(+)(G)(-) rails from a floating (+)(-) PS? (+)(G)(-) rails from a floating (+)(-) PS? - diyAudio
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(+)(G)(-) rails from a floating (+)(-) PS?
(+)(G)(-) rails from a floating (+)(-) PS?
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Old 20th June 2004, 05:19 PM   #1
2004ex is offline 2004ex  United States
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Default (+)(G)(-) rails from a floating (+)(-) PS?

Just acquired a Lambda regulated power supply (from a local flea market) that has 5 lablled wiring terminals:

(+s) - sensing
(+DCV) - positive floating
(Case) - case
(-VDC) - negative floating
(-s) - sensing.

Note that as is I could only see voltage between (+VDC) and (-VDC)
but not between (+VDC)(Case) or (-VDC)(Case) due to floating.

It is quite easy to wire it as a single (+VDC)(G) or (-VDC)(G) supply by grounding the (-V<->Case) or (+V<->Case) accordingly.

Is there a way to get both +ve and -ve rails simultaneously?
Plan to use it for an amp project.

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Old 20th June 2004, 05:43 PM   #2
Pabo is offline Pabo  Sweden
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If you design the power amplifiers carefully and make sure that the DC-offset on the output is really low and that the driver bias currents or other biasing currents does not flow into ground you can build a capacitive voltage splitter with a push pull emitter follower to make sure that the midpoint stays within +/-0,7V. Quad uses such a solution in one of their early amps and I have used it with success. The problem is that you end up with half the voltage swing i.e. if the converter delivers 60V you can only achieve +/-30V output swing.
If something that measures good doesn´t sound good, measure again!
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Old 20th June 2004, 05:45 PM   #3
Nelson Pass is offline Nelson Pass  United States
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(+)(G)(-) rails from a floating (+)(-) PS?
If not a large amount of current needs to run through the
ground (i.e. a balanced output) then two resistors and a
cap (to ground) are sufficient to establish a virtual ground
that the circuit can reference. If the load runs to ground
so that the current is high, I suggest fairly low value resistors
and a really big cap
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Old 20th June 2004, 05:53 PM   #4
Eva is offline Eva  Spain
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This supply may be suitable for a bridged design using single supply and taking the ground as the signal reference voltage
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Old 21st June 2004, 05:14 AM   #5
2004ex is offline 2004ex  United States
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Well, after poking around a bit the PS appears to be a variant of the discontinued LK351
model (Linear PS). It is adjustable from 0-40V (splitting would
be 0-20V rail), regulated to ~mV, and can source 18Amp at 40 deg. C. Weighs 95lb.

I was interested in its current capability and wanted to
try out a multi-channel amp (~8 for home theater) or a two
channel Aleph-X for music, which all seems to default to a +/-
rail configuration.

Would anyone see show stoppers trying to use this PS for
the above purposes?

Thanks for the responses and suggestions thus far.
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