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Old 6th November 2012, 01:03 PM   #2881
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Hello!
I am very interested in what is your opinion about changing:

-NJM4556AD to LME49720HA (TO99 package, better sound than NA, MA package)
-NJM2068D to OPA1612AID.

Anyone has tried these opamps in The Objective2 ?
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Old 8th November 2012, 02:12 AM   #2882
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Location: Winnipeg, Canada
Just checking in to see if anyone has heard from RocketScientist lately? He hasn't posted on his blog comments for a long time either.
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Old 8th November 2012, 09:45 AM   #2883
aphocus is offline aphocus  New Zealand
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Been running my O2 for a while now, and everything seems to be working fine and all measurements came out correctly.

Yet today I ran my batteries flat for the first time and I heard some extremely loud popping which I can only figure being it power cycling I have the revised board with the lower ohm Resistors, so I assume this modification hasn't helped.

Could someone offer me some advice on how to fix this, it was rather loud, far louder than power on/off transients, I'm worried it could ruin my headphones.

Thanks.
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Old 8th November 2012, 10:25 AM   #2884
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Turn off the O2 and recharge the batteries.
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It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
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Old 8th November 2012, 06:26 PM   #2885
aphocus is offline aphocus  New Zealand
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Quote:
Originally Posted by sofaspud View Post
Turn off the O2 and recharge the batteries.
No I'm just going to keep listening to the loud popping and hopefully ruin my headphones...

Seriously, is there no way to make it power off properly?
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Old 9th November 2012, 02:47 AM   #2886
fubar3 is offline fubar3  Canada
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Default O2 unstable with weak battery

>>I ran my batteries flat for the first time and I heard some extremely loud popping

Replace the fixed 12v regulators with something like LM317. Build circuit like "remote shutoff" in the datasheet example and then add a comparator to that. When batteries drop assert the remote shutoff. You might also need a relay so that "off" latches somehow.
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Old 9th November 2012, 01:28 PM   #2887
agdr is offline agdr  United States
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Quote:
Originally Posted by aphocus View Post
Could someone offer me some advice on how to fix this, it was rather loud, far louder than power on/off transients, I'm worried it could ruin my headphones.
If anyone would like to test a "fix", swap R9 for a 30k resistor and R25 for a 620k. You can do it without removing the existing resistors by just soldering a 1.0 meg ohm resistor across the existing 1.5 meg R25 on the back of the PC board, then solder a 330k resistor across the existing 33k R9 on the back of the board.

Use 1% resistors, or if using 5% test a bunch of them with DMM to find a couple close to the real value. Wattage doesn't matter for this, anything that fits works.

What you are doing is raising the voltage the batteries have to rise up to on their own again, once the O2 power management circuit turns off, to 1.35Vdc per cell or 9.45Vdc per battery, above the nominal 1.2Vdc but still less than the 1.45Vdc per cell or 10.15Vdc fully charged level.

The change should stop the oscillation entirely when the PM circuit shuts down, or at least slow the period way down.

Last edited by agdr; 9th November 2012 at 01:31 PM.
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Old 11th November 2012, 09:18 PM   #2888
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Quote:
Originally Posted by aphocus View Post
Been running my O2 for a while now, and everything seems to be working fine and all measurements came out correctly.

Yet today I ran my batteries flat for the first time and I heard some extremely loud popping which I can only figure being it power cycling I have the revised board with the lower ohm Resistors, so I assume this modification hasn't helped.

Could someone offer me some advice on how to fix this, it was rather loud, far louder than power on/off transients, I'm worried it could ruin my headphones.

Thanks.

Curious on how many people have experienced this same issue. Mine's a recent build by JDSlabs, I'm using some t50rp's and vintage ortho's which are f-ing indestructible but if I had some sensitive IEM's I'd definetly be concerned about it damaging them. only happens maybe 2% of the time to me after the batteries drain though.
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Old 12th November 2012, 05:05 AM   #2889
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Quote:
Originally Posted by qwertz View Post
Hello!
I am very interested in what is your opinion about changing:

-NJM4556AD to LME49720HA (TO99 package, better sound than NA, MA package)
-NJM2068D to OPA1612AID.

Anyone has tried these opamps in The Objective2 ?
pls read this first NwAvGuy: Op Amps: Myths & Facts
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Old 12th November 2012, 07:17 AM   #2890
Zoide is offline Zoide  United States
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Quote:
Originally Posted by dewasiuk View Post
Just checking in to see if anyone has heard from RocketScientist lately? He hasn't posted on his blog comments for a long time either.
Anyone? Is NwAvGuy OK?
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