Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Sijosae inspired SATRI amp
New Posts  All Forums:Forum Nav:

Sijosae inspired SATRI amp

post #1 of 12
12/5/10 at 3:58pm
Thread Starter 

I found this Sijosae design and thought I would try and

update it and improve on it a little.

Seeing as I am just learning design I thought I better get

some opinions before I let the magic smoke out of several

innocent transistors.

 

Here we go!

 

Sijosae - Satri v2.png

Reply
post #2 of 12
12/5/10 at 5:10pm

I'm not sure I'd trust an open loop diamond buffer without at least a servo to keep offset in leash. I'd either add a servo or replace the output stage by a jisbos like buffer. http://www.diamondstar.de/jisbos/jisbos_overview.html

Reply
post #3 of 12
12/5/10 at 5:43pm
Thread Starter 

I was thinking it might need a servo too.

Sijosae seemed to have some trouble with the offset

drifting (but I don't read Korean very well) but it

stayed less than 15 mV.

Where would be the least offensive place to inject

the servo? It would seem to have to go between
R11/R12 or at R13.

 

Quote:
Originally Posted by 00940 View Post

I'm not sure I'd trust an open loop diamond buffer without at least a servo to keep offset in leash. I'd either add a servo or replace the output stage by a jisbos like buffer. http://www.diamondstar.de/jisbos/jisbos_overview.html

Reply
post #4 of 12
12/6/10 at 8:05am
Thread Starter 

OK, I changed it a bit so I can inject the servo between R3 and R7.

How does that look?

 

Sijosae - Satri v2.1.png

Reply
post #5 of 12
12/6/10 at 8:23am
Thread Starter 

Here it is with the servo.

 

Sijosae - Satri v2.2.png

Reply
post #6 of 12
12/6/10 at 2:05pm

You could add a couple trimmers across R4 & R8 (ala dynalo) to allow for gross offset and bias adjustment before the servo is installed.

 

I bet the output transistor choice is going to contribute some to the sound signature of the amp due to the lack of global feedback.

I'm guessing the attraction to the no feedback design is some intentional non-linearity ?

The dynalo transistor choice of 2sa1815 & 2sc1015 are relatively stable HFE, which could help minimizing drift if needed.

MPS8599 & MPS8099 would be interesting combo because they are pretty fast, robust and cheap.

Reply
post #7 of 12
12/6/10 at 4:02pm
Thread Starter 

Thanks guys, but I think I am just going to build it exactly like Sijosae drew it and go from there.

My next project is the Dynalo anyway...I just wanted to try this for fun.

Reply
post #8 of 12
12/7/10 at 1:58pm

 

Quote:
Originally Posted by bada bing View Post

I'm guessing the attraction to the no feedback design is some intentional non-linearity ?

 


Feedback does not eliminate distortion, it simply moves it around. 

 

That said, this amp has way-a-lot of internal/local feedback if you consider the voltage followers all over the place. 

Reply
post #9 of 12
12/7/10 at 3:08pm

Yeah, I mispoke about all feedback, I was mostly looking at the output stage running with no global feedback.

It is an interesting schematic that looks like it would have an out of the ordinary sound to it.

I'm interested in hearing feedback on what it sounds like.

Reply
post #10 of 12
12/7/10 at 3:50pm
Thread Starter 

It's third in line for my projects right now, I will give you some feedback on how it

sounds after it's built and I tinker with it a bit...stay tuned...

 

The original used 2SK30ATM but they are unobtainium now.

The closest thing I could find was LSK846.

Maybe some one knows of a better substitute..?

Reply
post #11 of 12
12/7/10 at 3:52pm
Thread Starter 

Here is the original schematic from Sijosae:

 

Satri5.gif

Reply
post #12 of 12
12/8/10 at 5:38am

I like it too. I know very little about these kind of amps but if all goes "decent" for you I will build one too :)

Reply
New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › Sijosae inspired SATRI amp