[Lunatic]

Angel card has more emphasis on the vocal, makes it more smooth and forward. However, less driving power and less cleaner background. I heard the angel card has great synergy with Th900 though.

I don't have the Angel card but the optimized discreet card works great with my TH900s.

 

[Kiats]

Angel card has more emphasis on the vocal, makes it more smooth and forward. However, less driving power and less cleaner background. I heard the angel card has great synergy with Th900 though.

Yes, it does give a very alluring feel to vocals: Diana Krall is even more seductive on the Angel card. I am fine with less driving power because I tend to use only iems with my 901.

 

[Kiats]

Basically this mod bypasses the gain control design on the card. After the mod there won't be any difference when you use the gain switch on the 901. Bypassing gain control seems to have a more "direct" like effect, you get slightly wider and deeper soundstage with better extension on both ends of the spectrum. The ability to drive large headphones will also be improved.

However, because the gain control is disabled, it may make it less usable with sensitive iems which already require listening at low volumes on low gain because of the driving power of the discrete card.

 

[AnakChan]

Basically this mod bypasses the gain control design on the card. After the mod there won't be any difference when you use the gain switch on the 901. Bypassing gain control seems to have a more "direct" like effect, you get slightly wider and deeper soundstage with better extension on both ends of the spectrum. The ability to drive large headphones will also be improved.

 
How's hiss control after the resistors are removed?

 

[fengwei007]

How's hiss control after the resistors are removed?

I've been using mine w the resistors removed for a few weeks, really love the improvement. I never heard any hiss even w my jh16pro.

 

[awry]

I've been using mine w the resistors removed for a few weeks, really love the improvement. I never heard any hiss even w my jh16pro.

Hi Fengwei, could you please describe the improvements between having the resistors and without? Kiat told me it's mainly just staging and i think, power? Still on the fence about doing this. Lack of volume control sounds scary. 

 

[awry]

  Angel card has more emphasis on the vocal, makes it more smooth and forward. However, less driving power and less cleaner background. I heard the angel card has great synergy with Th900 though.

Hey man! I actually hear differently from you with these two cards. The angel actually outputs more power, couple of clicks lesser before it gets too loud for me. I don't have any way to rate the accurately rate the volume levels so I might be wrong and the angel just sounds louder due to the emphasis on mids but I'm pretty sure.
 
It sounds smoother and cleaner to me than the discrete as well. The discrete trumps the angel on quite a few other areas like staging, separation and details though.
 
I can attest to the TH900 having awesome synergy with the Angel card. More-so than the discrete. Like this combo very much.   

 

[fengwei007]

  Hi Fengwei, could you please describe the improvements between having the resistors and without? Kiat told me it's mainly just staging and i think, power? Still on the fence about doing this. Lack of volume control sounds scary. 

 
As Lunatic said above, the mod is to bypass the gain control circuit so you won’t be able to use low gain on the HM901 (the gain switch won’t have any effect), it’s on high gain all the time. This probably simplified the circuit and cleaned up the signal path. The sound is more extensive on both ends with slightly enlarged soundstage as well. I really love the improvement with my K701, RS1, GS1000i and T5p. Since I was on high gain all the time w/ this discrete card anyway, I don’t mind the lack of low gain setting.
 
Best of all, the mod is reversible. If you don’t like the result or if you want to have the low gain back, just solder back the resistors (I tried it, soldered the resistors back, but prefer the sound w/o those, so I removed them again). Those are very common 1K ohm resistors which cost like a few penny each. 

 

[Kiats]

[COLOR=1F497D]As Lunatic said above, the mod is to bypass the gain control circuit so you won’t be able to use low gain on the HM901 (the gain switch won’t have any effect), it’s on high gain all the time. This probably simplified the circuit and cleaned up the signal path. The sound is more extensive on both ends with slightly enlarged soundstage as well. I really love the improvement with my K701, RS1, GS1000i and T5p. Since I was on high gain all the time w/ this discrete card anyway, I don’t mind the lack of low gain setting.[/COLOR]

[COLOR=1F497D]Best of all, the mod is reversible. If you don’t like the result or if you want to have the low gain back, just solder back the resistors (I tried it, soldered the resistors back, but prefer the sound w/o those, so I removed them again). Those are very common 1K ohm resistors which cost like a few penny each. [/COLOR]

Awry, you could solder them back yourself or you could buy Fengwei07 lunch, he does it for you and best of all you get to meet the man!

 

[passionforroxk]

  Hey man! I actually hear differently from you with these two cards. The angel actually outputs more power, couple of clicks lesser before it gets too loud for me. I don't have any way to rate the accurately rate the volume levels so I might be wrong and the angel just sounds louder due to the emphasis on mids but I'm pretty sure.
 
It sounds smoother and cleaner to me than the discrete as well. The discrete trumps the angel on quite a few other areas like staging, separation and details though.
 
I can attest to the TH900 having awesome synergy with the Angel card. More-so than the discrete. Like this combo very much.   

 
Haha, good to see you enjoy the cards! I actually didn't know that angel card has more power than the discrete, maybe it's because you have the yellow one instead of the blue one? I don't know LOL, I always thought that the discrete card has more driving power than the balance card. Oh well, I think I might just have told many people the wrong staff :0

 

[fengwei007]

Awry, you could solder them back yourself or you could buy Fengwei07 lunch, he does it for you and best of all you get to meet the man!

 
That'd be sweet  

 

[Kiats]

That'd be sweet  

Then we can order more of the side dishes.

 

[514077]

I'm thinking of a 901 for purchase.  Are any of these discrete cards available in North America?  Could someone sum up the colour diferences I.E., yellow or blue,etc?

 

[jamato8]

  I'm thinking of a 901 for purchase.  Are any of these discrete cards available in North America?  Could someone sum up the colour diferences I.E., yellow or blue,etc?

I can't sum up the differences but the 3rd party cards, from what I have learned, are only available in China. You try and order from a seller there. 

 

[kkcc]

  I'm thinking of a 901 for purchase.  Are any of these discrete cards available in North America?  Could someone sum up the colour diferences I.E., yellow or blue,etc?

 
Nope.  These are made by an advanced DIYer in China and he is not willing to entertain overseas/crossborder transactions.  
 
He made total of 5 cards (4 versions of discrete cards + 1 version of angel card) that are circulated to public.  Listed in chronological order:
 
#1. First Gen Discrete Card version 1  - limited circulation, and is more like an alpha version)
#2. First Gen Discrete Card version 2  - a bit more being made, sort of like a beta version and sent to "testers" for minimal parts&labor fee)
#3. First Gen Discrete Card version 3  - this is the blue one and marked as "HP-A P-JI V1.1F Ksen_sang" one the card, was considered vastly improved upon the earlier ones)
#4. Angel Card - following critical reception of #3 he made the Angel card that is supposed to be tuned for chinese/asian female vocal/pop
#5. Second Gen Discrete Card - the yellow card, which is also regarded as better than any of the First Gen ones
 
I have #3, #4, and #5 and found them technically on par and I would prefer one over another depending on the album/tracks/my mood/which side of the bed I woke up from so YMMV