The Objective2 (O2) Headphone Amp DIY Project

Rocketscientist,

I've been listening this O2 for a week how and I love it !

Now I want to upgrade the component like the C3 and C14 to blackgate c series, does this improve the SQ ? Any sugesstion?

Or should I ask you this, which parts is the most critical to upgrade to?

I think this can improve more with more expensive parts ?

Cal
 
@calico88 the O2 already is completely transparent. It contributes no sound of it own to the music. How can you improve on that with "upgrades"? Changing parts in the O2 is more likely to make it perform worse (especially changing the op amps).

@desasiuk, it's pin one of the input jack as nezbleu suggested. You could also use the ground pin of P1 if you wanted.
 
The K1000 is really designed to be driven by a speaker output, not a headphone output. I don't recommend the O2 for the K1000. Even on AC power, 7 Vrms just isn't enough unless you like to listen to compressed pop music at modest levels. Wide dynamic range music requires peaks of at least 105 dB SPL with 110 dB SPL being a better number. The average SPL will still be below 90 or even 85 dB when peaks are hitting 105 dB with wide dynamic range music. If you haven't seen it, you might want to check out my article on headphone and amp compatibility:

More Power?

I've seen it, and figured out I could still drive them loud enough, but I didn't count with the peaks..., in that case I'll use it only with my Grados and Sennheisers.

Do you think that Sofaspud's way to measure the output voltage of my dac will be good enough ? (I know it won't be precise, but if I'm within 0.2 volts to the real output voltage, it is good enough for me.)

Thank, BTW will be there any article about the balanced operation ?
 
Hi Zsubbo. I'm around, but don't mean to speak for RS. If my idea is workable, I think the limiting factor is the meter. My cheapo multimeter here only has a lower AC range of 200 volts. I'd never get millivolt resolution with something like that. My Fluke 79 on the other hand has 40, 4, and 0.4 volt lower AC ranges. Much depends on the meter you'll be using.
 
I'm afraid you gonna say that.

My woody O2 wip.
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An externally hosted image should be here but it was not working when we last tested it.

Beautiful case work... :xmasman:


RocketScientist, my O2 also exhibited the cyclic on/off nature on low battery shut down with a pair of Uniross Ultra batteries, but worked fine with standard Energizer ones. Though it's a null issue as I'm now running it on AC only...

You've done a fantastic job with the O2 and I'm looking forward to the ODA.

Paul
 
"Should be good enough" indeed. That looks like a great DMM. You won't have any problems, and probably aren't restricted to the 50-60Hz mains frequencies (my 79 is good for 45Hz to 1kHz per the spec sheet. And yours is likely a better DMM).

I've tested it, downloaded a free tone generator, that was the easiest way.

So, Its around with sinus waves
50Hz 2,109V
100Hz 2,123V
500Hz 2,132V
1kHz 2,133V
5kHz 2,126V
10kHz 2,115V
15kHz 2,098V
20kHz 2,073V

So, I think I should count with 2,1V as for output voltage from my dac.
 
Excellent! For the benefit of others... lower budget multimeters are designed to measure the AC line frequency, so you can use a 50 or 60 hertz tone and accomplish much the same thing as shown above. My cheapo 200V range meter might have given a 2 volt reading, and the error would have increased the further I got from the 60Hz frequency.
 
@Zsubbo, Sofaspud's method is in my article and is valid as long as it's done correctly (with a 0 dBFS proper 60 hz signal). Your DAC seems to be following the Redbook standard as most home gear does. Sofaspud is also correct about meter error.

@Calico88, your casework looks great!

@Balanced Audio, I do plan a balanced article probably in the first few months of the new year. While there are some minor crosstalk benefits to a 4 wire headphone connection and balanced/bridged amplifiers at least on paper have one or two other possible benefits, their disadvantages usually outweigh these small advantages. All other things being equal, a balanced stage generally has more distortion and more noise than its unbalanced twin. It's also important to remember headphone drivers cannot tell if they are driven by a balanced signal or if one side is grounded--nor do they inherently perform any differently.

The main benefit to balanced audio is to avoid cable noise pick up in long cable runs. This makes it essential for live sound applications where audio cables are run long distances along with noisy stage lighting wiring, etc. It's also useful in recording studios for the long runs they typically have. For home headphone audio, however, cable noise is rarely an issue even with single-ended unbalanced cables. So balanced headphone audio is usually a big waste of money and often a step backwards in performance.
 
as ive said before in here, a benefit that is often forgotten about with portable balanced audio is complete immunity to any kind of cellphone or network chirps from your own or others nearby communications gear. this benefit is not to be understated with the sheer number of mobile devices on the average bus or train these days