[Foton]

Hello,
My name is Tom and I have just joined Head-Fi. Electronics used to be my hobby back in elementary school almost 40years ago. Unfortunately, my life took different course and I followed other opportunities than something what used to be in my heart. Of course music was and still is my passion and willingness to listen to it through home-built amplifier is back. Please treat me as a beginner with a little bit of patience.
 
So, the amplifier which I intend to build is YAHA as the safest aim at tube amplifier. I have all needed parts, but I would like to use slightly different output part than suggested on Headwize. Instead of operational amplifier I want to try to test Analog Devices BUF-03J ( I still have two of them ) buffer and discrete diamond buffer. And here I need your help...
In YAHA article it is being said than using buffer outside of negative feedback loop might cause oscillation (the reference is made to BUF 634). Can anyone point me to schematic or help me to alter the circuit to place the output buffers inside of the feedback loop?
I did search both forums, Headwize and Head-Fi, with no avail. The schematic would be the best way for me to understand the change. 
oh, I would like to mention that my version of YAHA will be stationary, not portable, powered from regulated PSU.
 
Thanks for the help !!! 

 

[Foton]

Hello again,
Can anyone assist me with the above question? Unfortunately Headwize forum is still down and I am not quite sure there are more forums like HeadFi and Headwize.
I just need help with inserting output stage into negative feedback.
 
Thanks !!!

 

[jageur272]

Well, if you want to use a buffer instead of the opamp, you don't have to worry about that feedback loop.  Replace the + pin on the opamp with the input with the buffer and because the monolithic buffers that you will use will have only 4 connection (V+, V-, input, output), you don't have to worry about the feedback loop.
 
Or at least I think, would be nice for some backup (and I'm terrible at explaining things).

 

[cobaltmute]

Take a look at the schematic:
 
http://www.fa-schmidt.de/YAHA/index.htm
 
The feedback loop is from the output of OP1 to the negative input.  If you remove the op-amp, there is no feedback loop. 
 
The BUF-03J is an open loop buffer meant to be inserted into that loop of the op-amp.    With the Buf-634 and the Buf-03j both being open loop buffers I would suspect the same issues to occur with both if you tried to just replace the op-amp.

 

[Foton]

Hello,
Thank you very much for the response.
I that case I will try to replace op-amp with buffer.
Cobaltmute,
You said thesame issues may occur with used buffers, do you mean oscillation?
What can be done to this circuit not to have oscillation problems?
 
Thanks