[f] AMB on Facebook

2SK170BL replaced with 2SK389FM-BL

beta22

2SK170BL replaced with 2SK389FM-BL

Postby zhanqian » April 1st, 2019, 1:11 am

Hi Ti,

I saw some 2SK389FM-BL on the taobao.com, the seller said the 2SK389FM-BL is basically two 2SK170BL pack together,
and they offers connection board.

I went on some search, what I see is 2SK389FM-BL has very similar parameter with 2SK170BL,
I want to be 100 percent sure, Can I replace two 2SK170BL with one 2SK389FM-BL?
If yes, the IDSS of the two JFET in 2SK389FM-BL are matched after production? So I don't need to care the matching problem?

Thanks.
zhanqian
 
Posts: 27
Likes: 14 posts
Liked in: 10 posts
Joined: October 24th, 2017, 8:02 pm
Location: Shenzhen
Country: China (cn)

Re: 2SK170BL replaced with 2SK389FM-BL

Postby amb » April 1st, 2019, 10:23 am

The Toshiba 2SK389 is indeed two 2SK170s in a single package. However, the package is not pin-compatible with the β22 PCB. I don’t recommend the use of any adapter boards.

The matching between the two JFETs within the 2SK389 is not as good as two carefully hand-matched 2SK170s.

Be very careful about purchasing these discontinued Toshiba devices, there are lots of counterfeits out there that do not behave and perform like a genuine one.
User avatar
amb
Site Admin
 
Posts: 10379
Likes: 175 posts
Liked in: 482 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)

Re: 2SK170BL replaced with 2SK389FM-BL

Postby zhanqian » April 5th, 2019, 5:37 am

You are right, Ti.

I trust the seller, Just for curious, bought two pieces from the him,
did the device matching, The IDSS is so match as those carefully hand-matched 2SK170BL.
zhanqian
 
Posts: 27
Likes: 14 posts
Liked in: 10 posts
Joined: October 24th, 2017, 8:02 pm
Location: Shenzhen
Country: China (cn)

Re: 2SK170BL replaced with 2SK389FM-BL

Postby zhanqian » May 3rd, 2019, 7:44 am

Hi Ti,

I am building an balance Beta22, in the input scheme showing in the picture, while using the RCA input,
the L-,R- are connected to the ground, does this mean the L-,R- board is instead are active ground boards,
I know active ground board has different resister settings,but I think since the input signal is ground actually,
the resisters used for the gain setting is not so important? And the ground channel seems actually is an 2X gain
board with signal input from ground.
You do not have the required permissions to view the files attached to this post.
zhanqian
 
Posts: 27
Likes: 14 posts
Liked in: 10 posts
Joined: October 24th, 2017, 8:02 pm
Location: Shenzhen
Country: China (cn)

Re: 2SK170BL replaced with 2SK389FM-BL

Postby amb » May 3rd, 2019, 11:11 am

In a 3-board active ground setup, the ground channel is set to a lower gain. But in a 4-board balanced system, the cold channels should have the same gain as the hot channels in balanced mode. When switched to unbalanced mode we keep the same gain to avoid a big switching mess. There is a slight degradation in the cold side S/N ratio (which acts as ground channels in unbalanced mode), compared to the 3-board scheme, but should still be acceptable.

zhanqian likes this post.
User avatar
amb
Site Admin
 
Posts: 10379
Likes: 175 posts
Liked in: 482 posts
Joined: March 29th, 2010, 9:49 pm
Location: Sunnyvale, CA
Country: United States (us)


Return to β22 amplifier

Who is online

Users browsing this forum: No registered users and 0 guests

Quick Links

AMB audio DIY resources
AMB audio shop