[MrEleventy]

It shouldn't be. If you bought it from JDS, I would contact them about it. Sounds like a loose solder joint.

 

[Mahdi8]

I bought it used. But it's only one month old. Thanks for the tip. Guess I'll try to open it and see if the jack has loose solder

 

[DuckSoup]

This can occur with other amplifiers as well, it's connected to the pot... You can have a look at it, or leave it as it is, it's not a problem at all unless you find that behavior annoying.

And yes, it usually occurs randomly... That's normal as well.

Thanks for the answer. I think I should remove batteries, as my amp is used mainly as desktop, so when I disasemble O2, I will take a look at the pot at the same time.

 

[mikeyb48]

Recently I found 1 small problem with my O2 (it is from Epiphany Acoustics). Sometimes when I turn the volume pot while something is playing I can hear some cracking in right channel, is not extremly loud, but easly audible. Strange thing for me is that it happens only sometimes. Anyone run into simililar issue? What's the most common cause of such behaviour (broken volume pot)?

Amp is ofc feed by ODAC. Any help is appriciated.

Hi,

I am sure I read this same problem somewhere else on a different amp and it was suggested to ease the volume knob back off the spindle a tiny bit to save it rubbing against the housing, no idea if help but worth a try, just be careful and not pull too hard or far.

Mike.

 

[Mahdi8]

Quote:

It shouldn't be. If you bought it from JDS, I would contact them about it. Sounds like a loose solder joint.

Just opened it definitely no movement in the solder joint. But looking more to it looks like the Australian adaptor plug that I've got from JDS has a slightly smaller dimension than the power adaptor hole. Might need to rewire the power adaptor with a new plug. I guess it's saver option than unsoldering the board to replace the adaptor connection

 

[DuckSoup]

Hi,

I am sure I read this same problem somewhere else on a different amp and it was suggested to ease the volume knob back off the spindle a tiny bit to save it rubbing against the housing, no idea if help but worth a try, just be careful and not pull too hard or far.

Mike.

Thanks for the suggestion, I will try it this evening.

 

[mikeyb48]

Quote:

Thanks for the suggestion, I will try it this evening.

Hi,
 
hope it helps, I think I read similar problem on PA2v2 portable amp and it cured it, not sure if same issue as yours but might be worth a try anyway.
 
Mike.

 

[adydula]

I have seen more issues with the plugs that are inserted into the O2....I had one that was 'scratchy', lubricated with Deoxit and its fine now..connectors and the O2 are the weakest link....
 
Alex

 

[DuckSoup]

Hi,

hope it helps, I think I read similar problem on PA2v2 portable amp and it cured it, not sure if same issue as yours but might be worth a try anyway.

Mike.

I tried it few minutes ago and despite adjusting volume like crazy I don't hear any cracks anymore, might be just lucky or it is solved

 

[lcooksl]

Am about to get an O2 and have the possibility to choose which two gain settings to get. Still don't find it being clear to me which will be optimal after reading the numerous posts in here. Thinking 1x gain for the first but dunno what second setting to get.
 
Use case will be either macbook air > EDac (Epiphany Acoustics) > O2 or iPhone5 > LOD via Lightning to 30 pin adapter > O2
 
It will mainly be used with Heir Audio Tzar 350 iems (350ohm) 
 
If someone could clarify what second gain setting is optimal to get considering the use case but with least hit to flexibility on which head phone/iems to use. Was thinking 3x but don't know enough about electronics to make a educated decision. Any help appreciated.

 

[mikeaj]

If you always use ODAC as source and never turn the volume down in software, 1x and 3.5x.  With max ODAC output, 3.5x is the max the O2 can handle anyway.
 
Otherwise, higher values could be appropriate.  Especially if you're focused on IEMs, 1x and 3.5x may still be reasonable choices regardless.

 

[Sat1re]

Why is it shipped 6.5x if 3.5x is the max?

 

[mikeaj]

They just want to follow the "default" values for the O2, for whatever reason.  Those are 2.5x and 6.5x.  It really doesn't make sense for those to be the defaults for the O2 / ODAC combo unless you think that people are using software volume control to reduce the level out of the DAC.
 
Default values for the O2 were decided by some guy who imagined that a lot of people would use the amp with sources like say an iPod or some portable device (some computers and laptops too) that has a lower output level than standard ~2V Redbook level that the ODAC follows.  For those kinds of devices, more than 3.5x can be handled, and furthermore it could be necessary some people with some headphones, to reach a loud enough volume level.
 
The smaller the signal out of the source, the more gain you need to reach an equivalent output level.

 

[RustA]

Quote:

They just want to follow the "default" values for the O2, for whatever reason.  Those are 2.5x and 6.5x.  It really doesn't make sense for those to be the defaults for the O2 / ODAC combo unless you think that people are using software volume control to reduce the level out of the DAC.
 
Default values for the O2 were decided by some guy who imagined that a lot of people would use the amp with sources like say an iPod or some portable device (some computers and laptops too) that has a lower output level than standard ~2V Redbook level that the ODAC follows.  For those kinds of devices, more than 3.5x can be handled, and furthermore it could be necessary some people with some headphones, to reach a loud enough volume level.
 
The smaller the signal out of the source, the more gain you need to reach an equivalent output level.

 
And is it only about an output level (loud enough = 100% quality)? Or does it help to use higher gain with high impedance headphones (regardless of their sensitivity)?

 

[mikeaj]

Quote:

And is it only about an output level (loud enough = 100% quality)?

 
Not really.  All amps have imperfections (e.g. there is nonzero noise, nonzero distortion, for starters), so you never get perfect fidelity.  Also, some people ostensibly prefer a sound with lower fidelity in a certain way and might (confusingly?) define quality in some way that doesn't really relate to fidelity.
 
 

Or does it help to use higher gain with high impedance headphones (regardless of their sensitivity)?

 
Higher gain usually means worse performance, but it really depends on the device you're talking about.  Certainly for the O2 you could demonstrate some worse performance on a test bench.  You're free to try whatever, but by the textbook you shouldn't intentionally set out to use more gain than is necessary.  Usually it shouldn't make too much practical difference other than the difference in volume and the ramifications of that, like having to use a different position on the volume control.  I wouldn't really overthink it.
 
All that is regardless of the impedance of the headphones.  Higher impedance just means you need a higher signal (voltage) level to transfer an equivalent amount of power to the headphones.  Thus you need to boost the level by a higher amount, i.e. higher gain.  There's nothing much there about sound quality or anything special to take into consideration.
 
 
 
The above discussion regarding gain settings was just about avoiding input clipping, which is a different concern than you need to have for many other amps and situations.