[X-MAN]

OK found it. Fixed it, and you guys were spot on !
The sound improvement is truly enough to make your eyes water.
I'm glad I found this place.

 

[trodas]

Digi-key offer many resistors. 1% 33 Ohm is not a problem, even in the very very small size...

 

[Lokonsky]

Hi Trodas
I'm still courius with your project to cure the -200mV offset.
Well maybe this can fresh your memories,this is what you write in that thread:
use TWO resistors and create a voltage divider on the output of the L7805 chip that feed the required 0.2V to the common ground and you got your 5.2V on the opamps witch might (or might not) cure the -200mV offset.
still waiting for your answer because maybe it's not safe to remove the coupling capacitor

 

[Kuze]

So how are the mods going with the new Creative drivers ?

 

[Lokonsky]

Quote:

Originally Posted by Kuze /img/forum/go_quote.gif So how are the mods going with the new Creative drivers ?

Bad!! I download yesterday and compare with my old YouP-Pax 5.25 driver (I have 2 bootable windows so i can easly spot the diffrence). With the new driver the bass is seem gone (it so deep with youp-pax and i often check my sub if it's on) and boomy. Tested with Lisa Ekdahl on music and "warrior of heaven and earth" on movie, it took 5 minutes to get rid my new driver...

 

[ashy79]

hi.. any chances anyone's keeping close-shot of elite-pro's PCB trace for front opamp?

thx in advance

 

[Apocalypsee]

Quote:

Originally Posted by ashy79 /img/forum/go_quote.gif hi.. any chances anyone's keeping close-shot of elite-pro's PCB trace for front opamp? thx in advance

You can look here. Its not mine, I take it from bichi

 

[trodas]

Lokonsky - Quote:

I'm still courius with your project to cure the -200mV offset.

Too bussy right now - and the offset is not important at all.
Not unless you are crazy, like me, and want to remove even the input coupling caps in your amp...

Quote:

Well maybe this can fresh your memories,this is what you write in that thread: use TWO resistors and create a voltage divider on the output of the L7805 chip that feed the required 0.2V to the common ground and you got your 5.2V on the opamps witch might (or might not) cure the -200mV offset

Yep, that is what I write. I'm not sure, if this is right, or if this can work, tough. It was just an idea. I gotta ask, if one can manipulate with the offset this way.
Another question is, if the offset is not comming from the DAC itself...

Quote:

still waiting for your answer because maybe it's not safe to remove the coupling capacitor

Maybe it is not safe to live on Earth

Got my point?
Nothing is safe, my friend. However the X-Fi did not have by default ANY cap between the opamps output and the jacks. So...

And the main point is, that the offset is neutralized on the amplifier input coupling caps. So nothing to worry about.

Unless you have custom amp with stripped input coupling caps, then you have absolutely nothing to worry about. It can only make your sound nicer and more detailed.

PS. even in some cases the input caps in the amplifier aren't need to be there, depending on the amp input opamps and their gain versus voltage. If the gain is low and voltages high, the DC offset is just amplified like the rest of the signal and that it is. No clipping happen then. But it is wise to let one last couplig caps to have in the input of power amplifier... if you did not want end up with like 16V DC offset on the speakers

 

[Lokonsky]

Thanks for your explanation trodas

dumb question: how i measured this dc offset? i see people write -200mV and 10 mV what that is mean? Yep, maybe it's safe for my amp but MAYBE not for my headphone...sorry but i very-very new in this

Other thing, is it good to use solid capacitor in C16,C46 and C72 (470uF/6.3v)?
Thanks before

 

[ashy79]

Quote:

Originally Posted by Apocalypsee /img/forum/go_quote.gif You can look here. Its not mine, I take it from bichi

thanks guys! it's been really helpful

 

[trodas]

X-Fi output DC offset measuring with original UK X-Fi, no heatsink and L+R channel NJM4556 opamp, rest NJM4558 opamps
---------------------------------------------------------------
L: 29.9mV DC, 9.8mV AC
R: 29.6mV DC, 9.8mV AC
RL: 0mV DC, 9.8mV AC
RR: 0mV DC, 9.8mV AC
CENTER: 0.2mV DC, 9.6mV AC
SW: 0.2mV DC, 9.7mV AC


X-Fi output DC offset measuring with LM4562 opamps
---------------------------------------------------------------
L: -190mV DC, 10mV AC
R: -174mV DC, 10.2mV AC
RL: -210.2mV DC, 10.1mV AC
RR: -204.7mV DC, 10mV AC
CENTER: -209.5mV DC, 10mV AC
SW: -231.9mV DC, 10.2mV AC


X-Fi output DC offset measuring with AD8599 opamps
---------------------------------------------------------------
L: -219mV DC, 9.5mV AC
R: -205mV DC, 9.8mV AC
RL: -209mV DC, 9.7mV AC
RR: -205mV DC, 9.3mV AC
CENTER: -210mV DC, 9.6mV AC
SW: -232mV DC, 9.7mV AC

The 9 - 10mV AC is a classic noise, around 5kHz. What is interesting is the VERY LOW DC offset on RL/RR as well as on CENTER/SUB channels of the original X-Fi (yours), while the L/R show around 30mV of DC offset, so not perfect at all, even at default. Looks like the X-Fi electronic design is perfectly finetuned for a NJM4558 (very low, next to none DC offset), while any other opamp is a problem there.

I think I should short the coupling caps between DAC and opamps first and then measure DC offset again with the original 4558 opamps...


Lokonsky - Quote:

how i measured this dc offset?

I did using my scope, you have to do the very same.

Quote:

i see people write -200mV and 10 mV what that is mean?

Value in milivolts (1/100 of V) that represent the value of DC offset on the outputs.

Quote:

Yep, maybe it's safe for my amp but MAYBE not for my headphone...sorry but i very-very new in this

Well, I tested it for couple of days and it worked fine with my headphones, so... it will with yours too.

Quote:

Other thing, is it good to use solid capacitor in C16,C46 and C72 (470uF/6.3v)?

Definitively not. I have couple that will fit there nicely and they pack a good deal more ripple current that the Samxon GD 470uF 6.3V d6.3, but polymers are very special caps, optimizes for high (way too high for audio, let's talk about 100kHz and more) operating frequency and they suxx BADLY at low frequency in the audio range.
For example a electrolyte cap Samxon GA has - as most others and polymers too - it's max allowable ripple current stated for 100kHz. At different frequency, there are different multipliers that need to be applied to the rated current to get the max allowable rupple current of that frequency. For 120Hz the multiplier is 0.5 ... However for polymer caps, and they are pretty much all the same, is the multiplier 0.05 (!!!) - Samxon ULR as well as all others (some has even lower multiplier...)...

So you see, using polymers are very specific and are NOT RECOMMENDED AT ALL for any audio applications at all. I always laugh my ***** off at the polymer-only soundcards or mainboard using polymers for audio... but, well...

So as you can clearly see, polymers with the multiplier 0.05 has no chance in 120Hz (and let's not even mention 50Hz). So polymers are good for output phase of hi-frequency VRM circuits and nowhere else. This nicely demonstrating and confirming the design of Intel D955XCS mainboard - or the overclockers mobo Intel D975XBX "Bad Axe":

 

[Lokonsky]

GREAT INFO TRODAS

I wonder why auzentech use it in prelude...
if i don't use solid cap,is it good (in audio quality) to change value from (470uF/6.3v) to (470uF/10v) in C16,C46 and C72 and nichichon fine gold in C177 because it's hard to find good cap in my country.thanks

 

[trodas]

Aurentech use solid polymer (as many of the makers) because of pure marketing only. Even the results are WAY worser with them, they want the "all solid caps only, bla bla bla" slogan to be pushed as if that is mean reliability.
Sadly, for most braniwashed users with experience only with bad caps, it does sound appealing. They never yet encountered a fake / bad brand polymer... nevermind.

About the cap - first at all, you give me no info about the Nichicon cap type, so I can't judge. But probably on HZ line oust the Samxon GD, so...

So not, definitively not. Higher voltage cap = worser specs running on low voltage that the low voltage one running very near its nominal voltage. These caps are VERY important to the audio result. Way more that the C177 for the main chip. Funny that everyone seems to go after him alone, lol. Another example of utter stupidity.
So, if you ask about cap, give the exact type or no-one can help ya.

 

[Lokonsky]

Quote:

Originally Posted by trodas /img/forum/go_quote.gif About the cap - first at all, you give me no info about the Nichicon cap type, so I can't judge. But probably on HZ line oust the Samxon GD, so... So not, definitively not. Higher voltage cap = worser specs running on low voltage that the low voltage one running very near its nominal voltage. These caps are VERY important to the audio result. Way more that the C177 for the main chip. Funny that everyone seems to go after him alone, lol. Another example of utter stupidity. So, if you ask about cap, give the exact type or no-one can help ya.

i have no problem with c177, Nichicon fine gold 1000uF/6.3v is VERY good cap for audio.It's C16,C46 and C72,I have to choose between Panasonic ceb 470/10v or nichicon 1000uF/6.3v (overkill but it's the right voltage) ...and yes that the only option for me.

 

[trodas]

Hardware question.

I bought my X-Fi Fatal1ty in USA, and it have heatsink on main chip and the DC coupling caps between DAC and opamps are Jamicon 22uF 16V.

Now I moded friend X-Fi Fatal1ty card, it did not have heatsink on main chip and the DC coupling caps between DAC and opamps are Wincap 10uF 16V ones.

Question - what are yours caps there?