Mini3 - Page 2

What gain did you use? If you built it with a high gain, that would explain the lack of headroom with any headphone. If it's a gain of 11 then that would be more than enough to have that effect on even high impedance headphones.

Again, the high performance, or extended runtime versions are not the issue, it's the gain.

Not only that, but the level of the source plays in this as well. What source are you using and what's the output voltage of it at full tilt (playing a 0dbFS file, for instance)?

One of my sources puts out about 3.5Vrms. With the Senns, and a gain of 5, I think I went till the volume was around the 9 o'clock position...which may be about 30 degrees.

You should be using the line-out (meaning no adjustable volume settings), if you have a source without a lineout, I'd say 80% volume to try to get a good balance of full volume without distortion.

Royewest,
I dont know how you managed to get a good sound like this without bad clipping. But you should really be using your iPod's Lineout, NOT the headphone out.

Try it, you should get Much better results.

The volume control in the taskbar is probably doing the work in software by munging the audio data. If that's the case, you'd be better off setting it to maximum so that you don't lose digital resolution.

I just tried a SendStation LOD via mini plug.

If my volume knob starts at 7 o'clock at off and I turn it clockwise to turn on the mini3 amp, I can't listen at a volume higher than 11 o'clock, maybe 12.

I will search the mini3 build forums for clues on whether this is a build error of some kind.

I have now built two of these that exhibit the same volume -- but hey, no complaints! They are just super : )

Royewest, as for the volume..erm.. you might know more than me. But there are two versions of the Mini3. One is a low gain/high current version.
If you cant turn more than a bit using HD650's, then you most likely built a high gain version (im guessing).

A friendly head-wizer figured it out for me: There is a table of resistor values that set the gain of the amp to different multiples. I built the default "5x" gain version and forgot about the table entirely until reminded just now.

I just ordered a bunch more resistors to experiment with changing the gain to a 2x or 3x setting, so I have a bit more play on the volume pot.

Will the high performance version drive 600 ohms?  More specifically I'm interested in the Beyer DT 770 600 ohm version (if anyone has firsthand knowledge)...

I don't think you'll put a lot of voltage from a 9V battery into 600 Ohm headphones.  They're generally not meant to be used with portable amps.  Both "versions" (opamp combinations) are rail-rail opamps and 600 Ohms won't need a lot of current.  You'll simply run out of voltage before the amp clips with those headphones at reasonable volume.

Would the 250 ohm version be a suitable compromise to pair with the mini3?

Should be reasonable.