Review: NwAvGuy's O2 DIY Amplifier - Page 2  

Quote:

Originally Posted by Willakan 

I assume he means that to achieve the same volume with batteries, he had to turn the volume knob up higher, leaving less additional headroom to turn it even higher than that on a quiet track vs AC power.

This is correct.  When I say headroom I mean available travel on the potentiometer to increase volume.  Obviously, running on batteries is going to decrease your voltage capability and decrease the ability to drive the headphones as loud.  Basically, headroom to me is how loud you can go before you either clip or max out the amplifiers ability to increase volume.

I should be able to try a few quietly mastered tracks tonight with larger dynamic range, take a picture of the board since it's been requested, etc.
 

I tried to get decent pictures, but if I use a flash I get some . . . I'm not sure what it's called, flashback?  The board lights up like a Christmas tree making it hard to see anything.  Without it everything is fuzzy/blurry.  Sorry everyone, maybe the full amp pic will turn out better though.

Listening to Holst The Planets as recommended I noticed it made a bit more use of the headroom available, but still got plenty loud in the areas that needed it.  I would say that some very insensitive headphones might not play as loud as some would like with it, but the K702 certainly doesn't mind with the amp.

Quote:

Originally Posted by limpidglitch 

Turn the flash off, macro on, steady the camera on something reasonably steady (like a stack of books), and point any available light at the board.

If if you have a nice powerful desk lamp on a flexible arm put it as close to the board, while being outside the frame of view of the camera.

 

And shoot! :)

 

 

I've tried to steady my camera and use independent lighting, but it just doesn't come out how I'd like currently.  I'll see if I can take better pics, but once again for those wanting a general template pic the designer probably has infinitely better than what I can get with my oldish point and shoot.

 

Oh, and when running from batteries and an iPod LOD you should be perfectly safe with a gain of at least 8X, unless I have missed something fundamental.

With these settings you should be able to achieve 97dB with your K701s and source material peaking at -20dBFS. I'd say that's quite sufficient.

 

This was a personal choice actually.  When I visit my parents or go on long trips that involve staying in a hotel I use my ipod as my main source.  This allows me to capitalize on the 1V output on the ipod up to 6V from the O2 on AC.  You're right about about the gain though, others may prefer an 8x - this was the best balance for me though :)

@B0ck3n

The volume substantially drops when kicking over to batteries due to less voltage, which is why headroom drops.  Messing with the volume control it's pretty easy to say it won't get as loud, but for most music it should still be sufficient - that's all I was getting at really.

Quote:

Originally Posted by bada bing 

I'm a bit curious. Why does the volume drop when the supply voltage changes ?

The voltage gain remains the same and unless the amp clips, the volume should be unchanged ?

The batteries may not have had a full charge and may have caused it to clip some, now that they're fully charged it doesn't seem to be an issue.  I don't know how long they will take to deplete to the point where they cause clipping on 6v RMS.

@Negakinu

Honestly, I'd say it's good enough as is to qualify for desktop position.  Just pick the gains required to do so and go for it (2 & 3 for a desktop only model would be my recommendation allowing 6v from 2v and 3v sources).  Seriously, it's that good of an amp as is.