[HeadphoneAddict]

Quote:

Originally Posted by richbass /img/forum/go_quote.gif which has better headphone amp ? D10 or D4 ?

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif That's not a fair question, because we don't know know how important battery life and ease of USB charging is to you. Based on battery life of over 24 hours and USB charging, and using it portable most often with portable phones, the D10 makes more sense. It sounds very similar to my RSA Predator amp, but with a better DAC. Later, when you can afford to swap opamps you can make the D10 sound close to the D4 and P-51 Mustang; but you can't make it as powerful as the D4 for when you move up to some harder to drive full size phones (HE-5, HD600 or HD800). The D10 USB DAC is extremely close to the detail and spaciousness of the D4 via USB, but the D10 via optical on my Mac can be slightly better than D4 if I use 24/96 files. If you want a slightly better stock sound without swapping opamps, don't mind swapping between a pair of rechargeable 9v batteries often, and would like the extra 9v power for full size phones later, then you could go for the D4 which is also 1/2" smaller in length. Plus you can run it 24/7 off USB 5v with no worry about running out of power because you wont be needing the battery. And in 5v mode it will still be about as powerful as the D10 ever was. As a bonus, with a simple OPA1611A class-A biased opamp swap from HiFlight, you can make the D4 sound almost identical to the P-51 Mustang which is one of the best sounding portable amps I have heard. The D10 with opamp swap is close but still a little behind in treble extension and presence vs the D4 with or without opamp swap.

I think the bolded areas make it clear enough for most people.

 

[trentino]

That's about the most thorough answer I could have wished for. Now I must read it a couple of times

Thank you HPA!

 

[trentino]

"Plus you can run it 24/7 off USB 5v with no worry about running out of power because you wont be needing the battery. And in 5v mode it will still be about as powerful as the D10 ever was."

Do you mean the amp here? Can I listen to the Ipod/D4 at home with usb power to the amp?

 

[kunalraiker]

Quote:

Originally Posted by richbass /img/forum/go_quote.gif which has better headphone amp ? D10 or D4 ?

D4.

 

[madwolf]

Initial Solution, quick remedy, (Have not spend much time thinking of the best solution). I decided the quickest solution to the problem is to reduce the gain of the AD8616. It original gain of the AD8616 is 2, by adding a resistor from the output of the 8616 to the negative input we could adjust the gain.
The original resistor across is 2.2K ohm.

The Gain resistors are located on the top side of the board, and to solder on that you need to remove the Big Nichicon HZ cap (On my case it is Rubycon ZL) to troublesome, to fix this way.

So instead of changing the resistor, I found a compensation capacitor beside the AD8616 which is connected in parallel to the feedback resistor. By adding a 2.2K ohm across this I reduce the gain to about 1.5. From the Picture the 2.2K resistor is sitting on top of the capacitor. label C26 and C28.

You could also solder the resistor directly on PIN 6,7 and PIN 1,2 on the AD8616. (If I do that I would be tempted to change the AD8616! )

I so happened to have a 2.2K 1% SMD 0805 resistor at home. How lucky.
So after adding the resistor I test it again and the Clipping would not occur.
Now I could feed signal at 100% resolution to the D4 instead of just 80%

It should be placebo, on initial testing I could hear more details from the DAC now. Sweet. Well in theory it is 100% now instead of 80%, so might not be placebo.

Quote:

Originally Posted by qusp /img/forum/go_quote.gif very cool madwolf, the crowd is easily impressed though as they are not from the dark side I feel your pain on finding this area after thinking you were done though. what I find most impressive is that you were able to take a photograph with one hand while using the probe with the other

The power is definitely stronger on the dark side.

 

[HeadphoneAddict]

Quote:

Originally Posted by trentino /img/forum/go_quote.gif "Plus you can run it 24/7 off USB 5v with no worry about running out of power because you wont be needing the battery. And in 5v mode it will still be about as powerful as the D10 ever was." Do you mean the amp here? Can I listen to the Ipod/D4 at home with usb power to the amp?

No, USB uses DAC, for iPod it's been said over and over you need the 9v battery. Sorry for the confusion.

 

[LionPlushie]

Quote:

Originally Posted by madwolf /img/forum/go_quote.gif Initial Solution, quick remedy, (Have not spend much time thinking of the best solution). I decided the quickest solution to the problem is to reduce the gain of the AD8616. It original gain of the AD8616 is 2, by adding a resistor from the output of the 8616 to the negative input we could adjust the gain. The original resistor across is 2.2K ohm. The Gain resistors are located on the top side of the board, and to solder on that you need to remove the Big Nichicon HZ cap (On my case it is Rubycon ZL) to troublesome, to fix this way. So instead of changing the resistor, I found a compensation capacitor beside the AD8616 which is connected in parallel to the feedback resistor. By adding a 2.2K ohm across this I reduce the gain to about 1.5. From the Picture the 2.2K resistor is sitting on top of the capacitor. label C26 and C28. You could also solder the resistor directly on PIN 6,7 and PIN 1,2 on the AD8616. (If I do that I would be tempted to change the AD8616! ) I so happened to have a 2.2K 1% SMD 0805 resistor at home. How lucky. So after adding the resistor I test it again and the Clipping would not occur. Now I could feed signal at 100% resolution to the D4 instead of just 80% It should be placebo, on initial testing I could hear more details from the DAC now. Sweet. Well in theory it is 100% now instead of 80%, so might not be placebo.

What do you mean by clipping? Sorry for not following the thread.

 

[qusp]

it seems the gain on the AD8616 (buffer with gain I imagine) is set too high, so the signal from the dac is clipping slightly no matter what opamps are used (an oversight by ibasso I must say) I realy cant believe that 86156 lasted through this mod madwolf

surely it is big danger now

 

[madwolf]

Yes possible candidate I have at home include AD8656, OPA2365, OPA2211, OPA1612, TLE2142 waiting to take over duty anytime. OPA1642 looks good here as well.

But I think I will let the Ad8616 stay it has been a good boy here. Not many good choices below 5V.

 

[qussl3]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif No, USB uses DAC, for iPod it's been said over and over you need the 9v battery. Sorry for the confusion.

I've been able to run the amp section of usb 5v power though.

ie ipod via LOD -> D4 amp (no batt, powered by usb through wall wart or computer) -> iems/headphones

I used the usb cable included with the D4, plugged into the computer or the included iphone wall charger, both can power the D4 amp section while using a DAP as source.

No idea whether this is a new revision but I bought my D4 on 17/01/2010.

 

[HeadphoneAddict]

Quote:

Originally Posted by qussl3 /img/forum/go_quote.gif I've been able to run the amp section of usb 5v power though. ie ipod via LOD -> D4 amp (no batt, powered by usb through wall wart or computer) -> iems/headphones I used the usb cable included with the D4, plugged into the computer or the included iphone wall charger, both can power the D4 amp section while using a DAP as source. No idea whether this is a new revision but I bought my D4 on 17/01/2010.

I don't know why you can do that.

What happens if you hook up the aux in/out to an amp since the D4 should automatically switch that jack to being the DAC line out when you are plugged into USB?

 

[qussl3]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif I don't know why you can do that. What happens if you hook up the aux in/out to an amp since the D4 should automatically switch that jack to being the DAC line out when you are plugged into USB?

I don't have another amp to try out what you suggest unfortunately.

Yes, I was very surprised when i tried running off usb power while using the iphone or ipod as a source and it worked.

Perhaps its a new revision?

To clarify further I can plug in the both usb and iphone via LOD to the aux in/out into the D4 simultaneously, and switch between the iphone or computer as a source.

The above works both with and without the battery installed.

Its not seamless but switching between either source is trivial, ie reloading itunes or disabling/renabling the usb audio whichever is more convenient.

Is there a way for me to check whether this is a new revision?

EDIT: Just fiddled with it more, while the iphone/ipod..etc is plugged into the D4 via the aux in/out volume, using the computer as source, volume is much lower. This is verified by unplugging the ipod/iphone from the D4 while playing music from the computer and hearing a clear boost in volume.

 

[HeadphoneAddict]

Quote:

Originally Posted by qussl3 /img/forum/go_quote.gif I don't have another amp to try out what you suggest unfortunately. Yes, I was very surprised when i tried running off usb power while using the iphone or ipod as a source and it worked. Perhaps its a new revision? To clarify further I can plug in the both usb and iphone via LOD to the aux in/out into the D4 simultaneously, and switch between the iphone or computer as a source. The above works both with and without the battery installed. Its not seamless but switching between either source is trivial, ie reloading itunes or disabling/renabling the usb audio whichever is more convenient. Is there a way for me to check whether this is a new revision? EDIT: Just fiddled with it more, while the iphone/ipod..etc is plugged into the D4 via the aux in/out volume, using the computer as source, volume is much lower. This is verified by unplugging the ipod/iphone from the D4 while playing music from the computer and hearing a clear boost in volume.

Hmm, so the D4 is seeing the LOD as an extra load on the output or something and reducing the volume. The thing is, anytime you are listening to the computer via USB and plug a 3.5mm cable into the Aux in/out jack, it should turn off the headphone jack and make the Aux in/out jack into a line out. That's why I want you to confirm that sound is coming out of the jack.

Can you plug in a second pair of headphones to that aux in/out jack, since you don't have a spare amp to connect? Then if sound comes out of the aux jack and not the headphone jack, at least you know the DAC line out is working, because for sure it should NOT be acting as an input.

 

[qussl3]

Quote:

Originally Posted by HeadphoneAddict /img/forum/go_quote.gif Hmm, so the D4 is seeing the LOD as an extra load on the output or something and reducing the volume. The thing is, anytime you are listening to the computer via USB and plug a 3.5mm cable into the Aux in/out jack, it should turn off the headphone jack and make the Aux in/out jack into a line out. That's why I want you to confirm that sound is coming out of the jack. Can you plug in a second pair of headphones to that aux in/out jack, since you don't have a spare amp to connect? Then if sound comes out of the aux jack and not the headphone jack, at least you know the DAC line out is working, because for sure it should NOT be acting as an input.

Perhaps my unit is defective, but if i get to use the usb power with my iphone, i'm not complaining

Now i'm wondering if the already fantastic sound is being compromised in any way lol

EDIT: With 2 headphones plugged in, the volume from the headphone jack is lower, the aux in/out seems unaffected regardless of whether there is another earphone on the headphone jack.

<strike>Also I notice that when using one pair of cans, when switching between the 2 jacks, the output from the headphone jack is inferior in both quality and volume when compared to the output from the aux in/out. This is with the usb plugged in and using the computer as source.

Is this normal? My limited understanding was that with the usb plugged in the aux in/out uses only the dac not the amp and the headphone jack outputs an amped signal from the dac, my above experience seems to suggest the reverse.

Completely confused lol</strike>

EDIT 2: The gain switch and volume works only with the headphone jack not the aux in/out.

Personally I dont find any of this to be problem, just a happy coincidence, so thank you for helping me figure out what's going on, but if its becoming bothersome please just ignore me

Please ignore the first edit thanks.

 

[qusp]

Quote:

Originally Posted by madwolf /img/forum/go_quote.gif Yes possible candidate I have at home include AD8656, OPA2365, OPA2211, OPA1612, TLE2142 waiting to take over duty anytime. OPA1642 looks good here as well. But I think I will let the Ad8616 stay it has been a good boy here. Not many good choices below 5V.

yep, they would be my choices too, OPA1612 or OPA2211 at the top. i've been meaning to try out 2365 as buffer s it does seem like a good choice and LMAO it seems all the forum opamp tweakers have already spotted OPA1642 and either have them on the way like I do or have just received them and about to try

we are sick I tell you...SICK I just couldnt help myself, I dont need it as I have plenty of excellent buffers, but while ordering some regu;lators for my dac I spotted the datasheet and found myself compelled to order them sight unseen

do you have them yet or have you just got your eye on them?