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The safest thing would be to do at least #1 on my list, but I would personally do both #1 and #2.
Cheers,
Russ
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If I read the schematic right, just removing either R4 or C7, and removing either R13 or C8 should be sufficient. No need to pull both resistor and capacitor on each rail.
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Beefy wrote:If I read the schematic right, just removing either R4 or C7, and removing either R13 or C8 should be sufficient. No need to pull both resistor and capacitor on each rail. Absolutely correct. In fact you can just cut, lift one leg of the resistor if you like. :)
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Are #1 and #2 recommended for all Placids?
Mine seem to work just fine.
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I would suggest #1 to everyone (the new boards are designed with this change). #2 is optional but is certainly safe.
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OK. I guess I'll just snip off R7 and R13 (too bored to desolder :p ) and replace C3 + C10 with 220pF.
The latter should still be C0G ceramics I suppose?
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C0G/NP0 are fine. I will be putting MKP films in the kits, but no difference really.
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Brian Donegan wrote:C0G/NP0 are fine. I will be putting MKP films in the kits, but no difference really. Do you have a part number Brian? MKP Film Capacitor 220pf? Just to confirm for Placid Single. a. Snip R7 to isolate it and C4 b. Replace C3 with 150-220pf Which resistor should I be replacing with (for Placid BP - R5/R11, normally 221R to about 75R) on the Placid single board. I presume it is R4?
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AudioBear wrote:
Which resistor should I be replacing with (for Placid BP - R5/R11, normally 221R to about 75R) on the Placid single board. I presume it is R4?
Yes R4 on the version 2.0 placid PCBs. :) Cheers! Russ
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Russ, I notice that the Placid 2.1.2 schematic has been posted, and there are substantial differences in addition to the changes you have recommended above. Any hints on what has changed, and why? Cheers! :) [EDIT] Ah, I see the point of R13 and R14 in the manual now. It is very neat to be able to measure shunt current directly! Still curious about the other changes on the front end, particularly the apparent replacement of the JFET with an LED/resistor. Edited by user Thursday, March 18, 2010 6:32:06 AM(UTC)
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We replaced the JFET with a resistor because it was simply too hard to get consistent JFETs, and the performance was virtually identical when using a straight resistor. So we went with the "simpler is better" approach. You can always still use a CLD or even a JFET there if you like.
Cheers!
Russ
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I notice the current adjustment resistor is now at the emitter (or is it drain?) of the power transistor. With 250mA of current, don't you exceed the .5W power rating? (I'm using I2R with R=50 and I get 3 watts)
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No it won't come even close to exceeding the power rating. :) It only ever sees < 2V. Edited by user Thursday, March 18, 2010 11:03:10 AM(UTC)
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Thanks for the replies, Russ. Last question, is the physical footprint the same? I have a project that currently has an LCBPS in there, but also drilled it with additional holes for the Placid BP 2.1.1 in anticipation of a future upgrade. I would really like to confirm that 2.1.2 will still fit these holes...... Edited by user Thursday, March 18, 2010 11:17:07 AM(UTC)
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Yes the size is the same :)
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Could you share the ideal IDSS value for the JFETs? Is it ideal IDSS value output voltage or current dependent? I'll be using my pair of bipolar regulators for +/- 24V and +/- 15 volt, both at about 500MA.
Thanks,
Tom
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10-15ma ma is great. But they both should match as closely as possible.
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The new PlacidBP kit parts are designed for current up to about 400ma. If you going to go higher than that I would simply short VR1 and VR2 and choose a suitably small R1 and R2, and make sure you have heat sinks fit for the job. :)
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I did the Placid and Placid BP modifications #1 and #2 yesterday. I used ceramic 220pf caps from a local DIY amp webstore. I have two Placid BSs and a Placid from the first patch you sold. The Placids are hooked into Buffalo 32s that is modded into a digital pre amp. I must say, there is definately a change in the sound. The music seems to be more rhythmic with more airy mids/highs. In general..hmm...maybe "more relaxing" is a correct word. To be honest, you should mention about these kind of changes in somewhere more visible place. This thread was already lost in the forum page 2 and it is hard to find and realize that it contains very useful information. Maybe a sticky post would be a good idea? Edited by user Monday, May 17, 2010 5:42:30 AM(UTC)
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Searching the matter of a "dirty" sound of Buffalo/IVY DAC with a scope I've found 350 mV 60MHz oscillation on + rail of Placid BP, - rail is silent (+/- 18V on rectifiers and +/-14,0V on output, 200mA idle current each rail). Changing of output voltage and current level haven't brought positive results -- the oscillations on + stayed still.
What could be the matter and how to suppress this oscillation on Placid BP 1.0?
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