John
Isolation. Prior to announcing the eponymously branded LIO at the New York Audio Show last September, Rossi made amplifiers, DACs, headphone amplifiers and phono stages under the Red Wine Audio (RWA) banner – its calling card was battery power. I’ve reviewed several RWA integrateds: the 30.2 LFP-V Edition (here), the Signature 15 (here) and the Signature 57 (here). Rossi has since ceased production of the RWA line but product support continues.
Now we have Vinnie Rossi the brand and its first offspring, LIO: a modular hi-fi system that can be configured as a loudspeaker amplifier, headphone amplifier, phono pre-amplifier, DAC, tube buffer, pre-amplifier (with either auto-former or resistor ladder volume control), or (almost) ANY combination thereof.
Modularity will be covered in Part 2 but before that let’s looks more closely at how LIO is powered. It’s different. This is the first showing of Vinni Rossie’s new PURE-DC-4EVR power supply. Circuit juice comes not from a battery but two banks of nine ultracapacitors.
Interested parties will likely start by asking, “What the Kenny Loggins is an ultracapacitor?” The simple answer is that it’s a beefed up capacitor that can hold more charge, and for longer, than a standard capacitor.
Capacitors, ultracapacitors and batteries each do essentially the same job: store electrical charge (electrons) for a short period of time. Batteries the longest, then ultracapacitors, then capacitors.
On storage capacity, batteries will typically hold the most amount of charge. Then ultracapacitors. Then standard capacitors.
As per batteries, the most obvious advantage of an ultracapacitor-powered device is isolation from mains power where quality is variable. Population density and time of day influence its voltage stability and line noise.
When you and your neighbours cook dinner, boil kettles, watch TV and run washing machines at 6pm there’ll be more noise andvoltage variation than there is at 2am when most folk are asleep and the demand on the local grid is diminished; that’s when your mains powered amplifier will probably sound its best. Like the battery-juiced RWA models before it, the LIO’s ultrapacitor banks mean you can still get that 2am feeling 24×7.
Moreover, the need for power regenerators, filters and deluxe power cords gets stamped out like a cigarette. An advantage not to be sniffed at.
A LessLoss DFPC power cord (reviewed here) will run you US$595. Improvements are palpable but it won’t be long before total spend tips US$2K should you want to spread Louis Motek’s skin-effect love system wide. For financial context, a basic LIO configuration of case, external AC/DC adaptor, ultracapacitor power supply and motherboard (into which modules are inserted) will run you US$1995.
At US$3495, PS Audio’s P5 Power Plant will regenerate mains power for four attached units. That’s around half the cost of a LIO suited and booted from top to toe.
Again like batteries, the second main advantage of using ultracapacitors is high current delivery – essential for proper loudspeaker dynamics. The promise of high current tends to get waved around a lot by amplifier manufacturers, very few of whom tend to design with batteries or ultracapacitors. Rossi might be in the minority in this respect but that doesn’t mean his way is the only way to connect with a high power. It’s perfectly possible to design a mains-powered transformer that can deliver current when it counts.
What does ‘high current delivery’ mean? The commentary that follows will mirror Vinnie Rossi’s own journey; batteries then ultracapacitors.
We’ll start with a car whose battery usually comprises six cells, each capable of holding 2.1V. That gives us a potential 12.6V from a full charge.
Why can’t we start a car with a pair of 6V lantern batteries instead of the heavier, more expensive version seen under the bonnet/hood of most cars? After all, two Duracells placed in series give us the 12V we are looking for.
The answer lies with current (I), measured in Amperes (or amps for short). A car’s starter motor requires a healthy dose of current to get going and a battery’s ability to deliver that current is largely dependent on its output impedance (R), measured in Ohms. This is sometimes called ‘output resistance’.
Drawing on high school science, Ohm’s Law says: V = I x R, the re-arrangement of which give us I = V / R. Current and output impedance are inversely related: the lower the output impedance of the battery, the higher its current delivery capability.
Different power supplies – transformers, batteries and ultracapacitors – have different output impedances, which in turn influences their ability to deliver current.
When current flows out of a battery and into a load – in this case, a car’s starter motor – there is a voltage drop, determined by the battery’s output impedance.
Picture a battery as a water tank where the volume of water contained therein represents its voltage potential and the diameter of the hose attached to the underside of the tank is its output impedance (where a lower value represents a wider hose).
Let’s now imagine an improbable scenario: if the hose is as wide as the water tank itself, the output impedance approaches zero and ALL of the water contained in the tank flows out (thanks to gravity). Narrow the hose (higher output impedance) even slightly, and the water (voltage) will exit the tank more slowly. In other words, we get less current.
Back to the car battery. For the sake of simplicity we’ll specify it as having an output impedance of 1 ohm. If the starter motor were to draw 1A of current from the battery, then the voltage output of the battery is defined by its terminal (output) voltage: V = emf – (I x R). In our case that’s 12V – (1A x 1 Ohm) = 11V. A solitary amp drawn from the battery caused its output voltage to drop by 1V. Draw 2A and the terminal voltage drops by another volt. Draw 10A and the battery’s terminal voltage drops to 2V. Why? 12V – (10 amps x 1 ohm) = 2V.
Here are those results tabulated:
Voltage potential (EMF) Battery output impedance (R) Current draw (I) IR (Ohm’s Law) Terminal voltage (EMF – IR)The table shows that a 12V battery with a 1 Ohm output impedance will give us a maximum of 12A of usable current before the battery’s terminal voltage drops to zero. It therefore follows that a battery with double the output impedance (2 Ohms) the current delivery will drop to 6A before the battery’s terminal voltage bottoms out. That’s nowhere near the several hundred Amps required to start a car.
Assuming we need 200A to bring the car’s starter motor to life, Ohm’s Law requires the battery’s output impedance to be 0.06 Ohms or lower, calculated by taking the quotient of V and R.
A single 6V Duracell lantern battery’s output impedance is specified at 0.6 Ohms. Two in series gives us 1.2 Ohms so now we’re waaay down on current delivery possibility. Fortunately an average car battery’s output impedance (when new) comes in at around 0.05 Ohms and we find ourselves with sufficient current to start our car.
The point? The output impedance of the power supply matters.
Now let’s move this thinking to an amplifier driving loudspeakers.
In an ideal world an amplifier should be a constant voltage source. The voltage should not drop – or ‘sag’ – as current demands increase (as seen above in the car battery results table).
Another high school science formula is required here: Power (watts) = voltage (volts) x current (amps). Or P = VI. Substituting in I = V / R gives us: P = (V^2) / R.
If a loudspeaker’s impedance falls from 8 Ohm to 4 Ohms, the amplifier should provide twice as much power from the same (constant) voltage. How well it does so depends largely on its current delivery. If the amplifier suffers too much voltage ‘sag’ in delivering current it will sound like it is running out of steam. The lower the power supply’s output impedance, the lower the voltage sag.
Back to LIO.
Ultracapacitors tend to have lower output impedance than batteries – probably the primary reason why Vinnie Rossi has moved from the former to the latter.
An external power brick is used to convert AC wall power for the 24V DC input on located on the rear of the unit via which an indirect, seamless power supply is maintained to the motherboard by alternating between two banks of nine ultracapacitors. Bank A is recharged whilst Bank B, disconnected from the incoming DC, powers LIO…until its charge dips below a pre-determined threshold, at which point a relay switches over power supply duties to Bank A whilst Bank B is recharged. Back and forth it goes. Clever.
Looking at the numbers: 9 x 2.7V gives the LIO a ~24V rail from which to draw power. With each ultracapacitor entering the scene at an output impedance of 0.002 Ohms, in series all nine sum to 9 x 0.002 Ohms = 0.018 Ohms. In other words, the total output impedance of the LIO’s power supply is 0.018 Ohms.
If the loudspeaker load were to draw 10A – a hefty amount of current – then the output voltage would drop to 24V – (10A x 0.018 Ohms) = 23.82V. Even when faced with a high current draw, the LIO’s output voltage barely drops. Impressive.
Rossi via elaborates via email: “Ultracapacitors are electrostatic devices so they can be charged and discharged much more rapidly than batteries. Drawing 100A from the LIO’s ultracapacitors would not be an issue if you really needed that much current. Drawing 100A from most batteries would cause their over-current protection circuit to trip, or if they don’t have this, could damage the cell(s) of the battery permanently. Worst case: they would overheat and possibly catch fire/explode.” Yikes.
LIO’s MOSFET loudspeaker module threatens 25wpc into 8 ohms, 45wpc into 4 Ohms and 65wpc into 2 Ohms. All RMS continuous. For those wanting more raw grunt from LIO, ultracapacitors per se are not the limiting factor. It’s the number of ultracapacitors – 18 in LIO – that keep a lid on watts per channel.
“To get more speaker output wattage we just need higher voltage rails to output a larger voltage signal to the speaker. Therefore we simply need more ultracapacitors in series,” says Rossi.
A more powerful unit is reportedly already in the works but the additional ultracapacitors will squeeze out all other modules – it’ll be an amplifier and an amplifier only.
Despite a good showing in the current department, LIO doesn’t arrive nit free. The first to be picked concerns the relay that switches between the ultracapacitor banks: it makes an audible ‘click’ from within the case that can be heard from the listening position during quieter passages. Rossi is apparently already working on a way to dampen its sound. The second? I’d like to see a longer cable betwixt power brick and amplifier.
Rossi again: “As far as ultracapacitors not holding as much charge per given size when compared to batteries, it doesn’t matter for LIO because the PURE-DC-4EVR switches between two ultracapacitor banks; the one supplying 24V to LIO’s circuit is disconnected from the incoming supply. Off-grid play time does not expire as it does with a battery.”
On longevity Rossi offers this: “Even the best batteries like the LiFePO4 battery packs that we were using [for Red Wine Audio] are rated for around 2,000 cycles. Ultracapacitors will give you anything between 500,000 and 1,000,000 cycles. You would not need to replace them for the life of the product.”
“But there are certainly applications where battery makes more sense, such as a portable headphone amp. You’ll get more play time with battery, and you want that since you are not plugged in when you are on the go.”
In Part 2 we’ll look more closely at LIO’s modules and their all-important sonic prowess.
Further information: Vinnie Rossi
