PMC cor

Hardware Review

PMC cor
Wednesday, September 6, 2017
integrated amplifier
René van Es

From the moment I learned that PMC was going to bring an amplifier to market I was wondering what it would be like, and when it did appear I wondered why it got the name cor. Some say it is an expression of interest, admiration or surprise, others say its means heart or soul, the Chinese translate cor as traditional or simplified (I reckon it’s because of the British saying ‘cor blimey’, Ed). I guess no one in the hi-fi world has ever gone so far to justify a name as PMC has with its first amplifier. First of all it’s pretty amazing that PMC, the Professional Monitor Company, has brought out an amplifier, the amp being the heart and soul of an audio system, and built in a traditional way with a relatively simple circuit. PMC not only took their time to develop this amplifier, they must have held long and secret sessions to come up with the name.

 

 

The cor is a very traditional amplifier built around a Darlington type of circuit with only a single pair of power transistors per channel, specified to deliver a healthy 95 Watts into 8Ω or 140 Watts into 4Ω. Taking the lid off reveals two power supplies, one dedicated to the control electronics and one for the audio circuits. The PCB combines SMD and traditional components chosen by ear and specifications by PMC’s technicians. The audio power supply uses a shielded power transformer to feed the rectifier bridges, and a total of eight 4700µF capacitors. Many other and smaller capacitors are used locally on the PCBs, mainly made by Nichicon. The power supply and the boards are protected against failures in the power lines by old fashioned fuses. The inputs are relay switched and lead to a sealed ‘Proprietary Hybrid Input Stage’ on the main amplifier board. Loudspeakers are coupled behind a Zobel network. An extra board is used for a balanced input on XLR connectors, but this amplifier is not a true balanced design, although the connections between boards are balanced, locking spurious RF and EMI emissions out of the audio path. The volume control is a rotary type, the faders for balance, bass and treble are from professional sources and they are all motorized. Bass and treble control? Indeed, the cor has traditional tone controls with a bypass on hand for the purists. The other switches are for mono operation, mute and input selection. Six line inputs in total, four RCA, one XLR and one RCA direct. When the logo is touched, it’s a soft red in standby, it turns to white and after some clicks inside the box the amplifier is ready to operate. On the front a headphone output comes in handy and a remote control eye sits next to the logo. On the back are the inputs and outputs, with a pre-out and of course the mains input with the power switch. The looks are special too. Somehow I am reminded of the seventies and eighties when companies like Meridian, Mission, Lecson and even Quad came up with timeless designs. The almost square box has ribs on three sides, between the ones on the front you find the sliders and push buttons. The lower part has no ribs and shows the logo. Nice details include small LEDs that glow only when the sliders are in the neutral position. This is very useful because they can be operated from the heavy, almost industrial looking remote handset. The cor is available in black or silver, for me the silver is the most fascinating design, but this is a matter of taste.

 

 

Company owner Peter Thomas and head of R&D his son Ollie Thomas say that the cor is as purist as possible, has no sound character of its own and is able to bring music to the listener as it was meant to be. As Peter says: “A dream came true, after delivering many amplifiers to the professional market we have designed a pure analogue amp for the consumer market. Without compromise, simple in operation, it’s a true PMC product”. The loudspeakers used for most of the development work were PMC fact.12, the speakers I have used on daily basis since their introduction. I have mine on Townshend Podiums that decouple them from the wooden floor, and I’ve added a pair of Maximum Super tweeters also from Townshend. My source is a NAD M50/M52 digital music player and a Metrum Acoustics Pavane Level II DAC. Cabling is Crystal Cable for interconnects and loudspeakers, Apogee for digital connections. The cor is plugged directly into the mains, the source components connected to a PS Audio P5 Powerplant. I found that although I use a Quadraspire rack the performance of the cor was slightly improved when stacked on a Quadraspire Soundstage platform. As well as the fact.12 I used Dynaudio Special Forty and Harbeth P3ESR standmount monitors.

Time to listen
The one thing that was clear after a couple of days is that PMC has manufactured an amplifier that does full justice to their loudspeakers. I chose the fact.12 because it sounds like the professional monitors used in studios and at the same time looks great and works in my room. The sound of the fact.12 is dependent on the amplifier, it is very transparent and changing amps can influence the sound quite drastically. I have been searching for an amplifier that gives me the power, drive and purity I hear in PMC’s studio monitors. An amplifier that does not alter the speaker’s character but enhances its capabilities, and here it is: the cor! With the fact.12 it shows no character of its own, it’s like the saying: “Behind every great man there’s a great woman”. The cor is an extension of the loudspeaker, giving the most pure sound PMC is capable of, a natural partnership in every way. I had the time to play many songs and one of them was ‘101 Eastbound’ by Fourplay. The bass impressed me from the start, but when more instruments join in the soundstage grows to fill the entire space behind my speakers. Depth is excellent and many percussion instruments are placed somewhere in front of me. Electric piano is clear, electronic sound effects seem to be everywhere, but most obvious is the drive and speed that this amp is capable of. It makes my fact.12 shine the way it normally only does with heavier power amps biased far into class A (Pass Labs).  The same happens with the latest Agnes Obel album Citizen of Glass, it’s wide open, very direct with a lot of impact, but not in your face. The sound bubble stays a meter a two away, virtually leaving no brick uncovered in the wall behind the speakers. Voices are not only full of warmth, they sound as human as can be and never fail to be clear in the sound field. Do I get all the detail in the music that my 20k amp offer? No, the cor leaves something to wish for, but what I miss are only minor things. The presentation of music is fluid, powerful, natural and impressive. Another reviewer joined me one day and after two or three tracks he mumbled: “this is such a great amp” and gave me a big smile.

 

 

There’s a lot of great music on the Scandinavian jazz scene, one band that stands out is the Tingvall Trio, and I have a high res download of their album Beat. Piano, bass and drums keep surprising me, light, tickling tones from cymbals hanging in the air, while bass provides a the firm foundation for the sometimes tender, sometimes hard piano notes. This is played with ease and comes towards the listener in such a fluid way that you can only consider it exceptional. It will keep you alert to enjoy every single note, yet it won’t make you tired, even if played loud enough to wake up the neighbours. ‘Bluesette’ was recorded live in the Netherlands by Toots Thielemans and a band of stellar musicians including Henning, Pass and Pedersen. It almost feels as if I’m in the audience, Toots is the show master with drums and bass pushing speed to the limit. This music so well suited to the cor and the fact.12 that I have to play other tracks too. ‘Round Midnight’ is a dream that comes true, maybe I should order the cor right now for myself. This is what you get with an analogue amplifier built with total dedication to the music following guidelines established during the golden years of class AB amplification. This compounds all that PMC has to offer, their specific sound quality that is chosen by so many recording studios to master the records you listen to at home. PMC has put that DNA deep into the PCBs of the cor.

 

 

 

I need a tender voice and the former French first lady springs to mind. Carla Bruni on her album Quelqu’un M’a Dit is a fine example, her voice clear and accompanied by guitar only, sometimes a soft bass, a little percussion. always gentle in presentation. The cor handles this sort of music with the same ease as thundering rock. I cannot remember when the funny track ‘La Dernière Minute’ sounded better, with that same sort of ease but retaining the power a human voice has, even with filles fragiles like Bruni. ‘Sous le Ciel de Paris’ by Juliette Gréco is as French as can be and brings back memories of the city of love. Her voice is more open and was very well recorded in the sixties. Music flows gently, never staying inside the loudspeakers, it is free of the cabinets existing in front of me, not pinpointed to the source. It’s a good time to roll in the Harbeth loudspeakers and listen to their own character or find out how much PMC DNA is added by the cor. There’s no need to be afraid, the Harbeth won’t change into a PMC. The P3ESR profits from the almost limitless drive, the open character of the amplifier and all of the other virtues the cor has to offer. Yet it still remains a small monitor with limited bass and a less open sound than a fact.12 offers. For this speaker the cor behaves like it is absent, it neither adds to or subtracts from the Harbeth sound. My smaller full class A Pass Labs or EL34 PrimaLuna add some extra warmth to fill out the bass from the P3ESR, the cor with the P3ESR is a bit of a cold combination especially in my larger listening room. Detail is excellent, lots of speed with jazz, and a singer like Mary Black has the kind of voicing Harbeth is famous for. So is the cor truly a piece of uncoloured wire with gain and does it bring forward only the character of the loudspeakers attached? Dynaudio time it is. The larger Special Forty monitor with a bigger woofer and a reflex port brings me more and deeper bass. On ‘101 Eastbound’ this is much more a pleasure to listen to than the smaller Harbeth. Again the Dynaudio does not turn into a PMC, so the cor seems truly transparent. The dynamic drive makes the Special Forty shine, makes me shiver, nevertheless I cannot wait to go back to the fabulous combination of cor and fact.12.

 

 

The name Professional Monitor Company implies that PMC is a manufacturer of loudspeakers and their presence on the amplifier battle field seems a bit odd, but with the cor they have proven to be not only capable of building the finest studio gear, but also able to let owners of domestic PMC speakers enjoy a close approximation of the pro sound. The cor amplifier did a great job with my fact.12 loudspeakers, I did not expect anything else. It delivered speed, dynamics, neutrality, tenderness and brute force on demand with loudspeakers made by other brands. The cor is a mighty fine amplifier that will make you smile as long as you play your music. It is one of the most transparent and characterless amplifiers that I have had the pleasure to use at home. Bring home the Metropolis or Wisseloord studio sound with the cor in combination with some fine PMC speakers, or use it on any other brand if you want to. I hate to see it go and the small batches being made by hand won’t make it rapidly available for everyone. But it is definitely worth waiting for. Recommended from the heart and soul.

For more about the story behind cor see our interview with design engineer Ollie Thomas.

Specifications: 

Type: Pure analogue Class A/B integrated amplifier
Inputs: 1 x balanced, 4 x single-ended, direct in
Outputs: 4mm binding posts, preamp out
Preamplifier
Frequency response: 20Hz - 20kHz +0/-0.2dB 5Hz - 80kHz +0/-1dB
Maximum gain: 15dB
Tone controls: +/- 10dB
Input impedance: 25 kOhms, unbalanced >14 kOhms, balanced
THD: 0.001% at 1kHz
Maximum input: 5.5Vrms
Maximum output: 10Vrms
Power Amplifier
Rated output power, 230V mains: 95W into 8 Ohms,140W into 4 Ohms
Frequency response: 20Hz - 20kHz +0/-0.2dB 5Hz - 80kHz +0/-1dB
Input impedance: 23.5 kOhms
Sensitivity: 1V = 100W into 8 Ohms
Gain: 28.9dB
THD (Rated output power into 8Ohms): 0.001% at 1kHz
Noise: -101dB A-weighted re. rated output
Damping factor: >160 into 8 Ohms, 20Hz - 20kHz
General
Dimensions: W 432mm H 87.5mm D 401mm (inc. feet)
Weight: 12kg

Price: 
£4,995
€5,835
Manufacturer Details: 

The Professional Monitor Company
T +44 (0)1767 686300
www.pmc-speakers.com

Distributor Details: 

Stageacoustics
T 06 29 53 11 09
www.stageacoustics.nl