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Old 10th March 2012, 06:48 AM   #2221
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@Fsatsil - You should be able to source one or a BOM substitute locally.

@Sorr - Yes, but it's kind of risky. It was discussed a little around page 214 or so.

Last edited by Cpl Clegg; 10th March 2012 at 06:55 AM.
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Old 11th March 2012, 12:33 AM   #2222
jtktam is offline jtktam  Canada
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Pics of the o2 i built today for a customer. Nothing special inside except I used sockets for solderless gain changes

the outside I used some stainless hex socket cap screws and a black metal knob. The back RCA is gold plated.

-joe
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Old 11th March 2012, 03:05 AM   #2223
jtktam is offline jtktam  Canada
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better pics, with size comparision

-joe
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Old 11th March 2012, 10:53 AM   #2224
dook13 is offline dook13  United States
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Default R1 & R2

Greetings to all. New guy here. Caught the DIY bug with this amp. So thanks much for any help.

I am looking to use 300mah 9v batteries (unless there are higher capacity battery options) and I'm considering changing the values of R1 & R2 as discussed in the blog with a 150ohm value..
My questions are:

Is it that slow to charge using the default value(220 ohm)? How long does take to charge?

Will going to the 150 ohm value be that much faster?

Do I have to worry about over charging with the 150 ohm value?

What is the longest the O2 should be plugged in for with 150 ohm value?

Also could I use the SIP sockets used in the gain resistors for R1 & R2?
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Old 11th March 2012, 08:09 PM   #2225
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I just finished my O2 build and it went surprisingly well! All of the resistances checked out and most of the voltages did too from the testing section of the O2 details page. I first used a pair of Apple earbuds to test the amplifier and the sound was hollow and lifeless, but then realized that the earbuds had to be pulled out of the jack by ~1mm before it made proper contact. The O2 sounds amazing and I can't wait to try it with my better headphones soon.

During testing, I noticed that the voltages on pin 4 and pin 8 of U2 were slightly different when powered up with the power adapter. Pin 4 measured around -11.55 - 11.6 V while pin 8 was ~11.7 V. I used the standard O2 BOM and did not notice any obvious solder bridges. Is this indicative of an issue with the build or is it a result of variation in parts, etc?
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Old 11th March 2012, 11:36 PM   #2226
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I'm still looking for a good dac to pair with my o2, and I was wondering if anyone had some opinions on the Audioengine D1?
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Old 11th March 2012, 11:54 PM   #2227
agdr is offline agdr  United States
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Quote:
Originally Posted by dewasiuk View Post
I'm still looking for a good dac to pair with my o2, and I was wondering if anyone had some opinions on the Audioengine D1?
Here is RocketScientist's take on it: NwAvGuy: ODAC Update
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Old 12th March 2012, 04:14 AM   #2228
a1095us is offline a1095us  United States
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Default O2 The Basic Utility Version

I needed to find a good solution for a simple, basic, and quality headphone amp. to use with my computer music and videos. I have a headphone amp. (AMB Beta 18) (with a real common ground) for the music server in the living room. I needed something for the bedroom system. I'm currently using an Audiotrak HD2 for the bedroom system that has a pretty good dedicated headphone amp. section. I noticed that the line out section had a cleaner output than the headphone amp but was not capable of driving the headphones very loud. I had a bunch of left over parts from various audio projects and decided to build a very basic version of the O2 for this application.
This may offend the sensibilities of some of you O2 purists. The amp. is built and hard wired on a left over Radio Shack perf board. Since part of my job is building test circuits on perf boards, this was right up my alley. The 4556 output opamps are mounted on a shared ic socket. I had a left over Marchand PS-10 regulated supply that I converted to 12 volt operation and it handles driving this amp. with ease. The cases are some rather utility, ancient Radio Shack left-overs.
This amp. has a surprising amount of power and control over my Sennheiser HD 580's. Definitely cleaner than the already pretty good Audiotrak on board amp. I'm driving the O2 with the line level output section from the Audiotrak. I also had a chance to drive it with my music server Acam-rdac DAC with very impressive results. Gain is set at 2.5X. This seems to be a good balance. There is no volume control as it is set with a 10K bridge resistor to simulate a wide open volume control. Volume is controlled with the HD2 interface or the media player volume control. No volume tracking error. The DC Level measured at the output was 3.2 mv. per channel. The output seen on my scope showed no oscillations and looks dead quiet. This amp. is extremely clean and quiet. I'm impressed!

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Old 12th March 2012, 05:46 PM   #2229
unsopa is offline unsopa  Germany
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Nice work, a1095us,

thank you. I like those basic designs. And never have seen those "shared ic socket", good idea! But aren't you afraid of burning your headphones with DC without the protection circuit? I planned something you did a few weeks ago, but was warned to do here: #2143


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Old 12th March 2012, 07:06 PM   #2230
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Consider me offended.

Seriously though, nice build. It may not measure quite as well but it probably still sounds rather nice!
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