More
compatible!
High Fidelity Audio Phono Interconnects: Cusat50
No piece of wire is "flat" from DC to light... at some
point strange things start to happen...
Reflections
All cables reflect: their frequency plot resembles a skipping rope with one
end tied to a post and the other end being waggled up and down...
Quite a few experts say it doesn't matter for audio because it doesn't happen
until way up in frequency beyond our hearing - that last bit is true!
But those experts seldom understand amplifier stability where there can still
be some gain left at frequencies of 10MHz and above - even a 1 metre
interconnect cable can start to reflect at those frequencies.
If an amplifier output (in the case of interconnects we're talking about a
preamp output) has to drive a capacitor instead of a pure resistance its phase
becomes more negative. If its response is already falling at a stable rate
of -6dB per octave (because no amp can keep going up in frequency forever),
adding a capacitor across its output will make its rate of fall steeper,
reaching -12dB per octave. That means its phase is -180 degrees. Its negative
feedback which is already -180 degrees obviously becomes positive having
reached 360 degrees (full-circle), and you have an oscillator, not an
amplifier! Such high frequency oscillations (even if they're low level) destroy the musicality of an
amplifier, so you'd never plug a capacitor into the output? Or would you?
All interconnect cables are capacitive to one extent or another, which means they're a capacitor!
They're also inductive, and an inductor delivers a reverse or back EMF, so
when hit with some circuit stimulation such as the harmonic of the now
oscillating amplifier, its going to swing back the other way. The result is
an even more exagerated swinging rope analogy (see above chart).
So it does matter. In fact two, three or four metres of interconnect cable
contributes two, three or four times the capacitance and inductance bringing
the reflections proportionally lower in frequency, causing more chaos to the
output.
Therefore, the choice of a low capacitance (and low inductance) interconnect cable is important.
Now, there are some that say you just need a high current (low impedance)
output and that will overcome such problems. Unfortunately that's not the
case. The effect can go positive, trying to lift the output -
the swinging rope analogy still applies. It all results in the amplifier
output doing things it wasn't intended to do and that distorts the sounds we
can hear, via negative feedback and the power supply.
Now, it's true, amplifier designers (in the interconnect's case:
pre-amplifier designers) move "heaven and earth" to make their amp outputs as stable as
possible given such unpredictable interconnect cable loads. You see, amplifier
designers know.
Keeping interconnect cable reflections as far out of the picture as
possible, is an important part of your system - and now you know why!
Shielded?
But it's not only cable reflections, it's shielding too! Some would have you
believe shielding is not important, but how else can you keep out radio
frequency interference? Without shielding you simply cannot.
You not only need shielding, but good shielding. Yesteryear's radio frequencies
were quite low - even after the introduction of FM (the VHF band). Today
they're in Gigahertz (GHz), and most of the time they don't come from a radio
transmitter but from computers and anything containing a "high-speed"
processor chip. Wavelengths are so small they can penetrate shielding braid - you
need both braid and foil coverage - double shielding!
You may have heard about lifting the shield at one end of an interconnect
cable to prevent hum and noise loops? Don't even think of it today: as any
"West End" theatre or studio sound engineer worth his salt will tell you,
these hyper short radio wavelengths will not see a shield at all if it's only
connected one end.
The only way around hum and noise loops is to make both chassis (the source
and what it's feeding) exactly the same potential (equi-potential bonding). A
"skinny" shield isn't going to do that, and will require both
the chassis to be
grounded together using some stout wire, but that isn't always possible.
What you need is a shield designed to handle some serious current so it has a
really low resistance that ties both equipment's chassis to a zero hum and noise
difference. If not, then that difference will appear on the shield, and the
shield will induce it into the signal - and that's where the hum/noise loop
comes from!
We are assuming here that the equipment you're using has its input
and output ground connections connected to the chassis by a low impedance
means? If not, then the equipment needs looking into too.
Lastly, it's no good having such a good hyper-conductive shield unless it's
clamped firmly 360 degrees to the socket's ground terminal - a good locking
connector having a collet locking mechanism is imperative.
Find such an interconnect and you're giving your equipment the best chance of
doing music really well!
What
is that interconnect?
The Cusat50 of course!
Available in a number of different stereo pair lengths
Directional?
OK, we admit we cannot explain this one, but one way it sounds better and
gives a more stable stereo image. The Cusat50 cable jacket is not normally
printed and so we have no real evidence of its "run off the mill" direction.
We just have our ears and a double-blind test to get it the right way round.
Try it for yourself - we're sure you'll sense the right direction.
Specification
Cable diameter: 6.5mm
Inner conductor: 1mm diameter solid soft annealed copper; DC resistance: 0.026
Ohms per metre
Dielectric: 5 cell semi air-spaced
Shield: Annealed copper braid over 100% copper foil wrap; DC resistance: 0.015
Ohms per metre
Jacket: PVC
Lay-up (1m +): Side by side stereo pair overall flexible PVC braided with
welded ends (separate pairs available)
Lay-up (<1m): Side by side stereo pair with central weld (separate pairs
available)
Direction: Marked
Capacitance: 55pf per metre
Characteristic impedance: 75 Ohms
Shielding efficiency: Better than 65dB
Velocity ratio: 0.82 (82%)
Min safe bend diameter: 150mm (6 in)
Terminations: Locking phono (RCA) plugs with gold plated contacts
Prices
0.6m £105.00; 1m £115.47; 1.5m £120.22; 2m £124.97; 3m £129.91; 4.5m £135.25. Prices in GBP (pounds sterling) ex VAT/GST
