Review: JDS Labs O2 (Black edition) + O2/ODAC discussion

[mikeaj]

Load impedance = headphone impedance, yes. In this system, the load is the headphone.
 
The system is the amp (voltage source) connected to the resistor (in the adapter) and headphones, as well as the amp's own output impedance, in series—all that for a single channel. It looks identical on the other channel.
 
As a result, the total load from the amp's perspective is the sum of its own output impedance, any impedance from cables or adapters or whatever else, and the impedance of the headphones. So 232 ohms, around. From the headphone's point of view, it's being driven by an amp with ~200 ohms output impedance (everything else connected in series that's not the headphones itself). The voltage the headphones get is proportional to its impedance compared to the total amount: so 32 / 232 = 13.8% of whatever comes out of the amp.
 
Yes, you could attenuate the input in the way the picture shows, but 200 ohms wouldn't be enough for that. As you said, input impedance is ~10,000 ohms, so to reduce the level in half you'd need 10,000 ohms there. And really, you'd want to reduce it by significantly more than half. There are other configurations you could do too.

 

[adamlr]

Quote:

Load impedance = headphone impedance, yes. In this system, the load is the headphone.
 
The system is the amp (voltage source) connected to the resistor (in the adapter) and headphones, as well as the amp's own output impedance, in series—all that for a single channel. It looks identical on the other channel.
 
As a result, the total load from the amp's perspective is the sum of its own output impedance, any impedance from cables or adapters or whatever else, and the impedance of the headphones. So 232 ohms, around. From the headphone's point of view, it's being driven by an amp with ~200 ohms output impedance (everything else connected in series that's not the headphones itself). The voltage the headphones get is proportional to its impedance compared to the total amount: so 32 / 232 = 13.8% of whatever comes out of the amp.
 
Yes, you could attenuate the input in the way the picture shows, but 200 ohms wouldn't be enough for that. As you said, input impedance is ~10,000 ohms, so to reduce the level in half you'd need 10,000 ohms there. And really, you'd want to reduce it by significantly more than half. There are other configurations you could do too.

thank you very much, your also one of the members who frequently answer my questions, and i do appreciate it very much.
 
you know? this business has got me thinking perhaps aspiring to have the lowest output impedance from an amp is also not as calved in stone as most people make it out to be, but i wont make my final judgment for atleast another week or two. i am starting to see the irony of using an O2 together with this adapter though XD

 

[xnor]

Well you can always increase the output impedance with adapters, but not decrease it without significantly reducing the output level.
So having a low output impedance amp like the O2 is a better starting point. And maybe you'll get a different headphone in the future that you prefer without the adapter.

 

[JakeJack_2008]

From my Toshiba Satellite's manual:
 
 

Using external speakers or headphones
 
To play back sound files through external speakers or headphones:
 
1 Locate the headphone jack on the computer.
 
2 Using any necessary adapters, plug the cable from the
headphones or external speakers into the headphone jack.
 
The headphone jack requires a 16-ohm stereo mini connector.
 

 
Any comments in the context of 

 the Toshiba Satellite laptop?
I think that they assume that one would use a very low impedance IEMs or headphones or external speakers?
 
Before I bought the ODAC and O2 from JDS Labs I was using the Sennheiser HD 595 (50 Ohm) and the sound was pretty good.
(Obviously my Beyerdynamic DT 880 (250 Ohm) sounded very anemic and not good.)
 
The O2 (along with the ODAC) improved the sound of both the HD 595's and above all the DT 880's.
 
 

 

[xnor]

My guess is that the minimal load should be 16 ohms.

 

[adamlr]

Quote:

Well you can always increase the output impedance with adapters, but not decrease it without significantly reducing the output level.
So having a low output impedance amp like the O2 is a better starting point. And maybe you'll get a different headphone in the future that you prefer without the adapter.

like using salt in your cooking, mum always said:"you can always add more, but you cant take it out once youve added it!" =]

 

[xnor]

Exactly.

 

[lukEM22]

random kid,

how is this amp with the HP100's?

 

[ostewart]

I didn't have them together, but I bet they pair really well, I used a C421 with the HP100

 

[Poetic]

Im using the DX100 lineout to the O2 with the HE-500. I know ur suppose to max out the volume on the source first. Then Adjust the volume with the amp. Im trying to figure out the sweet spot for the O2 on the HE-500 I assume putting it on High Gain and setting it past 12:00?
 
 
EDIT: I didn't make any changes to the amp section when I purchased the O2 So assume it's 2.5x when press the button in..
Anyways the HE-500 sound cleaner on low gain and way too messed up on high gain...

 

[mikeaj]

Quote:

Im using the DX100 lineout to the O2 with the HE-500. I know ur suppose to max out the volume on the source first. Then Adjust the volume with the amp. Im trying to figure out the sweet spot for the O2 on the HE-500 I assume putting it on High Gain and setting it past 12:00?
 
 
EDIT: I didn't make any changes to the amp section when I purchased the O2 So assume it's 2.5x when press the button in..
Anyways the HE-500 sound cleaner on low gain and way too messed up on high gain...

 
What's the source?
 
The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
 
On AC power, if source RMS output level is higher than 2.8 V with the 2.5x gain, the amp will clip (no matter what the volume is set to).
On AC power, if source RMS output level is higher than 1.08 V with the 6.5x gain, the amp will clip (no matter what the volume is set to).
 
If it clips, expect to hear some distortion on a lot of music: any time the level gets close to 0 dBFS (max). If you have a standard Redbook ~2 V output source, that means you want to use no higher than 3.5x gain. Many audiophile sources output higher than 2 V, so you really don't want to use the 6.5x. That was set in some fantasy land where a lot of users are using their phones or other portable sources (which often have weaker, quieter outputs) to feed the amp.
 
You'd generally be losing a usually insignificant amount of resolution by turning down the source volume a tad. Just turn it down, reconfigure the amp, or ignore the high gain.

 

[Poetic]

Quote:

 
What's the source?
 
The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
 
On AC power, if source RMS output level is higher than 2.8 V with the 2.5x gain, the amp will clip (no matter what the volume is set to).
On AC power, if source RMS output level is higher than 1.08 V with the 6.5x gain, the amp will clip (no matter what the volume is set to).
 
If it clips, expect to hear some distortion on a lot of music: any time the level gets close to 0 dBFS (max). If you have a standard Redbook ~2 V output source, that means you want to use no higher than 3.5x gain. Many audiophile sources output higher than 2 V, so you really don't want to use the 6.5x. That was set in some fantasy land where a lot of users are using their phones or other portable sources (which often have weaker, quieter outputs) to feed the amp.
 
You'd generally be losing a usually insignificant amount of resolution by turning down the source volume a tad. Just turn it down, reconfigure the amp, or ignore the high gain.

Im using the IBasso DX100 Digital Audio Player, im also using the Lineout of my music player to allow the O2 act as the amp for me. I turned the O2 back on Low gain and maxed out the volume of my source. Also i wasn't maxing out the volume on my music player when i was using the lineout, but i noticed the big improvement in resolution when maxing out the source volume.
 
EDIT But now im just trying to find out the Sweet spot on the O2 for my He-500

 

[JakeJack_2008]

Quote:

 
What's the source?
 
The defaults (from the docs of the designer, and also how most builders including JDSLabs set it up) are 2.5x out / 6.5x pushed in.
 
On AC power, if source RMS output level is higher than 2.8 V with the 2.5x gain, the amp will clip (no matter what the volume is set to).
On AC power, if source RMS output level is higher than 1.08 V with the 6.5x gain, the amp will clip (no matter what the volume is set to).
 
If it clips, expect to hear some distortion on a lot of music: any time the level gets close to 0 dBFS (max). If you have a standard Redbook ~2 V output source, that means you want to use no higher than 3.5x gain. Many audiophile sources output higher than 2 V, so you really don't want to use the 6.5x. That was set in some fantasy land where a lot of users are using their phones or other portable sources (which often have weaker, quieter outputs) to feed the amp.
 
You'd generally be losing a usually insignificant amount of resolution by turning down the source volume a tad. Just turn it down, reconfigure the amp, or ignore the high gain.

 
I am a bit confused.
I am using the JDS Labs ODAC and O2 (which has standard 2.5x &  6.5 X gain) as two seperates.
I always use the 2.5x gain with my Beyerdynamics DT 880 (250 Ohm).
(I never use the 6.5x gain because the sound is muddy and somewhat distorted.)
Well, the ODAC has about 2 V RMS output (and is connected via the USB cable to my laptop).
So the O2  will clip but not  

  too much?  There was a whole discussion about clipping in the ODAC/O2 thread.
It was suggested that to reduce clipping one should reduce the computer's  volume level to, say, 50%.  ...
...or to clip some resistors or capacitators or something else in the O2 amplifier. -
I am not a DIY'er or an engineer, so I don't know that at all.
 
On the other hand the instructions from the JDS Labs say that one should max

 the volume on the computer to 100%...
but max volume causes clipping.

 

[nothing4me]

The one thing I don't like about the O2/ODAC is that the power plug is in the front. I think it would be much tidier in the back.
 
That said, the laser engraving is only for the black edition, correct? Thank you!

 

[jseaber]

Quote:

The one thing I don't like about the O2/ODAC is that the power plug is in the front. I think it would be much tidier in the back.
 
That said, the laser engraving is only for the black edition, correct? Thank you!

 
Laser engraving is free for any aluminum surface (black or clear/silver).