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Dear friends,
I am feeding my Legato with 3 power suppliers (two LCBPs feeding stages 1 and 3, and one Placid bipolar feeding the Ballsie stage ). I would like to know how much current will the Ballsie stage need, so I can setup properly the Placid. I tried 200mah output and seems to work well, but in orden to save "transfomer" miliamps and also heat, it would be great to adjust the Placid to just what is required.
Thank you very much for your help,
Pepe
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I have the same question my friend, can anyone help?
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The BAL/SE stage uses very little current.
All you need to do is setup the placid so that it is shunting something like 50ma. Setting it up the CCS for about 70-80ma should get you really close.
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Ok,thanks Russ!
But before you answered i had set up the BPPlacid to 250mA outpout (as needed for the legato). But, i don't know why, i had no sound from the rca's...
I believe i have done everything allright, the legato has all the parts of the balse, i have set up tha BPplacid correctly, although with too much current, as i see know that you told me, and all the connections were right.
So, do you think it is the too much current or somethink else?
Thanks!
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Shunting to much current in the Placid will not lead to loss of output signal. Well, it will, if you have damaged the Placid. Do you have correct voltage entering the Ballsie part of the Legato ? Edited by user Monday, December 6, 2010 12:47:03 PM(UTC)
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Around 12V voltage and 250mA current
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Russ White wrote:The BAL/SE stage uses very little current.
All you need to do is setup the placid so that it is shunting something like 50ma. Setting it up the CCS for about 70-80ma should get you really close. so, 30mA + 50mA shunted is all it needs?
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If you follow my directions you will be all set. With no load setup the Placid BP for +/-15V with 80ma through the shunt resistors. Then connect it to the load and adjust the CCS pots until it is shunting about 50ma per rail. Done.
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Ok, so after i adjust VR3/VR4 for 15V, i adjust the CCS pots (VR1/VR2) until the measured voltage across R1 and R2 are ~ 0.08V, so the PlacidBP will supply current of up to 80mA. Then, i connect it to the load (ballsie)and measure the voltage across R13 and R14 and adjust CCS pots until this voltage is 0.05VDC. Right? Thanks Russ!!! ps. i suppose i doesn't mind that legato is powered with 12V (and not 15V) by 2 other BPPlacid's? Edited by user Tuesday, December 7, 2010 6:42:54 AM(UTC)
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You only ever really need to measure R13/R14. You just measure it first without a load, and then again after the load is connected. :)
Just make all of the supplies 12V, but it really should not matter even if the BAL/SE is 15V rails.
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OK, thanks a lot, i will just measure R13/R14 to be 50mA with the load.
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Actually i have a problem...when i connect the BPPlacid to the ballsie stage of the legato, i have a huge voltage drop from 12V to 1V in both rails! Any idea what can be the problem? I have all the right parts on it and all the soldering seems fine... p.s. I had disconnected the other 2 BPPlacids from the analog parts of the legato. Edited by user Friday, December 10, 2010 6:04:44 AM(UTC)
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Have you tried adjusting the output current of the Placid BP while it is connected the load(Legato BAL/SE stage)?
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Not until now, because the voltage drop is too high, but now with the load connected i set one rail to VR1max (around 500mA) and the Vout goes from about 0.5V to only 2.3V, so something else is needed here... Edited by user Friday, December 10, 2010 6:58:23 AM(UTC)
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To help you identify the problem, i tried to power it with another BPPlacid which powered previously the legato stage and is certainly working, but again the same voltage drop, something in the ballse stage is sucking the voltage!
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Thank Russ and Exp4nder for your comments and suggestions, all of them very helpfull !!.
Best
Pepe
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Russ,
is there any significant difference between having a LCBP feeding the Ballsie stage instead of a Placid bipolar ?, what do you recommend ?
cheers,
Pepe
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Problem solved, finally i discovered i had a bad soldering with the ΟpAmp, now it's singing in SE mode too! Edited by user Wednesday, December 29, 2010 12:03:26 AM(UTC)
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