Canor take it from the bridge
"You can hear the inside of his guitar," was my partner's comment on hearing the Lighnin' Hopkins you are there recording Goin' Away through the full Canor TP306+ phono front end, heard through Hammer Dynamics bass-mids and B&C DE-400TN-8 detailing the top end via Litz wired crossovers. "You know just what I mean; that's the great thing about metaphor," she added. "Indeed it is", your old scribe responds, knowing that recent fmri research indicates that more areas of the brain light up when metaphor is used or understood by test subjects than any other form of communication. This metaphor says it all.
Hence, this metaphor communicates more about the Canor Precision Tube Phono Amplifier TP306 VR+ than a raft of measurements or a page of purple prose description. It is not measurable, it is a special quality preserved by the all valve reproduction chain from Sam "Lighnin" Hopkin's valve microphone in 1963, the all valve Ampex 300, rebuilt for Doug Sax's remastering through an all valve cutting lathe to a 200g pressing heard through the Canor (née Edgar) all valve system direct to our ears.
It wasn't easy getting the system to this stage. The review sample of the Canor Precision Tube Phono Amplifier TP306 VR+ was no straight out of the box plug'n'play exercise. The TP 306 VR+ did not arrive with the previously reviewed Canor Precision Tube Amplifier TP106 VR+ and Precision Tube CD Player CD2 VR+, but came from the first batch produced, black finished and with the demand that it be collected in only 2 weeks after arrival. With its octal tubes, couture capacitors and substantial power supply there's be barely time to burn in and settle the sound before a quick listen and off it goes. With only 2 weeks to review the Canor the usual full range of tests and comparisons will not be available, dear reader.
"What's the point of the review then?" demand plebs chorus, stage left, "How will we know whether to inconvenience ourselves enough to audition this rare objet d'art?"
Unlike the amplifier and CD player, the Canor TP306 VR+ comes with valves un-installed, every valve was housed in its manufacturer's packet clearly numbered and every valve socket on the phono pre-amplifier's boards was numbered too. I tried the unit with it's heavy steel cover on and off during the run in period to establish whether the shielding and isolation of this ferrous Faraday cage outweighs the disadvantages of the metal coffin.
The main amplifying devices in the Canor Precision Tube Phono Amplifier TP306 VR+ are the famously lush 6SL7GT octal valves. Octal valves (so called for their 8 pins) are much larger than the B9a equivalents. The pin circle diameter of an octal is 17.45mm (IEC 67) while the B9a is just 11.89mm. This allows much more room in the glass envelope (GT=Glass Tube) for a bigger assembly of plates, heaters and getters (for some reason getters are far more common in octal audio valves) and is the reason that crosstalk between sections of double triodes is much worse (often less than -60dB) of B9a based double triodes like the ECC** family. However, the bigger, separate Bakelite based, large pin, octals are not universally superior. The octal small-signal triodes are notoriously microphonic compared with their B9a equivalents. A well reputed UK SET designer's immediate comment to me when he heard your old scribe was building a balanced phono stage with octals was "I wouldn't do that; they're too microphonic; stick to the ECC83". Your old scribe still chose the octals on sound quality grounds so I respect Canor's decision to work with the 6SL7, which also has a reputation among some American audiophiles as the finest phono pre-amplifier gain device. Hence, the choice between glass envelope sizes is not so clear cut and special measures may need to be taken to protect the valves from vibration.
The Canor Precision Tube Phono Amplifier TP306 VR+ tops their range of phono stages, described as the "Reference" adding Mundorf caps in the signal path and that promised extra vibration isolation. The TP206+ is their entry modele is an all valve phono stage for MM & MC cartridges. Even this base model features high-quality Teflon insulated metal RCA connectors, and well regulated HT (B+) to minimise noise and ensure more than adequate current delivery and a moving coil step up transformer to this recipe and, in common with the plus (+) specifications throughout the Canor range, includes Mundorf capacitors from Germany. Avoiding global feedback and using passive RIAA EQ between amplification stages puts greater demands on the selection of valves to ensure both channels are identical. The TP306 VR+ gains tighter valve specs, higher spec Mundorf caps, Lundahl step-up transformer and should have additional vibration isolation. With time constraints preventing proper testing of the MC input and the vibration isolation measures absent from the review sample,
[tube tester 1] [tube tester 1]
Canor pre-condition all the valves in their products and test them on their own proprietary TTM device, a policy they had to instigate due the the inconsistent quality of modern and NOS (New Old Stock) valves. These processes establish whether the valves meet their basic electrical performance criteria and also enable Canor to match them in pairs for consistent inter-channel performance. Canor also select the brand of valve that suits each circuit position, a technique I first witnessed employed by Doug Dunlop of Concordant over 20 years ago. Some designers of valve amplification believe that particular tube types should never be repeated in successive stages in any system to prevent their character dominating, while others believe that this is less important as long as different brands (and their different internal constructions) are varied and optimised for each circuit position. Some brands of valve are reputed to work best at very low signal levels while others excel in later higher signal amplification stages. Canor choose the more precise sounding Sovtek 6SL7 at the input of the Canor TP306 VR+ and the more euphonic modern Russian Tung Sol in the second gain stage between the passive RIAA sections. These Tung Sol's are the big offenders in the microphony stakes, one (right channel) being much worse than the other.
Until a second, fully specified sample of the Canor Precision Tube Phono Amplifier TP306 VR+ arrives in the TNT-audio test bunker, first impressions will have to count and there will not be time to test the amazing range of cartridge loading and gain options. Yes indeed, this is an all valve stand alone phono stage with the full range of input options we come to expect from high end solid state devices and just a handful of valve products. At this price competition is rarefied and fierce so Canor will need to offer something special to compete with established benchmarks from ancient legends like the Marantz 7C, merely venerable like the Audio Research SP11, and more recent like the ARC PH7 (nearly $6k) or it's kid sibling the ARC PH5 (around $2k), or the recently reviewed AAAVT (Yaqim) MS-12B weighing in at a mere 390€. and even the built in phono sections of classics like the old Audio Research SP11, Jadis JP-80, Concordant Excelsior, (some with active feedback EQ stages, some with passive filter poles like the Canor) and hybrids like the Manley Steelhead ($7k+) and ARC PH7 (valve regulated, valve gain with an added solid state stage) Even thorough comparison with the solid state Aqvox 2Ci, popular with tnt-audio.com scribes, cannot be done justice with a wide enough range of material in the time available.
The compressed time scale is such a pity as this phono stage promises so much. If I had been approached to design a single ended phono stage I would have connected the cartridge loading resistor straight to the grid of the perfect valve for the job, the 6SL7. Not to be confused with the ubiquitous octal, 6SN7 (the CV181 variant of which was reviewed in these pages), the 6SL7 has a reputation for TONE in the sense that guitarists use the term. The 6SL7's reputation was already the stuff of legend 20 years ago in the days of Sound Practices valve hedonism and is located in this very position in my own yet to be powered up breadboard DIY design. So your old scribes buttons are being pressed already. Having got some gain to the moving magnet output output the filter, why should RIAA equalisation (EQ) be handled by passive poles rather than feedback round the gain device (the 6SL7 in this case)? Because at ultra low signal levels the dominant narrative in some circles is that feedback EQ screws up the timing or generates TID (Transient intermodulation Distortion). Having said this, your old scribes favourite phono stages fall equally into the passive EQ/active feedback camps. Likewise your scribes favourites include Naim K boards alongside the valves, to the extent of owning two custom power supplies for one pair of them.
Sadly you won't read any comparisons using the now infamous judging system because this review sample (finished in black) has to go to a customer within 2 weeks. Hopefully a second sample might be forthcoming to make these comparisons and try the various gain and loading options. The first limitation obvious before being plugged in is that only 47kΩ is available on the moving magnet (MM) input, although 3 parallel capacitances are available. Generally, to flatten the response of a moving magnet cartridge above the midband up to the tip mass resonance, from about 2kHz to 20kHz, requires juggling of resistance and capacitance, Decca cartridges benefiting, in my experience, with 22kΩ, Shure M97 range from 33kΩ, and others like certain high inductance models from high Z. However, the Canor Precision Tube Phono Amplifier TP306 VR+ phonostage does offer a wide choice of loads and gains for the moving coil input. The extra gain for moving coil (MC) cartridges comes from a transformer. Valves capable of handling such low signal voltages, without overwhelming the tiny signals with noise, are rare as hen's teeth hence the choice of solution falls either to a transformer or an extra solid state stage. Canor take the transformer option but in the time available for this evaluation it just wasn't possible to change cartridge to rate the transformer's quality. All transformers have individual character depending on the design and materials.
Vinyl records are recorded with pre-emphasis of 6dB/8ve EQ around 3 frequencies, the high frequencies boosted and the low frequencies cut. The low frequency EQ allows reasonable levels to be cut on the disc without the wiggles being too big for the cartridge to follow and to allow about 25 minutes to an LP side, hence it is a constant amplitude (theoretical) cut from 50Hz to 500Hz. The only frequency where the phono amplifier must be linear gain as specified is at approximately 1000Hz as the low filter pole is below 500Hz and the high filter pole at 2122Hz. The high frequencies are cut with a boost to enable the signal level to be high enough not to be overwhelmed by noise, pre-emphasis from 2122 Hz. This gives time constants of 75uS (2123Hz) and 318uS (500Hz) another one to reduce rumble at 3180uS (50Hz) was sometimes adopted in the Western hemisphere by about the 1970s but some CCIR discs were still being made in the Eastern block, geographically where the Canor is made, until very recently. A fourth filter pole has been proposed (most vocally by Allen Wright of VSE) at 50kHz to counterbalance the natural roll-off of most cutting lathes. So the phono pre-amplifier job includes not only the task of raising the signal from 5mV (MM) or micro-Volts (MC) but also of de-emphasis of the cartridge output by the inverse of the RIAA (Recording Industry Association of America) recording equalisation curve. Inversion EQ circuits range from the simple 3 caps and 4 resistors to ludicrously complicated active circuits; accuracy is paramount as instrumental timbre is rendered unrecognisable by inaccurate RIAA EQ.
Older records had a variety of EQ arrangements, which some specialist collectors would need, but most of us will never encounter anything other than the RIAA of the Canor. Designing a phono pre-amplifier is probably the toughest assignment in audio electronics. It is a tough act to juggle the requirements of EQ, gain, noise, complexity and cost in a unit that consumers only notice now that they're not included onboard every integrated amplifier. Furthermore over half the gain in a MC cartridge turntable based system resides in this little box. Hence the phono stage has the capacity to screw up the whole sound of a disc replay system irredeemably. The phono pre-amplifier is the gateway between the turntable and the rest of the system, the more accurate the tonal balance and the wider the opening (dynamic range and S/N ratio) the better. The Canor TP306 VR+ circuit looks designed to maximise dynamic range. The only ways S/N ratio (SNR, signal to noise ratio, or music to noise in this instance) could be obviously improved would be vibration isolation or a balanced, or 'difference' circuit.
Hence for this review additional vibration control measures have had to be installed. Pearl Valve dampers have been fitted to every valve in the Canor TP306 VR+. The TP306 VR+ is supported by four Yamamoto MGB-2 magnetic floating bases standing on a Something Solid Dissipating shelf, which is mounted on a XR4 rack, which in turn stands on four Missing Link Feet. All this and the TP306 VR+ is still highly microphonic and further investigation reveals that the signal boards (separate for each channel) are screwed firmly to the chassis base, such that they are in tension. Hence, like any flexible (both PCB and chassis) arrangement held in tension, they ring like bells. Indeed the dong and bong of these boards is perfectly coupled to both pairs of 6SL7 and also the 6922, to ensure that every nuance of this vibration is perfectly manifested in valve microphony.
The TP306 VR+ is placed on the top shelf of the Something Solid XR4 rack, which remains the reference isolation rack, isolating each shelf from the others. The supplied IEC kettle lead remains in its packaging and the test was conducted with the RMS Mainline lead as the least likely to bridge the extra vibration isolation measures being very flexible. Naturally the TP306 VR+ is CE marked and RHOS2002 compliant (hence using lead free solder which I find sounds better than the old tin-lead mixes) this phono pre-amplifier arrived equally well packed as its recently reviewed siblings.
……..Reviewer: Mark Wheeler - TNT UK