Genesis Reference Amplifier 30
th
Anniversary Monoblock Owners Manual
9
Silent Running Voltage Supply
1
We recognized that published specifications for noise rejection of opamps
and even discrete small-signal amplification circuits did not always tell the
whole story. The problem is that Power Supply Rejection Ratio, or PSRR, is
specified at one frequency
– usually 1kHz, but the truth is that this rapidly
gets worse as the frequency rises. This is likely to have given rise to the
often heard audiophile statement that “opamps sound grainy”.
For the GRAmp, a new low-current regulated voltage supply was developed
that has broad bandwidth noise rejection so that incoming noise does not
intrude on your music.
The electronics used for
regulation have to be noiseless
and fast. Generally noiseless is
not a problem but fast is a great
problem. Most commercial
regulators are good for about 100
kHz. Most chokes are good for at
least 1 MHz.
The electronic regulator used in
the GRAmp exceeds the
specifications of an excellent
choke. It is an exceedingly fast
discrete circuit and not a generic
design. Spectrum analysis up to
16 MHz implies a very high
bandwidth, as there is no apparent degradation at that frequency. The circuit
is of low enough impedance to outperform commercial regulators by at least
10 dB. This is despite the fact that no loop feedback is used in this circuit. To
avoid any speculation, it is not a shunt device, it is not a capacitative
multiplier, and it does not employ chokes.
It will not surprise many to know that the avoidance of loop negative
feedback is the key to this design. Having established a design, the
components used were individually selected by extensive and laborious
listening sessions. A discrete design allowed that as each component is
hand picked to get the optimum result. Every component on the design was
individually chosen, as was the grounding paths.
1
Genesis would like to credit Engr. Nigel Pearson for the idea behind the
design of the SRVS.
Audio Band Noise Rejection (over
–90dB flat all the way up to 40kHz)
