O2 Build Complete: Let the objective, subjective listening tests commence! - Page 3  

Also, on the Slayer front, this was from an Ipod and the song was in ALAC, I'm going to try this again tonight with a flac file on the computer through my dac, as well as vinyl, and see if I get similar results.

Quote:

Originally Posted by samsquanch 

ok, did the readings, these readings were done twice, once with a source connected, once without.

 

With and without the wall wart, power on is 3mV on each channel

 

Now the ugly bits.

 

Power off, with wall wart, both channels:

When turned off: spikes at 200mV

Normalizes at: 130mV

 

Power off, without wall wart, both channels:

When turned off: spikes at 130mV, then quickly drops to 50mV and begins to slowly drop

Normalizes at: 25mV

 

clicks at turn on, muffled thump at turn off.

Sounds like the MOSFETS are dead to the uninitiated.
 

The mosfets appear to be just fine, I'm getting around 3 mega ohms across the drain and source pins on each.

Quote:

Originally Posted by samsquanch 

Also, on the Slayer front, this was from an Ipod and the song was in ALAC, I'm going to try this again tonight with a flac file on the computer through my dac, as well as vinyl, and see if I get similar results.

Ok, so I'm home, sitting here A/Bing between the O2 and the Beta22, each being fed by a laptop into a Cambridge Audio DacMagic, with Angel Of Death going the whole time.  Verdict, the Beta22 is much clearer, I can distinctly hear each guitar, sounds more like I'm listening to instruments, rather than a recording.  The O2 has a much narrower sound stage, less separation between instruments, less channel separation, and the high notes hit in the guitar solos sounded brittle.

I choose Angel of Death a while ago as a test song because it's got a lot going on, and can come off sounding like a mess (which is part of the appeal), so if a piece of gear can "clean it up," then I'm pretty happy with it, which is part of why I love my Beta22.  Now, do I hate the O2?  Nope, I'm not head over heals for it either, but I'm going to spend some more time with it, figure out it's strengths and weaknesses and go from there.

//end subjective test of objective amp.

@samsquanch

I can't quite remember but I think I had the same power off lingering offset. I think the power supply rails weren't being drained evenly, causing the offset. It might be because I didn't use batteries for mine, and that it was the very first revision of the power supply which went through a few changes that I was too lazy to do.

B22 is the reference design. It cost 20 ( or 100 if you are crazy) times more than O2.It's impressive  what it could hold against B22.

Vlad.

Quote:

Originally Posted by Vladco 

 

 

 

 

B22 is the reference design. It cost 20 ( or 100 if you are crazy) times more than O2.It's impressive  what it could hold against B22.

Vlad.

I brought it up because in the original thread it was speculated that the O2 would perform better than a B22, so I shared my impressions of both.  I wasn't necessarily trying to rip the O2 apart.

A more realistic comparison would be against a Mini3, but I don't have one, so I can't make the comparison.  But, hopefully someone will.

I can say that compared to a CMOY that I built a while ago, it does perform better.  By leaps and bounds?  Not really, BUT I do like the size and layout enough to make me happy with this as a portable amp, I also like the power supply design.

Quote:

Originally Posted by Vladco 

 

 

 

 

B22 is the reference design. It cost 20 ( or 100 if you are crazy) times more than O2.It's impressive  what it could hold against B22.

Vlad.

Not really. The O2 costs about 100 for a fully complete amp. You could build a complete 2 channel B22 build for 5-600 if you go no frills. A 2 box build with custom panels and some extras is more like 1000 ish. So yes the B22 is significantly more expensive, but only by 5-10 times, certainly not 100. If your B22 costs 10k you are doing something wrong.

Quote:

Originally Posted by samsquanch 

I can say that compared to a CMOY that I built a while ago, it does perform better.  By leaps and bounds?  Not really, BUT I do like the size and layout enough to make me happy with this as a portable amp, I also like the power supply design.

Without wanting to be too harsh on the CMoY, that's hardly a glowing recommendation. I'd be interested to hear how it scales with better sources - that seems to be where some of the more expensive amps pull away from the field.

Quote:

Originally Posted by bcg27 

If your B22 costs 10k you are doing something wrong.

 

Sir, I thank you - I really, really needed the belly laugh you have just provided ! 

Quote:

Originally Posted by samsquanch 

Ok, so I'm home, sitting here A/Bing between the O2 and the Beta22, each being fed by a laptop into a Cambridge Audio DacMagic, with Angel Of Death going the whole time.  Verdict, the Beta22 is much clearer, I can distinctly hear each guitar, sounds more like I'm listening to instruments, rather than a recording.  The O2 has a much narrower sound stage, less separation between instruments, less channel separation, and the high notes hit in the guitar solos sounded brittle.

 

I choose Angel of Death a while ago as a test song because it's got a lot going on, and can come off sounding like a mess (which is part of the appeal), so if a piece of gear can "clean it up," then I'm pretty happy with it, which is part of why I love my Beta22.  Now, do I hate the O2?  Nope, I'm not head over heals for it either, but I'm going to spend some more time with it, figure out it's strengths and weaknesses and go from there.

 

//end subjective test of objective amp.

Now do it blind and volume-matched! 
 

Quote:

Originally Posted by estreeter 

Without wanting to be too harsh on the CMoY, that's hardly a glowing recommendation. I'd be interested to hear how it scales with better sources - that seems to be where some of the more expensive amps pull away from the field.

 

Well, let's be honest, an O2 isn't that much more than three CMOY's crammed in a box.  One not attenuated with gain, followed by a volume pot, followed by two in parallel.

Quote:

Originally Posted by Willakan 

Now do it blind and volume-matched! 

 

 

Only if you come and move the cables for me.  My roommates already think I'm weird enough for putting as much money into this hobby as I do, I don't feel like explaining to them, "Well guys, some people on the internet want to know if I can tell the difference between these two headphone amps, so I'm going to wear a blindfold while you play these tracks while randomly unplugging and plugging in these headphones into these two amps, then writing down whether or not I can guess correctly the amplifier being used!  Sounds like fun right guys?  Guys?  Guys?"

In all fairness, volume matching isn't too difficult with a multimeter. Blind testing is admittedly a bit of a hassle.

Also, I found the source of the DC offset "problem" after measuring the same thing myself. We both made the incredibly stupid mistake of testing without any headphones plugged in - with a set of cheap earbuds my DC offset drops to zero incredibly quickly as the residual charge of the caps depletes. I'm assuming you made the same mistake, otherwise better get debugging.

Quote:

Originally Posted by Willakan 

In all fairness, volume matching isn't too difficult with a multimeter. Blind testing is admittedly a bit of a hassle.

Also, I found the source of the DC offset "problem" after measuring the same thing myself. We both made the incredibly stupid mistake of testing without any headphones plugged in - with a set of cheap earbuds my DC offset drops to zero incredibly quickly as the residual charge of the caps depletes. I'm assuming you made the same mistake, otherwise better get debugging.

good point on the dc offset, when I go back to work tomorrow (sick in bed today), I'll test with headphones plugged in.