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Miero's case I think was a bit different. I do strongly believe 221 should be plenty of bootstrap current.
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Originally Posted by: avr300  Originally Posted by: Stunts Unfortunately I don't have that many resistor values lying around here to do this :( I have but i cant reproducere  I have the same problem. :) I was able to reproduce it only two ways - completely omit R8 - or use very high value (1K or more)
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Originally Posted by: Russ White Miero's case I think was a bit different. I do strongly believe 221 should be plenty of bootstrap current. Ok I'll pick up some 221R resistors tomorrow and do some testing. Is 221R also a good R8 value for the positive half (although none of us experienced any problem there)? Or should we just leave R8A at 470R?
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For the sake of symmetry I would change both. :) But it will run fine even if you change only the R8B.
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I do not have 221R resistors to hand. Have installed 200R resistors in place of the stock 470R resistors. TP_VREF values are now all ±2.5V at start-up.
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Originally Posted by: Martin H I do not have 221R resistors to hand. Have installed 200R resistors in place of the stock 470R resistors. TP_VREF values are now all ±2.5V at start-up. Very good. 200R is fine (you can feel safe leaving it) but 221R should produce the same result. All the best! Russ
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Originally Posted by: Martin H I do not have 221R resistors to hand. Have installed 200R resistors in place of the stock 470R resistors. TP_VREF values are now all ±2.5V at start-up. Value is OK. Tablet is slow. Russ was quick Edited by user Monday, December 29, 2014 8:13:31 PM(UTC)
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One cool little factoid about Placid 2.1 is that that resistor(R8) ensures that the error amps (opamps) are always operating class A. :)
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Originally Posted by: Russ White One cool little factoid about Placid 2.1 is that that resistor(R8) ensures that the error amps (opamps) are always operating class A. :) Nice. Y'all got anymore of them factoids? :)
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General announcement... I will be altering the kits to include R8 of 221R. If you have this issue and need the replacement resistors, please contact me at parts@twistedpearaudio.com and I will send them to you.
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 2 users thanked Brian Donegan for this useful post.
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Replaced R8 by 221R last week and the problem hasn't occurred since. So, problem solved I guess! Thanks a lot for your help, guys! Edited by moderator Monday, January 5, 2015 9:49:07 PM(UTC)
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1 user thanked Stunts for this useful post.
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So this topic came to live for me as I decided a few weeks ago to lower the Shunt currents of the Placid HD BP's I have running at 100mA Shunt Current.
Walking trough my system to finalize and tweak into perfection I noticed the high Shunt current....
Why did I adjusted them that high!?
Suddenly the LH channel had troubles reproducing well modulated sound and volume.
When checking voltages I stumbled upon this old problem of one negative rail not providing the desired Voltage.
Increasing the Shunt Current again to 100mA instantaniously solved my problem (again) after restart.
Since I never had this problem with the higher Shunt Current and I am no fan of desoldering, I think I leave it like this unless someone tells me it's better to increase R8.
Higher Shunt Currents do produce more noise isn't it?......
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You dont have to desolder. Remember you have to decrese the value og r8. Parallelling r8 with 470R will do the trick
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That's true.
I only have one 470R left.
I've got 4x 560R
and 7x 270R
Can I go with 560?
Yesterday evening I lowered the Shunt to 90mA.
Start up went well.
I guess I could also leave it like this?
The scope gives a noiseless line at the power output...
Jordo
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Go for 560R in parallel. That should be fine.
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Today after the LH Placid negative rail surged again I decided to take action. I soldered 560R on top of the already installed R8 resisors without having to remove the placids  Shunt current dropped from 90 to 80mA. Edited by user Monday, November 30, 2015 10:09:16 PM(UTC)
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Trim the current again.
Most important part - is the start up sequence now predictable ?
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80mA is not that bad isn't it?
I have extra large coolers and they don't run nearly as hot as the smaller placid hd's which shunt 60mA.
Also with 100mA shunt previously the scope showed a clear supply.
But yes, eventless startups up to now!
Thx!
Jordo
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