Double Delphini Hi-Fi News Magazine Sept 2000
Double helpings of the Michell / Trichord Delphini phono stages, as we take
a closer look at the stereo and mono incarnations.
It was in April that I first looked at the Michell / Trichord Delphini phono
stage (Head cases p42), within the context of a group of five other
units. Since then I've spent more time trying the Delphini in all its guises,
as there are in fact three distinct versions available to suit budgets from
£1850 down to £534 (£499 plus £35 for the basic
PSU). The version seen in April was the 'standard '£895 (if there
can be such a thing), using two polished steel-wrap boxes; one for stereo
amplification/equalisation, the other power supply/regulaion. The cheaper
configuration uses a more humble 40VA AC plug-in power supply; while the
top-spec Delphini Mono uses a total of four polished steel boxes - two amps,
two PSU's - combined together as a truly dual-mono solution.
As a refresher of this phono stage's vital statistics; the Michell/Trichord
Delphini is a user configurable solid-state cartridge pre-amplifier, designed
to get the best out of high performance moving-coil cartridges. Since its
first release, though, it has been tacitly given moving-magnet capability
by virtue of a lower gain setting plus a high impedance 47Kohm input.
Within the Michell/Trichord electronics line-up it is the spiritual successor
to the regarded Iso phono amp, although the Delphini has been designed from
the ground up by Trichord Research and its added benefits include user-adjustability
and more upgrade options.
The phono amplifier circuit is based around heatsinked IC chips running
in class A, and uses passive RIAA equalisation implemented between two gain
stages, with 0.1% tolerance metal film resistors and 1% polystyrene and
polypropylene capacitors. Post-equalisation gain is with FET (Field Effect
Transistor) op-amps using current feedback. A servo circuit is used around
this stage to reduce any small DC offset which may trouble following amplifiers
and speakers, without resorting to series capacitors which may influence
sound quality. In the Mono version the capacitors are sourced from MCap.
Matching the input stage characteristics of the phono stage to the cartridge
and arm leads is crucial to get the best sound, and here the Delphini is
well equipped with a choice of four different input impedances, and four
gain settings. Most modern m-c cartridges are suited to a load of around
100 ohms, but to accommodate a wide range of requirements there is a choice
of 33, 100, 330, 1K and 47Kohms settings. This can also be useful for subtly
tweaking response of the cartridge, where a lower than suggested setting
may tame an overly bright sounding response. Matching level is as important,
and here the Delphini can be configured with an amplification factor of
54, 62.5, 68.5 or 70dB. As with impedance, changes are made internally by
first removing the two hex screws on the unit's front to slide forward the
stainless steel lid, and then by moving jumpers between pins on the actual
circuit board.
When dealing with the nano-volt level nuances from a phono pick-up, particularly
a low output moving coil design, the devil is certainly in the detail. But
unlike signals in the digital domain, music can survive to some extent below
a normal noise floor, albeit masked and indistinct.
A glance at the noise spectra in the plot of harmonic distortion against
frequency (fig 1) shows the noise level to rise at low frequencies; this
is usual for a high gain unit with RIAA de-emphasis, requiring almost 20dB
of additional gain by 20Hz, which makes mains related 50Hz interference
the predominant spoiler in signal-to-noise ratio figures.
Starting with the simplest and cheapest version of the Delphini, the stereo
unit with the basic power supply, the virtues that had impressed me with
the two box unit in April were still present, but without quite the same
finess or smoothness. Instrument separation, stage depth and revelation
of subtle low level detail were still all excellent within its category.
Top end treble quality was the biggest shift, with a granier side to the
Delphini showing itself for the first time. Putting a metal-box supply back
in charge of power brought back the sound that had previously impressed,
with its silkier and more natural treble. Soundstage widened marginally
and timbre was enriched. But what of the full spec Delphini Mono?
Stereo image was now, perhaps unsurprisingly given the dual-mono configuration,
further improved. Playing Miles Davis' Kind of Blue {Vynil Demand re-issue},
the already wide stereo cut was turned from wide screen to cinemascope.
The pervasive tape hiss that lies in the recording was altered between the
two-box and the four-box Delphini; with even the shhhh noise sounding
cleaner, yet easier to mentally filter out. The bass riff on 'So What?'
had a little more snap to it; but most interesting was the way the semitone
key change seemed a little better played, with trumpet and sax taking the
chromatic changes in their stride even more convincingly.
The differences noted were broadly true with two different turntable systems,
a Michell Orbe with Incognito'd RB300 and Ortofon MC Jubilee; and an LP12
Lingo with Ittok LVII and Audio Technica AT33PTG.
The LP12 combination was more effusive and engaging generally, and the differences
between the Delphini upgrades here were less striking. My guess is that
the Linn turntable's strengths were more timing and rhythm based where the
Michell centres on timbre and imaging nuances. But that's not to say that
a potential Linn owning buyer would be wasting their money. The benefits
of increased revelation and smoother details were there to be heard, but
as ever it is the law of diminishing returns that rears up. With this LP12
and its AT cartridge, some of the bright pyrotechnics were tamed, the
soundstage snapped back into a tighter - and wider, naturally - focus, and
the whole was certainly less 'rock-'n'-roll' and more relaxing to listen
to music through in the long term. Turning to the Michell Orbe, the Delphini
Mono's performance lift could be better appreciated with respect to the
extra dash of smooth refinement. Bass had a little more weight and extension
- not a night-and-day change, but enough to suggest that the electronics
were working more transparently to replicate the cartridge signal authentically.
As a phono stage for the modern record listener, the Michell/Trichord Delphini
can hold its head up with the best. It's intrinsic sound, if such a thing
can be described for such an ostensibly neutral sounding and measuring device,
is clean and analytical. That's 'analytical' in the best sense of the word,
of being able to resolve the many elements of a given complex waveform -
music! - rather than in the maligned sense that suggests over-analytical
and soulless. The Delphini Mono version especially will get the best from
low-output moving-coil cartridges without resorting to step-up transformers.
I tried it effectively with a Clearaudio Victory L, a cartridge that demands
plenty of clean gain for its minuscule output.
The full-blown Delphini Mono will suit the user wanting to expand on even
the two-box's performance, but at almost twice the price it needs a very
good system to justify the luxury. Best value I felt was to be had with
the two-box Delphini stereo. The improvement shown by the regulated outboard
supply easily justified its recommended use over the basic supply. But Michell
Engineering/Trichord Research will part-exchange a stereo for two monoblock
units, so investing in the stereo phono stage will not preclude later upgrading.
Andrew Harrison |