[A3rd.Zero]

I just built a basic rail splitter powersupply for a 9v battery (2 47k resistors, 2 420uf caps) and I am getting a significant difference in voltages in respect to the ground, some times as much as .8 volts. I switched to a small wallwart added two 2200uf caps and one 6800uf cap from the positive to the negitave rail, and i still am getting differences. The weirdest part is that its not always as bad, sometimes the rails are only off by .3 volts. Is there something that i am doing wrong? Do I just need to build a better railsplitter using FETS or Buffers? Thanks for the help.

Milo

 

[PeterR]

Quote:

Originally posted by A3rd.Zero I just built a basic rail splitter powersupply for a 9v battery (2 47k resistors, 2 420uf caps) and I am getting a significant difference in voltages in respect to the ground, some times as much as .8 volts. I switched to a small wallwart added two 2200uf caps and one 6800uf cap from the positive to the negitave rail, and i still am getting differences. The weirdest part is that its not always as bad, sometimes the rails are only off by .3 volts. Is there something that i am doing wrong? Do I just need to build a better railsplitter using FETS or Buffers? Thanks for the help. Milo

http://www.tangentsoft.net/audio/cmo...s.html#vground

 

[A3rd.Zero]

Thank you for the link.

can I do the same thing as the buffer with voltage regulators on either rail? Currently I have a few 5VDC voltage regs around so if I can use them then ill be happy.

milo

 

[tangent]

Quote:

can I do the same thing as the buffer with voltage regulators on either rail? Currently I have a few 5VDC voltage regs around so if I can use them then ill be happy.

That would be a much different sort of beast. Linear regulators will put out a fixed voltage no matter what, and if they're not LDOs, they will require about 2V greater on their input.

The only thing I can think of that might be at all helpful would be to use just one regulator to generate a 5V virtual ground and let the V+ rail drop towards vground as the battery runs down. You'd still get imbalance with this method, but vground would be stable in the short term, which is one of the things you're after with a buffered virtual ground. I.e. low impedance, high current drive. You'd still get clipping earlier with this setup than using a buffered vground.

If you don't want to go find a buffer or a TLE2426, do a search here for a post in the past few months by me containing "741". I gave a circuit you can make with Radio Shack parts to do the same thing as a TLE2426. See JeffreyJ's comments about bypass caps in the same thread if your implementation misbehaves.

 

[A3rd.Zero]

cool. thanks.

I think ill save the regulators for the wallwart powersupply that Im building and order some buffers in my next digikey order. I have an order that hasn't arrived in the mail yet and i make it a point to not have multiple orders out at the same time...its a little walet protection device. Thanks for the help.

Milo

 

[tangent]

I've updated that section of the CMoy tutorial. The graphics are clearer and more accurate, and I've added the 741 supply. Zero, you can get a 741 from Radio Shack if you want to hack something up quickly.

 

[A3rd.Zero]

Thanks again. Surprisingly one thing this hobby has taught me is to be patient.

Milo

 

[ITZBITZ]

Quote:

Originally posted by A3rd.Zero Thanks again. Surprisingly one thing this hobby has taught me is to be patient. Milo

That's funny you should say that particular statement. I develop software for a living and doing it 8+ hours a day makes a bad hobby. I've been programming for 20 years and it's always been a hobby of mine (albeit it a very frustrating one).

I actually find building these amplifiers to be VERY RELAXING. I don't need the stuff I make and it is easy to just take my time and watch it develop. It's not a job and I don't have a deadline, so it is nice to sit back and enjoy watching a bare PCB evolve into something nice.

Patience is definitely required. I find that is true with my daughter, my wife, electronics, and well, life.

On topic, use a TLE2426 or equiv. circuit -- they works very well.