Graham Slee PSU1 Power Supply
Improve the Power and Sound of Your Graham Slee Preamp
Improve the performance of your Graham Slee Gram Amp 2, Amp 2SE and Amp 3 with the same power supply used in the award winning Era Gold V and Elevator. The Graham Slee PSU1 is a beefy power supply, offering rock-solid power delivery. Adding the PSU1 will improve bass performance, open up the soundstage, expand the midrange and extend top end performance. Designed to be a remote power supply placed well away from
sensitive equipment like turntables and cartridges which are susceptible to
pick up of stray magnetic fields, the PSU1 is best sited off of your hi-fi rack for maximum isolation.
The PSU1 has a stabilized output voltage of +24VDC
as well as a nominal 30V DC, at a down-rated 200mA. Two mains voltages are available: 115VAC and 230VAC. They have sufficient
latitude to accommodate voltages from 90 - 130VAC and 180 - 260VAC
respectively, when powering Graham Slee products. It uses a specially manufactured mains transformer made using top
quality transformer steel, consuming minimal excitation (core
magnetisation) current while optimizing transformer regulation. Transformer buzz is kept to an absolute minimum.
Shielding is required for signal cables where there is some source impedance
(driving impedance). The DC output of the PSU1 does not supply a signal (although
Kelvin currents return to it which will be covered elsewhere) - it produces DC (direct
current). It is a virtual a short circuit to signal currents including radio
frequencies - it has virtually zero source impedance - similar to the output
of a power amplifier, it therefore does not need to be shielded.
As the input/output terminals of the voltage regulator are biased
apart by the input/output voltage differential, and that voltage is fixed,
then the PSU1 reservoir capacitors come into play. These are a quantity of
four 1000 microfarad low impedance electrolytic capacitors of the
variety used in switching regulators, so they exhibit low impedance at high
frequency, and they are arranged in parallel which decreases their impedance
four-fold. They will start to swamp the output impedance below 100kHz and
will be extremely low impedance all the way down to 40Hz (below hum and
ripple frequencies) where the impedance
will again rise to about 1 Ohm.
Therefore the PSU1 output impedance is never higher than 2 Ohms and mostly
below 0.01 Ohm for its intended use. As such it is a virtual short circuit
with respect to the current being drawn from it and signals cannot propagate from
a short circuit.
The PSU1 DC output cable features 13 filaments of 0.2mm diameter, rated at 2.5 amps,
is used to carry a current of 0.132 amps when delivering power to a Solo
Ultra-Linear headphone amplifier driving both channels at full output into
low impedance 32 Ohm headphones (to do 104 decibels). That's 19x "overkill".