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May 1, 2014 at 9:39 PM Post #4,426 of 14,084
  Speaking of the user replaceable battery, how the hell can you guys take the back plate off?  I tried for over 10 mins but I gave up.

 
Wasnt terribly difficult for me 
confused_face.gif

 
May 1, 2014 at 9:44 PM Post #4,428 of 14,084
 
I read in the DX50 manual that you need to press down right in the center of the back cover as you slide it off. Doing that seemed to work for me.

I tried that, hard, but it still won't budge...  Will try again.
 
p.s. my DX90 comes with ZERO documentation...
 
p.p.s. I did it!  But it was freaking hard to the point I almost broke the thing -_-;
 

 
May 1, 2014 at 9:45 PM Post #4,429 of 14,084
Speaking of the user replaceable battery, how the hell can you guys take the back plate off?  I tried for over 10 mins but I gave up.


Hold the DX50 in both hands with the back facing up and with the top toward you. Place both thumbs on the cover, press down and push away from you using thumb pressure.
 
May 1, 2014 at 9:49 PM Post #4,430 of 14,084
 
Just quickly did some calculations using an excel sheet from http://www.apexhifi.com/specs.html
 
Please correct me if my maths/use of specifications are wrong (DT880 600ohm + DX90 on High gain)
 

 
Seems like at maximum power from DX90, we can acheive 107dBSPL on the DT880 600ohm?

 


That is correct if we assumed @ 600Ohm load the DX90 has constant voltage of 2.8V which iBasso rated as maximum output V at 32 Ohm load.

Still that is the maximum level (theoretical) you can get for DT880. If you are used to listening at very low volume level maybe that will be ok but it will definitely not enough for music with high dynamic range like classical or some acoustics. Soft passages might not be audible and pop/rock music might sound anemic.

I have a Beyerdynamic T1 which @ 102 dB/W plays very loud for most of the music I tried. My volume range starts from 240 all the way to 255. I usually listen at a slightly louder than usual volume (at least compared to a few of my friends listening to the same tracks). However, for classical music, it stays at 255. Which for me is just enough.

You can shoot a mail to iBasso just to confirm the max voltage/power DX90 can put out for a 600 Ohm load.
 
May 1, 2014 at 9:49 PM Post #4,431 of 14,084
  Speaking of the user replaceable battery, how the hell can you guys take the back plate off?  I tried for over 10 mins but I gave up.

Mine is real tight also. I took a really thin knife edge and very carefully got it between the body and the back and opened it about 1/8 of an inch. At least you know it won't come off when you don't want it to. :^) The edge could mar the back though so another way is to use some velcro to the back and on another surface and use that to open it by pulling it open towards the end and then lifting it off.  
 
May 1, 2014 at 9:58 PM Post #4,432 of 14,084
Mine is real tight also. I took a really thin knife edge and very carefully got it between the body and the back and opened it about 1/8 of an inch. At least you know it won't come off when you don't want it to. :^) The edge could mar the back though so another way is to use some velcro to the back and on another surface and use that to open it by pulling it open towards the end and then lifting it off.  

 


It's the other way around for me. I got no problem taking the backplate off. I just pressed on the backplate with my thumb firmly but not very hard and it slide off easily wih a firm push. However, when putting it back on, it won't go all the way and stuck at 1/8 inch of a gap. No matter how hard I push with my thumb it won't budge. I had to push it aginst the wall to completely shut it close. I tried it the 2nd time and it's the same. I examine the edges of the plate and compared it to my DX50 but I can't see any noticeable difference.

Maybe it's just too tight by a hair.
 
May 1, 2014 at 10:05 PM Post #4,433 of 14,084
BTW, I think this set of 2300mA batteries, charger, and OTG cable bundle is perfect.
 
http://www.amazon.com/Onite-2300mAh-Battery-Sensitive-Capacitive/dp/B00815EOOO/ref=sr_1_48_m?s=wireless&ie=UTF8&qid=1398996126&sr=1-48&keywords=samsung+galaxy+s3+battery
 

 
May 1, 2014 at 10:24 PM Post #4,434 of 14,084
 
   
Just quickly did some calculations using an excel sheet from http://www.apexhifi.com/specs.html
 
Please correct me if my maths/use of specifications are wrong (DT880 600ohm + DX90 on High gain)
 

 
Seems like at maximum power from DX90, we can acheive 107dBSPL on the DT880 600ohm?

 


That is correct if we assumed @ 600Ohm load the DX90 has constant voltage of 2.8V which iBasso rated as maximum output V at 32 Ohm load.

Still that is the maximum level (theoretical) you can get for DT880. If you are used to listening at very low volume level maybe that will be ok but it will definitely not enough for music with high dynamic range like classical or some acoustics. Soft passages might not be audible and pop/rock music might sound anemic.

I have a Beyerdynamic T1 which @ 102 dB/W plays very loud for most of the music I tried. My volume range starts from 240 all the way to 255. I usually listen at a slightly louder than usual volume (at least compared to a few of my friends listening to the same tracks). However, for classical music, it stays at 255. Which for me is just enough.

You can shoot a mail to iBasso just to confirm the max voltage/power DX90 can put out for a 600 Ohm load.

It was actually measured that you hit 1%THD at ~2.2Vrms for 32ohm load.  The measured value could be lower than spec'ed max V because it could have it the current limit of the device.  With such a high load, 600ohm probably would not hit the current limit, so it's a possiblity it would get higher voltage(possibly the 2.8Vrms on the specs), and @2.8Vrms, it's only 13mW used, whereas at 32ohms, max power was measured to be 147 mW.  So, that 147mW could be max power draw or limit by the DAP.  So, the current limit is 66.8mA?
 
May 1, 2014 at 10:41 PM Post #4,435 of 14,084
It was actually measured that you hit 1%THD at ~2.2Vrms for 32ohm load.  The measured value could be lower than spec'ed max V because it could have it the current limit of the device.  With such a high load, 600ohm probably would not hit the current limit, so it's a possiblity it would get higher voltage(possibly the 2.8Vrms on the specs), and @2.8Vrms, it's only 13mW used, whereas at 32ohms, max power was measured to be 147 mW.  So, that 147mW could be max power draw or limit by the DAP.  So, the current limit is 66.8mA?

 


Yeah, based on the published measurements, 2.8V on 600-Ohm load is plausible and for DT880, DX90 can supply up to 13mW of power. But still a peak of 107dB is still not enough imo. 110dB - 115dB is my ideal sweet spot for "just enough".
 
May 1, 2014 at 11:06 PM Post #4,436 of 14,084
 
I decided to ask for a full refund since I intended to sell this when I got my unit back from ProStudio Sound and Music. I will report back here as to whether they honor the warranty and refund my full purchase price. They said something about a restocking fee, but they will need to replace my unit with a new one anyways, so it does not seem right to charge me a restocking fee.

Welcome to the world of returning audio equipment. 90+% of all retailers charge a restocking fee to try and eliminate people from using them as a demo test site, that is why they told you they will replace it with a new one or, regardless of the reason for returning the unit  you will be charged a restocking fee usually 15% of the purchase price. Sucks for honest people returning for honest reasons but they do get a lot of people, "Myself included" who would buy a product, decide they did not like it for whatever reason, like sound signature of headphones, and return it.
 
May 1, 2014 at 11:35 PM Post #4,437 of 14,084
  Welcome to the world of returning audio equipment. 90+% of all retailers charge a restocking fee to try and eliminate people from using them as a demo test site, that is why they told you they will replace it with a new one or, regardless of the reason for returning the unit  you will be charged a restocking fee usually 15% of the purchase price. Sucks for honest people returning for honest reasons but they do get a lot of people, "Myself included" who would buy a product, decide they did not like it for whatever reason, like sound signature of headphones, and return it.


Yes, if the screen had not cracked when I put on the screen saver, I would have just sold the DX90 here on headfi. But since I am returning it to them anyways, I decided to ask for the refund. We will see what they do, again given that they will need to replace my unit under the warranty anyways.
 
I would have no problem with a 10-15% fee if I was just returning it due to changing my mind.
 

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