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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 10 years ago
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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 10 years ago
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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 9 years ago
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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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