graham slee psu1

Graham Slee PSU1 - 24V DC Power Supply

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Upgrade your Graham Slee products with this external 24v power supply. It will take the sound quality of your Graham Slee products to a whole new level!!

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".

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