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Old 25th May 2005, 09:17 PM   #11
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OPA134 is a very good OP, but look at "carlosfm"s posts and try the OPA627 with "close to the pins" decoupling. Like 100nF nearest and 100-300uF el.cap just behind on the OPA627s pins.
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Old 25th May 2005, 09:22 PM   #12
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Quote:
Originally posted by Mike Gergen
For the opamp/buf634 circuit, look up the Meta42 amp. Or go to headwize.com.
Have you seen the PIMETA? I'm trying to understand what's going on with the 3rd ground channel...

http://tangentsoft.net/audio/pimeta/
http://tangentsoft.net/audio/pimeta/misc/schematic1.pdf




Quote:
Originally posted by tobias_svensk
For home use i think you can skip the "TLE2426" that thing is just usefull with batteries and can't give "that" much current that you could have had.
Althought this will be for home use, it'll run off batteries. Our power quality here is REALLY, REALLY bad. So far I'm thinking dual 12V panasonic lead acid batteries with a TLE2426 as the voltage divider and then the BUF634 just to make sure I'm not going to be short on current (haven't done any calcs, yet, may run multiple).

When I was still thinking about using AC, I was planning on running regulated power to the OPA637, but with batteries I can't really see a good reason too....
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Old 26th May 2005, 01:21 AM   #13
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If you going for the pimeta i would suggest you to do better with the caps, n00ber and i have been pushing the caps as close as possible to the OP's supply pins

http://www.diyaudio.com/forums/attac...amp=1116272644

http://www.ettnet.se/~tobias/diy/opabuf/opabufwoic.jpg

I can't say that i've tried it but the PCB is on it's way soon, but common sense says that it "should" be good to have the caps as close as possible. In that Pimeta board they are not close
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Old 26th May 2005, 11:59 AM   #14
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If you were thinking of powering a pimeta like headphone amplifier from a regulated mains supply, it would definatley be a good idea to try and rework the design to get the decoupling caps closer to the supply pins.(you could even solder them directly from the pad to the pin)

However if you plan on using batteries to provide the power to your amp, I don't think the decoupling caps have to be so close. As there will be very little ripple from the batteries during normal operation.
They will of course prove more usuful, closer to the supply pins, when the battery output drops below the recomended minimum voltage for the opamp.

If you read posts over at head-fi , there is alot of people that hold the pimeta in high regard as an amplifer, and the next step up is considered to be the PPA or the M3, which is quite a jump in terms of sound quality.

But if your going to DIY I personally would move the caps closer.
It would be interesting to hear a rework design head to head witht the original.

Hope this has added to your confusion

n00b
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Old 26th May 2005, 10:51 PM   #15
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Quote:
Originally posted by n00beR


Hope this has added to your confusion

n00b
Actually, that all made sense And I think I understand that 3rd amp channel now too...
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Old 26th May 2005, 11:31 PM   #16
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Quote:
Originally posted by n00beR
However if you plan on using batteries to provide the power to your amp, I don't think the decoupling caps have to be so close. As there will be very little ripple from the batteries during normal operation.
Wrong.
The caps must always be at the chips' pins.
No matter what the PSU.
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Old 27th May 2005, 12:20 AM   #17
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Because they want that big energy fast

Heh, didn't even know that i've posted tonight
but hey, 02.21 i was home 21min after closing
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Old 27th May 2005, 12:29 AM   #18
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Default I can respect that :)

Quote:
but hey, 02.21 i was home 21min after closing
Laughing my **** off
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Old 27th May 2005, 10:23 AM   #19
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Robselina: If your going to use 2x12V batteries just skip tle2426 and use the batteries to get +-12V directly.

And DO put the caps directly on the chippins! See attachment.
Attached Images
File Type: jpg opa627buf634.jpg (20.4 KB, 288 views)
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Old 27th May 2005, 02:06 PM   #20
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Quote:
Originally posted by Lovan
Robselina: If your going to use 2x12V batteries just skip tle2426 and use the batteries to get +-12V directly.

And DO put the caps directly on the chippins! See attachment.
Agreed on the caps, but why do you suggest using the batteries to make the virtual ground? Just convenience? current capacity?

I'm concerned about DC offset on the output but maybe I don't need to be....
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