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Product Review - Monolithic Sound PA-1 Line-Stage Preamplifier and PS-1 Phono Stage - July, 2000


Paul Knutson

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PA-1

 

PS-1

Input impedance: 

20K

Loading Resistance:

47K, 10K, 1K, 100 ohms

Frequency Response:

DC-100Khz

Capacitance:

100 pf, 270 pf, 370 pf

Gain:

6 dB

Gain:

26, 35, 44 or 53 dB

Power Supply:

16 VAC

Power Supply:

16 VAC

Size:

8.5” x 6” x 2.5”

Size:

8.5” x 6” x 2.5”

Weight:

6 lbs.

Weight:

6 lbs.

Warranty:

1 year parts & labor

Warranty:

1 year parts & labor

Upgrades:

HC-1 power supply  ($259)

Upgrades:

HC-1 power supply  ($259)

MSRP USA:

$499

MSRP USA:

$399

 

Monolithic Sound, 515 Sandydale Road, Nipomo, California 93444; Phone 805-929-3251;E-Mail info@monolithicsound.com; Web http://www.monolithicsound.com

Introduction 

For many years, Monolithic Sound has done design and manufacturing work for some of the best-known companies in the hi-fi industry, including Infinity, Genesis, and Vandersteen. Monolithic Sound is now building products using its own brand name, with a corporate goal of offering "superb sound quality, solid construction, and the best reliability in the business  . . . the best value in high-end audio today." To assist in making Monolithic's vision a reality, Greg Schug, the original founder, has teamed with Dusty Vawter, whose name you will recognize from Audio Alchemy repair and Channel Islands Audio mod/upgrade fame. Together, they're a formidable duo. In a small company, everyone has a variety of roles, but most of their time is spent with Greg handling the duties of Chief Engineer and Dusty contributing his design concepts and marketing ideas.

As you read this, Monolithic is in full production mode, and we at Secrets are pleased as heck to be bringing you the premier internet coverage of their new PA-1 line-stage preamplifier, PS-1 phono stage, and the HC-1 upgraded power supply.

Do you need a preamp?

First, let’s talk about the PA-1 line-stage and under what circumstances you can avoid using it.  Oh, great . . . Monolithic Sound will love me for this – I’m beginning the review of the PA-1 by telling you that you may not need it, or any other preamp for that matter.  (But if you do, then you’ll certainly want to read on.)

The case for eliminating a line-stage preamp is that the output voltages of many digital playback sources are more-than-adequate (<2V) to drive a power amplifier directly.  Assuming you listen to only a digital source, and if your amplifier has provisions for adjusting volume (or if the digital source has a variable output level), then you don’t need a line-level preamp.  Running the analog signal (that emanated from a digital source) directly into a power amplifier is the most direct signal path.  This is theoretically ideal if you listen to digital sources only, and if your goal is hearing exactly what’s on those compact discs. Of course, that assumes you have only one source that you listen to, or don't mind unplugging and plugging cables if you have more than one source.

This is a simple example of why some of you may not need a preamp.  But wait, I hear the majority of you shouting, “Hey, that example doesn’t apply to me – I need a preamp!”  Well, that’s good – I hear you loud and clear . . . so keep reading.

Most of you, I am guessing at least 90+%, do need a preamp in your system, for one reason or another.  Does that make it a necessary evil?  Nope, that’s way too strong a term.  One of audio’s “Golden Rules”, however, is that you want to keep the signal path as short and clean as possible.  Your amplifier will amplify whatever signal it receives, good or bad.  Remember, once an analog music signal leaves your source component, you can never improve it, only make it worse.  If your preamp mucks it up, you aren’t going to get the fidelity back, so if you need to use a preamp, it darn well better be a good one.  This is where Monolithic’s PA-1 becomes a really interesting option . . . it certainly isn’t going to muck anything up.  If you think that’s faint praise, you’re right, but I’ve got more to say about this little $499 wonder.

What should a preamp do?

So your system needs a preamp – great, now whaddya’ want it to do?  Personally, my preamp better do the following:

  1. Select the input source

  2. Adjust volume and provide voltage gain if needed

  3. Pass the signal from input to output with as little degradation as possible

Yeah, you guessed it – it’s # 3 that trips up some preamps.  The basic stuff (input switching, volume) is a relative no-brainer, but passing a signal from input to output with minimal degradation isn’t as easy as it sounds. 

All active preamps, whether tube or solid-state, tend to impart something, a “character” if you will, as the signal passes through the circuit – it’s truly unavoidable.  The character may very well be a good match with your system, and can sound simply excellent, but it isn’t absolute to the original source signal.  With a true passive preamp, however, there’s much less happening to the signal as it flows from input to output - nothing ideally - and that can be a very good thing if your goal is hearing what’s on the recording – nothing more, nothing less.

It's the circuit  

The Monolithic Sound PA-1 line-stage is passive . . . and active, too.  “How’s that,” you ask?  Without giving away any secrets of this clever circuit, here’s the concept:

The signal is directed in two separate paths after the input.  One route is the true passive track, essentially through the volume control, then to the preamp’s output. The other route goes to a simple, Class A, dual-mono, solid state gain-stage, the output of which is directed back to the 0 dB position at the top of the volume pot.  The custom Alps attenuator allows the completely passive (and unbuffered) signal to be paralleled by an active signal when the volume control hits 0 dB (12 o’clock position), where there is a slight but noticeable detent in the otherwise smooth turning motion.  Once engaged, the active gain continues as the volume control is rotated clockwise, to about the 5 o’clock end position of the control.  At that point, the active stage is providing  its maximum 6 dB of gain.  This gain is available to the user, but only when you need it; otherwise, the PA-1 is operating completely passive.  Also, it’s worth mentioning that 6 dB of gain is much less than most other active preamps, and therefore less imposing of itself on the signal.

As I mentioned, this is a clever circuit, and best of all, very effective.  Monolithic considered a number of options, and performed a ton of listening tests, before finally settling on the circuit that is now the PA-1.  It came down to choosing a design that would do as little as possible to the signal, and in my opinion that was a great choice.

The chassis of the PA-1 is compact at 8.5” x 6” x 2.5”, which means you can place it and the optional HC-1 power supply (more on that later) side-by-side on a single component shelf.  Peering internally, the PA-1 is tidy and the parts quality is good.  Looking inside inspires confidence and offers no unpleasant surprises.  This also reinforces that you don’t have to go overboard with designer parts to come up with a great result.  There is an external power supply that connects to the PA-1 via a 5-pin DIN connector.  The stock PS sounded good, but I preferred the PA-1 with the upgraded HC-1 power supply option.

Why passive? 

In theory and in practice, a well-implemented passive line-stage like the PA-1 maintains the most possible fidelity to the original signal.  This allows what’s on the recording to burst through, uncolored and unadorned, remaining utterly true to the source.

A passive preamp is not a substitute for tone controls (as some preamps are used), nor is it meant to correct for harshness or any other sonic failing of the source component.  With a passive preamp, you retain the control functions you need while otherwise doing nothing detrimental to the signal.  This is cool.  Better yet, what sets the PA-1 apart from other passive preamps is that if you should require a little voltage gain, it’s there for you.  It’s like having your cake and eating it, too.  Make mine a piece of German-chocolate with coconut cream frosting, thanks.

The PA-1, even though operating in its passive mode (along with any other passive preamp or attenuator), will still have a small effect on the signal because of the RCA jacks, input switch, signal wire, and the type and implementation of the volume control.  Everything impacts the sound.  Even so, there’s still precious little being done to the signal compared to any active line-stage. 

Even when I listened to the PA-1 in active mode, I found that the tonality varied little and it still sounded especially uncolored (especially with the upgraded HC-1 power supply providing the juice).  The difference in sound as the PA-1 moved into the active mode was a tiny lessening of top end sparkle and clarity, and also a perception that the soundstage shifted approximately one-foot closer.  At the same time, I felt the dynamics improved slightly, and the lower bass was a touch more authoritative.  Overall, the change in sound of the PA-1 from passive to active was subtle, and still first-rate, a tribute to the quality of the active stage as Monolithic implemented it.

The whole truth, and nothing but the truth

In my months of listening to the PA-1, I’ve nicknamed it “George”.  Like the Father of our Country, the PA-1 cannot tell a lie.  The PA-1 made it obvious to me that every other preamp that I had in the system for comparison did something to the signal.  That does not imply that the other preamps sounded bad, which certainly wasn’t the case, but every preamp except the PA-1 contributed some discernable element of its own “character” to the sound.  Not the PA-1, however. It doesn’t seem to have a character that I can describe.  The words neutral and uncolored litter my listening notes.

The torture test for a preamp is to listen to how sonics change while the preamp is either in or out of the signal path.  To do this, you must have an amplifier that has a variable input control, or a digital source with adjustable output.   One of my amps, a single-ended, triode unit called the Randall Amp, has variable input control.  I ran the output of my MSB Link DAC directly into the amp and established a sonic baseline using familiar recordings.  Next, I inserted the PA-1 (and other preamps for comparison) between the DAC and amp.  This is a ruthlessly revealing test for preamps.  Because of certain impedance matching, level control, and interconnect issues, it isn’t a perfect test (few in audio ever are), but it is unquestionably instructive.  What it told me is that the PA-1 is great at what it does, or more appropriately, what it doesn’t do.

I’m not going so far as to say that the preamp in/out test revealed that the PA-1 was absolutely transparent, but it certainly wasn’t colored.  As far as transparency, the sonic difference of having the PA-1 in the signal as compared to a straight digital pass-through is a slight loss of see-through clarity, with a barely perceptible blunting or rounding of some sharp transient attacks.  Remember, though, that installing the PA-1 also involves adding a pair of interconnects along with their associated RCA connectors.  Who am I to say that it wasn’t the interconnects that contributed to the effect?  It was most likely a combination of the two.  Either way, I can’t say that it bothered me, but my audio reviewer’s creed compels me to point it out.

I know that it drives some of you nuts when a review isn’t chock-full of new and creative audio adjectives describing the “sound” of a component.  If that’s what you want, go check out some of the other magazines. They like to use such adjectives because it gets them quoted in advertisements. Hey, don’t blame me, blame Monolithic Sound for designing this darn thing to be so neutral and resolving.  If I could tell you that the PA-1 had a warm, bloomy midrange, sweet treble, and prodigious bass output, I would . . . but it doesn’t!  The PA-1’s sound is pretty much the signal that it’s being fed – that being the sound of my MSB Link DAC or the Monolithic PS-1 phono stage.  The source is what I’m hearing, not the PA-1. 

Another hallmark trait of the PA-1 is that it is dead silent – this baby makes no noise whatsoever that I could hear.  I could turn the volume control all the way up, stick my ear two inches from the speaker and hear no extraneous noises apart from whatever sound the amps generate even when the preamp is turned off.   Obviously, the lack of noise can be attributed to the fact that the preamp is either passive or providing just 6 dB of gain, but even so, the lack of noise is in stark contrast to a couple of the tube preamps that I’ve built myself.  Gee, maybe I need a few more lessons on shielding and layout?

Any sonic drawbacks?  Yeah, sorta’  . . . but they are minor, and likely more indicative of passive preamps in general than anything particular to the PA-1.  To elaborate, with certain active preamps I used for comparison during the PA-1 review (the Myryad MA-100, Electronic Tonalities DIY kit preamp), I heard a better sense of dynamic contrast with the active preamps, especially macro-dynamics, particularly when comparing those full-active preamps to the Monolithic while operating in its true passive mode.  Also, I thought the low bass was a bit stronger with active preamps, and the same goes for the PA-1 in its active mode compared to the passive mode.  The Wright Sound Company WPA 3.5 monoblock amps I used during much of this review are only moderately sensitive, and therefore, they present a reasonable challenge for a DAC to drive directly.  The low-bass difference was less noticeable with other amps that are easier for the MSB Link to drive through the PA-1 in passive mode. 

Those of you who have read my other reviews know that I’m not a bass-monger anyway, preferring to hear pitch and precision in the bass notes to sheer rumble and thunder (and I’m sure my downstairs apartment neighbors agree).  I would always rather hear accuracy than bloat.  In that respect, in the right setup, I thought that the bass speed and definition through the PA-1 was as good as I’ve heard elsewhere.

Ergonomics

The rear panel RCA input jacks are spaced a bit too closely for some of the more beefy RCA connectors such as the WBT type used with the Analysis Plus Silver Oval-In interconnects.  They still fit, but it’s tight.  I can forgive this design trade-off, however, as Monolithic has provided a lot of connection flexibility on the back of the compact PA-1, as you’ll read in the next paragraph.

Apart from the closeness of the RCA input jacks, the PA-1 is ergonomically strong.  It’s an especially flexible control center.  There are four rear-panel RCA inputs, a positive motion selector switch, two sets of outputs (for bi-amping or adding a subwoofer), and a three-position toggle switch on the front panel that allows you to 1) listen to the selected source, 2) mute the signal, or 3) listen through the tape monitor loop.  The volume control has a nice, solid feel that lets you know you are doing something when you turn it, plus it looks super (as does the input switch) with its brushed-aluminum finish contrasting the black background of the PA-1.  Lastly, and this is a personal fetish, the PA-1 has a small, blue LED that shows when the unit is powered – I love blue LEDs and wish that they were standard wherever LEDs are found.  It just looks terrific.

Wrapping up the PA-1

I alluded to it earlier, but it’s time to get back to the price – the PA-1’s retail price is $499.  That’s great value for this level of performance.  It’s also right in-line with Monolithic Sound’s design goal.  This inaugural product succeeds wildly in offering just about any music lover access to a product that is not sonically compromised, as would typically be the case anywhere near a price point of five large bills.  I’m not going to throw out the all-too-common “it competes with preamps costing X times as much” line of praise.  The bottom line is that you deserve to hear this preamp in your own system, even if you have a whole pile more money budgeted for your next preamp purchase.  Personally, I’m not letting the PA-1, or should I say “George”, get away – it’s going to be added to my stable of reference components.

The PA-1 allows my system to resolve more of what’s on the recording – the natural nuance, sense of space, timbre, detail and most importantly, the emotion.  You get deeper into the tune when you hear a jazz guitarist bend a note subtly in a way that was previously obscured; you hurt, too, the first time you hear the distinct sense of loss and pain in the voice of a blues singer who mourns through a song you’ve heard a hundred times before, but never quite like this.   These are examples of how the right equipment, in this case the Monolithic Sound PA-1, allows you to understand the message of the music more clearly – to me that’s what this audio game is all about.

Moving on - The PS-1 Phono Stage, with comments on the HC-1 power supply  

Joining the PA-1 in Monolithic Sound’s list of preamp offerings is the PS-1 phono stage.  Those of us who still groove to vinyl are reaping the benefits from a surge of market competitors offering phono stages in the sub-$1K price range.  Unless you operate on the fringes of vinyl playback, there are some nice options in the three-figure price category – the new Monolithic PS-1 is definitely one of them.

The PS-1 phono stage is housed in the same style of chassis as the PA-1, and it includes my beloved little blue LED to indicate power on – in other words, it looks all business.  There aren’t a lot of controls you can put on the faceplate of a phono stage, but the rear panel is a different story – therein lies part of the beauty of the PS-1.

If you have a phono cartridge that isn’t compatible with the PS-1 (an ultra low-output MC for example), then you likely have something so exotic that a reasonably priced phono stage isn’t on your radar screen anyway.  The PS-1 is flexible, and I mean really flexible – we’re talking Mary Lou Retton here, or Stretch Armstrong.  As evidence, there are DIP switches on the rear panel of the Monolithic that allow the user to choose any configuration of the following:

This flexibility is useless if you have to tear your phono stage apart to change the settings – but that’s not the case with the PS-1.  All settings are changeable by the rocker-type DIP switches that I mentioned.  These switches are so easy to use and so intelligently implemented that it’s hard to believe a company would do it any other way.

The PS-1 also utilizes a stock outboard power supply, but the 5-pin DIN power connector on the rear panel shares with the PA-1 the ability to utilize the dual-mono, high-current HC-1 upgraded power supply.

Setup

I did a lot of experimenting to determine where I wanted those DIP switches set to obtain what I felt was the best sound from my vinyl playback rig.  Part of the reason for all this experimenting is that just after I received the PS-1, I traded my trusty ol’ Rega P3/RB300 Turntable/Sumiko Talisman cartridge combo for a hot, new Rega P25/RB600/Dynavector 10X4 MkII setup.  Unfortunately, I had a bit of initial trouble with the new Rega P25/RB600 so I ended up losing a lot of potential review time while things got fixed (and then I needed a complete month or so to break-in the new vinyl gear).  I also broke a somewhat cardinal rule of reviewing in that you don’t want to change more than one variable at a time.  Well, I changed a second major variable just after I installed the PS-1 – I changed my entire vinyl playback system!  Not ideal, but also not an insurmountable hurdle.  The end result was that I needed to experiment quite a bit with the settings on the PS-1 as I got acquainted with the new P25 and friends.

I ended up settling on the gain selection of 44 dB.  My great and affordable Dynavector 10X4 MkII cartridge ($325) is a 2.0V high-output moving coil design.  (Moving coil cartridges [MC] have tiny coils of wire attached to the stylus and have lower mass than moving magnet [MM] cartridges where magnets are attached to the stylus instead.) What I found with the 35 dB setting was that the PS-1 offered a full-sounding, quiet, and musical performance, but I ended up needing to adjust the volume control on the PA-1 well into the active gain stage even at moderate volume levels.  Since I prefer to keep the PA-1 operating in the passive mode if possible, to minimize the signal path, I settled on 44 dB as the ideal gain setting – and how nice it was to have that flexibility.  I still occasionally bump the gain of the PA-1 into active mode depending on at what level the particular record I’m listening to was cut, but most of my listening is done with the PS-1 moving through the PA-1 while it’s in passive mode.  As long as the interconnects I used were reasonably short and not high-capacitance, the PS-1 had no trouble driving the amps through the passive PA-1.

For the other settings, I turned the subsonic filter “ON” (I couldn’t hear a difference either way, and seeing as how I live in seismic San Francisco, I figured what the heck).  The load resistance was set at 47K, which is appropriate for my cartridge, and finally, the chosen capacitance loading was 270 pf (pf = picofarads, where pico means 10-9, so 270 pf = 0.000000270 Farads).  I found the 100 pf setting a bit bright and the 370 pf setting a bit blunted on the top end – 270 pf was juuuuust right.

The final setup note is that the PS-1, in my opinion, needs the HC-1 power supply to really strut its stuff.  The difference was smack-you-in-the-face audible – especially in the bass, soundstage, and dynamics.  More on this in the “Performance” section below.

Performance

As I mentioned before, since receiving the PS-1, the road to listening to vinyl in my system has taken all sorts of twists and turns.  Again, this makes the review process more difficult.  For that reason, I’m going to be shorter with my comments on the performance of the PS-1 and will likely re-visit the topic again in the future.  I may even follow-up with a comparison of the PS-1 with one of the other worthy contestants in the sub-$1K phono stage market (Basis Phonomena, Lehmann Black Cube, EAR 834P, Musical Fidelity X-LP, etc.), assuming I can get my hands on one . . . and I intend to.

So, even though I don’t have as many listening hours logged with the Monolithic as I’d like, it isn’t hard to tell that the sun is bright, and it’s equally obvious that the PS-1 is a special product.  My previous phono stages that were paired with the Rega P3/RB300, and used for comparison on the new Rega P25/RB600, were the Audio Alchemy VAC-in-the-box and the DB Audio PS-8.  These are good, listenable and musical phono stages at their low-budget sub-$200 price points – I would recommend them to anyone with a starter vinyl setup.  But man, did the Monolithic PS-1 ever eat them for lunch!  Yummy. 

Yeah, yeah, I know – the comparisons to the Audio Alchemy and DB Audio seem silly.  I wish that I could throw one of the other contenders into the mix, but note that the PS-1 retails for just $399 – that’s pretty much dirt cheap for true, no-concessions build and sound quality.  Sure, you need the HC-1 to bring out its best, and that moves it closer in price to the “competition” mentioned above, but in stock format with the regular power supply, it still walks on the other budget phono stages. 

The PS-1 defines an image and lays it out in a wide and deep soundstage in a way that I find simply enthralling.  That’s the characteristic of the Monolithic that juiced my mojo the most.  The tonal balance, top to bottom, was spot on and nothing if not robust, full, and musical with very natural midrange timbre and presence.  Ella Fitzgerald’s "Let no Man Write My Epitaph" LP is just mesmerizing through the PS-1, with every growl, wail, whisper, and weep coming to life.  “Street in the City” from Pete Townsend and Ronnie Lane’s astounding "Rough Mix" album came to life by giving each musical event in this dynamic, complex mix its proper place.  To me, that’s coherence, and it’s a trait that separates the wheat from the chaff; many phono stages can do notes and sounds, but the PS-1 offered me real, musically coherent listening through my Rega P25 setup.

The only quibble was that I noticed a touch of congestion and a loss of soundstaging in the mids to upper-mids when the music got excessively hectic.  That may have been caused or at least contributed to by a setup problem, such as isolation, or the fact that the PS-1 was essentially being asked to drive the amps directly (because of the passive PA-1).  Again, I don’t know the Rega P25 quite well enough yet to determine exactly what’s doing what, but that’s what I heard.  Reigning in the volume control a tad would set things straight. 

Initially, I also found the foundation of the bass to be somewhat weak, but the low-end performance of the PS-1 improved rather dramatically as it got to 50-60 hours of break-in.  Especially when mated to the HC-1, the bass eventually got to the point of bordering on exceptional.  The liability literally transformed to a positive after break-in was complete.  After about 100 hours, I was totally satisfied with how well it plays the low notes – punchy, deep and quick – completely on par with my MSB Link DAC, whereas my old vinyl setup didn’t have it in the bass compared to my digital rig. 

Finally, though I haven’t tried these in my own system, I’ve heard phono stages in other demos that I felt fattened things up a bit in the mid-bass and mid-range, perhaps also rolling the top-end, thereby making things more lush and plummy.  To contrast those experiences with the Monolithic, I would never call the PS-1 a “warm” sounding phono stage – I don’t believe that’s what Dusty was shooting for.  The other phono stages may be pretty easy on the ears, but I always prefer accurate and musical, which the PS-1 is.  Like its brother the PA-1, the PS-1 was designed to be accurate all the way.

The HC-1 Power Supply - Just get it

Moving back to the HC-1 again, let me just put it this way – you MUST buy this power supply if you choose to own either the PA-1 or PS-1, but especially the PS-1.  At a retail price of $259, it is worth every cent.  I think the improvement is major league – dynamics are unleashed and the soundstage explodes in all directions with the HC-1 installed.   It’s a dual-mono, high-current design that includes the option for a detachable power cord, which I fitted with a TG Audio HSRi, or the Harmonic Technology Pro AC-11.  I like both the PA-1 and PS-1 with their stock power supplies, but I’m smitten with them when the HC-1 joins the fray.  In fact, I’ve only got one HC-1 right now, but I’m planning to get another so neither preamp ever has to be without it.

Conclusion on the PS-1

I’ll welcome the chance to compare the Monolithic PS-1 to other quality phono stages in the future, and I’m putting in many more listening hours over the next couple of months to solidify my opinions.  That’ll solidify my impressions so far and further define the PS-1’s true position in the market.  For now, however, I’m as content as can be with the PS-1 sitting proudly on my equipment rack just one floor down from its brother, the PA-1.  I’m 100% pleased with my new Rega P25 ‘table and its rich, analog sonic beauty.  It’s done all that I hoped it would in upgrading my vinyl playback.  There’s no doubt in my mind, however, that the Monolithic PS-1 has made its own big-time contribution to making my LP playback system complete, and a complete joy to listen to.

Fellow music lovers, I’m here to tell ya’ that listening to vinyl is fun (and searching for used LPs is even more fun).  Talk about a great way to re-connect with the joy of the hobby.  If you haven’t already done it, I suggest each of you jump on the vinyl bandwagon (it’s not too late) and invest in one of the many affordable ‘tables out there.  Choosing a player is the hard part, because when it comes time to pick a phono stage, you can confidently begin shopping with a real short list – one that has Monolithic Sound’s PS-1 at the top.

- Paul Knutson -

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