In article , Peter Chant
wrote:

QUAD used for the PSU in their 34 preamp might avoid switchon
thumps/clicks. That uses an op-amp to center the ground about
the
polarities of a single psu potential difference. Means 'both
rails come on
together' as soon as that op amp wakes up. :-)

If I follow you correctly then the ground, phono screens on input
output, are connected to 0V which is as op-amp output?

If I get a chance I'll dig out my copy of the diagram and put a scan of the
relevant bit on the web so the details will be clear. But the trick they
employed was to use a nominally floating single pd from the PSU. Then had
an op-amp generate a mid-way voltage which is then used to define and hold
a '0V' line for the bulk of the circuitry. This then is connected to the
screens on the phono sockets, etc, so becomes 'ground'. They also chose to
make the mid-point *not* the half-way point and produced asymetric rail
voltages for other reasons. Quite an interesting design.

Slainte,

Jim

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