[StanD]

  Oops my bad
I meant specifically:
 
Are BT headsets with 3.5mm Headphone-Out essentially wireless amps or wireless DAC/amps? 
 
If they are wireless DAC/amps does it mean that the phone/transmitter is just a transport and doesnt matter if they sound good or bad originally as long as the BT connection is good like aptX and the BT receivers have good hardware?
 
Examples of the BT headsets:

Yes they are wireless DAC/Amps. Some have playback controls, nice and convenient. Some have microphones you you can answer calls from your phone.
I wouldn't quite call these examples you gave as BT Headsets, they are not one piece integrated products.

 

[fnkcow]

  Yes they are wireless DAC/Amps. Some have playback controls, nice and convenient. Some have microphones you you can answer calls from your phone.
I wouldn't quite call these examples you gave as BT Headsets, they are not one piece integrated products.

 
Yes I agree they shouldn't be called as BT headsets since they are not the one-piece like gaming headsets, that's why I was confused and called them as BT receivers in my initial post
 
Strangely they are named as BT Headsets by their own companies:
http://www.samsung.com/hk_en/consumer/mobile/mobile-phones/accessories/BHS3000UMECWDT?subsubtype=bluetooth-headset
http://www.aptx.com/product/lg-bts1-bluetoothr-stereo-headset
Maybe it's because they came with their own earphones along with the receiver with mic

 

[cityle]

   
I only have tried one receiver for wired headphones with not detachable cable, the Avantree Clipper.
The quality of sound of the adapter is excellent, I am trying it now with my Sennheiser PX200ii and the adapter make them sound better than wired (wired they have too much bass and low mids, the adapter balances them).
It is nice, little, and with a clip.

Do you have a hiss sound with them when their is no music? Are we doom to have this white noise with any BT receiver?

 

[Giogio]

  Do you have a hiss sound with them when their is no music? Are we doom to have this white noise with any BT receiver?

Zero Hiss. Not even the lesser. It is really an excellent product. I plug the headphones into the receiver, unplug them, and there is no difference. At first I thought it was broken
I play music, pause it, and zero hiss (most bt headphones turn the amp off after a few seconds without sound, and if there was a little hiss you can notice the difference).

 

[cityle]

  Zero Hiss. Not even the lesser. It is really an excellent product. I plug the headphones into the receiver, unplug them, and there is no difference. At first I thought it was broken
I play music, pause it, and zero hiss (most bt headphones turn the amp off after a few seconds without sound, and if there was a little hiss you can notice the difference).

Lucky you. There was definitely a hiss on my unit when I stop the song which last for 2-3 sec (and seemed to have also a faint white noise while playing songs). It annoyed me enough that I resend it to amazon for a refund and grab instead a AT-PHA50BT (it was at 89$ CDN so definitevely a good price for them)

 

[StanD]

 
Lucky you. There was definitely a hiss on my unit when I stop the song which last for 2-3 sec (and seemed to have also a faint white noise while playing songs). It annoyed me enough that I resend it to amazon for a refund and grab instead a AT-PHA50BT (it was at 89$ CDN so definitevely a good price for them)

That AT-PHA50BT outputs only 50 mW per channel at 16 Ohms so don't expect it to be able to drive many headphones. I'd keep it to sensitive IEMs. I checked the Japanese website, I can't understand Japanese but did see an apt-x logo.

 

[cityle]

  That AT-PHA50BT outputs only 50 mW per channel at 16 Ohms so don't expect it to be able to drive many headphones. I'd keep it to sensitive IEMs. I checked the Japanese website, I can't understand Japanese but did see an apt-x logo.

I will use it with my K553, so it will not have so much trouble to run these cans.

 

[Giogio]

Lucky you. There was definitely a hiss on my unit when I stop the song which last for 2-3 sec (and seemed to have also a faint white noise while playing songs).

are you talking of the Avantree clipper?

 

[cityle]

Yup, I'm speaking of the Avantree Clipper.

 

[Giogio]

Yup, I'm speaking of the Avantree Clipper.

You may have got a defective unit, or it may depends on what StanD said, maybe depending on which headphones is being used the Apm behaves differently, maybe it "overcharges"???
@StanD, can you explain that better? How do the mW and how the ohm values influence the performance? Can you make examples?

 

[StanD]

 
You may have got a defective unit, or it may depends on what StanD said, maybe depending on which headphones is being used the Apm behaves differently, maybe it "overcharges"???
@StanD, can you explain that better? How do the mW and how the ohm values influence the performance? Can you make examples?

The Amp's mW and headphone's sensitivty determines how loud your headphones can get, consider that against one's average listening volume one can deterimine how much headroom they have. The headhone or IEM's sensitivity determines how the ambient noise level of your amp plays into what you can hear. The mroe sensitive, the more apparent the background noise of the amp becomes. So for 50mW to play loudly one needs sensitive headphones/IEMs. but that makes the amp's noise more apparent.

 

[Giogio]

  The Amp's mW and headphone's sensitivty determines how loud your headphones can get, consider that against one's average listening volume one can deterimine how much headroom they have. The headhone or IEM's sensitivity determines how the ambient noise level of your amp plays into what you can hear. The mroe sensitive, the more apparent the background noise of the amp becomes. So for 50mW to play loudly one needs sensitive headphones/IEMs. but that makes the amp's noise more apparent.

So the best would be powerful amp and insensitive headphones?
What is insensitive, a bigger or a lower value of ohm? As far as I know, it should be a bigger. I had the AKG K240 Monitor (mk1) 600ohm. The most cold insensitive headphones ever made, probably.

 

[StanD]

 
So the best would be powerful amp and insensitive headphones?
What is insensitive, a bigger or a lower value of ohm? As far as I know, it should be a bigger. I had the AKG K240 Monitor (mk1) 600ohm. The most cold insensitive headphones ever made, probably.

Sensitivity is not impedance.It is either given in dbSPL/mW or dbSPL at 1V RMS. An amp doesn't have to be powerful, just enough for the headphones you like and should have low noise. IMO for most mainstream headphones 50 mW/channel isn't going to do a great job.
For example: My HE-500's are not sensitive and do well at 1W RMS, they are 38 Ohms and their sensitivity 89  dbSPL at 1 mW which reaches 119 dbSPL at 1W RMS, which is good headroom.
Higher impedance headphones require a greater voltage swing to reach power levels, Ohms law. So a 300 Ohm or 600 Ohms headphone has additional demands that many low powered small portable amps have great difficulty with.
Another example: My HD600's are 97 dBSPL at 1V RMS, they are 300 Ohms so their sensitivity is 102.2 dbSPL at 1V RMS. It takes 158.5 mW RMS to reach the same 119 dBSPL. Although it requires less power it requires about 6.9 V RMS to reach 158.5mW, yet the HE-500 reaches 1W with only 6.2 V RMS. That's because of the impedance difference and Ohms law. Amps amplify voltage and supply current to meet that voltage, if it cannot do either it clips (distorts).
A SS amp that can only deliver 50 mW at low impedances is very unlikely to do well at higher impedances.

 

[Giogio]

I've always read that low impedance means you can use it with any device without need of an extra amp.
So, being newbie with these things i cannot really follow you.
If it is the sensitivity to determine how well they sound with a less powerful device, then what's the impedance for?
What's to be considered a good sensitivity for use with bt?

 

[StanD]

I've always read that low impedance means you can use it with any device without need of an extra amp.
So, being newbie with these things i cannot really follow you.
If it is the sensitivity to determine how well they sound with a less powerful device, then what's the impedance for?
What's to be considered a good sensitivity for use with bt?

Sensitivity determines how much voltage or power is required to drive the headphones to a particular loudness. Impedance determines the amount of current they will draw. A pure bluetooth headphone has everything built in, done correctly you are good to go, otherwise you have a turkey. When using a bluetooth adapter with an external headphone then all of this technical mumbo jumbo is important because the adapter must be able to drive your headphones and do so properly.