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Old 6th August 2012, 07:29 PM   #2701
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Quote:
Originally Posted by jpak View Post
Do you populate R1 and R2 for the AC only version? In the schematic it is shown as part of battery and AC operation.
I think this is about an earlier post (#2647) about the desktop AC-only version I built? (apologies if not)

On the O2 circuit diagram there's a dotted line around BT1, BT2, D2, D6, R1, and R2, with the text 'Battery Power (omit for AC only operation)'. If there aren't any batteries, then R1, R2, D2, and D6 aren't in circuit so can be safely left out.

All of the power management section (U2, Q1, Q2 etc) is present - if it's left out there's a big switch-on transient, as described by NwAvGuy (and it's true - I tried it just out of curiosity).

One thing I did notice in my earlier post - I said that the gain switch S2 and associated resistors were left out because I was running with a gain of 1. I must have been on autopilot when I assembled the board, because although I left out the gain switch I actually put in the default gain resistors R17, 19, 21, and 23 as you can see from the picture I posted. They have no effect because the switch S2 is absent, and the O2 runs with a gain of 1.

D
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Old 6th August 2012, 10:46 PM   #2702
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The dotted line for both the battery and AC circuits both encompass R1 and R2. It makes it seem like they can be removed if the amp is battery only, or AC only, but need to be there if its built with both?
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Old 6th August 2012, 11:08 PM   #2703
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That is correct. R1 & R2 are current limiters for recharging. If built for battery only use you have to use primary cells or employ an alternate charging method for rechargeables.
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Old 13th August 2012, 05:20 PM   #2704
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Is anyone using the Audeze LCD-2 or HiFiman HE-500 on the O2? Is it a nice combo?



The gain resistors(R17 - R21 and R19 - R23). If i don't add any resistors there, then the gain switch wount work. But if I add:

133ohm to R19-R23 will the gain be 12x when I push in the gain button?

And if I add the 499ohm to R17-R21 will that give 4x gain with the gain button not pushed in?
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Old 13th August 2012, 05:39 PM   #2705
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I use the LCD-2s as standard with my O2 and it sounds spectacular. The HiFi Choice reviewer tried the amp with his HD800s and again was nothing short of very impressed. The amp really can drive pretty much any headphones you can through at it (and well).
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Old 13th August 2012, 07:00 PM   #2706
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Nice! Which gain resistors are you using then?
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Old 13th August 2012, 07:03 PM   #2707
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none for low gain and 365 Ohm for high.
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Old 13th August 2012, 07:07 PM   #2708
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Do you place the 365ohm resistors on the r17-r21 or r19-r23?
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Old 13th August 2012, 07:10 PM   #2709
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19-23 off the top of my head. So that high gain is when the button is pushed in.
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Old 13th August 2012, 10:23 PM   #2710
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Default Any info on ODA progress?

Does anyone have information on the status of ODA, the desktop version, or the esteemed scientist himself? Rocketscientist's last blog entry was back in May.

I hope all is well.

Francois
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