On 2012 Apr 27, at 11:39 AM, Tony Duell wrote:
[1] Vff = 6.3V nearly always implies an
indrectly-heated cathode,
so the
polarity and whether it's AC or DC make very little difference.
The datasheet specifies AC.
Yes, but AFAIK it doesn't specify if this supply has to be floating,
centre-tapped to ground, or whatever. That implies to me an isolated
filament heating a separate cathode. So I can't see why AC is
essential.
The datasheet shows only a single connection for Vff, not a floating
connection.
AC is required by the WOM for two reasons:
- Vff is used in a critical area of the chip. DC used here would
create a unidirectional field-differential which promotes asymmetric
migration of ions or impurities in the cystalline structure of the
chip. This critical region holds a few atoms in a particular quantum
state where - in accordance with the principles of quantum
computation - they are able to sink bits with a probability of 1,
thus allowing an infinite number of bits to be written to the device
(like a digital black hole).
- The AC is also used as a clock to periodically empty the WOM bit-
bucket caches. This is the WOM equivalent to RAM refresh; without the
clock, the bit-buckets would fill up. The bit-bucket caches are a
performance improvement, they sit between the write interface and the
quantum sink, every now and then the bit-buckets are emptied into the
quantum sink.
The quantum sink was top-secret military technology when developed
over 30 years ago. The military didn't really want the WOM device
released but Signetics wanted to try marketing it, so a compromise
was reached: the drain shown on the chip in the datasheet. This was
actually a misdirection, so people wouldn't ask how the device was
able to sink an infinite number of bits.
The military need not have feared, there wasn't much of a commercial
market at the time. People thought the WOM was a joke, or at best a
pointless device. Recently however, WOMs have found a significant
application in digital audio systems. New design and research has
resulted in digital reflection-suppressor (DRS) technology (patent
applied for) - an alternative to the green-pen solution for
suppressing unwanted reflections in a CD. With DRS technology, the
reflections (photons) are allowed to bounce around in the CD,
eventually being detected and making it out into the (electronic) bit
stream intermixed with the desired audio bits. Sophisticated
proprietary digital filter algorithms identify the unwanted
reflections in the bit stream, separate them from the true audio
bits, and send them to the WOM where they disappear. Obviously, if
Vff is not AC the WOM will eventually not be able to sink the
reflections, leading to degraded audio quality.
NDAs prohibit me from disclosing full details of the quantum sink,
but quantum computation is now public enough that this much can be
disclosed without concern of legal consequences.
Finally, you can benefit at home from this taxpayer-funded military
technology - it's about time. Standalone DRS products will be
available soon, or contact to discuss incorporating DRS technology
into your production audio systems.
We're currently working on new filter algorithms to send noise bits
into the WOM. If you thought digital audio was quiet before - just wait.