(+)(G)(-) rails from a floating (+)(-) PS?

2004ex · 20th June 2004, 06:19 PM

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.

TIA.

Pabo · 20th June 2004, 06:43 PM

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.

Nelson Pass · 20th June 2004, 06:45 PM

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

Eva · 20th June 2004, 06:53 PM

This supply may be suitable for a bridged design using single supply and taking the ground as the signal reference voltage

2004ex · 21st June 2004, 06:14 AM

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.

20th June 2004, 06:19 PM	#1
2004ex diyAudio Member Join Date: Jun 2004 Location: California	(+)(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. TIA.

20th June 2004, 06:43 PM	#2
Pabo diyAudio Member Join Date: Feb 2003 Location: Helsingborg, southern sweden	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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20th June 2004, 06:45 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	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

20th June 2004, 06:53 PM	#4
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	This supply may be suitable for a bridged design using single supply and taking the ground as the signal reference voltage

21st June 2004, 06:14 AM	#5
2004ex diyAudio Member Join Date: Jun 2004 Location: California	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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