[Trogdor]

+1. Would be interested to hear more about this amp board. Presumably a SE amp board?

Odd ball question, is the 901 board specs available for DIYs?

 

[kkcc]

Quote:

 
+1. Would be interested to hear more about this amp board. Presumably a SE amp board?

 
Yes, this is an SE amp board.  This started as a DIYer's who is an electronic engineer's personal project, and garnered some light interests on the erji board.  What I posted is the 3rd revision - the first and second revisions are prototypes with components soldered by hand.  The maker gathered inputs from the users whom he sent his first (I didn't have that), and second revision and improved the tuning and get the current version to be made on a production line though it is still of limited availability and no published price (I got it at cost and under $100 but no idea how much it would be sold at if he decided to make it generally available).  
 
No specs were published but some testing wave forms were posted at erji:
http://erji.net/read.php?tid=1488276&fpage=0&toread=&page=2
 
It caused some sensitivity on the hifiman official board with the latest iteration and some disgruntled early 901 users who wanted to trade-in or refund the standard board by proclaiming this is better than the balanced board.  Fang had even locked one of these threads and made a thread asking users to not exaggerate its performance, as well as putting up an idea of official certification for 3rd party made amp board/accessories.
 
Personally, I do agree it has even higher output based on the volume level of the same IEMs.  I may like it better than the balance board with SE cable, but need more time A/Bing, and ideally with 2 901 units as swapping amp boards create a bit of a gap time.   Was hoping it may have a very different sound sig than the balance board but seems they are more alike than different.  I don't have any proper full size cans with me now but according to others it drives full size very well, there is also reports that users using the PO with this card as LO for AUX-IN in his car with good result.
 
I look forward to more variety of sound sig - cold, warm, hot, spicy whatnot lol to play with the 901!

 

[czqdtc]

Quote:

 
Yes, this is an SE amp board.  This started as a DIYer's who is an electronic engineer's personal project, and garnered some light interests on the erji board.  What I posted is the 3rd revision - the first and second revisions are prototypes with components soldered by hand.  The maker gathered inputs from the users whom he sent his first (I didn't have that), and second revision and improved the tuning and get the current version to be made on a production line though it is still of limited availability and no published price (I got it at cost and under $100 but no idea how much it would be sold at if he decided to make it generally available).  
 
No specs were published but some testing wave forms were posted at erji:
http://erji.net/read.php?tid=1488276&fpage=0&toread=&page=2
 
It caused some sensitivity on the hifiman official board with the latest iteration and some disgruntled early 901 users who wanted to trade-in or refund the standard board by proclaiming this is better than the balanced board.  Fang had even locked one of these threads and made a thread asking users to not exaggerate its performance, as well as putting up an idea of official certification for 3rd party made amp board/accessories.
 
Personally, I do agree it has even higher output based on the volume level of the same IEMs.  I may like it better than the balance board with SE cable, but need more time A/Bing, and ideally with 2 901 units as swapping amp boards create a bit of a gap time.   Was hoping it may have a very different sound sig than the balance board but seems they are more alike than different.  I don't have any proper full size cans with me now but according to others it drives full size very well, there is also reports that users using the PO with this card as LO for AUX-IN in his car with good result.
 
I look forward to more variety of sound sig - cold, warm, hot, spicy whatnot lol to play with the 901!

Lucky you!
I'm stuck with the balanced amp module T.T

 

[AnakChan]

First two prototypes were hand soldered. Meaning 3rd isn't? If its not then its automated? That's quite a DIY !!

I was gonna say Fang must be unhappy but thought there'd be patent violations, etc. There's more to be said but probably inappropriate.

Still as a product that is interesting. Am quite keen to try. Please do elaborate more on its sonics. How is it "better" than the balanced module?

 

[kkcc]

First two prototypes were hand soldered. Meaning 3rd isn't? If its not then its automated? That's quite a DIY !!

I was gonna say Fang must be unhappy but thought there'd be patent violations, etc. There's more to be said but probably inappropriate.

Still as a product that is interesting. Am quite keen to try. Please do elaborate more on its sonics. How is it "better" than the balanced module?

Just saw the maker clarified on erji he got no plans for commercialization or mass production. My guess is he might run some sort of his own circuit board manufacturing business or at least have good access to one and was curious on his own theory on amp section.

Not sure if "better" is accurate in the absolute sense but thus far it does drive my 1plus2 with SE gold/silver cable better than the balanced amp board in SE mode. There is even more clarity and vocal became more full and a little more upfront which I like more personally.

I hope Fang can work something out with this guy and either odm it from him or purchase the design as I see a place for it in the 901 amp lineup.

 

[jamato8]

Quote:

 
Personally, I do agree it has even higher output based on the volume level of the same IEMs.  I may like it better than the balance board with SE cable, but need more time A/Bing, and ideally with 2 901 units as swapping amp boards create a bit of a gap time.   Was hoping it may have a very different sound sig than the balance board but seems they are more alike than different.  I don't have any proper full size cans with me now but according to others it drives full size very well, there is also reports that users using the PO with this card as LO for AUX-IN in his car with good result.
 
I look forward to more variety of sound sig - cold, warm, hot, spicy whatnot lol to play with the 901!

Being louder doesn't mean it has more power. It means it has more gain, which will make the board louder at the same volume setting when a board that has less gain is compared to. The balanced board is optimized for running balanced so the best comparison would be the balanced board as balanced even if comparing to a SE board.  

 

[kkcc]

Quote:

Being louder doesn't mean it has more power. It means it has more gain, which will make the board louder at the same volume setting when a board that has less gain is compared to. The balanced board is optimized for running balanced so the best comparison would be the balanced board as balanced even if comparing to a SE board.  

 
True and agree on all counts.  Hence I only mention "higher output".  I refer to Power only when responding to "what it is for" as it was the maker's design goal and I don't have enough data/experience to determine if it is achieved or not.  Hope I don't give anyone the wrong impression.
 
Also agree the value of the balanced board is to run it in balanced mode, and hence I only mentioned I like SE on this diy board better on SE setting, as I don't have the same cable on SE and balanced to compare.  This is actually the key to why I think it has a place in the lineup - not everyone is willing to balance all the cable to use exclusively with HM901.  I had been struggling to find a quality TRRS to SE 3.5 convertor and this had prevented me from balancing my "go-to" cables (tralucent/whiplash) as I do use them with my AK120 and I noticed a difference in the sound with the convertor I got with RE600.  This amp board provide close enough if not better performance on SE for me and my setups.
 
Guess all these are moot as it will not be commercially available anyway.  I'm just glad I do get one for minimal cost albeit quite a lot of hassle getting payment to this guy as he don't even have a taobao seller account.  

 

[kkcc]

Lucky you!
I'm stuck with the balanced amp module T.T

Now come on man, we both know how great the balanced amp board sounds and it is just a new toy to complement. I feel the balanced board is more neutral while this DIY board is more mid forward. Works well with 1plus2 but not with tg334 or re600. If I can only have one then it has to be the balanced board without a doubt.

 

[jonckr]

Quote:

Now come on man, we both know how great the balanced amp board sounds and it is just a new toy to complement. I feel the balanced board is more neutral while this DIY board is more mid forward. Works well with 1plus2 but not with tg334 or re600. If I can only have one then it has to be the balanced board without a doubt.

How much did this board cost you? I'm looking to get a board for JH16s

 

[Trogdor]

So I have a question, what adapter do I need for standard 1/4" SE connector to use the balanced card?

I think I go it. 1/4 -> 1/8 (3.5) in normal mode.

 

[kkcc]

Quote:

How much did this board cost you? I'm looking to get a board for JH16s

 
Well the maker isn't gonna mass produce or commercialize this so it is moot.  Will keep you posted if thing changes.  
And as such, will probably keep further impression to myself so as not to derail this into monolithic opamp vs discrete "science" debate.....
 
Cheers 

 

[kkcc]

Quote:

So I have a question, what adapter do I need for standard 1/4" SE connector to use the balanced card?

I think I go it. 1/4 -> 1/8 (3.5) in normal mode.

 
Yup that's right and will work.

 

[jelt2359]

When the HM901 has the balanced card installed, does it have a hunchback like the HM801?
 
The HM801's hunchback makes it tough to tie to other amps. Sounds awesome, so I won't be giving it up, but limits my use cases.

 

[kkcc]

When the HM901 has the balanced card installed, does it have a hunchback like the HM801?
 
The HM801's hunchback makes it tough to tie to other amps. Sounds awesome, so I won't be giving it up, but limits my use cases.

No. 901 has built-in trrs balanced jack that doubles as normal SE jack and can swtich between them with a selector.

 

[jonckr]

Quote:

Seems like 901 has a safety feature. Yesterday when my 901 suddenly turned off, I thought the battery was flat. Today tried to power it on but to no avail. I decided to remove the battery pack and to my horror the balanced amp card somehow got poped out of the safety latch. I clipped it back on, battery went back in and powered on my device. Fortunately the safety short circuit implementation was good

 
hope nothing's wrong with the catch. Anyone else had this? I guess i probably didn't insert the standard amp board firmly enough.