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iBasso D42 "Mamba" with dual dacs! !! Hey Hey! Improved Starting on Page 76 . - Page 45

post #661 of 1153
Thread Starter 
Looks like fun. Also would seem to have plenty of power.
post #662 of 1153
Quote:
Originally Posted by Rain100 View Post
My amp isn't clipping, clipping would be in the dac (I think?). Anyways, when I turn the 9v on with the stock buffers, it works for about 20-30 seconds, then starts going to nothing, then full volume and back about once per second.

Putting in the bypass buffers fixed this, but I like the sound of the buffers better.
I can confirm that clipping is in D4's DAC, not amp. Also, this only happens in some recording. As suggested by previous poster (sorry, I'm too lazy to go back to check who posted it, but, thanks for the solution, albeit, not perfect solution), if I lower the volume in iTune, the clipping goes away, even if I crank up amp to a higher volume.
post #663 of 1153
Quote:
Originally Posted by pyp007 View Post
I can confirm that clipping is in D4's DAC, not amp. Also, this only happens in some recording. As suggested by previous poster (sorry, I'm too lazy to go back to check who posted it, but, thanks for the solution, albeit, not perfect solution), if I lower the volume in iTune, the clipping goes away, even if I crank up amp to a higher volume.
the clipping,is it happening often.

I noticed some distortion yesterday,when the concert presentation I was listening went to a very high vocal pitch,the Grado's distorted a little.
post #664 of 1153
I have added the SMD 2.2k resistors to my D4 as per Madwolfs photos, and find that it noticeably improved the overall detail of the DAC output. I suspect that the lower input voltage is in a more linear portion of the operating envelope of the AD8616 opamp.

Quote:
Originally Posted by kunalraiker View Post
the clipping,is it happening often.

I noticed some distortion yesterday,when the concert presentation I was listening went to a very high vocal pitch,the Grado's distorted a little.
post #665 of 1153
Currently, I only have a few songs that have clipping while using D4 DAC/amp. For example, Eva Cassidy-Live At Blues Alley-Autumn Leaves (Apple Lossless) from 4:10-4:18 when her vocal is loud. I just did a test between my headroom total bithead (my very first DAC/amp) and D4 with Shure SE530s. Total bithead does not have clipping at 100% iTune volume even if I adjusted the amp to a higher volume than D4. During passage from 4:10-4:18, the clipping is very obvious with D4 even at a low amp volume but with 100% iTune volume.

Edited:
Just did another test. Use D4 DAC, with 100% iTune volume, to feed total bithead as amp, the clipping is even worse than D4 DAC/amp. Again, if I reduce iTune volume, clipping is gone.
post #666 of 1153
Seems it will take a while before D4 is back in stock:

"Dear Sir,
Thank you for your email again.
The order period of the component from the manufacturer is more than a month.
We are trying to obtain the components from retail market now, but still do not find any availability.
Sincerely
iBasso Audio"
post #667 of 1153
Thread Starter 
Quote:
Originally Posted by madwolf View Post
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.

The power is definitely stronger on the dark side.
Ok, I am going to go ahead and do this. Ron likes the results, you like the results so why not.
post #668 of 1153
Hello everyone,
I got my ie8 today and so I can now try my d4 and d10 both with topkit. I must say so far I prefer the d10 with the ie8. The d4 sounds a bit warmer and more laidback imho but since the ie8 already has those two characteristics its a bit much. AlsoI have to be VERY careful witht he d4s volume or there will be lcipping on some tracks.

I must say the d4 does seem to have a bit more space around the notes, so a bit better imaging but the ie8 already is a soundstage king so I do not mind missing this with the d10.
The d10 does seem to hiss a bit more but it goes away with low gain.
Greetings, Anouk,
post #669 of 1153
So what would be the highest impedance phones this little amp could drive properly ?
post #670 of 1153
Thread Starter 
Ok, so I broke the smd cap. What value is it, .1 or .01? I should have just gone from above or directly to the pins. Oh well.

I guess I will email iBasso and find the value. Since it must be a blocking cap I don't know what they used as those vary by application.
post #671 of 1153
must the resistor be soldered on top of the smd cap? can't the resistor be the non-smd kind?
post #672 of 1153
Thread Starter 
Quote:
Originally Posted by LionPlushie View Post
must the resistor be soldered on top of the smd cap? can't the resistor be the non-smd kind?
It could be but there is little room between the bottom of the board and the case. A smd would work best but I was using a leaded resistor but messed up as I was resoldering the cap back to the board after desoldering it, which I did not intend to do.
post #673 of 1153
I am very sorry to hear that you broke the cap,
But since it is connected between the output and negative input it should be a compensation cap likely 47pF only. If it act as a filter at max it is 1nF.

Adding a .1uF or a 0.01uF with make this to a low pass filter. Not advisable.

If I have a D4 I could desolder and measure with a capacitance meter.
If iBasso didn't give you an answer let me know, I see if I could borrow a D4.
and measure.

Quote:
Originally Posted by jamato8 View Post
Ok, so I broke the smd cap. What value is it, .1 or .01? I should have just gone from above or directly to the pins. Oh well.

I guess I will email iBasso and find the value. Since it must be a blocking cap I don't know what they used as those vary by application.
post #674 of 1153
madwolf the D4 already sent to the owner? D: didn't get the chance to try.

why not you go and get a D4? lol
post #675 of 1153
Thread Starter 
I am sure iBasso will get back. Thanks madwolf. I wish I had my cap tester with me. I have a large one that can form caps, measure esr and do a few other things. A rather expensive piece of equipment but in storage 1000 miles away. I have a nice little hand help cap checker that would tell me the value but again, in storage. :^)
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