RCM Sensor 2 MK II Phono Preamplifier
Words and Photos by Dave McNair
I’m one of those audiophiles that started my listening obsession with vinyl records. You know, those flat round black things that sound amazing unless they don’t. I love records. I hate records. It’s all so confusing. Listening to records using the RCM Sensor 2 MK II phono preamp takes all that confusion away.
As a recording engineer (now mastering engineer) who started during the heyday of magnetic tape and polyvinylchloride disks, I’ve had a front-row seat to the arc of technology for recording and playing back music. At some point, records and tape disappeared from my listening habits and I stopped caring about what medium was employed in service to the music. That changed when I bought a turntable about four years ago and started listening to records again.
Long about this time, as an addition to my mastering business I decided to get into the anachronistic and lunatic fringe world of lacquer cutting for vinyl record production. This insane decision was fueled by my rediscovery of vinyl. Which of course required me to upgrade my home system to check the quality of my cutting work right?
What followed was a perfect storm of G.A.S. (gear acquisition syndrome) justification – complete with a mental flashing neon sign with arrows pointing to the entrance of the Black Hole of Audiophile System Upgrades.
The latest component to have my G.A.S. target painted on it is the phono preamp.
How Low Can You Go?
When I know to expect delivery of something on a certain day, I get a subtle tingle. An itch that I know will soon get scratched. Not like the anticipation for that 50 Shades Of Gray starter kit I might have ordered off Amazon, or the Complete Monty Python’s Flying Circus DVD set off eBay – no, something MUCH more important, a new piece of hi-fi gear.
So when Mehran at SORASound sent me the new ZYX Ultimate 100 cartridge I had recently purchased, he kindly offered to send the new and improved RCM Sensor 2 MkII phono stage along for me to hear. Oh Hell Yes.
Mehran suggested I go for the low output version of the ZYX which is just .24 mV. There certainly are carts with lower output, but .24 mV is low enough that I wondered two things: Is it really gonna rock with that minuscule yet handcrafted, Japanese artisanal output of the ZYX, and how hella hard (and expensive) is it going to be to find a preamp with crazy amounts of gain that still sounds amazing? He said my Simaudio 310LP would handle it no problem but…..
Enter the RCM Sensor 2 Mk II.
The RCM Sensor 2 is medium-sized in the world of phono pres. It’s not the full component size of an Audio Research Reference Phono or Pass Labs XP-27 or the behemoth LampizatOr Vinyl Phono MC1, but it’s not a little unobtrusive box that sits behind your turntable either.
It uses a separate power supply which makes it a two-box affair with the bizness end being a black box about 10” x 5” and 8” deep and the power supply about a third that size. The well constructed looking cable from the power supply to the main box is long enough for the recommended placement to be away from noise-generating supplies in other gear. An itsy bitsy emerald-colored LED in the middle of the front panel makes you squint to see if it’s on.
On the back is an extensive array of dip switches for gain and loading options. The usual RCA ins and outs are joined by a pair of XLR connectors for optional use as a balanced output. Also, a grounding post which the manual recommends using (complete with a diagram for how to hook up) so that your cartridge output is seen by the phono pre input as a balanced connection.
You Say Tomato, I Say Vacuum Tubes
After hearing several excellent phono pres of the vacuum tube persuasion, I was convinced I would probably not hear massive improvement and more importantly, organic types of colors in the presentation by using another solid-state phono stage. The Simaudio 310LP I typically use is clean, quiet, and full-bodied with awesome handling of the lowest frequencies and a silky smooth top end. How much better could another chipped op-amp, solid-state pre be?
BREAKING NEWS – The Sensor 2 is significantly better in several areas including a lush, complex, and refined sense of harmonic richness I thought was only possible with tubes.
To backtrack a bit, after unboxing and reading the manual (I always read the manual even if it’s weeks later in the bathroom) I hooked up the RCM Sensor 2, deciding to go all-in using the balanced outputs to start my listening. I always do a quick listen before the deep dive which generally happens after letting the device under test warm-up for a few hours (or days in some cases). In this case, the RCM sounded amazing from the first needle drop and I’m not sure it changed much at all over the course of several months. YMMV.
There are six dip switches to set the gain that give seven options if you count the all-off setting. At first I chose the highest gain switch which seemed like it would be the best match for the .24 mV output of the ZYX. As time went on and experimentation ensued, I realized even the lowest setting yielded enough juice to get the party started, partially because you get 6db more output when using the balanced outs. And yes, I experimented with the single-ended RCA outs but wasn’t sure if I liked what the needed extra gain setting did to the sound. In the end, I settled for balanced out and with the next to lowest gain setting cause it simply seemed to sound better – even beyond the lowered noise floor performance benefit. Isn’t that the point? Loading stayed the same as used on my Simaudio 310LP, the ZYX recommended 100 ohms.
One thing I did NOT try was using the RCM Sensor 2 in balanced input mode. Unlike some other phono pres with this feature, the RCM has one set of RCA inputs as opposed to those AND a dedicated XLR input – or XLR only, like the balanced input Tidal Audio phono stage. Since my Rega P10 tonearm with its stock cable does not provide a ground wire and I never got around to substituting one, I did not test this feature out. Along with using proper wiring, there is a rear-panel switch to turn balanced input mode ON.
Did I miss out on hearing the box in all its balanced input glory? Yeah, but unless there exists a radical change to the nature of the sound, I was plenty satisfied with the noise floor in standard input mode. OKAY! I’ll get a balanced tonearm cable and let y’all know if the heavens open up and Saint Jimi descends to play my Fender Strat while I listen to “Spanish Castle Magic.”
Circumstances allowed me to keep the RCM Sensor 2 in my system for many months before returning it. This meant a lot of gear rotated in and out of my little sound palace and got to meet and greet Mr. Sensor 2. On a wide range of speakers, line preamps, and power amps, the Sensor 2 never failed to sound amazing. Occasionally, there was a combo of gear that seemed better served sonically by the more congealed, slightly bigger mid-bass, and generally warmer vibe of the Simaudio. I also had the opportunity to compare to several other top-shelf phono pres.
In the uber-clean category, the phono pre in Tidal Audio’s Prisma preamp was the only thing that improved on the clear, fast, articulated style of sound from the RCM Sensor 2. In my system, the Tidal phono stage portrayed a similar level of extreme groove information retrieval but without the teeny-tiniest hint of extraneous glare I heard from the Sensor 2, an amount so small I wasn’t even aware of it until the Prisma came along with its clear but slightly smoother sound.
When comparing to the phono stage in the stunning Vinnie Rossi L2i, the RCM once again held its own, save for the finely shaded harmonic textures and sense of liquidity that is a hallmark of Vinnie components. Comparisons among very good sounding components like these are concrete evidence of why system matching is key when in pursuit of summit-level sound. They all sound great but which one plays best with the rest of your system? Equally important to many, which purchase of that sonic marvel will still allow you to go on that vacation to Patagonia with your significant other?
To be complete, the components comprising the analog portion of my system during the review period were as follows:
- Rega P10 turntable with RB 3000 tonearm
- ZYX Ultimate 100 and Dynavector DV 10X5 cartridges
- Tidal Audio Prisma preamplifier. PS Audio Stellar Gain Cel preamp.
- Vinnie Rossi L2i, Naim Supernait 3 and Octave V 80 SE (all integrated amplifiers, all with inboard phono stages)
- RCM Sensor 2 Mk II, Simaudio Moon 310LP, Rega Fono MC, Schitt Mani, separate phono preamps
- Pass Labs XA-60.8 monoblockss, Audio Hungary Qualiton APX-200 II, power amps
- QLN Prestige Three, Dynaudio Confidence 50, Alta Audio – Alyssa, and Dynaudio Special 40, speakers
- Gigawatt PF 2 EVO power strip/filter with lots of fancy, pretty looking cables.
More Stuff About The Sound Of Music
I had a heavy crush on Julie Andrews and growing up we had a white fluffy cat named Edelweiss, but I digress.
During the months that rolled by while my ears caressed the clear and euphonic sounds emanating from my system with the RCM Sensor 2 in the phono pre hot seat, a few things rolled around in my head. Will we ever grow up as a species? What viruses await us as the polar ice caps melt? Can time travel ever be possible? How many holes from speaker stand spikes are acceptable on a hardwood floor?
Things like that.
When I wasn’t pondering deep questions, I was constantly impressed and satisfied when listening to musical vibrations being amplified by the RCM Sensor 2. I honestly don’t know much about the Polish geniuses behind RCM except it’s a small company and they have been at it for a while. When it comes to phono pres, it’s clear to me they know what they are doing. The Sensor 2 MKII represents an evolution in design and builds from their earlier phono pres. Aiming for the top in any hi-fi component design seems to attract folks who are obsessed with sonics more than profit. In the case of a vinyl specific product, maybe more so. I seem to gravitate to off-the-beaten-track gear that has been lovingly put together by passionate audiophiles. In a way, that’s all I need to know.
The other thing I know is that playing record after record – great sounding ones, poor sounding ones, and ones in between, the Sensor 2 always delivered the goods. Jazz, Metal, Classical, Folk, Acid Polka, wait, is that a thing? Wide, deep imaging. Black backgrounds. Clarity and detail without annoying sharpness. Deep lows and dynamic slam while never sounding messy.
The current US price for an RCM Sensor 2 MKII is $4,950. Should you spend that much on a phono pre? In my experience, there are quite a few phono preamps costing substantially more. Some might sound better, quite a few will not sound as good – even given system matching considerations.
I can assure the reader that an RCM Sensor 2 gets you very close to the summit as part of that chain of vinyl specific components required for groove-oriented bliss. I loved it. Audition one. Find out for yourself where it puts your system on that long climb to the top. Your vinyl collection will thank you. You can go to Patagonia next year.