 inputs. Independent AudioQuest Coffee USB cables from the outputs of my Baetis Prodigy X server fed both DACs. Monoblocked Benchmark AHB2s were connected to the balanced outputs.

Listening to the LA4
As soon as everything powered up, there was a big smile on my face. With the LA4 in control of the system, everything sounded right, and subtle differences among recordings, amplifiers, and speakers were clear. I have omitted DACs from that listing because, after trimming the gain on the Benchmark and exaSound DACs to match within 0.5dB (the limit of my control resolution), they were indistinguishable in non-blind A/B comparisons. Was the LA4 masking any difference?

1219bench.rem300Recently, two Stereophile writers have been discussing a listening comparison of two excellent power amplifiers. The two agreed on their perceptions of the audible difference, but not on its likely basis. One suggested that it could be due to one amp doing something to reveal more low-level recorded detail. The other, who heard the same difference, insisted it is due to the other amp removing something. In the absence of any objective reference or evidence, we can only regard these as expressions of philosophical differences. However, with the LA4, I had an objective reference.

By physically connecting the input XLR cables directly to the output XLR cables, I could compare the sound of the LA4 at unity gain to that of a bypass with the DACs connected directly to the power amps—ie, it was the LA4 vs nada. I failed to hear any change in balance, tonality, dynamics, details, or soundstage. The LA4 seemed to neither add nor subtract anything. On the other hand, compared to the other preamps on hand, the LA4 was consistently quieter, more open, and more revealing of detail. What the LA4 offers over the bypass is the convenience of control and switching of the LA4 and a bit less noise. Yes, insertion of the LA4 actually resulted in less noise, although the difference could be appreciated only within 1"–2" of the speaker. I suspect this has to do with the ability of the LA4's potent output stage and low output impedance to drive the amps through my 30' balanced interconnect cables. As for the relay clicking that originally bothered me, I quickly adapted to it and now find it trivial when the music is playing.

I will decline to list specific details about individual recordings where the LA4 improved what I heard, because I believe that it would really be a list of what other components fail to do. Instead, and somewhat gratuitously, I offer two new recordings that I particularly enjoyed with the LA4. The first is a refreshing performance of Mussorgsky's Pictures at an Exhibition by pianist Natasha Paremski (CD, Steinway & Sons STN 30093). Her adjustments and phrasing, generally subtle and always appropriate, seem to restore the colors of this familiar art tour. Her technique is formidable and is also demonstrated in Fred Hersch's delightful Variations on a Theme by Tchaikovsky, which I found a suitable companion piece. But listen to the body and presence of the pianos—a Hamburg Steinway in Pictures and a New York Steinway in the Variations, recorded in different halls with different teams—and see if you can appreciate those differences, made apparent to me via the LA4.

1219bench.2

When I listened to the various formats of the Beatles' Abbey Road Super Deluxe 4 Disc Edition (Y4CDBE003), the experience benefitted from using the LA4 (at times, three of them). I almost do not hear the sound of the original much anymore because, having lived with Abbey Road since its original release, it really lives mostly in my mind. Playing it now via the LA4, and with focused attention, I renewed my appreciation of the art, effort, and intent. I found the new stereo remix to be strikingly clearer, more open, and with much better bass definition, but it doesn't taste the same. Only time will tell if the new stereo mix, even via the LA4, even in 24/96, can win me over. The new 5.1 mix is another story, since the new spatial cues clash with and distract me from my embedded memories. That said, the sound of the original and the new mix both delighted with the LA4.

Conclusion
The LA4 is probably the most transparent and revealing audio component I've ever used. It does not seem to leave any fingerprints on the sound. It has a useful array of inputs, outputs, and functions, and the use of sealed relays for volume and input selection assures a long and noise-free life. Benchmark might improve on the display and remote control, but I do not have any criticism of the LA4's sonic performance.


Footnote 2: The DAC3 B is offered as a companion to the LA4 line amplifier and HA4 headphone amplifier because it eliminates functions from the HGC and L versions of the DAC3 that would be redundant when used with those devices: The DAC3B has no volume control, analog inputs, mute/polarity controls, or headphone amplifier. It is said to be equal in DAC performance to the HGC but priced lower, at $1699.
COMPANY INFO
Benchmark Media Systems, Inc.
203 East Hampton Place, Ste. 2
Syracuse, NY 13206
(315) 437-6300
ARTICLE CONTENTS

COMMENTS
Bogolu Haranath's picture

Can it get any better than this for a pre-amp? ....... Add to the list, another nominee for Stereophile 2020 product of the year award, Benchmark LA4 ....... The headphone-amp output version Benchmark HPA4 was reviewed by Hi-Fi News :-) .........

supamark's picture

a riff on the classic Urei LA-4 compressor (both in name and form).

Kal Rubinson's picture

Seems to me coincidental. Line Amp 4 is a logical name and they do very different things. OTOH, the Urei is much better looking, imho.

Bogolu Haranath's picture

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

dial's picture

Hello, yes I agree but the NAD recently reviewed is the ugliest for me.

Bogolu Haranath's picture

"Beauty is in the eye of the beholder" ......... Margaret Hungerford (1878) :-) ........

Poor Audiophile's picture

Please excuse an ignorant question, but these two are on the same CD? Or are they 2 different ones?

Kal Rubinson's picture

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

DH's picture

Very nice, You can stream it, too.

georgehifi's picture

"widest-dynamic-range I have encountered"

Hi JA, wouldn't it be more informative to know.
To compared it to the sources "direct connection measurement" dynamic ability. And then how much lower in dynamic range this preamp is going to measure.
As then these measurements would then mean something, that then tells you if your getting every morsel or close to it, of the sources dynamic swing that it has.

Cheers George

Bogolu Haranath's picture

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' :-) .......

Douglas_Harrison's picture

I'd buy 1 in a heartbeat if they offered a 1 unit Multi-Channel option

Kal Rubinson's picture

Let's start a petition!

Bogolu Haranath's picture

May be you (KR) could also petition for a 8-channel Benchmark HGC DAC :-) .........

Kal Rubinson's picture

I have asked about 8channel DACs and preamps but I am only one voice.

Bogolu Haranath's picture

Who else could be more influential voice than KR for promoting multi-channel audio for music? :-) .......

Bogolu Haranath's picture

Andrew Quint from TAS could be the other influential reviewer/promoter for multi-channel audio for music :-) .......

Kal Rubinson's picture

deleted

Kal Rubinson's picture

Andy and I see eye-to-eye on many things.

Bogolu Haranath's picture

You both contribute to two very influential hi-end audio magazines .......Good idea to keep promoting surround sound for music ......... Let your voices be heard :-) .......

JRT's picture
Bogolu_Haranath wrote:

"...petition for a 8-channel Benchmark HGC DAC"

This one looks interesting, if you have a relatively simple system that only needs eight channels of PCM.
https://www.oktoresearch.com/dac8pro.htm

Bogolu Haranath's picture

Yes ...... DAC8 Pro also does DSD 128 in addition to PCM ........ Audio Science Review gave the Okto Research DAC8 Pro a glowing review ........ May be KR could also review it :-) ......

Kal Rubinson's picture

The production Okto DAC8 Pro is on the way to me. FWIW, ASR reviewed a prototype, I believe, since it was done months before any product was shipped to customers.

Bogolu Haranath's picture

Looking forward to reading your review ...... Question is, would JA1 measure it? :-) ........

JRT's picture

Kal, I am looking forward to your review and JA1's measurements of the Okto Research DAC8 Pro. And I am hoping that they find a better means of selling into the US market, as I would prefer to buy from a domestic source rather than play with overseas mailorder.

Kal Rubinson's picture

Yeah. Unfortunately, it is not likely that a product with no US dealers and available only from overseas web/mailorder will qualify for a full review.

JRT's picture

You know your business and are probably right in your statement.

Perhaps, on electronics assemblies (not loudspeakers), Stereophile might consider further relaxing those requirements to better accommodate the global economy and modern changes in business models.

Kal Rubinson's picture

It is not my decision to make but I do know that the editors are aware of the issues and are considering options.

georgehifi's picture

Any "active circuitry in an analog preamp" has to impact the dynamic range a little compared to the source going direct to the amps, unless there is some kind of "dynamic range expansion" circuitry inside to make up for any losses, and I doubt that very much, as they sound ****.

Cheers George

Kal Rubinson's picture

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

Bogolu Haranath's picture

It would be interesting to see a follow-up review by KR with dCS Bartok or Rossini players with LA4 ...... Both those dCS players have digital volume controls ....... KR could compare their sound with and without LA4 in the signal path :-) .......

Bogolu Haranath's picture

Both of those dCS players have approximately the same SNR as LA4 :-) ........

Kal Rubinson's picture

I suspect that the exaSound is in the same class. See:
https://www.exasound.com/Products/e32MarkIIDAC.aspx#tabs1633-2

Bogolu Haranath's picture

I could not find any Stereophile measurements of exaSound ....... I saw your (KR) reviews of exaSound for Stereophile :-) ........

Bogolu Haranath's picture

Instead of dCS, you (KR) could compare LA4 with the Benchmark DAC3 HGC, DAC/headphone-amp/pre-amp ...... After measuring the DAC3 HGC, JA1 said, "Wow" ...... Need I say more? :-) .......

Kal Rubinson's picture

Not likely as I do not have any of those "in house."

There have been measurements of the e32 at Audio Science Review Forum, fwiw.

Herb Reichert's picture

there would be no need for extra amplifier gain stages - just to make gain for feedback

or 49 output devices - just to drive inefficient speakers with complex crossovers

yes?

hr

Kal Rubinson's picture

True dat but these are the consequences of history as well as of other choices we make. Change can come from a complete re-imagining of system topology. Until then, each component has to be respectful of what comes before it and what follows.

Bogolu Haranath's picture

Like 'cruise control'? ....... See Benchmark media blog about 'feed forward' technology used in their amplifiers :-) ....... ........

Bogolu Haranath's picture

If you want to see how feedback levels change the FR and distortion levels, see JA1's measurements of CH Precision integrated amp measurements :-) ........

Bogolu Haranath's picture

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 :-) .......

Jim Austin's picture

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

Bogolu Haranath's picture

It is interesting to read, JA1's review and measurements of Ayre Acoustics KXR-Twenty pre-amp ...... Charles Hansen's (manufacturer) approach and his discussion about pre-amp design are an interesting read ...... Also, Ayre previous design KXR pre-amp review and measurements are an interesting read, as well :-) ......

Long-time listener's picture

Mr. Rubinson, I notice that in the past you have used much more expensive Audioquest speaker cables, perhaps in a different system. Could you please give your impressions of the Blue Jeans speaker cables? Thank you

Kal Rubinson's picture

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.

Long-time listener's picture

Thanks for taking the time to respond--I should have remembered that you are a "denier." As far as cables go, I think your term "competent" potentially covers a lot of territory, and perhaps "competent" cables "should" sound about the same--just as all "competent" preamps should aim for the same transparency as this Benchmark preamp. Life would certainly be easier for me if I could be a denier too, but I can't. Over a long period of time, and with different equipment, I have found that my $1,200 Siltech interconnects consistently sound marginally more transparent, but also less warm and full-bodied, than my $600 Ortofon ones. I wish the Siltechs sounded better to me: they look nicer and cost more, but I generally use the Ortofons.

Yes, I do consider your outlook a bias. Remember, serious reviewers of stereo equipment once said the same thing about amplifiers that you say about cables, which is that any two competently designed amplifiers "should" sound the same. Perhaps they "should," but they don't. Today we certainly consider that viewpoint a serious bias. Best regards, LTL

Long-time listener's picture

...It seems to me that as soon as you say some cables are "competent," and others aren't, that you've already admitted there are differences between cables. And further, you seem to be saying that all the competent ones are not only competent, but perfect too--they're all so good that they sound absolutely identical. Does that really make sense? Your own comments seem to contradict your idea that there is no difference.

Kal Rubinson's picture

I would define "competence," in this case by mechanical and electrical engineering standards, and, yes, the competent ones are probably closer to perfection than is required by the rest of the audio chain. This, of course, is not the best forum for such a discussion but my position is based on my experience, just as is yours.

Ortofan's picture

... one need?
What is the difference between the noise floor of your listening room and the peak output capability of your power amp and speakers?

Would the performance of a sub-$400 pre-amp, such as the Pro-Ject Pre Box S2 Analog(ue) or the Parasound Zpre3 be sufficient - and indistinguishable from the Benchmark unit?

https://www.project-audio.com/en/product/pre-box-s2-analogue/

https://www.parasound.com/zpre3.php

Bogolu Haranath's picture

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

jeffhenning's picture

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."

Ortofan's picture

... Benchmark quotes the S/N as 116dB (A weighted) when using the unbalanced outputs (vs. 137dB when using the balanced outputs) and a THD spec of 0.00005% (when using the balanced outputs - no THD spec is stated when using the unbalanced outputs) for an output level of 2V rms at 1kHz.

Pro-Ject specifies a "noise floor" of 105dB (A weighted) and THD of 0.0005%. Test conditions are not explicitly stated, but mention is made of "output voltage typically: 1V at 1kHz". The Pro-Ject unit only handles unbalanced signals. Their product literature claims "neutral sound with superior low noise floor" and "incredibly low harmonic distortion levels guarantee a listening experience which has never been available in this price range."

Bogolu Haranath's picture

Pro-Ject Pre-Box S2 doesn't have any analog inputs and so, cannot be used as an analog pre-amp ...... not exactly apples to apples comparison :-) ........

Ortofan's picture

... three analog inputs.
https://www.project-audio.com/wp-content/uploads/2018/04/Pre-Box-S2-Analogue.jpg

Are you, perhaps, mistakenly looking at the Pre-Box S2 Digital?

https://www.project-audio.com/en/product/pre-box-s2-analogue/

https://www.project-audio.com/en/product/pre-box-s2-digital/

Bogolu Haranath's picture

Oops .... I didn't see your earlier comment ..... I assumed it was Pre-Box S2 Digital, which was reviewed and measured by Stereophile ...... I could not find any measurements of S2 analog ...... Given the very good measurements of S2 Digital by Stereophile, most likely the analog S2 could have very good measurements also ...... There is a DS2 version of Pre-Box analog, which has more inputs for, $550 ......... Anyway, none of the Pre-Box analog versions have balanced inputs and outputs like the Benchmark LA4 :-) ........

Ortofan's picture

... you replied to it.

For about $2,000 above the price of the Pro-Ject Pre Box S2 Analogue, you can buy the Benchmark unit and get balanced inputs and outputs, which will have better noise performance.

But the question remains, does the rest of your system allow you really take advantage of the extra dynamic range from the lower noise floor with those balanced connections?

Bogolu Haranath's picture

Yes, I saw your earlier comment, but I missed the 'analog' part of it ....... Ok, from now on I will read your comments word by word, may be even half a dozen times, before I make my comments/replies ....... I didn't say it makes any significant 'audible' difference at such very low noise levels ...... Balanced connections not only reduce common mode noise levels, but also make more secure connections ........ As far as the price is concerned, it is up to the buyers to make that decision ....... I would say Benchmark makes reasonably priced gear for all that performance their gear offers :-) .......

Bogolu Haranath's picture

I forgot to mention ........ Benchmark LA4 also offers 256-step technically advanced volume control :-) .......

Bogolu Haranath's picture

A better comparison for Pro-Ject Pre-Box S2 would be the Benchmark DAC3 HGC ...... Even so, DAC3 HGC has two analog inputs and can also be used as an analog pre-amp :-) .......

Bogolu Haranath's picture

A better comparison for Pro-Ject Pre-Box S2 would be the new iFi Audio Zen DAC/headphone-amp/pre-amp, $130 :-) .......

Glotz's picture

So funny...

Thanks man!

The Benchmark website has all of the manuals for the current lineup, and full measurements and descriptions / interpretations. These are an excellent compliment to JA's Measurements section.

In fact, the whole website is an eye-opener, especially their cable area! I am intrigued.

FredisDead's picture

The debate is like dirt in a horse corral; a mixture of ancient alluvial soil and recent organic waste. JA measures and the rest of us spend our money. JA measures what he can measure. The rest of us listen. The people who have bought Benchmark products based upon their belief structure in measurements have largely been bored by the result. Noise is not evil. Noise is ever-present and a good thing. It is the glue that holds music together. The place for headroom happens to lie with transducers and recordings, not electronics. I admire JA. I truly do. But he is a man trapped within his own skill-set. That has always been his primary limitation as an equipment reviewer. That limitation has been far eclipsed by his editorial skills. 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. If you don't, there is a very good chance it will end up for sale on the used secondary market.

Kal Rubinson's picture

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!

FredisDead's picture

ever-present on the used market for years. Then the fervor died down. JA's measurements of amps and preamps are rather innocuous; they tend to more or less correlate (i.e. not compete) with SQ upon lengthy subjective listening. JA's measurements of DAC's and loud speakers have always conflicted with long term listening impressions. So here we are with a line stage. It is probably fine but still, at the end of the day, boring and sterile. Sort of like a typical septuagenerian in need of vigorous exercise, a better diet, and some viagra.

Jason Victor Serinus's picture

Glad to know that I'm atypical...

Kal Rubinson's picture

Was that ever in doubt? :-)

Bogolu Haranath's picture

Thou shall not 'covet' expensive audio equipment :-) .........

Ortofan's picture

... 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?

Bogolu Haranath's picture

Those same reviewers 'extol' the virtues of 'blacker backgrounds' whenever they review any new interconnect, any new speaker cable, any new isolation device, any new equipment rack, any new power purifier, any new ........ and, the list goes on :-) ........

Glotz's picture

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.

dclark2171's picture

I'd be curious to see what the LA4 does in my system replacing my current BHK preamp

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