The Objective2 (O2) Headphone Amp DIY Project
- Thread starter RocketScientist
- Start date
@Alexium the LED's role is described under Circuit Description.
Basically it's being used as a voltage reference for the power management circuit. If you change the LED it may change what voltage the O2 shuts down at, or worst case, prevent it from even turning on when running on battery power. If you want to use a different LED that's covered under Circuit Board Construction and Enclosure Options. Also, it's a high-efficiency type to run on very low current (only 0.5 mA) to maximize battery life. Most LEDs need at least 10 times more current to be reasonably bright.
Basically it's being used as a voltage reference for the power management circuit. If you change the LED it may change what voltage the O2 shuts down at, or worst case, prevent it from even turning on when running on battery power. If you want to use a different LED that's covered under Circuit Board Construction and Enclosure Options. Also, it's a high-efficiency type to run on very low current (only 0.5 mA) to maximize battery life. Most LEDs need at least 10 times more current to be reasonably bright.
That's it. The name "NwAvGuy" (and probably "RocketScientist" too, but I've never tried it) has gone basically gone into the memory hole over there. It was a fight just to be allowed to mention the O2 without reference to who designed it.
I've never even read any of the Harry Potter books or seen any of the movies, but that meme seems to have spread pretty far on its own. I figured if I got it with out ever reading or seeing the books/movies myself it must be pretty widespread, but I guess not widespread enough.
Sorry if that confused anybody. Unfortunately I probably can't clarify that any further in the review without breaking a rule or two...
There are at least two users who have ordered front panels and should have them by this weekend or Monday. Hopefully they'll report if everything thing lines up, fits, etc. If so, I'll revise the blog link and also provide a file with basic lettering.
A very popular classic headphone are the AKG K240's, these are 600 ohm 94 db mW according to the box. In actuallity to listen to high dynamic range material they need a solid low distortion 7V's across the driver. With this O2 amp being solid state I don't think anyone would want to be anywhere past the "knee" in the distortion curve where the distorion increase go vertical by a factor in the thousands with a tiny movement of the volume knob.
Have you considered a desktop version with higher rails such that the "knee" can be pushed farther toward the 10V range for typical studio monitors like the 600 ohm AKG's ?.
I like your design philosophy except using the 1% THD power rating, you don't want to be any where near this straight shot from less than .01 THD to 1% THD, this area is highly non-linear and can't be recommended IMHO. I appreciate the honest plot, but should be clear with folks that the real max power is before the knee not the "industry standard 1% THD" which is a big reason folks don't like SS high NFB amps, simply because the manufacturer over rates their power.
Have you considered a desktop version with higher rails such that the "knee" can be pushed farther toward the 10V range for typical studio monitors like the 600 ohm AKG's ?.
I like your design philosophy except using the 1% THD power rating, you don't want to be any where near this straight shot from less than .01 THD to 1% THD, this area is highly non-linear and can't be recommended IMHO. I appreciate the honest plot, but should be clear with folks that the real max power is before the knee not the "industry standard 1% THD" which is a big reason folks don't like SS high NFB amps, simply because the manufacturer over rates their power.
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It has been suggested that a desktop version use a LM317/337 based supply, which would give adjustable voltages (up to the opamps' rated maximum of +/-18 V) that would be quieter to boot. Maximum output would increase to about 11 Vrms, giving some 3 dB more headroom. That should do, though it doesn't reach the impressive ~20 Vrms for Lake People / Violectric amps or even 32 Vrms for the SPL Phonitor / Auditor (all much fancier concepts, of course).
In fact most any self-respecting hi-fi (speaker) power amp is specified at the "knee". 1% THD is industry standard for portable devices.
They said they are interested in helping us. Basically I need a FPE file. I’m going to work on creating one while heading in to town today, and will post the image to see how people like it. I'll also send a file to them, for pricing.
All of the panels basically would have to be ordered at the same time, and they would likely help us with that.
All of the panels basically would have to be ordered at the same time, and they would likely help us with that.